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2008, Vol. 38, No. 2 (pp. 119-138)
ISSN: 0112-1642
Review Article
Physiology of Rugby League
Sports Med 2008; 38 (2): 119-138
R
EVIEW
A
RTICLE
0112-1642/08/0002-0119/$48.00/0
2008 Adis Data Information BV. All rights reserved.
Applied Physiology of Rugby League
Tim Gabbett,
1
Trish King
2
and David Jenkins
2
1 Brisbane Broncos Rugby League Club, Red Hill, Queensland, Australia
2 School of Human Movement Studies, University of Queensland, Brisbane,
Queensland, Australia
Contents
Abstract .................................................................................... 120
1. Description of Rugby League ............................................................. 120
2. Rationale for the Review .................................................................. 121
3. Physiological and Anthropometric Characteristics ........................................... 121
3.1 Body Composition ................................................................... 121
3.2 Maximal Aerobic Power .............................................................. 122
3.3 Speed .............................................................................. 123
3.4 Repeated Sprint Ability ............................................................... 123
3.5 Agility ............................................................................... 124
3.6 Muscular Strength and Power ......................................................... 124
3.7 Physiological and Anthropometric Characteristics of Female Rugby League Players ........ 126
3.8 Changes in Physiological and Anthropometric Characteristics Over a Competitive Season 126
4. Relationship Between Physical Fitness and Playing Ability ..................................... 127
4.1 Physiological, Anthropometric and Skill Characteristics .................................. 127
4.2 Influence of Fatigue on Skill ........................................................... 127
5. Performance Analysis ..................................................................... 128
5.1 Time-Motion Analysis ................................................................. 128
5.2 Physiological Demands of Competition ................................................ 129
6. Thermoregulatory Responses during Training and Competition ................................ 130
7. Relationship Between Physiological Factors and Injury ....................................... 131
7.1 Influence of Player Fatigue on Injury Rates.............................................. 131
7.2 Influence of Playing Intensity on Injury Rates ............................................ 131
7.3 Influence of the Limited Interchange Rule on Injury Rates ................................ 131
7.4 Influence of Training Load on Injury Rates .............................................. 132
7.5 Relationship Between Training Load, Injury and Fitness ................................... 132
7.6 Risk Factors for Injury ................................................................. 133
8. Strength and Conditioning ................................................................ 133
8.1 Specificity ........................................................................... 133
8.2 Skill-Based Conditioning Games and Interval Training .................................... 133
8.3 Training and Adaptation in Junior and Senior Rugby League Players ...................... 134
9. Conclusions ............................................................................. 135
120 Gabbett et al.
Rugby league football is played in several countries worldwide. A rugby
Abstract
league team consists of 13 players (6 forwards and 7 backs), with matches played
over two 40-minute halves separated by a 10-minute rest interval. Several studies
have documented the physiological capacities of rugby league players and the
physiological demands of competition, with the physiological capacities of play-
ers and the physiological demands of competition increasing as the playing level
is increased. However, there is also evidence to suggest that the physiological
capacities of players may deteriorate as the season progresses, with reductions in
muscular power and maximal aerobic power and increases in skinfold thickness
occurring towards the end of the rugby league season, when training loads are
lowest and match loads and injury rates are at their highest.
Player fatigue and playing intensity have been suggested to contribute to
injuries in rugby league, with a recent study reporting a significant correlation (r =
0.74) between match injury rates and playing intensity in semi-professional rugby
league players. Studies have also reported a higher risk of injury in players with
low 10-m and 40-m speed, while players with a low maximal aerobic power had a
greater risk of sustaining a contact injury. Furthermore, players who completed
<18 weeks of training prior to sustaining their initial injury were at greater risk of
sustaining a subsequent injury. These findings provide some explanation for the
high incidence of fatigue-related injuries in rugby league players and highlight the
importance of speed and endurance training to reduce the incidence of injury in
rugby league players.
To date, most, but not all, studies have investigated the movement patterns
and physiological demands of rugby league competition, with little emphasis on
how training activities simulate the competition environment. An understanding
of the movement patterns and physiological demands of specific individual
positions during training and competition would allow the development of
strength and conditioning programmes to meet the specific requirements of these
positions. In addition, further research is required to provide information on the
repeated effort demands of rugby league. A test that assesses repeated effort
performance and employs distances, tackles and intensities specific to rugby
league, while also simulating work-to-rest ratios similar to rugby league competi-
tion, is warranted.
1. Description of Rugby League two 40-minute halves, separated by a 10-minute rest
interval. Players compete in a challenging contest
Rugby league football originated in the north of involving frequent bouts of high-intensity activity
England in the 1890s and is played at junior and se- (e.g. running and passing, sprinting, tackling), sepa-
nior levels in several countries worldwide, including rated by short bouts of low-intensity activity (e.g.
Australia, New Zealand, France, Russia, Wales, standing, walking and jogging). The physiological
Scotland, Ireland, Papua New Guinea, Fiji, Samoa demands of rugby league are complex, requiring
and South Africa.
[1,2]
The game is played over players to have highly developed speed, agility,
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 121
muscular strength and power, and maximal aerobic requiring defensive players to retreat 10 m (rather
power.
[3]
than 5 m) following each tackle,
[10]
and the introduc-
tion of the limited interchange replacement rule,
A rugby league team consists of 13 players, with
have resulted in increased physiological demands on
junior and amateur rugby league matches typically
rugby league players.
[11,12]
With this in mind, the
(but not always) played under an unlimited in-
purpose of the present article is to provide a compre-
terchange rule, whereas professional rugby league
hensive review of the applied physiology of contem-
teams are permitted a maximum of 12 interchange
porary rugby league football.
movements during the course of a match. Each team
is allowed six tackles with the ball. The objective is
3. Physiological and
to advance the ball down the field into the opposi-
Anthropometric Characteristics
tion’s territory and score a try (touch down).
[4,5]
The
ball must be passed backwards, but can be carried or
kicked into the opposition’s territory.
[5]
At the com-
3.1 Body Composition
pletion of each set of six tackles, the ball is immed-
Excess body fat has been shown to negatively
iately given to the opposition team to commence its
influence sporting performance (e.g. power to body
set of six tackles.
[4]
Therefore, the same players are
mass ratio, thermoregulation and aerobic capa-
involved in both attack and defence.
city).
[2]
Rugby league players have been shown to
The two major playing groups within a rugby
have higher body mass and percentage body fat than
league team are the forwards and backs. Team posi-
other team sport players, such as soccer and Austra-
tions can also be classified according to the specific
lian footballers.
[7]
Mean body mass measurements
individual position played (i.e. prop, hooker, second
of senior rugby league players have been reported to
row, lock, halfback, five-eighth, centre, wing and
be in the range of 86–90 kg
[13-15]
with no significant
fullback), or according to four subgroups reflecting
differences amongst amateur, semi-professional and
positional commonality (i.e. props, hookers and
professional players.
[14]
Most,
[2,13,14,16-18]
but not
halves, back-rowers and outside backs).
[2,6-8]
The
all,
[19]
studies have shown a higher body mass in
demands placed on players vary according to the
forwards than backs. Interestingly, body mass is the
specific position played.
[2,6-8]
Forwards are predom-
only physical characteristic that successfully
inantly involved in large numbers of physical colli-
predicts selection into a first-grade rugby league
sions and tackles, while backs spend more time in
team,
[14]
or as a forward or back.
[19]
Amateur rugby
free running. Due to the high intensity of the game
league players have 31% higher percentage body fat
and the large number of physical collisions and
than professional players, however, percentage body
tackles, musculoskeletal injuries are common.
[9]
fat is reported to be similar for forwards and
backs.
[13]
The percentage body fat of professional
2. Rationale for the Review
rugby league players is reported to be significantly
A review article addressing the applied physiolo- higher in forwards (15.2%) than backs (12.6%)
gy of rugby league has been published.
[1]
However, [table I].
[16]
Props and back-rowers are predominant-
a paucity of scientific literature existed at the time ly responsible for the higher percentage body fat of
this review was published, and the majority of the forwards.
[7]
Meir
[17]
reported that elite forwards had
scientific research was conducted on elite-level significantly greater skinfold thickness than elite
players. In addition, since the review of Brewer and backs at all stages during the competitive season.
Davis
[1]
was published, a change in defensive rules, Forwards spend significantly more playing time in-
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
122 Gabbett et al.
Table I. Height, body mass, skinfold thickness and estimated body fat of rugby league forwards and backs competing at amateur, semi-
professional and professional levels
Amateur
[13]
Semi-professional
[23]
Professional
[16]
forwards backs forwards backs forwards backs
Height (cm) 178.4 ± 8.7 178.0 ± 5.2 178.2 ± 7.2 176.0 ± 5.9 184.0 ± 7.0 178.0 ± 7.0
Body mass (kg) 90.8 ± 10.2 79.7 ± 10.1 90.3 ± 14.0 80.7 ± 10.4 92.1 ± 10.4 79.8 ± 8.0
Skinfold thickness (mm)
a
52.4 ± 14.7 46.1 ± 18.6 47.3 ± 17.9 38.8 ± 13.9 NR NR
Estimated body fat (%) 19.9 ± 3.7 17.5 ± 5.0 17.6 ± 4.4 15.2 ± 4.1 15.2 ± 3.4 12.6 ± 3.2
a Data are sum of four skinfold sites (biceps, triceps, subscapular, suprailiac).
NR = not reported.
volved in tackles
[20]
and physical collisions
[21,22]
tively poor aerobic fitness of amateur rugby league
than backs, so it is likely that the larger body mass of
players has been attributed to a low playing intensi-
forwards assists in the development of greater im-
ty, infrequent matches of short duration, and an
pact forces associated with these events. It has also
inappropriate training stimulus,
[13]
although the
been suggested that higher percentage body fat in
higher percentage body fat may also contribute to
forwards may act as a means of protection from
the lower estimated
˙
VO
2max
in these players. The
impact injuries;
[17]
however, to date, no scientific
mean estimated
˙
VO
2max
of semi-professional rugby
evidence exists to support or refute this claim.
league players at the beginning of a competitive
season was reported to be 46.0–48.5 mL/kg/
3.2 Maximal Aerobic Power
min
[14,28]
and 50.0 mL/kg/min during the competi-
tive phase of the season after players had gained
Several studies have documented the physiologi-
match fitness.
[19]
Mean estimated
˙
VO
2max
measure-
cal characteristics of rugby league players, with the
ments of junior sub-elite rugby league players are in
fitness of players increasing as the playing level
the range of 32.1–46.1 mL/kg/min and progressive-
increases.
[2,7,13,14,16,19,24,25]
Professional rugby league
ly improve as the playing level increases.
[19]
How-
players train 5–6 days per week,
[22,26]
often perform-
ever, Gabbett and Herzig
[24]
reported significantly
ing multiple training sessions each day.
[14]
As a
higher mean estimated
˙
VO
2max
scores (48.7–54.6
result, the physiological characteristics of profes-
mL/kg/min) in junior elite rugby league players.
sional rugby league players are well developed.
Despite having contrasting match-play activities,
Larder
[21]
reported a mean maximal oxygen uptake
the physiological characteristics of rugby league
(
˙
VO
2max
) of 62.6 mL/kg/min in an international
forwards and backs are remarkably similar, sug-
squad prior to an overseas tour, while Allen
[27]
re-
gesting that fitness training for rugby league is simi-
ported a mean
˙
VO
2max
of 55.8 mL/kg/min in region-
lar for all positions.
[15]
Brewer et al.
[16]
reported
al (and national) representative rugby league players
mean
˙
VO
2max
values of 56.4 and 55.4 mL/kg/min
at the completion of a competitive rugby league
for professional rugby league forwards and backs,
season. Other studies of the physiological character-
respectively. Consistent with this finding, Gab-
istics of professional rugby league players have re-
bett
[13,14]
has reported similar mean
˙
VO
2max
values
ported mean estimated
˙
VO
2max
scores in the range
between amateur rugby league forwards (38.1 mL/
of 48.6–56.4 mL/kg/min.
[7,15,16]
In contrast, the max-
kg/min) and backs (40.0 mL/kg/min) and semi-pro-
imal aerobic power of amateur rugby league players
fessional rugby league forwards (45.8 mL/kg/min)
is poorly developed, with a recent study demonstrat-
and backs (48.0 mL/kg/min). The finding of similar
ing that estimated
˙
VO
2max
was 20–42% lower than
in professional rugby league players.
[13]
The rela- physiological characteristics between amateur rugby
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 123
league forwards and backs most likely reflects the tivity.
[20]
This is particularly true for forwards, who
similar training patterns of players, with a recent seldom sprint further than 10 m in a single bout of
study finding no significant differences between intense activity.
[20]
While no significant differences
forwards and backs in the training time devoted to have been observed between forwards and backs for
the development of muscular power, speed and aer- 10-m speed, backs are consistently faster over 40 m
obic fitness.
[13]
Although most studies have found than forwards.
[2,6,7,13,14,16,24]
No significant differ-
no significant differences in the physiological char- ences were reported between junior sub-elite rugby
acteristics of rugby league forwards and backs, in a league forwards and backs for 10-, 20- or 40-m
study of 260 professional rugby league players, speed.
[19]
However, junior elite backs are reported to
O’Connor
[7]
reported significant differences be significantly faster than forwards.
[24]
A progres-
amongst positional playing groups for
˙
VO
2max
. Pro- sive increase in speed has been reported as the
ps (48.6 mL/kg/min) and back-rowers (51.1 mL/kg/ playing level is increased.
[14,19,24]
Mean times of
min) had significantly lower
˙
VO
2max
scores than 2.58 and 6.63 seconds over 10 and 40 m, respective-
outside backs (52.8 mL/kg/min), hookers (55.2 mL/ ly, have been reported for amateur rugby league
kg/min) and halves (52.0 mL/kg/min). Using dis- players.
[13]
Semi-professional rugby league players
tance achieved during a 5-minute run as an estimate are significantly faster than amateur players, with
of endurance, Meir et al.
[2]
found no significant mean 10- and 40-m times of 2.17 and 6.04 seconds
differences between forwards and backs for distance reported, respectively.
[14]
The mean 10- and 40-m
achieved. However, distributors (hookers and half- sprint times of professional rugby league players is
backs) achieved a significantly greater running dis- in the range of 1.71–1.83 and 5.08–5.66 seconds,
tance (1353 m) than all other positions respectively.
[2,7,16,30]
Outside backs are typically the
(1264–1309 m). In a study of 415 sub-elite rugby fastest over 10–40 m.
[6,7,23]
In a study of professional
league players, Gabbett
[23,29]
reported significant rugby league players, Clark
[6]
reported that outside
differences amongst positional playing groups for backs were significantly faster than props, hookers
˙
VO
2max
. In agreement with results from profession- and halves, and back-rowers over 10 and 40 m.
al rugby league studies,
[7]
props (42.6 mL/kg/min) O’Connor
[7]
also reported that outside backs and
and back-rowers (44.9 mL/kg/min) had significantly halves were significantly faster than back-rowers,
lower
˙
VO
2max
scores than outside backs (46.1 mL/ props and hookers in professional rugby league. In a
kg/min) and hookers and halves (46.5 mL/kg/ study of sub-elite rugby league players, Gabbett
[23]
min).
[23]
Finally, the
˙
VO
2max
of Under-16 backs reported that the outside backs and hookers and
(49.5 mL/kg/min) is reported to be significantly halves were significantly faster over 10 and 40 m
higher than forwards (42.9 mL/kg/min), suggesting than the props and back-rowers. Centres (5.81 se-
that the volume and intensity of training may differ conds), fullbacks (5.84 seconds) and hookers (5.88
between forwards and backs in this age group.
[19]
seconds) had the fastest speed over 40 m.
[23]
3.3 Speed 3.4 Repeated Sprint Ability
Rugby league players require the ability to move Given the highly intense, intermittent nature of
quickly in order to position themselves in attack and rugby league, repeated sprint ability is extremely
defence.
[2]
However, professional rugby league important. For example, a player who makes the
studies have shown that players rarely sprint dis- effort to move quickly off the defensive line, make a
tances of >40 m in a single bout of intense ac- cover-defending tackle, and then chase from first
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
124 Gabbett et al.
marker requires the ability to generate high levels of 3.5 Agility
power, and then recover quickly in order to produce
Rugby league players require the ability to rapid-
further high-intensity efforts. Surprisingly few stud-
ly accelerate, decelerate and change direc-
ies have investigated the repeated-sprint ability of
tion.
[20,31,32]
Given that several different tests have
rugby league players.
[6,7]
Clark
[6]
and O’Connor
[7]
been used to assess agility in rugby league players,
used a 6 × 40 and 8 × 40-m sprint (each sprint
comparisons between studies is difficult. Using the
performed every 30 seconds), respectively, to assess
L-run to assess agility in professional rugby league
repeated sprint ability. The objective of the repeated
players, Meir
[18]
reported an average agility time of
sprint ability test was for players to complete each
5.46 and 5.37 seconds for forwards and backs, re-
repetition as close as possible to his maximum sprint
spectively. Gabbett
[14]
reported mean Illinois agility
time.
[7]
O’Connor
[7]
reported no significant differ-
times of 17.1 seconds in semi-professional rugby
ences amongst playing positions for repeated sprint
league players. No significant differences in agility
ability in professional rugby league players. How-
were found between first-grade (16.9 seconds) and
ever, a subsequent study found significant differ-
second-grade (17.4 seconds) players; however,
ences amongst playing positions, with hookers and
backs (16.6 seconds) showed significantly greater
halves demonstrating the lowest speed decrement
agility than forwards (17.2 seconds).
[14]
Illinois agil-
(5.1%), followed by back-rowers (6.2%), outside
ity scores for junior (Under 13–19) sub-elite rugby
backs (6.2%) and props (7.1%).
[6]
Furthermore, a
league players are in the range of 17.9–22.0 seconds,
lower speed decrement in elite players (3.0%) com-
with agility improving as the playing level is in-
pared with lower grade (6.8%) players was also
creased.
[19]
However, no significant differences
reported. Research is yet to investigate the repeated
were found between junior forwards and backs for
sprint ability of junior, amateur, or semi-profession-
agility. O’Connor
[7]
evaluated the agility of profes-
al rugby league players. A limitation of the 6 × 40
sional rugby league players using the ‘glycolytic
and 8 × 40-m sprint test performed every 30 seconds
agility test’. No significant differences were de-
is that repeated sprint efforts in rugby league can
tected amongst outside backs, halves, back-rowers
vary in distance and recovery duration.
[10]
In a time-
and hookers, although as expected, props had signif-
motion study of professional rugby league players,
icantly lower agility scores than outside backs. Gab-
Meir et al.
[10]
reported that every 4 seconds of high-
bett
[23]
also reported no significant differences
intensity activity was followed by approximately
amongst outside backs, hookers and halves, and
30–80 seconds of low-intensity activity. Further-
back-rowers for agility; however, props had the
more, sprint efforts ranged over distances of
slowest agility scores for all positional playing
5–60 m.
[10]
These findings suggest that the repeated
groups.
sprint ability tests employed previously
[6,7]
may not
provide an accurate assessment of the high-intensity
3.6 Muscular Strength and Power
intermittent nature of rugby league. Further research
is required to provide information on the repeated
The capacity to rapidly generate high levels of
effort demands of rugby league. A test that assesses
muscular force is a key characteristic of successful
repeated effort performance and employs distances,
rugby league players. Players are required to have
tackles and intensities specific to rugby league,
high levels of muscular strength in order to effec-
while also simulating work-to-rest ratios similar to
tively tackle, lift, push and pull opponents during a
rugby league competition is required. match.
[2]
In addition, high levels of muscular
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 125
strength and power are required to provide fast play- Most investigations that have examined strength
the-ball speed and to facilitate effective leg drive in
in rugby league have assessed leg muscular power
tackles. Several studies have examined the strength
using the vertical jump test.
[7,13,14,19]
A progressive
characteristics of rugby league players.
[2,7,30,33-41]
improvement in muscular power as the playing level
Meir
[18]
reported significant differences in one repe-
increased has been reported in junior elite
[24]
and
tition maximum (1RM) squat (188 vs 168 kg) and
sub-elite
[14,19]
rugby league players. Vertical jump
bench-press (119 vs 113 kg) strength in forwards
scores for junior (Under 13–19) sub-elite rugby
and backs, respectively. These findings were con-
league players ranged from 28.2 to 37.9 cm, with no
firmed by O’Connor
[7]
who reported significantly
significant differences between forwards and
greater 3RM squat, bench-press and power-clean
backs.
[19]
Junior elite rugby league players have
results in props and back-rowers compared with
been reported
[24]
to have significantly greater verti-
hookers, halves and outside backs. Baker and col-
cal jump scores (50.0–58.9 cm) than junior sub-
leagues
[30,38,39]
reported 3RM squat and power-clean
elite
[19]
and junior regional development
[41]
rugby
values of 158 and 102 kg, and 1RM bench-press and
league players. A progressive improvement in
squat values of 130 and 165 kg in professional rugby
muscular power was also observed among amateur,
league players. Significant differences have been
semi-professional and professional rugby league
reported between younger (<24 years) and older
players.
[14]
Studies of amateur rugby league players
(>28 years) professional rugby league players for
have reported vertical jump scores of 38.1 cm, a
strength, with younger players having higher 1RM
value 30% lower than professional rugby league
squat (183 vs 153 kg) and bench-press (143 vs
players.
[13]
The high percentage body fat of amateur
127 kg) scores than older players.
[37]
However, pro-
fessional rugby league players had significantly
rugby league players most likely contributes to the
greater upper-body strength and power than college-
inferior speed and muscular power of these athletes
aged and junior high school-aged rugby league play-
by attenuating the power to body mass ratio and
ers.
[34,36]
The greater strength and power in profes-
reducing performance in match-specific tasks.
[42]
sional rugby league players was attributed, in part,
The vertical jump height of amateur rugby league
to neural adaptations (e.g. increased efficiency of
forwards (37.1 cm) and backs (39.3 cm) is reported
neural patterning of the skill of strength exercises,
to be similar.
[13]
No significant differences existed
diminished levels of antagonist co-contraction, syn-
between first grade and second grade semi-profes-
chronous firing of motor units, and reduced inhibito-
sional rugby league players for vertical jump height,
ry feedback from force receptors) that occurred with
although forwards had a significantly lower vertical
long-term periodized strength and power training.
[36]
jump than backs (40.7 vs 46.7 cm).
[14]
Furthermore,
The greater strength and power of professional rug-
there were no positional differences amongst profes-
by league players has been attributed to more exten-
sional rugby league players for muscular power,
sive myogenic adaptations (e.g. changes in the
with vertical jump scores ranging from 52.2 to
muscle fibre or myosin heavy chain).
[36]
Warman
56.1 cm.
[7]
Finally, Baker
[37]
reported significant
et al.
[40]
reported 3RM squat and bench-press
differences between younger and older professional
strength of 158 and 112 kg, respectively, in semi-
rugby league players for upper- and lower-body
professional rugby league players. No study has
muscular power, as measured from a bench-press
investigated the muscular strength of amateur rugby
league players. throw and jump-squat test, respectively.
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
126 Gabbett et al.
3.7 Physiological and Anthropometric 3.8 Changes in Physiological and
Anthropometric Characteristics Over a
Characteristics of Female Rugby
Competitive Season
League Players
While several studies have documented the phys-
While rugby league is predominantly played by
iological and anthropometric characteristics of rug-
by league players, few studies have investigated the
male competitors, women have also recently begun
changes in fitness of rugby league players over a
playing the game. There are female rugby league
competitive season.
[28,48-50]
The physiological and
competitions in Australia, with elite players selected
anthropometric characteristics of amateur,
[28]
semi-
to the Queensland, New South Wales and Australian
professional
[48]
and junior elite
[49]
rugby league
National Rugby League teams based on playing
players significantly change over the course of the
season. The greatest improvements in fitness occur
performances at state- and national-level competi-
in the early stages of the season
[28,48-50]
and there is
tions. Gabbett
[43]
investigated the physiological and
evidence to suggest that fitness may deteriorate as
anthropometric characteristics of elite female rugby
the season progresses.
[28,49]
The significant improve-
league players competing in the Australian national
ments in fitness in the early stages of the season
women’s rugby league team. Measurements of
have been attributed to the high training loads ex-
perienced during this period,
[28,48]
while reductions
skinfold thickness, speed, agility, vertical jump, gly-
in fitness as the season progresses may be due to
colytic capacity and estimated
˙
VO
2max
were
increased playing commitments.
[28,49]
Indeed, Gab-
6.0–38.1% poorer than previously reported for other
bett
[28]
reported increases in
˙
VO
2max
and muscular
elite female team sport athletes (e.g. touch football,
power and reductions in skinfold thickness in ama-
soccer and hockey) [table II].
[44-47]
These findings
teur rugby league players during the early phases of
the rugby league season when training loads were
demonstrate the need to develop all physiological
highest. However, muscular power and
˙
VO
2max
de-
parameters to allow elite female rugby league play-
creased and skinfold thicknesses increased towards
ers to more effectively tolerate the physiological
the end of the rugby league season, when training
demands of competition, reduce fatigue-related er-
loads were lowest and match loads and injury rates
rors in skill execution and decrease the risk of inju-
were at their highest. These findings were attributed
ry. to a high overall playing intensity in end-season
Table II. Comparison of physiological and anthropometric characteristics among elite female team sport athletes
Rugby league
[43]
Soccer
[44,45]
Hockey
[46]
Touch football
[47]
Age (y) 18.9 ± 5.7 23.1 ± 3.4 NR 22.1 ± 3.2
Height (cm) 167.6 ± 6.1 164.5 ± 6.1 166.7 ± 5.1 162.5 ± 7.6
Body mass (kg) 70.1 ± 11.6 58.5 ± 5.7 61.1 ± 5.5 56.8 ± 4.2
Skinfold thickness (mm)
a
128.0 ± 32.4 95.9 ± 23.0 68.2 ± 13.6 71.3 ± 11.8
10-m sprint (sec) 2.00 ± 0.11 1.85 ± 0.07 1.98 ± 0.07 1.82 ± 0.09
40-m sprint (sec) 6.46 ± 0.36 NR 6.04 ± 0.22 5.71 ± 0.22
Vertical jump (cm) 35.4 ± 7.0 51.0 ± 5.0 46.0 ± 4.0 NR
Estimated
˙
VO
2max
(mL/kg/min) 33.8 ± 4.2 50.3 ± 5.1 51.3 ± 4.7 50.8 ± 3.2
a Data are sum of seven skinfold sites (biceps, triceps, subscapular, supraspinale, abdomen, thigh, calf).
NR = not reported;
˙
VO
2max
= maximal oxygen uptake.
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 127
matches, increases in injury rates in the latter half of a high level of skill under fatigue. Gabbett et al.
[53]
the season, and residual fatigue associated with lim- investigated the physiological, anthropometric and
ited recovery time between successive matches.
[28]
skill characteristics of rugby league players compet-
In a subsequent study of junior rugby league players, ing at three distinct playing levels to determine
Gabbett
[50]
reported an improvement in physiologi- which, if any, factors discriminated between suc-
cal capacities during the early phases of the rugby cessful and less successful athletes. In addition, the
league season when training loads were highest. relationship between physical fitness and playing
However, in contrast to the results from amateur ability was evaluated. First-grade players had great-
rugby league players, match intensity and match er basic passing and ball carrying ability, and superi-
loads decreased throughout the season. As a result, or skills while fatigued, tackling and defensive
maximal aerobic power and muscular power were skills, and evasion skills (i.e. ability to beat a player
maintained throughout the competitive phase of the and two vs one skills) than second- and third-grade
season. These findings suggest that high training players. While no significant differences were found
loads in the general preparatory phase of the season among playing levels for body mass, skinfold thick-
and low match loads in the competitive phase of the ness, height, 10-, 20-, or 40-m speed, agility, vertical
season allow junior rugby league players to maintain jump height, or estimated
˙
VO
2max
, all of the physio-
a high level of fitness throughout an entire competi- logical and anthropometric characteristics were sig-
tive season.
[50]
nificantly associated with at least one measure of
playing ability. The results of this study demonstra-
4. Relationship Between Physical Fitness
ted that selected skill characteristics, but not physio-
and Playing Ability
logical or anthropometric characteristics discrimi-
nate between successful and less successful rugby
league players. However, all physiological and an-
4.1 Physiological, Anthropometric and
thropometric characteristics were related to playing
Skill Characteristics
ability. These findings suggest that while physiolog-
The superior playing performance of elite level
ical and anthropometric characteristics do not dis-
rugby league players is often attributed to the greater
criminate between successful and less successful
physiological capacities of these athletes.
[51]
Al-
rugby league players, a high level of physical fitness
though successful performance in rugby league is
contributes to effective playing ability in these ath-
dependent (at least in part) on well developed physi-
letes.
[53]
ological capacities, players also require the ability to
constantly execute complex skills under pressure
4.2 Influence of Fatigue on Skill
and while fatigued.
[14,52]
Indeed, the significance of
high physical fitness levels is reduced if the physio- Success in rugby league is dependent, at least in
logical parameter does not transfer to improved part, on tackling ability, the ability to tolerate physi-
playing performance. For example, an increase in cal collisions, and the ability to ‘win’ the tackle
muscular power is redundant unless the enhanced contest.
[54]
In addition, the demands of the game
physiological capacity transfers to improved leg (and subsequent fatigue), is increased through the
drive in tackles, or greater play-the-ball speed. Simi- large numbers of physical collisions and tackles that
larly, the value of an increase in aerobic fitness is players are involved with during a match. Gabbett
[55]
negated if the ability of players to defend for multi- investigated the influence of fatigue on tackling
ple sets is unchanged or players are unable to exhibit technique in rugby league players and examined the
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
128 Gabbett et al.
relationship between selected physiological capaci- professional rugby league players before and after
ties and fatigue-induced decrements in tackling
the introduction of the 10-m defensive rule. These
technique. Players performed a one-on-one tackling
studies have revealed that the majority of match-
drill before strenuous exercise, and again following
play is spent in low-intensity activities such as
game-specific repeated-effort exercise comprised of
standing, walking and jogging. However, while the
progressively increasing intensities (corresponding
majority of match-play is spent in low-intensity
to ‘moderate’, ‘heavy’ and ‘very heavy’ intensity),
activities, high-intensity activities, such as sprinting,
in order to induce fatigue that was representative of
physical collisions and tackles place considerable
match conditions. Video footage was taken from the
demands on the anaerobic energy systems.
[20]
The
rear, side and front of the defending player, and
respective mean running distance of forwards and
tackling technique was objectively assessed using
backs increased from 6647 and 7336 m during
standardized technical criteria. In addition, all play-
matches played under the 5-m defensive rule to
ers underwent measurements of standard anthro-
9929 and 8458 m during matches played under the
pometry, speed, muscular power, agility and esti-
10-m defensive rule.
[10,20]
Forwards spent a greater
mated
˙
VO
2max
. Consistent with a progressive in-
percentage of time in high-intensity activities (e.g.
crease in fatigue, total repeated effort time, heart
jogging backwards and sprinting) during matches
rate, blood lactate concentration and ratings of per-
played under the 10-m defensive rule (3.3%) than
ceived exertion each increased throughout the re-
during matches played under the 5-m defensive rule
peated effort protocol. Fatigue resulted in progres-
(0.8%). However, the work-to-rest ratio of forwards
sive reductions in tackling technique. Players with
and backs increased from 1 : 6 and 1 : 8 during
the best tackling technique in a non-fatigued state
matches played under the 5-m defensive rule to
demonstrated the greatest decrement in tackling
1 : 10 and 1 : 7 for the hooker and prop, respective-
technique under fatigued conditions. In addition, a
ly, and 1 : 12 and 1 : 28 for the halfback and winger,
significant association was found between
˙
VO
2max
respectively, under the 10-m defensive rule.
[10]
Col-
(r =
–
0.62) and agility (r = 0.68) and fatigue-induced
lectively, these findings suggest that the aerobic
decrements in tackling technique. From a practical
energy demands on professional rugby league play-
perspective, these findings suggest that strength and
ers have increased with the introduction of the 10-m
conditioning programmes designed to develop en-
defensive rule. However, it has also been suggested
durance, change of direction speed and anticipation
that the increased work-to-rest ratios may reflect the
skills may reduce fatigue-induced decrements in
increased intensity of work performed when active-
tackling technique. Furthermore, any defensive
ly involved in play, resulting in the need for longer
drills designed to improve tackling technique should
periods of recovery between high-intensity ef-
be performed prior to, and under fatigue.
[55]
forts.
[10]
Research is yet to compare time-motion
analysis between amateur and semi-professional
5. Performance Analysis
rugby league players. It is possible that due to differ-
ences in fitness and skill (e.g. poor ball control), the
5.1 Time-Motion Analysis
time spent in low-intensity activities may be greater
in amateur than in semi-professional and profession-
Time-motion studies have been used to deter-
al rugby league. It has been suggested that the
mine the movement patterns of rugby league play-
greater running distances required during match-
ers.
[10,20]
Early studies, performed by Meir and col-
leagues
[10,20]
investigated time-motion analysis of play under the 10-m defensive rule would provide
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 129
an additional challenge to amateur rugby league their try-line or attempting to score against the oppo-
sition. Collectively, these findings demonstrate that
players in defence, thereby reducing the likelihood
modern rugby league is considerably more demand-
of effective tackles, and increasing the risk of inju-
ing than previously reported by Meir and col-
ry.
[9]
Studies investigating the impact of the 10-m
leagues.
[10,20]
defensive rule change on the physiological demands
of amateur rugby league players are warranted.
5.2 Physiological Demands of Competition
While the studies by Meir et al.
[10,20]
were the first
to provide important insight into the demands of
The physiological demands of competition have
rugby league, these studies are dated. To address
been investigated in amateur (unpublished observa-
these concerns, several recent rugby league time-
tions), semi-professional
[58]
and junior elite
[59]
rugby
motion analysis studies have been published.
[56,57]
In
league players. As expected, the intensity of match-
a preliminary study of elite (National Rugby
es increases as the playing level is increased. In one
League, first grade) and semi-elite (National Rugby
amateur rugby league match, Gabbett (unpublished
League, second grade) rugby league players, it was
observations) found an average heart rate of 152
shown that elite players covered a greater total dis-
beats/min, which equated to 78% of maximal heart
tance than semi-elite players and greater distance in
rate (HR
max
). The average heart rate of semi-profes-
high-intensity running.
[56]
A limitation of this study
sional and junior elite rugby league players during
was that no information was provided on the de-
competition was 166 beats/min
[53]
and 172 beats/
mands of tackling, or the repeated-effort demands of
min,
[59]
respectively. These values corresponded to
rugby league. King et al.
[57]
completed a time-mo-
an exercise intensity of 84% and 93% of HR
max
,
tion analysis on professional rugby league players
respectively. Moreover, players spend a considera-
during three matches of the Australian National
ble percentage (30–44%) of total match-play in
Rugby League competition and reported an average
high-intensity (>85% HR
max
) activities,
[58,59]
with
work-to-rest ratio of 1 : 6 for the outside backs and
the average intensity of semi-professional matches
hit-up forwards positional groups, and 1 : 5 for the
reported to be 81.1%
˙
VO
2max
.
[58]
Mean blood lactate
adjustables positional group. The average numbers
concentrations of 5.2, 7.2 and 9.1 mmol/L have been
of tackles and collisions for hit-up forwards, outside
reported during competition for amateur (unpub-
backs and adjustables were 51, 27 and 35, respec-
lished observations), semi-professional
[58]
and pro-
tively. It was also reported that the longest periods
fessional
[60]
rugby league players, respectively, with
of high-intensity exercise players endured without
blood lactate concentration significantly higher in
recovery were 27, 35 and 22 seconds for the outside-
the first half of matches (8.4 vs 5.9 mmol/L).
[58]
The
backs, adjustables and hit-up forwards, respectively.
blood lactate concentration during competition is
Furthermore, some passages of high-intensity play
higher for forwards (8.5 mmol/L) than for backs (6.5
included striding, sprinting, tackling and lateral
mmol/L).
[58]
Collectively, these findings demon-
movement for periods of up to 25 seconds with rest
strate that competitive rugby league places consider-
periods where the players stood, jogged or walked
able physiological demands on both the aerobic and
for a short time (sometimes for as little as 2–3 anaerobic glycolytic energy systems.
seconds) before repeating a high-intensity effort
To date, most
[10,20,58,59]
studies of the movement
lasting from 10–20 seconds. Many of these repeated
patterns and physiological demands of rugby league
bouts of high-intensity efforts were at critical stages
competition have investigated matches played under
of the game where players were either defending
an unlimited interchange rule (i.e. unlimited number
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
130 Gabbett et al.
of interchanges during a match). In 2001, the Aus- than backs (0.9 kg, 1.1%). Over the course of the
tralian National Rugby League introduced the limit-
study, 13% of players experienced a 2–3% reduction
ed interchange rule. This rule change, which allows
in body mass, with 71.4% of players experiencing
teams a maximum of 12 interchange replacements
2–3% reductions in body mass when the tempera-
during a match, and which has also recently been
ture exceeded 29ºC. The mean reduction in body
adopted by sub-elite rugby league competitions, is
mass following training for rugby league is reported
likely to increase the physiological demands on
to be 0.5–1.1 kg.
[61]
players, forcing many to compete in a fatigued
Meir et al.
[64]
investigated the effect of three
state.
[12]
Research is required to evaluate the move-
different jersey types on thermoregulatory responses
ment patterns and physiological demands of players
during warm, humid conditions. Subjects were re-
competing under the limited interchange rule.
quired to perform four, 50-minute treadmill efforts
at 50%
˙
VO
2max
in an environmental chamber with
6. Thermoregulatory Responses during
mean temperature and relative humidity of 27.6ºC
Training and Competition
and 65%, respectively. The four trials were conduct-
Several investigators have studied the thermoreg-
ed with subjects wearing: (i) a traditional rugby
ulatory responses during rugby league training
[61]
league jersey with plastic patching; (ii) a traditional
and competition.
[59-65]
Strategies to prevent thermo-
rugby league jersey without plastic patching; (iii) a
regulatory stress are imperative as even a small
lightweight alternative rugby league jersey without
amount of dehydration (1% or greater reduction in
plastic patching; and (iv) no upper-body garment.
body mass) can impair performance and may be
The reduction in body mass was greater with the
medically dangerous.
[66]
Meir et al.
[63]
investigated
traditional rugby league jersey with plastic patching
the thermoregulatory responses of 22 Australian
(1.05 kg) than with the traditional rugby league
professional rugby league players during matches.
jersey without plastic patching (0.99 kg) and light-
Body mass and estimated core (tympanic) tempera-
weight alternative rugby league jersey without
ture were measured pre-match, at half-time and im-
plastic patching (0.96 kg). In addition, the mean skin
mediately post-match. The mean temperature and
temperature throughout the entire exercise bout was
relative humidity for the matches were 24ºC and
significantly lower in the lightweight alternative
67–73%, respectively. Mean tympanic temperature
rugby league jersey without plastic patching than
for the forwards increased from 37.7ºC pre-match to
with the traditional rugby league jerseys. The au-
38.2ºC at half-time, and 38.8ºC post-match. Mean
thors concluded that the traditional rugby league
tympanic temperature for the backs increased from
jersey worn by professional rugby league players
37.9ºC pre-match to 38.3ºC at half-time, and 38.5ºC
may have a negative effect on heat dissipation
post-match. Body mass decreased by 2.2 kg (2.4%)
mechanisms in warm, humid conditions. Collective-
and 1.2 kg (1.5%) in forwards and backs, respective-
ly, these results suggest that rugby league training
ly. Jennings et al.
[62]
investigated body mass changes
and competition may pose considerable thermoregu-
during 16 matches in professional rugby league
latory demands on players. Strategies to reduce the
players competing in the English Super League. The
impact of thermoregulatory stress on rugby league
mean temperature and relative humidity was 22.9ºC
players may include weighing players before and
and 73%, respectively. The mean reduction in body
after training and matches, educating players about
mass was 1.1 kg (1.2%) with the reduction in body
the role of fluid intake and its relevance to perform-
mass significantly greater in forwards (1.5 kg, 1.5%)
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 131
ance and recovery, and implementing appropriate addition, a progressive increase in match injuries
fluid intake and acclimatisation protocols.
[61]
occurs from the beginning to the end of the season.
These findings have been attributed to accumulative
7. Relationship Between Physiological
microtrauma and/or residual fatigue associated with
Factors and Injury
limited recovery between matches.
[28,67]
Studies that
have examined semi-professional rugby league inju-
ry rates have also found a progressive increase in
7.1 Influence of Player Fatigue on
injury rates during the course of a season, with
Injury Rates
injury rates peaking in the latter half of the season.
[9]
The finding of high match injury rates towards the
Over 70% of amateur rugby league injuries occur
end of the competitive season in semi-professional
in the second half of matches, suggesting that fa-
rugby league players has been attributed to increases
tigue, or a fatigue-induced reduction in skill contrib-
in playing intensity as the ‘finals’ series approach-
utes to injuries in amateur rugby league players.
[67]
es.
[9]
These findings have been supported by Gab-
Conversely, comparatively fewer (38.5%) injuries
bett
[71]
who found a significant correlation (r = 0.74)
are sustained by semi-professional players in the
between match injury rates and match intensity in
second half of matches.
[9]
These findings are some-
semi-professional rugby league players. Hodgson
what expected given the poor aerobic fitness of
Phillips et al.
[26]
and Alexander et al.
[70]
reported that
amateur players compared with semi-professional
more injuries occurred towards the end of the com-
players.
[13,14]
The lower second-half injury rates of
petitive season in professional rugby league players,
semi-professional players highlights the importance
while Seward et al.
[68]
and Gissane et al.
[72]
reported
of aerobic fitness in preventing fatigue-related inju-
more injuries in the early stages of the season in
ries in rugby league. Studies that have examined the
professional rugby league players. No study has
incidence of injuries in professional rugby league
documented the seasonal variations in injury rates of
players have found that second-half injuries are sim-
junior rugby league players.
ilar,
[68]
or only slightly greater than
[69,70]
first-half
injuries. Research is yet to examine injury occur-
7.3 Influence of the Limited Interchange
rence in relation to the time of play (i.e. first-half or
Rule on Injury Rates
second-half) in junior rugby league players. The
majority (55.3%) of training injuries occur in the
Despite the suggestion that the physiological de-
latter stages of the training session.
[9]
Rugby league
mands on players have increased under the limited
teams often integrate skills and conditioning ses-
interchange rule, a recent investigation showed that
sions in order to facilitate the development of skills
significantly fewer professional rugby league play-
under fatigued conditions.
[14]
The finding of higher
ers left the field through injury during matches
injury rates in the latter stages of training sessions
played under the limited interchange rule compared
again implicates fatigue as the major contributor to
with the unlimited interchange rule.
[12]
However, a
rugby league training injuries.
[9]
subsequent study found that the percentage of pro-
fessional rugby league players missing through inju-
7.2 Influence of Playing Intensity on
ry each week increased from 12.7% under the un-
Injury Rates
limited interchange rule (seasons 1999–2000) to
The majority of amateur rugby league match 15.2% under the limited interchange rule (seasons
injuries occur in the latter half of the season.
[71]
In 2001–3).
[73]
Gabbett
[11]
reported that the relative risk
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
132 Gabbett et al.
of injury decreased by 30% in sub-elite rugby league
˙
VO
2max
in the initial season. These results demon-
players following the introduction of the limited strate that reductions in pre-season training loads
interchange rule. The risk of sustaining thigh and may reduce training injury rates and result in greater
calf injuries, muscular strains and high-intensity improvements in
˙
VO
2max
in rugby league play-
running injuries was reduced following the intro- ers.
[74]
duction of the limited interchange rule. It was hy-
pothesized that the limited interchange rule in-
7.5 Relationship Between Training Load,
creased the physiological demands on players,
Injury and Fitness
thereby reducing match speed, and minimising im-
In a subsequent study, Gabbett and Domrow
[75]
pact forces associated with physical collisions and
developed a statistical model that related training
tackles.
[11]
with performance and estimated the influence of
training load on training injury and physical fitness
7.4 Influence of Training Load on Injury Rates
in rugby league players. 183 rugby league play-
Recent data from semi-professional players have ers underwent measurements of height, body mass,
shown that the majority of rugby league training skinfold thickness, vertical jump, 10-, 20- and 40-m
injuries occur in the early stages of the season.
[9,74]
speed, agility, and estimated
˙
VO
2max
in the off-,
The early season incidence of injury of 116.1 per pre-, mid- and end-season training periods. Training
1000 training hours is 2.6-fold higher than the sea- load and injury data were summarized into pre-
sonal average injury rate (45.3 per 1000).
[9]
Training season, early-competition and late-competition
loads have been shown to be greatest during the training phases. While physical fitness improved
early stages of the season.
[74]
In addition, training with training, there was no significant association
injury rates are significantly correlated (r = 0.86) between training load and changes in physical fit-
with increases in training loads, suggesting that the ness during any of the training phases. However,
harder rugby league players train, the more injuries increases in training load during the early-competi-
they will sustain.
[71]
Based on this evidence, the tion training phase were significantly related to a
influence of reductions in pre-season training loads decrease in agility. A significant relationship was
on the incidence of training injuries and improve- observed between the log of training load and injury
ments in fitness was investigated in 220 semi-pro- risk during each training phase, resulting in a
fessional rugby league players over three consecu- 1.50–2.85 increase in injury risk for each unit in-
tive pre-season periods.
[74]
Following the initial pre- crease in training load. Furthermore, during the pre-
season period, training loads were reduced by season training phase, there was a significant rela-
10.6–15.7% through reductions in training duration tionship between training load and injury incidence
and training intensity. The reductions in training within the training load range of 155 and 590 units.
loads were associated with a 39.8–50.0% reduction During the early- and late-competition training
in training injury rates. Furthermore,
˙
VO
2max
pro- phases, increase in training load of 175–620 and
gressively increased across the three seasons. Using 145–410 units, respectively, resulted in no further
the minimum clinically important difference to de- increase in injury incidence. The authors concluded
termine practical significance, there was a 62–88% that increases in training load, particularly during
probability that the pre-season improvements in the pre-season training phase, significantly in-
˙
VO
2max
in the latter seasons were of greater physio- creased the risk of injury in rugby league players.
logical significance than the improvements in Furthermore, these findings demonstrated that while
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 133
moderate increases in training load during the early- playing the ball after being tackled to the ground), it
competition training phase result in no further in-
is necessary to develop the strength and power of
crease in injury incidence, significant reductions in
players. In addition, King et al.
[57]
found that in
agility performances may occur. From a practical
professional rugby league, on average, every 4 se-
perspective, these findings suggest that reductions in
conds of high-intensity activity was followed by
training load during the early-competition training
approximately 21 seconds of low-intensity activity,
phase may reduce the odds of injury without com-
and that continuous periods of high-intensity work
promising agility performances in rugby league
could be as long as 35 seconds. Collectively, these
players.
findings implicate the need for specific training of
the anaerobic alactic (adenosine triphophate-crea-
7.6 Risk Factors for Injury
tine phosphate), anaerobic glycolytic and aerobic
energy systems in rugby league players.
The implementation and evaluation of effective
injury prevention strategies is dependent on the
8.2 Skill-Based Conditioning Games and
identification of injury risk factors.
[76]
To date, only
Interval Training
one study has investigated risk factors for injury in
rugby league players.
[77]
In a 4-year prospective
Interval training using distances and activities
study of sub-elite rugby league players, Gabbett and
specifically related to competition, such as moving
Domrow
[77]
reported a higher risk of injury in play-
up and back over 10 m for periods of 30–90 seconds,
ers with low 10-m and 40-m speed. Players with a
repeat tackling efforts on a bag for 5–10 repetitions,
low estimated
˙
VO
2max
had a greater risk of sus-
and sprint efforts over distances ranging from 5 to
taining a contact injury. In addition, players who
60 m with varying work-to-rest ratios have been
completed <18 weeks of training prior to sustaining
their initial injury were at greater risk of sustaining a suggested as a specific training stimulus for rugby
subsequent injury. These findings provide some ex-
league players.
[10]
More recently, skill-based condi-
planation for the high incidence of fatigue-related
tioning games have been used to develop the skill
injuries in rugby league players.
[67]
Furthermore,
and fitness of rugby league players. The advantage
these findings highlight the importance of speed and
of skill-based conditioning games over traditional
endurance training to reduce the incidence of injury
interval training is that skill-based conditioning
in sub-elite rugby league players.
games also provide the opportunity to develop deci-
sion-making and problem-solving skills.
[79]
Gab-
8. Strength and Conditioning
bett
[79]
investigated the incidence of training injuries
in semi-professional rugby league players and iden-
tified the training activities that were most likely to
8.1 Specificity
result in injury. The majority of training injuries
(90.9 per 1000 training hours, 37.5%) were sus-
The greatest training benefits occur when the
tained in traditional conditioning activities that in-
training stimulus simulates the specific movement
volved no skill component (i.e. running without the
patterns and physiological demands of the sport.
[78]
ball). In contrast, the incidence of injuries sustained
Based on observations from time-motion studies,
while participating in skill-based conditioning
several recommendations for training have been
games (26.0 per 1000 training hours, 10.7%) was
made.
[57]
Due to the high number of physical con-
frontations in a match (e.g. tackling, being tackled, low.
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
134 Gabbett et al.
In a subsequent study, the specificity of skill- 8.3 Training and Adaptation in Junior and
Senior Rugby League Players
based conditioning games as a training stimulus was
investigated (unpublished observations). Using
Several studies have reported various adaptations
skill-based conditioning games designed to develop
of rugby league players to training.
[40,41,79-85]
scrambling defence and support play, play-the-ball
Warman et al.
[40]
reported a 1.5–30.4% increase in
speed, defensive line speed, ball control and pa-
3RM squat and bench-press strength, chin-ups to
tience, it was shown that the mean heart rate and
failure and
˙
VO
2max
in response to a 6-month pre-
blood lactate responses during skill-based condi-
season strength and conditioning programme in
semi-professional rugby league players. Baker
[35]
tioning games (155 beats/min and 5.2 mmol/L) were
reported a significant improvement in 1RM bench-
almost identical to those obtained during competi-
press strength and unchanged upper- and lower-
tion (152 beats/min and 5.2 mmol/L).
body muscular power over a 19-week in-season
Gabbett
[80]
compared skill-based conditioning
strength programme in semi-professional rugby
games and traditional conditioning for improving
league players. A 29-week in-season strength pro-
speed, agility, muscular power and maximal aerobic
gramme failed to elicit significant changes in 1RM
power in rugby league players. Players completed a
bench-press strength, and upper- and lower-body
9-week in-season conditioning programme consist-
muscular power in professional rugby league play-
ing entirely of skill-based conditioning games or
ers.
[35]
O’Connor
[81]
conducted a 10-week in-season
anaerobic training programme in professional rugby
traditional conditioning (i.e. running activities with
league players, and this resulted in a significant
no skill component). Skill-based conditioning
increase in the anaerobic capacity of the players (as
games induced a significant improvement in 10-,
evidenced from greater lactate tolerance and total
20- and 40-m speed, muscular power and maximal
work outputs during a 60-second maximal effort
aerobic power, whereas traditional conditioning ac-
test). Coutts et al.
[82]
investigated changes in
tivities improved 10-m speed and maximal aerobic
˙
VO
2max
in semi-professional rugby league players
power only. Both groups won six of their eight
in response to over-reaching. Two groups completed
matches played within the training period, resulting
either 6 weeks of being well trained or deliberately
in a win-loss ratio of 75%. However, on average, the
over-reached. The
˙
VO
2max
was significantly re-
skill-based conditioning games group scored more
duced in the over-reaching group throughout the
training period. However, following a 7-day taper,
points in attack, and had a greater points differential
˙
VO
2max
increased to a greater extent in the over-
than the traditional conditioning group. Collective-
reaching group.
ly, these findings suggest that skill-based condition-
Gabbett
[83]
investigated the relationship between
ing games offer a safe, effective and specific method
training loads and changes in physical performance
of conditioning for rugby league players. In addi-
in response to a 14-week field conditioning pro-
tion, given that skills learnt from skill-based condi-
gramme in junior and senior rugby league players.
tioning games are more likely to be applied in the
Improvements in agility, muscular power and maxi-
competitive environment, their use may provide a
mal aerobic power were observed in both the junior
practical alternative to traditional conditioning for
and senior players following training; however, the
improving the physiological capacities and playing
improvement in maximal aerobic power (8.6% vs
performance of rugby league players. 5.1%) and muscular power (7.7% vs 4.7%) were
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
Physiology of Rugby League 135
greatest in the junior players. Training loads were son progresses, with reductions in muscular power
significantly higher in the senior players (448 vs 341
and maximal aerobic power and increases in
units). These findings demonstrated that despite
skinfold thickness occurring towards the end of the
having lower training loads, junior rugby league
rugby league season, when training loads are lowest
players exhibit greater adaptations in maximal aero-
and match loads and injury rates are at their highest.
bic power and muscular power than senior rugby
Player fatigue and playing intensity have been sug-
league players.
[83]
gested to contribute to injuries in rugby league, with
The adaptive responses to training have also been
a recent study reporting a significant correlation
investigated in young (Under-15) and older
between match injury rates and playing intensity in
(Under-18) junior rugby league players.
[84]
Gabbett
semi-professional rugby league players. Studies
et al.
[84]
performed a 10-week pre-season training
have also reported a higher risk of injury in players
programme in junior rugby league players, monitor-
with low 10- and 40-m sprint times, while players
ing changes in anthropometry (body mass and sum
with a low maximal aerobic power have greater risk
of seven skinfolds), speed, muscular power, agility
of sustaining a contact injury. Furthermore, players
and estimated
˙
VO
2max
before and after training. In
that completed <18 weeks of training prior to sus-
addition, changes in upper-body (push-ups, sit-ups
taining their initial injury are at greater risk of sus-
and chin-ups) and lower-body (multiple effort verti-
taining a subsequent injury. These findings provide
cal jump) muscular endurance were monitored at
regular intervals throughout the training period. The
some explanation for the high incidence of fatigue-
Under-15 players recorded larger increases in body
related injuries in rugby league players and highlight
mass, and greater improvements in speed, muscular
the importance of speed and endurance training in
power, muscular endurance and
˙
VO
2max
than the
reducing the incidence of injury in rugby league
Under-18 players. Collectively, these results suggest
players.
that young and slightly older junior rugby league
To date, most, but not all, studies have investigat-
players adapt differently to a given training stimulus
ed the movement patterns and physiological de-
and that training programmes should be modified to
mands of rugby league competition; however, there
accommodate differences in maturational and train-
has been little emphasis on how training activities
ing age.
simulate the competition environment. An under-
standing of the movement patterns and physiologi-
9. Conclusions
cal demands of specific individual positions during
training and competition would allow the develop-
The purpose of this article was to provide a
ment of strength and conditioning programmes that
comprehensive review of the applied physiology of
specifically meet the requirements of these posi-
rugby league football. Several studies have docu-
tions. In addition, further research is required to
mented the physiological capacities of rugby league
provide information on the repeated sprint ability of
players and the physiological demands of competi-
rugby league players. A test that assesses repeated
tion, with the physiological capacities of players and
sprint performance that employs distances and in-
the physiological demands of competition generally
tensities specific to rugby league, while also simu-
increasing as the playing level increases. However,
lating work-to-rest ratios similar to rugby league
there is also evidence to suggest that the physiologi-
cal capacities of players may deteriorate as the sea- competition is warranted.
2008 Adis Data Information BV. All rights reserved. Sports Med 2008; 38 (2)
136 Gabbett et al.
17. Meir R. Seasonal changes in estimates of body composition in
Acknowledgements
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Correspondence: Dr Tim Gabbett, Brisbane Broncos Rugby
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