Content uploaded by Peter Frykman
Author content
All content in this area was uploaded by Peter Frykman on Jan 13, 2015
Content may be subject to copyright.
Comparison of the physical fitness of men
and women entering the U.S. Army:
1978 –1998
MARILYN A. SHARP, JOHN F. PATTON, JOSEPH J. KNAPIK, KEITH HAURET, ROBERT P. MELLO,
MAX ITO, and PETER N. FRYKMAN
U.S. Army Research Institute of Environmental Medicine, Natick, MA; and U.S. Army Center for Health Promotion and
Preventive Medicine, Aberdeen Proving Ground, MD
ABSTRACT
SHARP, M. A., J. F. PATTON, J. J. KNAPIK, K. HAURET, R. P. MELLO, M. ITO, and P. N. FRYKMAN. Comparison of the
physical fitness of men and women entering the U.S. Army: 1978–1998. Med. Sci. Sports Exerc., Vol. 34, No. 2, pp. 356–363, 2002.
Purpose: To compare the physical fitness levels of recruits entering the U.S. Army in 1998 to those entering in 1978 and 1983.
Methods: In 1998, 182 men and 168 women were tested before beginning basic training at Fort Jackson, SC. The measurements were
1) skin-fold estimation of percent body fat (%BF); 2) maximum oxygen uptake by treadmill running (V
˙
O
2max
); and 3) upper-body (UB),
lower-body (LB), and upright pulling (UP) isometric strength. These data were compared to data from basic trainees at Fort Jackson
in 1978 (skin folds, V
˙
O
2max
, UB, and LB) and 1983 (skin folds and UP). Results: Body weight (BW) of 1998 recruits was greater
(P ⬍ 0.05) than 1978 recruits (men, 12%; women, 6%) and 1983 recruits (men, 8%; women, 7%). %BF of 1998 recruits was greater
(P ⬍ 0.05) than 1978 recruits (men, 15%; women, 5%) and 1983 recruits (men, 15%; women, 17%). The 1998 men had more fat-free
mass (FFM) (P ⬍ 0.05) than men in 1978 (8%) or 1983 (5%), whereas 1998 women were only different from those measured in 1978
(4%, P ⬍ 0.05). The V
˙
O
2max
of men (50.6 ⫾ 6.2 mL·kg
⫺1
·min
⫺1
) was equivalent to men in 1978, whereas that of women (39.7 ⫾
5.2 mL·kg
⫺1
·min
⫺1
) was 6% greater (P ⬍ 0.05). The 1998 recruits were stronger (P ⬍ 0.05) on all measures of muscle strength than
recruits measured in 1978 (men, UB ⫽ 16%, LB ⫽ 12%; women, UB ⫽ 18%, LB ⫽ 6%) and 1983 (men, UP ⫽ 7%; women, UP ⫽
6%). Conclusion: The aerobic capacity, muscle strength, and FFM of 1998 recruits is comparable to or greater than that of 1978 and
1983 recruits; however, 1998 recruits tended to have more BW and a greater %BF. Key Words: EXERCISE, V
˙
O
2max
, STRENGTH,
MUSCLE CONTRACTION, BODY COMPOSITION, PHYSICAL FITNESS
T
here is a public perception that the youth of today are
less physically fit and fatter than in previous years
(3). Although there is evidence that the prevalence of
obesity has increased across all age and demographic groups
during the last 20 yr (16), there is less evidence concerning
physical fitness levels. Data from youth physical fitness
tests have been interpreted to show a decline in youth
physical fitness, particularly aerobic fitness, as measured by
running performance (17). Others argue that youth physical
fitness tests have changed over time from skill-oriented tests
to health-related tests, making long-term comparisons dif-
ficult (5). The comparisons that can be made between skill-
oriented test items do not strongly support a decrease in
youth physical fitness (5). Although not a retrospective
study, the Surgeon General’s report on physical activity
stated that only about 50% of today’s youth participate in
regular vigorous physical activity and 14% are completely
inactive (27). If the youth today are less active, have greater
percentages of body fat, and have lower aerobic fitness than
those of previous decades, they present a national health
concern.
Basic training drill sergeants are also of the opinion that
the physical fitness of today’s youth is significantly lower
than in previous years. This opinion is supported by Knapik
et al. (12), who reported 5% slower 2-mile run times for
basic trainees over a 10-yr period (1988–1997), indicating a
decline in the aerobic fitness of recruits. In a time of low
unemployment, a decrease in youth physical fitness makes
the Army’s task of recruiting and training physically capa-
ble people even more challenging. Lower levels of physical
fitness have been shown to reduce the likelihood for suc-
cessful completion of basic training and increase the like-
lihood of training-related musculoskeletal injury (14).
Because many entry-level Army jobs are physically de-
manding, soldiers who are not physically fit may be unable
to perform critical aspects of their jobs even if they are able
to complete basic training.
Soldiers are required to take the Army Physical Fitness
Test (APFT) semiannually, which consists of timed sit-ups,
push-ups, and a 2-mile run (7). The extent to which the test
results represent an individual’s maximum ability can be
questioned. Soldiers know the minimum score needed to
pass and may not put forth a maximum effort on any of the
events. In a sample of more than 6000 soldiers asked to give
a best effort APFT to be recorded in their personnel files,
0195-9131/02/3402-0356/$3.00/0
MEDICINE & SCIENCE IN SPORTS & EXERCISE
®
Copyright © 2002 by the American College of Sports Medicine
Submitted for publication November 2000.
Accepted for publication April 2001.
356
10% clearly gave a submaximal effort (20). Although the
APFT is useful as a field-expedient measure of physical
fitness for large numbers of soldiers, measures of physical
fitness with greater precision are needed to objectively eval-
uate population changes over time.
Researchers from the U.S. Army Research Institute of
Environmental Medicine have measured the physical fitness
of recruits entering basic training at Fort Jackson, SC, pe-
riodically over the past 20 yr. Maximal oxygen uptake
during treadmill running (21) and upper- and lower-body
isometric strength (15) of male and female recruits were
measured before basic training in 1978. In 1983, a test of
isometric lifting strength (upright pull strength) was mea-
sured on men and women before basic training (26). Skin-
fold estimates of percent body fat (%BF) were made on
male and female recruits during the 1978 (15) and 1983 (26)
studies and in female recruits before basic training in 1993
(28). These studies provide historical data to compare the
pre–basic training physical fitness of 1998 U.S. Army re-
cruits to those measured during the period 1978–1993. The
purpose of this article is to compare the physical fitness of
men and women entering the U.S. Army in 1998 to original
data collected from similar samples at the same basic train-
ing site during the previous 20 yr to determine if the phys-
ical fitness of young people entering the U.S. Army has
changed during this time period.
MATERIALS AND METHODS
Subjects. Volunteers were recruited from men and
women about to enter basic training at Fort Jackson, SC, in
May 1998. Recruits were briefed on the procedures and
voluntary nature of the study. Of those who were briefed,
the overall volunteer rate was 57% (53% of men and 63% of
women). Volunteers read and signed an informed consent
document and were medically cleared by a physician. The
study was approved by a human-use review committee and
by the Human Subjects Research Review Board. Recruits
entering basic training in 1998 were required to pass a
physical fitness screening test before they began training.
The test included a 1-mile run for time, sit-ups, and push-
ups. Recruits who failed the test were sent for remedial
physical training and did not participate in the study. Of
those who volunteered to participate in this study, it is
estimated that five men and six women failed the run, five
men and nine women failed the push-ups, and two men and
five women failed the sit-up screening test. Testing of 350
recruits (182 men and 168 women) was conducted May
1–13, 1998.
Comparison data sets. The data sets used for com-
parison with the 1998 data were 1) body weight and %BF
measured in 1978 by Knapik et al. (15), in 1983 by Teves et
al. (26) and in 1993 by Westphal et al. (28); 2) V
˙
O
2max
measured in 1978 by Patton et al. (21); 3) upper- and
lower-body isometric strength measured in 1978 by Knapik
et al. (15); and 4) isometric upright pull strength measured
in 1983 by Teves et al. (26). As with the 1998 study, all of
these studies were conducted before basic training at Fort
Jackson. All volunteers were briefed on the procedures and
risks of the respective study, signed an informed consent
document, and were medically cleared before participation.
The racial distributions of the previous samples are not
available; however, the racial distribution of the total Army
for 1980, 1983, 1993, and 1998 is provided in Table 1 (data
extracted from the Total Army Injury and Health Outcomes
Database (2)). These data are listed by gender for the age
group 17–25, which includes the majority of soldiers enter-
ing basic training. The racial distribution of the recruit
sample reported here is also shown and is representative of
the Army in 1998. From 1980–1998, the percentage of
black males has dropped from 29% to 20%, whereas that of
black females has remained fairly constant. The percentage
of white males has remained stable, whereas that of white
females has decreased from 59% to 49%. The percentage of
soldiers classified as other (Hispanic, Asian/Pacific Is-
lander, and Native American/Alaskan Indian) has increased
nearly fivefold in men and nearly threefold in women,
primarily because of an increase in the percentage of His-
panics (from approximately 4% to 8% of the total
population).
Measurements. A four-site skin-fold estimate of %BF
was made (8) using procedures and equipment identical to
those of previous studies (15,26,28). Three measurements
were made at each site (biceps, triceps, subscapular, and
suprailiac) by a trained technician using Harpenden calipers
(Country Technology, Inc., Gays Mills, WI). Subjects were
asked their age (years). Height (centimeters) was measured
using a stadiometer (Model GPM, Seritex, Inc., Carlstadt,
NJ). Body weight (kilograms) was measured using a digital
scale (Model 770, Seca Corp., Columbia, MD) with subjects
in T-shirts, shorts, underclothes, and socks, which was the
same as in previous studies (15,26,28).
Maximum oxygen uptake was measured using open-cir-
cuit, indirect calorimetry during a continuous uphill tread-
mill running protocol. An initial 5-min warm-up was per-
formed at 0% grade and 2.68 m·s
⫺1
(6 mph) for men and
2.24 m·s
⫺1
(5 mph) for women. If the heart rate was less
than 150 beats·min
⫺1
by minute 5 of the warm-up, treadmill
TABLE 1. Racial distribution of U.S. Army soldiers aged 17–25 during the years 1980, 1983, 1993, and 1998 (% of 17- to 25-yr-old enlisted soldiers) and the male and female
volunteers for the 1998 study (% of sample).
Men Women
Black White Other Black White Other
1980 29.4 67.3 2.9 35.6 58.8 5.6
1983 28.9 63.6 6.4 39.7 53.9 5.9
1993 22.0 68.9 7.9 40.2 50.4 9.4
1998 20.2 66.2 13.6 37.0 48.7 14.3
1998 sample 23.1 61.0 15.9 33.3 50.0 16.7
PHYSICAL FITNESS OF ARMY MEN AND WOMEN Medicine & Science in Sports & Exercise
姞
357
speed was increased 0.45 m·s
⫺1
(0.5 mph) for the remainder
of the test. After the warm-up, the treadmill grade was
increased by 2% every 3 min until voluntary exhaustion. If
a plateau in oxygen uptake (⬍ 0.15 L·min
⫺1
increase with
an increase in treadmill grade) was not achieved, criteria for
assessing maximal oxygen uptake were 1) heart rate in
excess of 90% age-predicted maximum heart rate, and 2)
respiratory exchange ratio in excess of 1.0. The protocol was
similar to the interrupted protocol previously used in 1978 at
Fort Jackson (21). The differences between the 1998 pro-
tocol and that used previously were that the earlier protocol
was discontinuous and used treadmill grade increments of
2.5% instead of the 2% increase used here. The warm-up
loads were identical, as were the speed adjustment and
frequency of load adjustments. Differences between contin-
uous and discontinuous treadmill running tests tend to be
small (1.2%), with a discontinuous protocol producing a
slightly higher V
˙
O
2max
(18).
Volunteers wore a nose clip and were connected to an
on-line oxygen uptake system via a low-resistance, two-
way, nonrebreathing valve (Hans Rudolf, Inc., Kansas City,
MO) and a mouthpiece. The on-line oxygen uptake system
was developed in our laboratory and consisted of an Applied
Electrochemistry S-3A oxygen analyzer (AEI Technologies,
Pittsburgh, PA), a Beckman LB-2 carbon dioxide analyzer
(SensorMedics, Inc., Yorba Linda, CA), a K.L. Engineering
turbine flowmeter (K.L. Engineering Turbine Company,
Northridge, CA), and a Yellow Springs Instrument Com-
pany Thermister (YSI, Yellow Springs, OH), interfaced
with a Hewlett-Packard computer (model 9122, Hewlett-
Packard, Palo Alto, CA). The gas analyzers were calibrated
with certified gas cylinders (4% CO
2
, 17% O
2
) from Sen
-
sorMedics. The turbine was calibrated with a Harvard Ap-
paratus Dual-Phase Respiration Pump (Harvard Apparatus
Corp., Holliston, MA). In the laboratory, the pump flow rate
is routinely checked with a Collins 120 L Chain-Compen-
sated Gasometer (Warren E. Collins Inc., Braintree, MA).
During the field study, the turbine flow rate was checked
daily with a 3-L calibration syringe (SensorMedics). The
output of the 3-L syringe has been verified in our laboratory
with both the Harvard Respiration Pump and the Collins 120
L Chain-Compensated Gasometer (Tissot).
There were differences in the equipment used to measure
oxygen uptake in the 1978 study (21) and in this study. In
1978, volunteers breathed through a mouthpiece attached to
a Koegel valve, and expired volume was collected into
Douglas bags (30 s collection) during the final 60 s of each
3-min bout of exercise. The same O
2
and CO
2
gas analyzers
(AEI S-3A and Beckman LB-2) used in the above-described
on-line system were used to analyze aliquots of air extracted
from the Douglas bags. A Collins Tissot was used to mea-
sure expired gas volume and temperature. This same Doug-
las bag system is routinely used to validate the on-line
system that was used in this experiment. Exercise heart rate
was monitored using a Hewlett-Packard model 1511B Elec-
trocardiograph during the 1978 and 1998 tests.
Three measures of maximum voluntary isometric strength
were made. Upper-body (UB) strength and lower-body (LB)
strength were measured on the same triple-strength device
as used in 1978 (15). The volunteer was seated with a seat
belt securely tightened over the pelvic area to prevent body
movement. For UB, a handle was positioned such that the
upper arms of the volunteer were parallel to the floor and the
elbows were flexed to 90°. The volunteer grasped the sus-
pended handle (45.7 cm long ⫻ 3.2 cm diameter aluminum
tubing) using an underhand grip. On verbal command, the
volunteer pulled maximally downward. For LB strength
(isometric leg press), the volunteer remained seated with the
back against the seat back and the pelvis tightly secured with
a seat belt. A footrest was adjusted to obtain a knee angle of
90°. The volunteer grasped handles parallel to the seat
bottom and pushed maximally against the stationary footrest
on verbal command from the experimenter. The test-retest
reliability of UB and LB measures were r ⫽ 0.97 and r ⫽
0.92, respectively (15).
The third measure of isometric strength, the upright pull
(UP), was designed to assess isometric lifting strength at a
low point in a lift from the floor (26). The volunteer stood
on a wooden platform with feet shoulder width apart, strad-
dling the pulling handle. The volunteer bent over to grasp
the aluminum handle 38 cm above the level of the platform
and assumed a semisquat position with knees bent, head up,
and back straight. The handle was identical to that used for
the UB test and was attached via aircraft cable to a load cell
mounted on the wooden platform. On command, the vol-
unteer pulled maximally upward. This measure has a test-
retest reliability coefficient of r ⫽ 0.97 for three trials (26).
For all three measurements (UB, LB, and UP), force was
applied smoothly, without jerking, reaching maximum
within a 2-s period and was held for 4 s. The maximum force
was measured by a BLH load cell and displayed on a BLH
model 450A transducer indicator (BLH, Waltham, MA).
The mean of two of the highest of three trials within 10% of
one another was recorded as the score for each test. Addi-
tional trials (to a maximum of five) were performed if the
greatest trial was more than 10% different than the second
greatest trial. A minimum 1-min rest period was provided
between trials. To examine differences in strength relative to
fat-free mass (FFM), each individual’s strength score was
divided by their FFM.
The three testing stations were 1) V
˙
O
2max
test, 2) skin
folds, and 3) muscle strength. When groups of 15–20 vol-
unteers arrived, their age, height, and weight were recorded
before they were evenly divided among the stations. Vol-
unteers proceeded from station to station until all stations
were completed. A minimum of 20 min of rest was provided
between each station.
Sample size estimation and data analysis. Statis-
tical Power: A Computer Program by M. Borenstein and J.
Cohen was used to estimate the necessary sample size for
the physical fitness measures with an alpha level of P ⬍
0.05 and a beta of 0.85. The sample size estimates for most
variables ranged from 20 to 70 men and women. Additional
men and women were recruited to provide adequate power
to assess the relationship between physical fitness and basic
358
Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
training–related injuries, which has been reported elsewhere
(13).
Descriptive statistics were calculated for each gender.
Statistica software was used (’99 edition, StatSoft, Inc.,
Tulsa, OK) to compare samples within gender using t-tests
(when there were only two samples for a given variable) or
one-way ANOVAs (when there were more than two sam-
ples). Tukey’s HSD post hoc tests for unequal sample sizes
were used to examine the significance of differences be-
tween more than two means.
RESULTS
Table 2 lists the age, height, and weight of volunteers
from the 1998 study and from studies conducted in 1978
(15), 1983 (26), and 1993 (28). The 1998 men tended to be
older than men measured in 1978 and 1983 and taller than
those measured in 1978 (P ⬍ 0.05). The 1998 sample of
women was 1 yr older than the 1983 sample (P ⬍ 0.05), but
was not different from the other samples of women. There
were no differences in the height among the four samples of
women. Men and women in 1998 had a greater body weight
than those measured in 1978 or 1983. In 1998, the men
averaged 8% greater body weight than 1983 males and 12%
greater than 1978 males. The 1998 female recruits had 6%
more body weight than those measured in 1978 and 7%
more than those in 1983. The body weight of 1998 women
did not differ from those measured in 1993.
Although the 1998 group of male recruits was signifi-
cantly taller, the greater body weight cannot be solely at-
tributed to greater height. Table 3 presents the %BF and
FFM data for male and female recruits from each of the
available samples. FFM and %BF were greater over time in
male recruits. The %BF of the 1998 sample of men was 15%
greater than both of the earlier samples. The 1998 sample of
men had 5% and 8% more FFM than the 1983 (26) and 1978
(15) samples, respectively (P ⬍ 0.05). Similar to the men,
the %BF of the 1998 female recruits was greater than that of
1978 and 1983 female recruits (P ⬍ 0.05), but less than (P
⬍ 0.05) the 1993 female recruits (28). FFM of female
recruits in 1998 was 4% greater than that of women mea-
sured in 1978 or 1993 (P ⬍ 0.05), but not different from
women measured in 1983.
The cardiorespiratory variables measured during the
V
˙
O
2max
test are listed for men and women from the 1998
sample and the 1978 sample (21) in Table 4. On an absolute
basis, the V
˙
O
2max
of the 1998 sample of men and women
was greater (11% and 15%, respectively) than for men and
women measured in 1978 (P ⬍ 0.05). When expressed
relative to body weight, however, the V
˙
O
2max
of the 1998
men was equivalent to the sample of men measured in 1978.
The mean V
˙
O
2max
(mL·kg
⫺1
·min
⫺1
) of women measured in
1998 was 6.2% greater than (P ⬍ 0.05) those measured in
1978 (21). The heart rate at V
˙
O
2max
of the 1998 sample was
3% greater than those measured in 1978 (P ⬍ 0.05). The
mean ventilation rate at V
˙
O
2max
was 7% and 17% greater in
TABLE 3. Comparison of percent body fat (%BF) and fat-free mass (FFM) of 1998 recruits with those from 1978 (15), 1983 (26), and 1993 (28).
Year
Men Women
N Mean ⴞ SD N Mean ⴞ SD
%BF 1978 955 16.2 ⫾ 5.3
a
506 28.0 ⫾ 4.8
a
1983 980 16.2 ⫾ 5.2
a
1004 25.1 ⫾ 3.9
b
1993 ** ** 176 31.4 ⫾ 4.5
c
1998 182 18.7 ⫾ 4.8
b
167 29.3 ⫾ 4.2
d
FFM (kg) 1978 955 58.8 ⫾ 6.9
a
506 42.3 ⫾ 4.3
a
1983 980 60.7 ⫾ 6.8
b
1004 43.7 ⫾ 4.2
b
1993 ** ** 174 42.4 ⫾ 4.9
a
1998 182 63.7 ⫾ 8.3
c
167 43.9 ⫾ 5.5
b
a
Different letters represent a significant difference between year groups within each variable and gender (P ⬍ 0.05). For example, the %BF of 1978 males (
a
) is not different from
1983 males (
a
), but both are significantly less than the 1998 males (
b
)(P ⬍ 0.05).
** No men were tested during this study.
TABLE 2. Comparison of age, height, and body weight of 1998 recruits with those from 1978 (15), 1983 (26), and 1993 (28).
Year
Men Women
N Mean ⴞ SD N Mean ⴞ SD
Age (yr) 1978 955 19.9 ⫾ 2.7
a
506 20.7 ⫾ 3.2
a,b
1983 980 19.5 ⫾ 2.5
b
1004 20.4 ⫾ 3.3
a
1993 ** ** 176 21.4 ⫾ 3.4
b
1998 182 21.8 ⫾ 3.4
c
168 21.4 ⫾ 3.4
b
Height (cm) 1978 955 174.3 ⫾ 6.6
a
506 162.5 ⫾ 6.8
a
1983 980 175.1 ⫾ 6.8
b
1004 162.6 ⫾ 6.3
a
1993 ** ** 174 163.0 ⫾ 6.5
a
1998 182 176.5 ⫾ 7.0
b
168 163.0 ⫾ 6.1
a
Body weight (kg) 1978 955 70.7 ⫾ 10.8
a
506 59.0 ⫾ 7.2
a
1983 980 72.9 ⫾ 10.8
b
1004 58.5 ⫾ 6.7
a
1993 ** ** 174 62.2 ⫾ 9.0
b
1998 182 78.9 ⫾ 12.8
c
168 62.6 ⫾ 9.8
b
a
Different letters represent a significant difference between year groups within each variable and gender (P ⬍ 0.05). For example, the 1978 males
a
are older than the 1983 males
b
, and younger than the 1998 males
c
(P ⬍ 0.05). The 1983
b
males are younger than the 1998 males
c
and younger than the 1978 males
a
(P ⬍ 0.05).
** No men tested.
PHYSICAL FITNESS OF ARMY MEN AND WOMEN Medicine & Science in Sports & Exercise
姞
359
1998 than in 1978 in men and women, respectively, but no
statistical analysis was conducted, since the 1978 individual
ventilation data were not available.
Table 5 compares the strength values in 1998 to those in
1978 (15) and 1983 (26). Compared with recruits in 1978,
the mean UB strength of men and women tested in 1998 was
17% and 18% greater (P ⬍ 0.05), respectively. A frequency
distribution of the UB strength measured in 1978 and 1998
for male recruits is shown in Figure 1A and for female
recruits in Figure 1B. Because the sample sizes were not
equal, the bars represent the percentage of each sample that
scored within each interval. It can be seen that the entire
curve is shifted to the right of the distribution in 1998, so the
greater average score is not because of a few strong indi-
viduals. Compared to recruits tested in 1978, the mean LB
strength of men and women in 1998 was greater by 6% and
11%, respectively (P ⬍ 0.05). As with UB and LB strength,
the UP strength of 1998 recruits was significantly greater (P
⬍ 0.05) than that of 1983 recruits.
As noted above, the men tested in 1998 had more FFM
than those tested in 1978 and 1983, and the women tested in
1998 had more FFM than those tested in 1978. For this
reason, each individual’s strength scores were divided by
FFM, to examine the differences in strength relative to FFM
(Table 5). The differences in UB isometric strength remain
even when normalized for FFM. This suggests the superior
UB strength of 1998 recruits was not simply a result of
greater quantities of FFM. Unlike UB strength, the differ-
ences in LB strength disappeared when normalized for
FFM, which would suggest that group differences in LB
strength were primarily attributable to differences in FFM.
The magnitude of sample differences in absolute isometric
strength was smaller for LB than for UB.
The 1998 men had a greater absolute UP strength than the
1983 men (26) but, when normalized for FFM, the differ-
ence was no longer significant. This suggests the difference
in UP strength was because of group differences in FFM.
The 1998 women had a greater UP, but were not different
from 1983 women in terms of FFM. Therefore, when ex-
amined relative to FFM, UP was still greater in the 1998
sample (P ⬍ 0.05).
DISCUSSION
Recruits in 1998 entered basic training with levels of
aerobic fitness, muscle strength, and FFM that were similar
to, or greater than, those entering the Army 15–20 yr earlier.
However, they also had more body weight and a greater
%BF. The greater body weight and %BF reflects a national
trend of an increased incidence of obesity (16). The ACSM
guidelines place the male recruits in the 30th to 35th per-
centile or between the “fair” and “poor” categories for %BF,
whereas the women are in the 15th percentile and rated
“poor” (1).
Although the body weight and %BF of 1998 recruits were
greater than in previous years, 1998 recruits also had more
FFM than recruits 20 yr earlier (15). FFM is correlated with
better performance on strength-demanding tasks, particu-
larly military tasks requiring movement of an external load
such as heavy lifting, or lifting and carrying (10). Box lifting
performance, both repetitive and maximal lifting, does not
appear to be negatively affected by an increase in %BF (10).
TABLE 5. Upper-body (UB), lower-body (LB), and upright pull (UP) isometric strength (N) and strength relative to FFM for recruits in 1978 (15), 1983 (26), and 1998.
Measure Year
Men Women
(n) Mean ⴞ SD (n) Mean ⴞ SD
UB (N) 1978 (923) 954 ⫾ 183
a
(493) 539 ⫾ 110
a
1998 (182) 1111 ⫾ 170 (166) 637 ⫾ 110
LB (N) 1978 (947) 1395 ⫾ 370
a
(495) 897 ⫾ 287
a
1998 (148) 1556 ⫾ 417 (148) 953 ⫾ 243
UP (N) 1983 (977) 1224 ⫾ 208
a
(1002) 756 ⫾ 132
a
1998 (182) 1309 ⫾ 243 (166) 803 ⫾ 167
UB (kg)/FFM (kg) 1978 (923) 1.65 ⫾ 0.26
a
(493) 1.30 ⫾ 0.26
a
1998 (182) 1.78 ⫾ 0.21 (166) 1.48 ⫾ 0.20
LB (kg)/FFM (kg) 1978 (947) 2.42 ⫾ 0.60 (495) 2.16 ⫾ 0.66
1998 (148) 2.49 ⫾ 0.52 (148) 2.21 ⫾ 0.47
UP (kg)/FFM (kg) 1983 (977) 2.06 ⫾ 0.29 (1002) 1.77 ⫾ 0.28
a
1998 (182) 2.10 ⫾ 0.34 (166) 1.86 ⫾ 0.31
a
Significantly different from 1998 within gender (P ⬍ 0.05).
TABLE 4. Cardiorespiratory measures from the V
˙
O
2max
test of recruits entering the Army in 1998 (men, N ⫽ 171; women, N ⫽ 155) and 1978 (men, N ⫽ 122; women, N ⫽
122 (21)).
Men Women
Mean ⴞ SD Range Mean ⴞ SD Range
V
˙
O
2max
(L䡠min
–1
)
1978 3.53 ⫾ 0.47
a
2.3–4.8 2.13 ⫾ 0.28
a
1.5–3.1
1998 3.92 ⫾ 0.54 2.4–5.9 2.45 ⫾ 0.42 1.7–3.9
V
˙
O
2max
(mL䡠kg
–1
䡠min
–1
)
1978 50.7 ⫾ 4.8 34–59 36.9 ⫾ 3.8
a
28–47
1998 50.6 ⫾ 6.2 36–70 39.2 ⫾ 5.1 30–57
V
˙
E
(L䡠min
–1
)*
1978 132.0 ⫾ 19.7 NA 84.9 ⫾ 15.6 NA
1998 141.6 ⫾ 20.2 70–197 99.6 ⫾ 15.0 53–137
Heart rate (beats䡠min
–1
)
1978 190.5 ⫾ 6.3
a
180–210 190.5 ⫾ 7.8
a
164–210
1998 196.7 ⫾ 8.0 170–216 196.2 ⫾ 9.5 160–220
a
Significantly different from 1998 within gender (P ⬍ 0.05).
* Individual V
˙
E
data from 1978 not available; means determined on the basis of 87 men and 57 women.
360
Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
Muscle strength is a physically limiting component in 80%
of entry-level Army jobs (23); therefore, greater levels of
FFM and upper-body strength should benefit the 1998 re-
cruits when performing strength-demanding tasks. Tasks
such as loaded marching, which have both strength and
aerobic components, may be negatively affected by greater
quantities of body fat, but the relationship is not as strong as
that between performance and FFM (10).
On the basis of the aerobic fitness categories of Shvartz
and Reibold (24), the values for V
˙
O
2max
of the 1998 male
recruits place them between the “average” and “good” cat-
egories, whereas the women were in the “average” category
for their age. Whereas 1978 men are in the same aerobic
fitness category as the 1998 men, the 1978 women recruits
would only be rated “fair.” Figure 2 displays the distribution
of scores within each of the aerobic fitness categories for
men (Fig. 2A) and women (Fig. 2B). Because the sample
sizes differed, each bar represents the percentage of the
sample within the category, rather than a count. The 1998
men ranged from poor to excellent, whereas 1978 men were
more tightly clustered in the average and good categories.
The 1998 women ranged from poor to excellent, whereas
the 1978 women ranged from the poor to good categories.
The ACSM guidelines for 20- to 29-yr-olds rate the aerobic
power of the men “excellent” or 85th percentile, and the
women “good” or 75th percentile (1). The differences be-
tween the ACSM guideline rating and the rating of Shvartz
and Reibold are probably attributable to the populations
from which they were developed. The ACSM guidelines are
derived from data from the U.S. population (1), whereas the
categories of Shvartz and Reibold are derived from western
European as well as North American samples (24).
Knapik et al.’s (12) finding of slower 2-mile run times in
1997 recruits compared with 1988 recruits suggests that the
aerobic power of recruits was lower in 1997 than 10 yr
earlier. The 2-mile run times of the 1998 recruits were not
different than those reported for 1997 recruits, confirming
Knapik et al.’s (12) findings. The fact that the maximal
aerobic power of the 1998 recruits was equal to or greater
than the 1978 recruits is somewhat surprising, as V
˙
O
2max
and 2-mile run times are reported to be highly correlated
(r ⫽⫺0.76 to ⫺0.91) (11,19). In the 1998 sample, the
correlation was r ⫽⫺0.71 (P ⬍ 0.01).
The 2-mile run test is a field performance test. It is less
reproducible than a V
˙
O
2max
test and can be influenced by
environmental conditions, the method and location of test
administration, course conditions, and the personnel con-
ducting the test. Although aerobic power is an important
component of the test, individual differences such as moti-
vation and running experience can play a significant role in
run times (20). Some recruits are not experienced runners
and may not be able to pace themselves or tolerate exercise-
induced discomfort. The V
˙
O
2max
tests in 1978 and 1998
were conducted under controlled laboratory conditions, are
reliable (test-retest reliability is r ⬎ 0.95 (J. F. Patton,
personal communication)), and provide a superior method
FIGURE 1—Upper-body isometric strength (N) frequency distribu-
tion for male (panel A) and female (panel B) recruits measured in 1978
(15) and 1998. Each bar represents the percentage of recruits scoring
in that interval.
FIGURE 2—Distribution of men (panel A) and women (panel B)
measured in 1978 (21) and 1998 according to the aerobic fitness
categories of Shvartz and Reibold (24). Each bar represents the per-
centage of recruits scoring in that interval.
PHYSICAL FITNESS OF ARMY MEN AND WOMEN Medicine & Science in Sports & Exercise
姞
361
for examining differences in aerobic fitness across samples
than does the 2-mile run test.
Unlike previous samples of recruits, those entering basic
training in 1998 were required to pass a physical fitness
screening test before they began training. Since this was not
the case for the previous samples, the least fit recruits may
have been underrepresented in the 1998 sample. Although
the push-up and sit-up tests measure upper-body and ab-
dominal muscular endurance, they may be considered tests
of muscle strength for individuals who are too weak to
perform one repetition. The maximum muscular strength
measures reported here were not correlated with sit-ups
(range: men, r ⫽ 0.04–0.14, women; r ⫽⫺0.06–0.06) and
only mildly correlated with push-ups (range: men, r ⫽
0.21–0.35; women, r ⫽ 0.05–0.19 (r ⬎ 0.164 required for
significance at the P ⬍ 0.05 level)). The measure most
likely to have been affected by the loss of volunteers is
aerobic capacity. Of those who volunteered to participate in
the 1998 study, it is estimated that six women and five men
did not participate because they failed the physical fitness
screening test run. It is felt that this small number is not
likely to have significantly affected the means.
Other variables that may have affected group compari-
sons are smoking history, racial distribution, and differences
in test methodology and equipment. In the 1998 sample,
52% were nonsmokers, 23% had quit smoking (most within
the previous 6 months), and 23% were smokers. The prev-
alence of smoking for the previous groups was not recorded;
however, the prevalence of smoking has decreased substan-
tially Army-wide from 51% in 1980 to 30% in 1998 (4).
Smoking has been banned in basic training since 1987, so
none of the 1998 sample were smoking within 48 h of
testing. During 1978, soldiers were required to refrain from
smoking for 2 h before testing. Therefore, the acute effects
of smoking, which last about 25 min (18), would not have
affected the results of either the 1978 or 1998 V
˙
O
2max
test.
The chronic effects of smoking are not likely to have af-
fected the outcome of the V
˙
O
2max
test either, as this is a
young population (mean age, 21.6 yr). Using the same
treadmill protocol as Patton et al. (21), it has been shown
that V
˙
O
2max
in young soldiers (mean age, 22 yr) was not
affected by smoking status (6). This was also true in the
1998 sample, as there was no significant difference in the
V
˙
O
2max
of smokers and nonsmokers.
The data in Table 1 suggest there may have been racial
differences among the samples measured in 1978, 1983,
1993, and 1998. The percentage of black men and white
women ages 17–25 in the Army appears lower, whereas the
percentage of soldiers classified as “other” appears higher in
1998 versus 1978. There are reports that black adults (25)
and adolescent girls (22) have a lower capacity for aerobic
exercise than their white counterparts. In a large sample of
soldiers (964 males, 238 females) tested using the same
continuous treadmill protocol as the 1998 study, the effect
of race on V
˙
O
2max
was not significant (9). In the 1998
sample, there was no significant difference in relative
V
˙
O
2max
attributable to race in men. It is possible that the
lack of change in aerobic fitness in men from 1978 to 1998
was affected by a decrease in the distribution of black men,
but the lack of a significant race effect in both a previous
sample (9) and in the 1998 sample of men would tend to
refute this. The V
˙
O
2max
of black women (36.4
mL·kg
⫺1
·min
⫺1
) was 9.5% less than that of white women
(40.2 mL·kg
⫺1
·min
⫺1
, P ⬍ 0.05) and 14% less than that of
Hispanic women (42.5 mL·kg
⫺1
·min
⫺1
, P ⬍ 0.05) in the
1998 cohort, but the percentage of black women in the
Army has not changed appreciably since 1980. There was
no significant difference in V
˙
O
2max
between white and
Hispanic women, so an increase in Hispanic women and
decrease in white women in the 1998 sample should not
have greatly affected the sample comparison.
Changes in the racial distribution of the Army may also
have affected the body composition comparisons. The data
of Fitzgerald et al. (9) seem to indicate that white males
(%BF, 17.4%) and Hispanic males (%BF, 18.2%) have a
greater %BF than black males (%BF, 15.4% as estimated
using skin folds), but the statistical significance of these
differences was not reported. As the percentage of Hispanic
males has increased and the percentage of black males has
decreased over time, this may account for some of the
increase in %BF seen from 1978 to 1998. The Fitzgerald et
al. (9) data also show the same relationship among women,
with white (%BF, 26.2%) and Hispanic (%BF, 26.1%)
women tending to have greater %BF than black women
(%BF, 24.0%; statistical significance of difference not re-
ported). Because the percentage of black females has not
changed greatly over time, changes in racial distribution are
not likely to have affected the outcome of the body com-
position comparison in women. In the 1998 data, there were
no significant differences in %BF attributable to race in men
or women.
As mentioned in the Methods section, there were some
differences in the V
˙
O
2max
testing methodology and equip
-
ment used for the 1978 study and the 1998 study. An
interrupted protocol with 2.5% grade increments was used
in 1978, whereas a continuous protocol with 2% grade
increments was used in 1998. The differences between sim-
ilar treadmill running protocols have been shown to be
small, with an interrupted test producing slightly greater
results (18). In 1978, a Douglas bag system was used, as
opposed to the on-line system used in 1998. To compare
these systems, a small group of subjects (N ⫽ 9) running at
various intensities (warm-up through maximal) were
switched back and forth between the Douglas bag and
on-line systems. There were significant correlations be-
tween the two systems for V
˙
O
2
(r ⫽ 0.99, P ⬍ 0.01) and V
˙
E
(r ⫽ 0.99, P ⬍ 0.01), and the mean differences were small
(V
˙
O
2
, 0.05 L·min
⫺1
, 0.83 mL·kg·min
⫺1
;V
˙
E
, 0.83 L·min
⫺1
).
These data suggest that the differences in protocol and
equipment would have only a minimal effect on the differ-
ences in maximal oxygen uptake between 1978 and 1998.
There were several positive findings. These data show
that recruits entering basic training in 1998 were as aerobi-
cally fit as those entering 20 yr previously, and women had
a greater aerobic capacity. The muscle strength of recruits
was as good or better than it was 15–20 yr previously.
362
Official Journal of the American College of Sports Medicine http://www.acsm-msse.org
Although the body weight, %BF, and FFM of 1998 recruits
was greater than recruits measured 15–20 yr earlier, the
benefit of enhanced occupational task performance attribut-
able to increased FFM may overcome the drawback of
having a greater body weight and %BF.
We gratefully acknowledge the assistance of the following US-
ARIEM personnel who worked many long days to collect these data
(alphabetical order): SGT Rebecca Gregg, SPC Greg Loomis, Mr.
Clay Pandorf, SPC Ty Smith, SSG Roberta Worsham, and SGT
Tanya Zigmont. We are indebted to the staff and volunteers from the
1–28th and the 3–13th Infantry Battalions at Ft. Jackson, SC, as well
as the staff of Moncrief Army Community Hospital, particularly Mr.
Howard MacCollum, COL Dale A. Carroll, COL Stephen G. Oswald,
and MAJ Daniel Harms.
The views and opinions, and/or findings in this report are those of
the authors, and should not be construed as an official Department
of the Army position, policy, or decision.
Address for correspondence: Marilyn A. Sharp, USARIEM,
MRMC-UE-MPD, Natick, MA 01760-5007; E-mail: marilyn.sharp@
na.amedd.army.mil.
REFERENCES
1. ACSM’s Guidelines for Exercise Testing and Prescription. Balti-
more: Williams & Wilkins, 1995, pp. 1–373.
2. A
MOROSO, P. J., M. M. YORE,B.WEYANDT, and B. H. JONES. Total
Army injury and health outcomes database: a model comprehen-
sive research database. Mil. Med. 164:1–36, 1999.
3. B
LAIR, S. N. Are American children and youth fit? The need for
better data. Res. Q. Exerc. Sport 63:120–123, 1992.
4. B
RAY, R. M., R. P. SANCHEZ,M.L.ORNSTEIN,etal.Highlights:
1988 Department of Defense Survey of Health Related Behaviors
among Military Personnel. Research Triangle Park, NC: Research
Triangle Institute, 1999. PB99–13207.
5. C
ORBIN, C. B., and R. P. PANGRAZI. Are American children and
youth fit? Res. Q. Exerc. Sport 62:96–106, 1992.
6. D
ANIELS, W. L., J. F. PATTON,J.A.VOGEL,B.H.JONES,J.M.
Z
OLTICK, and S. F. YANEY. Aerobic fitness and smoking. Med. Sci.
Sports Exerc. 16:195, 1983.
7. D
EPARTMENT OF THE ARMY,HEADQUARTERS. Physical Fitness Train-
ing. Washington, DC: U.S. Government Printing Office, 1992. FM
21–20.
8. D
URNIN, J. V. G. A., and J. WOMERSLEY. Body fat assessed from
total body density and its estimation from skinfold thickness:
measurements on 481 men and women aged from 16 to 72 years.
Br. J. Nutr. 32:77–96, 1973.
9. F
ITZGERALD, P. I., J. A. VOGEL,W.L.DANIELS,etal.The Body
Composition Project: A Summary Report and Descriptive Data.
Natick, MA: U.S. Army Research Institute of Environmental
Medicine, 1986, pp. 1–53. 5/87.
10. H
ARMAN, E. A., and P. N. FRYKMAN. The relationship of body size
and composition to the performance of physically demanding
military tasks. In: Body Composition and Physical Performance,
B. M. Marriott and J. Grumstrup-Scott (Eds.). Washington, DC:
National Academy Press, 1992, pp. 105–118.
11. K
NAPIK, J. The Army Physical Fitness Test (APFT): a review of
the literature. Mil. Med. 154:326–329, 2000.
12. K
NAPIK, J., J. CUTHIE,M.CANHAM,etal.Injury Incidence, Injury
Risk Factors and Physical Fitness of Army Basic Trainees, Ft
Jackson, SC 1997. Aberdeen Proving Ground, MD: U.S. Army
Center for Health Promotion and Preventive Medicine, 1998, pp.
1–49. 29-HE-7513–98.
13. K
NAPIK, J. J., M. A. SHARP,M.CANHAM-CHERVAL,K.HAURET,J.F.
P
ATTON, and B. H. JONES. Risk factors for training-related injuries
among young men and women in basic combat training. Med. Sci.
Sports Exerc. 33:946–954, 2001.
14. K
NAPIK, J. J., M. A. SHARP,M.L.CANHAM,etal.Injury Incidence
and Injury Risk Factors among U.S. Army Basic Trainees (Includ-
ing Fitness Training Unit Personnel, Discharges, and Newstarts)
Fort Jackson, SC, 1998. Aberdeen Proving Ground, MD: U.S.
Army Center for Health Promotion and Preventive Medicine,
1999, pp. 1–113. 29-HE-8370–98.
15. K
NAPIK, J. J., J. E. WRIGHT,D.M.KOWAL, and J. A. VOGEL. The
influence of U.S. Army basic initial entry training on the muscular
strength of men and women. Aviat. Space Environ. Med. 51:1086–
1090, 1980.
16. K
UCZMARSKI, R. J., K. M. FLEGAL,W.M.CAMPBELL, and C. L.
J
OHNSON. Increasing prevalence of overweight among U.S. adults.
JAMA 272:205–211, 1994.
17. K
UNTZLEMAN, C. T., and G. G. REIFF. The decline in American
children’s fitness levels. Res. Q. Exerc. Sport 63:107–111,
1992.
18. M
CARDLE, W. D., F. I. KATCH, and V. L. KATCH. Exercise Phys-
iology: Energy, Nutrition and Human Performance. Media, PA:
Williams & Wilkins, 1996, pp. 200–257.
19. M
ELLO, R. P., M. M. MURPHY, and J. A. VOGEL. Relationship
between a two mile run for time and maximal oxygen uptake.
J. Appl. Sport Sci. Res. 2:9–12, 1988.
20. O’C
ONNOR, J. S., M. S. BAHRKE, and R. G. TETU. 1988 active Army
physical fitness survey. Mil. Med. 155:579–585, 1990.
21. P
ATTON, J. F., W. L. DANIELS, and J. A. VOGEL. Aerobic power and
body fat of men and women during Army basic training. Aviat.
Space Environ. Med. 51:492–496, 1980.
22. P
IVARNIK, J. M., M. S. BRAY,A.C.HERGENROEDER,R.B.HILL, and
W. W. W
ONG. Ethnicity affects aerobic fitness in U.S. adolescent
girls. Med. Sci. Sports Exerc. 27:1635–1638, 1995.
23. S
HARP, M. A., J. F. PATTON, and J. A. VOGEL. A Database of
Physically Demanding Tasks Performed by U.S. Army Soldiers.
Natick, MA: U.S. Army Research Institute of Environmental
Medicine, 1998, pp. 1–42. T98–12.
24. S
HVARTZ, E., and R. C. REIBOLD. Aerobic fitness norms for males
and females aged 6 to 75 years: a review. Aviat. Space Environ.
Med. 61:3–11, 1990.
25. S
IDNEY, S., W. L. HASKELL,R.CROW, et al. Symptom-limited
graded treadmill exercise testing in young adults in the CARDIA
study. Med. Sci. Sports Exerc. 24:177–183, 1992.
26. T
EVES, M. A., J. E. WRIGHT, and J. A. VOGEL. Performance on
Selected Candidate Screening Test Procedures before and after
Army Basic and Advanced Individual Training. Natick, MA: U.S.
Army Research Institute of Environmental Medicine, 1985, pp.
1–61. TR13/85.
27. U.S. D
EPARTMENT OF HEALTH AND HUMAN SERVICES. Physical Ac-
tivity and Health: A Report of the Surgeon General. Atlanta, GA:
Centers for Disease Control and Prevention, 1996. ISSN/ISBN
017–023–00196–5.
28. W
ESTPHAL, K. A., K. E. FRIEDL,M.A.SHARP,etal.Health,
Performance, and Nutritional Status of U.S. Army Women during
Basic Combat Training. Natick, MA: U.S. Army Research Insti-
tute of Environmental Medicine, 1995, pp. 1–146. 2/96.
PHYSICAL FITNESS OF ARMY MEN AND WOMEN Medicine & Science in Sports & Exercise
姞
363
