Figure - available from: Scandinavian Journal of Medicine and Science in Sports
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Representation of one step in accelerative sprint gait cycle. Leg retraction (forward rotation) begins as the foot leaves the ground and continues up until peak hip flexion. Leg protraction (backward rotation) commences as the hip extends and continues up until toe‐off. For each step, data were obtained as the hip transitioned from flexion (i.e., late retraction) to extension through to toe‐off (i.e., protraction phase).
Source publication
During initial acceleration, the first steps of a maximal‐effort (sprint) run often determine success or failure in the capture and evasion of an opponent, and is therefore a vital factor of success in many modern sports. However, accelerative events are commonly performed after having already run considerable distances, and the associated fatigue...
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Citations
... Although speculative, a similar recommendation was mentioned in a previous study involving elite sprinters (15). However, in track and field, it could be argued that reducing t may not be as significant because it is well established in the scientific literature (15,21,28) that sprinters require longer distances to reach Vmax, which also results in a shorter deceleration phase. In brief, working toward reducing t values would be important for rugby players when the aim is to attain higher velocities over shorter periods (and distances). ...
... The latter differs from the abovementioned recommendation in elite sprinters, although reinforces on the critical importance of Vmax and team sports like rugby union (17,31). The critical importance of initial acceleration and Vmax in determining success or failure in capturing and evading opponents in modern sports has been previously highlighted (22,28). Therefore, gaining a better understanding of the mechanistic link between acceleration and Vmax may ultimately help to improve an athlete's performance. ...
Zabaloy, S, Freitas, TT, Alcaraz, PE, Gálvez-González, J, Pereira, LA, Comyns, T, Loturco, I, and Healy, R. Relative acceleration and maximum velocity in rugby players according to age category and playing position. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to (a) assess the intrasession reliability of the acceleration time constant (i.e., t) and t-derived measures; (b) analyze the influence of t and maximum velocity (Vmax) on 40-m sprint performance and to compare various sprint-related outcomes among rugby players from different playing positions and age categories; and (c) explore the associations between t and several sprint performance metrics. A total of 300 male rugby players volunteered to participate in this study and were divided into age categories (i.e., under-14 [U14]: n 5 91, age: 12.6 6 0.5 years; under-16 [U16]: n 5 85, age: 14.8 6 0.5 years; under-18 [U18]: n 5 75, age: 16.6 6 0.5 years; and Seniors: n 5 49, age: 24.2 6 4.1 years). The results demonstrated good to excellent reliability for all measured parameters (intraclass correlation coefficient .0.75 and coefficient of variation ,9.0%). Younger players (i.e., U14 and U16) displayed lower t values (effect size: moderate to large; p , 0.02) compared with their older peers (i.e., U18 and Seniors), regardless of their playing position. Moreover, t was associated with sprint performance metrics at varying levels of correlations (Rho: small to almost perfect; p , 0.001). In conclusion, younger players exhibited lower t values than their older counterparts, irrespective of their playing positions. The model employed in this study demonstrated its accuracy in assessing several key sprint performance metrics, offering insights that can enhance sprint training programs for rugby players, which can be based on the associations observed among these different variables.
... On the other hand, it may be related to the nature of the applied sprinting task (ie, 30 m), which involves a greater component of acceleration and hip extension force production dependence, thus inducing specific hip extension fatigue. 35 Future research is wanted to further explore this topic. ...
Background: The effect of 10 × 30 m repeated sprints on passive and active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh), and knee flexor maximal voluntary isometric contraction (MVIC) and rate of force development (RFD), and whether athletes with previous hamstring injury have a different response, is unknown.
... On the other hand, it may be related to the nature of the applied sprinting task (ie, 30 m), which involves a greater component of acceleration and hip extension force production dependence, thus inducing specific hip extension fatigue. 35 Future research is wanted to further explore this topic. ...
Background:
The effect of 10 × 30 m repeated sprints on passive and active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh), and knee flexor maximal voluntary isometric contraction (MVIC) and rate of force development (RFD), and whether athletes with previous hamstring injury have a different response, is unknown.
Hypothesis:
Repeated sprints would (1) increase BFlh stiffness and decrease ST stiffness and knee flexors MVIC and RFD in healthy participants; and (2) greater magnitude of response would be seen in athletes with previous hamstring injury.
Study design:
Case series (experiment I) and case control (experiment II) study designs.
Level of evidence:
Level 3.
Methods:
Healthy nonathletes attended 2 replicated sessions (experiment I, n = 18), while soccer players with (n = 38) and without (n = 67) previous hamstring injury attended 1 testing session (experiment II).
Results:
In both experiments, the knee flexors MVIC and RFD decreased after the sprints (P < 0.05). In experiment I, the ST and BFlh passive stiffness reduced after the sprints (P < 0.02), while a small BFlh active stiffness increase was noted (P = 0.02); however, no correlation was observed between the 2 testing sessions for the postsprint muscle stiffness responses (r = -0.07-0.44; P > 0.07). In experiment II, only an ST passive stiffness reduction was observed after the sprints (P < 0.01). No differences were noted between injured and noninjured lower limbs for any variable (P > 0.10).
Conclusion:
Repeated sprints are likely to decrease the knee flexor's maximal and rapid strength, and to alter the hamstring stiffness in the nonathlete population. Previous hamstring injury does not apparently affect the footballer's hamstring functional and mechanical responses to repeated sprints.
Clinical relevance:
The responses of hamstring stiffness and knee flexor strength to repeated sprints are unlikely to be associated with hamstring injury.
