Sprint Speed Research Articles

Spatiotemporal kinematics during top speed sprinting in male intercollegiate track and field and team sport athletes

ABSTRACT We investigated spatiotemporal kinematics during top speed sprinting and biomechanical running strategies in 98 male intercollegiate athletes from a range of athletic backgrounds in track and field (TF, n = 28) and team sports (TS, n = 70). Participants completed 40 m running trials with sagittal plane motion analyses of high-speed video captured from 30 m to 40 m. Across the entire sample, measures of contact time, step rate, step length, flight length and duty factor (ratio of contact duration to stride duration) were meaningfully correlated with top speed (p < 0.05, 0.51 ≤ |r or ρ| ≤ 0.78). Flight time and contact length were weakly correlated with top speed (p < 0.05, 0.27 ≤ |r or ρ| ≤ 0.34). When comparing sub-groups of Slow TF (n = 14) and Fast TS athletes (n = 22) with similar top speeds (~9.3 m/s), Fast TS athletes clearly demonstrated a more ground-based strategy, with longer ground contact times and contact lengths, shorter flight times and flight lengths, and larger duty factors. Therefore, the results of this study suggest that existing technical models and normative metrics based on data from TF athletes could require modification when evaluating and coaching sprinting performance with TS athletes.

Analysis of the Validity and Reliability of the Photo Finish® Smartphone App to Measure Sprint Time

In athletic training and research, the evaluation of sprint speed is widely used, and its accurate measurement is especially demanding. High-cost photocells are the gold-standard system for sprint time assessment, although low-cost smartphone applications can be a suitable option. This study assesses the validity and reliability of an application to measure sprint time compared to photocells. Five physically active subjects completed six sprints of 10 m and 20 m at maximal speed and a 5 m go and return sprint to evaluate the validity of the Photo Finish® app (Version 2.30). To assess reliability, six trials of 5 m go and return sprints were measured by two smartphones. The validity results showed a mean bias of 0.012 s (95% CL: 0.000, 0.024) between the application and the photocells for the 10 m sprint, 0.007 s (95% CL: −0.007, 0.022) for the 20 m sprint and 0.005 s (95% CL: −0.005, 0.017) for the 5 m go and return test. The results also found R2 between both systems (R2= 0.9863, 0.990 and 0.958) for each distance (10 m, 20 m and 5 m go and return, respectively). As for reliability, the application showed outstanding consistency between two smartphones operating simultaneously (ICC 0.999; R2: 0.999). This study shows that the Photo Finish® app is an accurate and reliable tool to measure sprint time with an error of 0.09 s.

The effect of multi-directional sprint training on change-of-direction speed and reactive agility of collegiate tennis players.

The aim of this study was to evaluate the effect of random route multi-directional sprint training (MDST) compared to fixed route MDST on change-of-direction speed (CODS) and reactive agility (RA), and to investigate the correlation between CODS, RA and short-distance straight sprint speed (SDSS). A total of 19 collegiate tennis players from Beijing Sport University were randomly assigned to either the random route MDST group (RR group, N = 9, age: 22.22 ± 2.22 years) or the fixed route MDST group (FR group, N = 10, age: 21.90 ± 1.66 years). Both groups completed a progressive load intervention training for 3 weeks, three times a week. The RR group's random route, mirroring the distance and number of change-of-direction (COD) in the FR group's fixed route, was specifically designed. The spider run, T-drill, RA test and 5-m straight line sprint test were performed before and after the intervention. Both groups showed improved performance in the spider run (p < 0.05), T-drill (p < 0.01) and 5-m straight (p < 0.001) line sprint test after the intervention. Additionally, there was no significant difference in the improvement of CODS and SDSS between the two groups (p > 0.05). The RA of the RR and FR groups after the intervention was significantly higher than before intervention (p < 0.001), and RR group showed greater improvement in RA compared to the FR group. There was a moderate correlation between spider run and T-drill (r = 0.523), RA (r = 0.388), and no significant correlation between spider run and 5-m straight sprint (p > 0.05). T-drill was moderately correlated with RA (r = 0.347) and 5-m straight sprint (r = 0.321). RA was moderately correlated with 5-m straight sprint (r = 0.551). Three-week multi-directional sprint training can effectively improve the change-of-direction speed, reactive agility and short-distance straight sprint speed of collegiate tennis players. And random route multi-directional sprint training has better effect on improving reactive agility.

The Slithering Dead: Does locomotor performance affect post-capture death feigning in dice snakes (Natrix tessellata, Laurenti 1768)?

Abstract Functional constraints between different types of antipredator behavior should be common, especially if they are on the opposite sides of the behavioral spectrum such as flight and post-capture immobility. We examined a potential compromise between post-capture immobility displays and sprint speed in dice snakes (Natrix tessellata), using a field-based approach. We sampled snakes (N = 238) from two populations: from a dense island population free of mammal predators, and from a less dense mainland population, preyed upon by both bird and mammal predators. We explored the effects of sexual maturity, temperature, body size, presence of palpable food in the gut, and injuries on the occurrence and duration of post-capture immobility as well as sprint speed. Our results confirm the existence of functional constraints between locomotor performance and post-capture immobility in dice snakes. Faster dice snakes start escaping promptly after release, while slower individuals utilize more passive antipredator behaviors such as death feigning. Local adaptations seem to have great influence on behavioral compromise, since the mammal-free island population exhibited a higher incidence of post-capture immobility and a significantly lower sprint speed, compared to the less dense mainland population. Additionally, immature individuals tended to avoid death feigning and their post-capture immobility lasted shorter compared to adult individuals. It remains to be seen how individuals adjust their behavior to accomodate locomotor constraints, and in which specific phases of the predator-prey interaction these adjustments occur.

An Experimental Approach for the Quantitative Assessment of Downstream Swimming Fish Behavior

ABSTRACTBehavior of fish influences the mortality risk during turbine and pump passages. Knowledge about species‐specific behavior and its triggers is necessary for improving numerical models and the development of autonomous sensor probes to estimate fish mortality in turbines and pumps. A primary objective of the RETERO project is the study of fish behavior in hydraulic conditions similar to turbine and pump intakes in controlled conditions. For this purpose, an experimental conduit was constructed at the Hubert‐Engels Laboratory of the TUD Dresden University of Technology (Germany) equipped with a 3D camera infrared tracking system. The conduit was designed to model hydraulic conditions typical for turbine and pump intakes. In the experimental setup, the effects of flow velocities exceeding the maximum swim speed of fish, as well as spatial velocity gradients and illumination conditions on the fish behavior are studied. The data from brown trout (Salmo trutta) allow for an analysis of how these fish react to flow accelerations and velocities surpassing their sprint speed, using quantitative metrics for movement and activity. An initial evaluation of these experiments highlights the potential of this approach for further research.

Acute Changes in Hamstring Injury Risk Factors After a Session of High-Volume Maximal Sprinting Speed Efforts in Soccer Players.

Maximal sprinting speed (MSS) overexposure is associated with increased risk of injury. This study aimed to describe changes in sprint performance-related factors and hamstring strain injury (HSI) risk factors after a high-volume sprinting session in soccer players. A high-volume sprinting session can induce acute changes in several sprint performance-related factors (sprint time and mechanical properties) and HSI risk factors (posterior chain muscle strength, hamstring range of motion, and dynamic lumbo-pelvic control [LPC], measured as changes in anterior pelvic tilt [APT] during maximal speed sprinting). Prospective observational case series. Level 4. Fifteen active male amateur soccer players participated. Changes in sprint performance-related factors and HSI risk factors were examined for 72 hours after high-volume MSS efforts (H-VMSSE) using a soccer-contextualized multifactorial approach. Muscle damage proxy markers (hamstring perceived soreness and creatine kinase) were also examined. H-VMSSE induced decrements in sprint performance-related factors. Significant reductions in theoretical maximal horizontal velocity (P < 0.01; effect size [ES], -0.71) and performance (P = 0.02; ES, -0.59) were observed for 48 and 72 hours after H-VMSSE. Small but significant reductions in posterior chain muscle force-generating capacity were detected for 48 and 72 hours after H-VMSSE for the nondominant (P < 0.03; ES, -0.60) and dominant (P < 0.04; ES, -0.40) leg. Finally, players exhibited persistent small, albeit nonsignificant (P = 0.06; ES, 0.53), decreases in dynamic LPC (APT increases) for 72 hours after H-VMSSE. H-VMSSE induced declines in both sprint performance-related factors and HSI risk factors. Sprinting can alter a player's anatomic structure by increasing APT during the maximum speed phase of the sprint. A soccer-contextualized multifactorial approach might allow for the regulation of MSS dosage depending on individual HSI risk factor status, thereby serving as a tailored "vaccine" for sprinting needs.

A narrative review of velocity-based training best practice: The importance of contraction intent vs. movement speed.

Explosive movements requiring high force and power outputs are integral to many sports, posing distinct challenges for the neuromuscular system. Traditional resistance training can improve muscle strength, power, endurance, and range of motion; however, evidence regarding its effects on athletic performance, such as sprint speed, agility, and jump height, remains conflicting. The specificity of resistance training movements, including velocity, contraction type, and joint angles affects performance outcomes, demonstrates advantages when matching training modalities with targeted sports activities. However, independent of movement speed, the intent to contract explosively (ballistic) has also demonstrated high velocity-specific training adaptations. The purpose of this narrative review was to assess the impact of explosive or ballistic contraction intent on velocity-specific training adaptations. Such movement intent may predominantly elicit motor efferent neural adaptations, including motor unit recruitment and rate coding enhancements. Plyometrics, which utilize rapid stretch-shortening cycle (SSC) movements may augment high-speed movement efficiency and muscle activation, possibly leading to improved motor control through adaptations like faster eccentric force absorption, reduced amortization periods, and quicker transitions to explosive concentric contractions. An optimal training paradigm for power and performance enhancement might involve a combination of maximal explosive intent training with heavier loads and plyometric exercises with lighter loads at high velocities. This narrative review synthesizes key literature to answer whether contraction intent or movement speed is more critical for athletic performance enhancement, ultimately advocating for an integrative approach to resistance training tailored for sports-specific explosive action.

Investigation Of The Matrix S-drive Treadmill On Top Sprint Speed In Female Soccer Players

Investigation Of The Matrix S-drive Treadmill On Top Sprint Speed In Female Soccer Players

Agreement and Sensitivity of the Acceleration–Velocity Profile Derived via Local Positioning System

Sprint performance is commonly assessed via discrete sprint tests and analyzed through kinematic estimates modeled using a mono-exponential equation, including estimated maximal sprinting speed (MSS), relative acceleration (TAU), maximum acceleration (MAC), and relative propulsive maximal power (PMAX). The acceleration–velocity profile (AVP) provides a simple summary of short sprint performance using two parameters: MSS and MAC, which are useful for simplifying descriptions of sprint performance, comparison between athletes and groups of athletes, and estimating changes in performance over time or due to training intervention. However, discrete testing poses logistical challenges and defines an athlete’s AVP exclusively from the performance achieved in an isolated testing environment. Recently, an in situ AVP (velocity–acceleration method) was proposed to estimate kinematic parameters from velocity and acceleration data obtained via global or local positioning systems (GPS/LPS) over multiple training sessions, plausibly improving the time efficiency of sprint monitoring and increasing the sample size that defines the athlete’s AVP. However, the validity and sensitivity of estimates derived from the velocity–acceleration method in relation to changes in criterion scores remain elusive. To assess the concurrent validity and sensitivity of kinematic measures from the velocity–acceleration method, 31 elite youth basketball athletes (23 males and 8 females) completed two maximal effort 30 m sprint trials. Performance was simultaneously measured by a laser gun and an LPS (Kinexon), with kinematic parameters estimated using the time–velocity and velocity–acceleration methods. Agreement (%Bias) between laser gun and LPS-derived estimates was within the practically significant magnitude (±5%), while confidence intervals for the percentage mean absolute difference (%MAD) overlapped practical significance for TAU, MAC, and PMAX using the velocity–acceleration method. Only the MSS parameter showed a sensitivity (%MDC95) within practical significance (&lt;5%), with all other parameters showing unsatisfactory sensitivity (&gt;10%) for both the time–velocity and velocity–acceleration methods. Thus, sports practitioners may be confident in the concurrent validity and sensitivity of MSS estimates derived in situ using the velocity–acceleration method, while caution should be applied when using this method to infer an athlete’s maximal acceleration capabilities.

Understanding How Eccentric Hamstring Strength Affects Football Performance: The Scientific Secret To Fast Running

This study aimed to investigate the impact of eccentric hamstring strength, identified as a significant factor in the risk of hamstring injury, on maximum sprinting speed. Twenty-three football players competing in the Turkish Super League, with an average age of 25.12±3.22, were included in the study. The eccentric hamstring muscle strength of the athletes was measured using the N3 Nordic Hamstring Curl Exercise device. The maximum sprinting speeds of the players were determined by a GPS analyst. It was found that there was no significant relationship between eccentric hamstring strength on both dominant and non-dominant sides and maximum sprinting speed. Similarly, no significant relationship was found between the difference in eccentric hamstring strength between the two sides and maximum sprinting speed values (p&gt;0.05). The study concluded that there is no association between eccentric hamstring muscle strength parameters and maximum sprinting speed in football players. As confirmed in this study, isolated maximum eccentric hamstring muscle strength alone does not appear to be the sole determinant parameter for horizontal force production during sprinting. However, further research is needed in this area.

Analysis of the impact of different intensities and time periods on the physical and technical performance of professional soccer players

Soccer match simulations provide valuable information on player performance and training methods but how intensity during a game affects a player's physical/technical performance has yet to be explored. The objective of the study was to analyse the impact of variable intensity intervals during the first block of the Copenhagen Soccer Test. A repeated measures study was designed to compare three intensity levels, three time periods and their effects on sprint speed, perceived effort, goal shooting accuracy, dribbling, and long pass accuracy in professional soccer players. The comparison analysis between different phases showed a significant decrease in sprint speed (p &lt; 0.001) and an increase in perceived effort (p &lt; 0.001), however, the technical variables did not change (p &gt; 0.05). When comparing the data based on intensity, significant decreases were observed in all variables (p &lt; 0.001). The combined analysis of the results indicates that the speed decreases and the rate of perceived exertion increases as the simulation progresses. Meanwhile, the accuracy of goal kicks, dribbling, and long passes are negatively affected by high-intensity efforts, but demonstrate recovery over the course of the simulation. The increase in intensity affects the speed more than the accuracy of shots on goal, dribbling and passing. Keywords: Performance, Soccer, Intensity, Physical performance, Technical performance.

The Importance of Physical Fitness Parameters in Rhythmic Gymnastics: A Scoping Review.

This scoping review presents an overview of physical fitness parameters in rhythmic gymnastics as well as the association of fitness with gymnasts' performance, competitive level, and age. PubMed, Scopus, and Sport Discus databases were searched. Of the 586 records retrieved, 41 studies met the inclusion criteria (n = 1915 participants). The included studies examined flexibility, aerobic capacity, muscle power, muscle endurance, muscle strength, sprint speed, agility, balance, and coordination. Performance was associated with flexibility, aerobic capacity, lower-limb muscle power, agility, muscular endurance, balance, and coordination from a young age. Flexibility, aerobic capacity, and muscle power were, in general, higher in high-level gymnasts than in low-level gymnasts or controls. Older rhythmic gymnasts demonstrated higher scores than the younger ones in flexibility, aerobic capacity, balance, and sport-specific coordination but not in muscle endurance, while some studies reported a decline in muscle power with age. Supplementary physical fitness training improved all physical abilities irrespective of the gymnasts' level. Rhythmic gymnastics training alone improved muscle power, agility, speed, muscular endurance, and balance to a lesser extent than targeted fitness training. Muscular strength, speed, and agility are largely under-researched in rhythmic gymnastics. Emphasis should be given to targeted strength and power training due to the high mechanical loads placed on skeletally immature athletes.

Effects of In-Season Strength Training on Physical Fitness and Injury Prevention in North African Elite Young Female Soccer Players

BackgroundStrength training (ST) primarily enhances physical fitness (e.g., muscle strength, power, speed) and bone density in female soccer players. Less information is available on the injury preventive effects of ST in female athletes. Accordingly, this study aimed to investigate the effects of a 12-week in-season ST on measures of physical fitness and injury occurrence in young elite female soccer players.MethodsThirty elite female soccer players (15.4 ± 1.9 years; maturity offset + 2.3 ± 1.1 years) participated in this study, and were randomly assigned to a strength training group (STG, n = 14) or an active control (CG, n = 16) group. ST lasted twelve weeks and included full body muscle strengthening exercises using primarily weight machines at progressive intensities ranging between 40 and 85% of the one-repetition-maximum (1-RM). The CG practiced a traditional soccer training program. Overall, training volumes of the two groups were similar with a training load (rating of perceived exertion × time) of 1158.4 ± 67.7 arbitrary unity (AU) for the STG and 1188.8 ± 44.1 AU for the CG. Pre and post training, the following physical fitness tests were applied: dynamic muscle strength (relative [to body mass] and absolute 1-RM bench/leg press, lat-pull down), jump performance (countermovement jump [CMJ], squat jump [SJ], five-jump-test [5JT]), linear-sprint speed (5-m, 10-m, 30-m), change-of-direction speed (T-test with and without ball), sport-specific performance (Yo-Yo Intermittent Level1 [YYIRTL1], and repeated shuttle sprint ability [RSSA]). The injury rate per 1000-h exposure was monitored throughout the soccer season.ResultsNo significant baseline differences were observed between groups. Statistically significant group-by-time interactions were found for absolute (p < 0.001, d = 2.59) and relative 1-RM bench press (p < 0.001, d = 2.39), absolute 1-RM lat-pull down (p < 0.001, d = 1.68), and relative 1-RM leg press (p < 0.001, d = 1.72). Significant group-by-time interactions were observed for CMJ (p = 0.005, d = 1.27), RSSAmean (p = 0.007, d = 0.81), and RSSAtotal (p < 0.001, d = 1.90). Post-hoc tests indicated that the STG group demonstrated greater improvements in all tested variables compared to CG (1.2 < d < 2.5). However, no significant interaction effects were noted for measures of linear sprint speed and YYIRTL1 performance. Additionally, non-contact injuries during the season were significantly lower (p = 0.003, d = 1.31) in the STG (0.48/1000 h of exposure) than the CG (2.62/1000 h of exposure).ConclusionsTwelve weeks of an in-season ST resulted in larger physical fitness improvements and fewer injuries compared with an active control in elite young female soccer players. Accordingly, ST should be systematically applied in female soccer to enhance performance and prevent injuries.

Anthropometric and physical fitness characteristics of male South African youth soccer players.

This study comparatively investigates the anthropometric and physical fitness characteristics of male South African players by age group, competitive level and playing position. The sample consisted of 201 youth soccer players drawn from six sports academies in South Africa. Players were subjected to standardized protocols for anthropometric measurements (stature, body mass and body fat percentage) and physical fitness tests (flexibility, vertical jump, push-ups, sit-ups, muscle strength, agility, 30-m sprint and V̇O<inf>2max</inf>). A series of two-way analyses of variance was performed to determine the interactions between playing position (goalkeeper, defender, midfielder or attacker) or age group (13, under-15, under-17 or under-19) and competitive level (elite or non-elite). The results show significant interaction effects of agility, body fat percentage and sprint speed between the players' competitive levels and age group (P<0.05). No interaction effect was found between playing position and competitive level in any anthropometric or physical fitness variable (P>0.05). However, playing position exhibited significant main effects in the youth players' aerobic endurance and body mass (P<0.05). The results provide practical implications for tailoring position-specific conditioning regimes that optimize effective soccer performance.

The Effectiveness of Warm-Up Using an Assistive Device in Wheelchair Basketball: A Feasibility Study of Able-Bodied Participants.

Introduction A warm-up is often performed to prevent injury and prepare for optimal performance. Nonetheless, research on its impact on performance, particularly in para-sports, remains limited. We hypothesized that the use of an assistive device during warm-up would enable wheelchair basketball players to perform full-body movements efficiently and effectively, contributing to enhanced wheelchair mobility. Therefore, this feasibility study aimed to assess the safety of warm-up exercise with an assistive device and the changes in wheelchair mobility performance before and after warm-up in able-bodied participants. Methods Thirteen able-bodied participants (nine males and four females; mean age: 34.3 ± 6.11 years) were analyzed. Warm-up consisted of a five-minute stand-up exercise using the lumbar-type Hybrid Assistive Limb®. Before and after warm-up, a 3-3-6 m sprint was performed as a wheelchair mobility performance test. The 3-3-6 m sprint is a test in which the athlete repeatedly accelerates, decelerates, and stops while driving at maximum effort for a total of 12 m (0-3 m, 3-6 m, and 6-12 m). The time required for the 3-3-6 m sprint and maximum instantaneous speed, acceleration time, deceleration time, hip joint angle, and average muscle activity of the lower limb and trunk muscles during the acceleration/deceleration phase of each section were compared before and after warm-up exercise. Results Warm-up with an assistive device was safe in healthy participants. The time required for the 3-3-6 m sprint was significantly reduced after the warm-up compared to that before the warm-up (p=0.005). Although not significant, there was a trend toward shorter deceleration times after the warm-up for participants herein. Conclusions In able-bodied participants, warm-up with an assistive device is safe; it may improve wheelchair mobility performance. Further research is required to determine its impact on para-athletes with disabilities.

A Comparison of the Instantaneous Effects of Spinal Manipulation and Mobilization Techniques Applied to L3 Level on Jumping, Agility, and Sprint Speed in Male Volleyball Players

A Comparison of the Instantaneous Effects of Spinal Manipulation and Mobilization Techniques Applied to L3 Level on Jumping, Agility, and Sprint Speed in Male Volleyball Players

Let's include the ladies: Do morphology-performance relationships vary between sexes in lizards?

An animal's morphology influences its ability to perform essential tasks, such as locomoting to obtain prey or escape predators. While morphology-performance relationships are well-studied in lizards, most conclusions have been based only on male study subjects, leaving unanswered questions about females. Sex-specific differences are important to understand because females carry the bulk of the physiological demands of reproduction. Consequently, their health and survival can determine the fate of the population as a whole. To address this knowledge gap, we sampled introduced populations of common wall lizards (Podarcis muralis) in Ohio, USA. We measured a complete suite of limb and body dimensions of both males and females, and we measured sprint speeds while following straight paths and curved paths on different substrates. Using a multivariate statistical approach, we identified that body dimensions relative to snout-to-vent length in males were much larger compared to females and that body dimensions of P. muralis have changed over time in both sexes. We found that sprint speed along curved paths increased with relative limb size in both males and females. When following straight paths, male speed similarly increased as body dimensions increased; conversely, female speed decreased as body dimensions increased. Female sprint speed was also found to have less variation than that of males and was less affected by changes in body size and hindfoot length compared to males. This study thus provides insights into how selective pressures might shape males and females differently and the functional implications of sexual dimorphism.

Jump Squat Vs. Resisted Sprint Training Programs Applied to Elite Youth Soccer Players: Effects on Sprint and Power-Related Performance.

Loturco, I, Pereira, LA, Mercer, VP, Oliveira, LP, Zanetti, V, Lima, L, Bastos, T, Moura, TBMA, and McGuigan, MR. Jump squat vs. resisted sprint training programs applied to elite youth soccer players: effects on sprint and power-related performance. J Strength Cond Res XX(X): 000-000, 2024-This study examined the effectiveness of 2 different and widely used training programs on the sprint and power-related performance of youth soccer players. Two distinct training strategies-vertically oriented jump squats (JSs) or horizontally oriented resisted sprints (RSs)-were executed under the same absolute loading conditions (i.e., 30% of the athletes' body mass [BM]) during a 4-week preseason period. Training schemes, loading intensities (based on %BM), and the number of experimental sessions were designed in conjunction with the soccer club's coaching staff, considering the calendar, available resources, and regular training programs. Twenty-five under-17 soccer players performed a series of speed, power, and jump tests before and after 10 resisted training sessions, consisting solely of loaded JS or RS. Overall, neither group (i.e., JS or RS training groups) exhibited any improvement in linear sprint and change-of-direction (COD) speed. Conversely, vertical jumping ability and peak velocity in the loaded JS increased significantly only in the JS group, which may positively affect players' performance and training prescription during short soccer preseasons. Given the challenges in enhancing sprint speed among soccer players during preseasons (and even over the competitive season), coupled with the limited effectiveness of RS in improving sprinting, COD, and jumping capabilities within congested and short training phases (i.e., ≤4 weeks), the regular use of RS training methods during these phases may be highly questionable. Coaches should carefully consider these critical limitations and potential disadvantages when designing neuromuscular training programs for soccer players during the preparatory phases of the annual training season.

Performing Lower-Limb Strength Exercises Before or After Training Does not Influence Fatigue Indices in Competitive Youth Soccer Players.

Gantzer, C, Huff, D, Butterick, B, Chalmers, S, Marshall, P, Lovell, R, and Siegler, JC. Performing lower-limb strength exercises before or after training does not influence fatigue indices in competitive youth soccer players. J Strength Cond Res XX(X): 000-000, 2024-A multicenter approach was used to conduct a controlled, laboratory-based study (Part A) in conjunction with an ecologically focused, field-based study (Part B) of the influence of timing on hamstring fatigue induced by lower-limb strength exercises. Part A required players to perform the FIFA 11+ warm-up before a simulated soccer training session, whereas the other session involved removing the lower-limb strength exercises from the warm-up and delivering them after the simulated session. For Part B, players completed 2 live training sessions, where one session included the Nordic hamstring exercise (NHE) as part of a standardized warm-up before training and the other session incorporated the NHE at the end of training. Maximal hamstring force (MVC), rate of force development (RFD), countermovement jump (CMJ), and sprint speed (SS) were assessed before, during, and after the simulation and field training, respectively, to quantify fatigue across both study cohorts. There was no suggestion that timing of the intervention had an influence fatigue in either Part A or B, with no condition (MVC [Part A & B]: p > 0.43; RFD: p = 0.43; CMJ: p = 0.10; SS: p = 0.62), time (MVC: p > 0.30; RFD: p = 0.72; CMJ: p = 0.87; SS: p = 0.85), or interactions (MVC: p > 0.93; RFD: p = 0.78; CMJ: p = 0.99; SS: p = 0.94) evident. Our findings suggest youth soccer coaches should not be concerned with the timing of interventions, allowing them to focus instead on adherence and player buy-in.

The Effects of Volume-Matched 1- and 2-Day Repeated Backward Sprint Training Formats on Physical Performance in Youth Male Soccer Players.

Bouguezzi, R, Negra, Y, Sammoud, S, Uthoff, A, Moran, J, Behrens, M, and Chaabene, H. The effects of volume-matched 1- and 2-day repeated backward sprint training formats on physical performance in youth male soccer players. J Strength Cond Res XX(X): 000-000, 2024-This study examined the effects of a 6-week, 1 vs. 2 sessions of volume-matched weekly repeated backward sprint training (RBST) on measures of physical fitness in youth male soccer players. Thirty male youth soccer players from a regional soccer team were randomly assigned to a 2-day group (n = 15; age = 16.40 ± 0.64 years; Maturity-offset = 2.19 ± 0.65 years) or a 1-day group (n = 15; age = 16.27 ± 0.51 years; Maturity-offset = 1.91 ± 0.40 years). Measures of jumping ability, linear sprint speed, change-of-direction (CoD) speed, aerobic endurance (AE), and repeated sprint ability (RSA) were measured before and after 6 weeks of training. The training interventions involved 1 to 2 sets, each comprising 7 repetitions over a 20-m distance of RBST in the 2-day group, and 2 to 4 sets, also with 7 repetitions each over the same distance, in the 1-day group. Statistical analyses were conducted using the analysis of covariance model with baseline measurements entered as covariates. Results indicated that RBST over 2 days generated greater benefits compared with a single day for improving CoD speed (∆4.91 vs. 0.04%; effect size [d] = 0.78 vs. 0.00, respectively), linear sprint speed (10-m: ∆4.74 vs. 0.36%; d = 0.96 vs. 0.00, respectively; 20 m: ∆3.34 vs. 0.82%; d = 1.00 vs. 0.49, respectively), and RSA performances (RSAbest: ∆2.61 vs. 0.29%; d = 0.71 vs. 0.16, respectively; RSAmean: ∆2.86 vs. 0.89%; d = 0.59 vs. 0.16, respectively; RSAtotal: ∆2.86 vs. 0.89%; d = 0.62 vs. 0.41, respectively). However, similar improvements in the 2 RBST formats were observed on jumping (2-day group: ∆6.9%; d = 0.75; 1-day group: ∆10.6%, d = 1.26) and AE performance (2-day group: ∆17.24%, d = 1.04; 1-day group: ∆27.25%, d = 2.25). In summary, the findings suggest that, when volume is matched, spreading the RBST regimen over 2 days may result in greater improvements compared with a single-day approach for enhancing CoD speed, linear sprint speed, and RSA performance.