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Narrative Review on the Use of Sled Training to Improve Sprint Performance in Team Sport Athletes
Abstract
Sprinting is a key component for many individual and team sports. Therefore, to enhance sprint performance, various training methods are widely used by coaches and practitioners, including maximum sprint speed and resisted sprint training. Resisted sprinting with sled towing is a method that has recently received considerable attention from the sport science community. However, to date, no consensus exists regarding its acute and chronic effects in team sport athletes. This narrative review aimed to (a) review and analyze the mechanics of sprinting under unresisted and resisted conditions with a specific focus on team sport disciplines; (b) provide a thorough and
applied discussion on the importance of considering acute and chronic effects of sled loading on technique, electromyographic activity, and force production, as well as on the role of muscle architecture and neural factors in sled training; (c) analyze the effects of increasing sled loads during acceleration and maximum velocity phases on contact and flight phases, while concomitantly examining kinetic, kinematic, and neuromuscular aspects, because all these factors affect each other and cannot be properly understood in isolation.
... Resisted sprint training (RST) with sled towing is commonly used by practitioners in soccer and other team sports, which, in turn, has led to an increased number of studies on this topic. [4][5][6] Nevertheless, there are important controversies regarding the optimal magnitude of sled loads to be used during RST as several studies recommend a limit of 20% of body mass (BM), 4,6 whereas recent investigations recommended the utilization of heavier loads (ie, 50%-90% BM) to increase horizontal force production and, therefore, mechanical efficiency during acceleration efforts. 5,7,8 This theoretical discussion has crucial implications for the prescription of RST, and researchers are currently engaged in efforts to better evaluate and understand the actual effects of using different sled loading conditions. ...
... Resisted sprint training (RST) with sled towing is commonly used by practitioners in soccer and other team sports, which, in turn, has led to an increased number of studies on this topic. [4][5][6] Nevertheless, there are important controversies regarding the optimal magnitude of sled loads to be used during RST as several studies recommend a limit of 20% of body mass (BM), 4,6 whereas recent investigations recommended the utilization of heavier loads (ie, 50%-90% BM) to increase horizontal force production and, therefore, mechanical efficiency during acceleration efforts. 5,7,8 This theoretical discussion has crucial implications for the prescription of RST, and researchers are currently engaged in efforts to better evaluate and understand the actual effects of using different sled loading conditions. ...
... 5,7,8 This theoretical discussion has crucial implications for the prescription of RST, and researchers are currently engaged in efforts to better evaluate and understand the actual effects of using different sled loading conditions. [4][5][6][7][8][9][10] Undoubtedly, these questions remain to be addressed and require further investigation. ...
Purpose:
We examined the effects of two 8-week resisted-sprint training programs under different magnitudes of velocity loss (VL) on the speed-related performance of highly trained soccer players.
Methods:
Twenty-one soccer players (age: 25.9 [5.4] y) were randomly assigned to 1 of 2 groups: (1) the "moderate-load group," players who trained with sled loads that induced 15%VL relative to unloaded sprint velocity (n = 11); and (2) the "heavy-load group," players who trained with sled loads that induced 40% VL relative to unloaded sprint velocity (n = 10). Linear sprint (10 m), curve sprint, change-of-direction speed, resisted-sprint performance at 15% VL and 40% VL, and vertical jumping ability were tested pretraining and posttraining. A 2-way repeated-measures analysis of variance was used to test for differences between groups. In addition, percentage changes were calculated for speed-related abilities and compared with their respective coefficients of variation to determine whether individual changes in performance were greater than the test variance (ie, "true change").
Results:
A main effect of time was detected for 10-m sprint, curve sprint, change-of-direction speed, and 15% VL and 40% VL resisted-sprint times, with significant decreases in sprint times (P = .003, P = .004, P = .05, P = .036, and P = .019, respectively). Jump variables did not change significantly over time. There were no group-by-time interactions for any tested variable (P > .05), but the "true change" analysis revealed meaningful individual changes in both groups.
Conclusions:
Both moderate- and heavy-sled loading conditions may optimize the development of speed-related abilities in highly trained soccer players. Nevertheless, resisted-sprint training responses may differ meaningfully when assessed on an individual basis.
... During this sprint-specific training method, athletes execute sprints as fast as possible while resistance is added; a sled or vest is the most used equipment (Fernández-Galván et al., 2022). Although resisted training with a loaded sled seems to provide benefits in early acceleration (Alcaraz et al., 2018), the load that provides the greatest positive adaptations remains a controversial parameter (Petrakos et al., 2016;Zabaloy et al., 2023). Studies have proposed training at maximal power in resisted sprinting based on the optimal load determination . ...
... The sled sprint groups from the included studies prescribed loading as either absolute load (kg), relative to body mass (% BM) or based on velocity loss (% VL) ( Table 3). Classifications of loading were based on the system used by Zabaloy et al. [56] and are as follows: low (0-20% BM or 2.5-10% VL); moderate (> 21-50% BM or > 10 to < 30% VL), heavy (> 50-80% BM or 30 to < 50% VL), very heavy (≥ 80% BM or ≥ 50% VL). The results of the meta-regression are found in Fig. 4, Tables 4, 5 and the ESM S12 and S13. ...
Background
Two specific sprint training methods that are present to varying degrees in research and practice are combined uphill–downhill sprinting (UDS) and resisted sprint training methods (RS). Both methods seem to improve sprint performance, but to the author’s knowledge a comparison does not exist investigating the differences between the two training protocols and traditional sprinting.
Objective
The present systematic review and meta-analysis investigated sprint performance changes between combined uphill–downhill sprinting and resisted sprinting methods (sleds, cables/bands, vests, uphill) and how these compared with traditional sprinting.
Methods
A literature search was performed on 19 December 2022, in the databases PubMed, SPORTDiscus, Web of Science and SCOPUS, which from 22 studies yielded a total of 24 eligible groups (UDS, n = 6; RS, n = 18). Studies that measured sprint performance, had a traditional sprinting control, and used either training intervention in healthy individuals of any age for ≥ 4 weeks were eligible for the meta-analysis. The change in sprint performance from baseline to post intervention was compared between the interventions and their traditional sprinting control group. Outcomes were expressed as standardized mean differences (SMD).
Results
The standardized changes in sprint performance between intervention groups and traditional-sprinting controls (negative in favour of intervention, positive in favour of traditional sprint) and 95% confidence interval (CI) were as follows: small for UDS (SMD − 0.41 [− 0.79, − 0.03]; p = 0.03), trivial for RS (SMD − 0.14 [− 0.36, 0.07]; p = 0.19).
Conclusion
Combined uphill–downhill sprinting was more effective than traditional sprinting, while resisted sprinting was not. It appears that resisted sprint interventions do not increase sprint performance any more than traditional sprinting. Subgroup analysis and meta-regression appear to show differences between sled loads and possible differences across distances tested. The results of this review and meta-analysis seem to warrant further investigations into the possibility that UDS may be a superior sprint training method to resisted and traditional sprinting.
... Loads beyond 3.628 kg were not tested in this study. A review by Zabaloy et al. (4) indicated that applying too high of a load during RST became counterproductive, as the athlete exhibited detrimental changes in sprint technique, such as "marching," instead of normal propulsive sprinting mechanics. However, it is unclear whether the long-term effects of heavy RST training on unresisted sprinting techniques are negative. ...
Sport performance coaches use a range of modalities to apply a horizontal force ( F h ) to athletes during resisted sprint training (RST). These modalities include parachutes, weighted vests, pulley devices, motored tethered devices, and, most notably, weighted sleds. Despite the widespread use of these devices, the resistance forces of the pulley devices have not been evaluated for reliability and accuracy. Therefore, the primary aim of this study is to quantify the F h of a commercially available pulley device (EXER-GENIE®) and determine how resistance force is related to the load settings on the device. The secondary aim is to identify the differences in the F h values between three EXER-GENIE® devices that use 36 m and 60 m ropes. The F h values in the Newtons (N) of the three EXER-GENIE® devices were analyzed using a motorized winch, a lead acid battery, and an S-beam load cell. Four 10 s winch-driven trials were performed using 15 different EXER-GENIE® loads, ranging from 0.028 kg to 3.628 kg, employing two different 36 m devices and one 60 m device. The mean ± standard deviation for F h was reported across the four trials for each load setting. All devices produced similar F h values across lighter load settings (loads ≤0.141 kg). However, at heavier loads (loads ≥0.226 kg), the 60 m device had F h values 50–85 N greater than those of the 36 m device. The coefficient of variation across the four trials was extremely high at light loads but sharply decreased to <10% at heavy loads. Absolute reliability was high for each device [intraclass correlation coefficient (ICC) = 0.99]. A regression analysis for F h values and EXER-GENIE® load indicated a strong positive relationship between load and F h values across all devices ( R 2 = 0.96–0.99). Caution should be exercised when using identical loads on the different-length pulley devices, as the 60 m device produced greater F h values than the 36 m devices at load settings higher than 0.226 kg. These results can provide coaches and practitioners with a better understanding of the magnitude of resistance that is applied when prescribing EXER-GENIE® devices for higher training loads.
... Maximal sprinting speed (MSS) is an essential component of success in many sports [1][2][3][4][5][6]. Therefore, the best training methods to improve sprint performance are of interest to many strength and conditioning coaches and scientists [7][8][9][10][11]. Valid and reliable MSS measurements are critical for the effective monitoring of performance and depend on standardized procedures and the accuracy of devices. ...
Background: Maximal sprinting speed (MSS) is an essential component of success in many sports. Currently, many systems are used to accurately evaluate athletes’ MSS, including laser or radar guns, single- or dual-beam photocells, high-speed cameras, and high-frequency global positioning systems. However, the cost of these devices may be an obstacle to their implementation into practice. The least expensive but most likely less accurate alternative method of MSS evaluation is the hand-held time measurement of a 30m flying-start sprint. Therefore, the aim of the study was to assess the concurrent validity and inter-rater reliability o the hand-held method of MSS measurement. Materials and Methods: The study involved 3 experienced raters and 18 amateur runners. Runners performed 2-3 trials of the 30m maximal flying-start sprint. In total, 40 observations were collected. Each sprint time was measured simultaneously by raters using a hand-held stopwatch and an electronic timing system. Criterion validity (hand-held vs. electronic timing) was assessed using linear regression analysis. Inter-rater reliability between hand-held timers was evaluated using interclass correlation coefficients (ICCs), standard error of measurement (SEM), and minimal detectable change (MDC). Results: Results showed that single and average hand-held methods are affected by -0.17 to -0.07m·s-1 (-2.5 to -1.6%) and -0.12m·s- 1 (-1.7%) errors, respectively. Linear regression analysis parameters (free parameter not statistically significant, directional coefficient 0.994-1.057, standard error of estimation 0.073-0.125, R2 0.981-0.994) indicated statistically excellent absolute agreement between a hand-held (single and average) and electronic timing. ICCs of 0.980-0.994, SEM of 0.12m·s-1 (1.87%), and MDC of 0.34m·s-1 (5.18%) indicated statistically excellent absolute agreement and consistency for single and average measurements between hand-held timers. Conclusion: The proposed manual method of MSS measurement underestimates athletes’ speed performance. Moreover, the hand-held 30m flying-start sprint time measurement is affected by a 2% error, and a minimum 5% time change in an individual athlete demonstrates that the change is not simply attributable to measurement error.
On behalf of the Strength and Conditioning Society (SCS) and the Nucleus of High Performance in Sport (NAR), we are pleased to present the abstracts of the SCS 5th Annual Conference, which, for the first time, took place outside of Europe. The event was held at NAR’s state-of-the-art facilities in São Paulo, Brazil, on 3–5 November 2022, and comprised several invited sessions from international and national speakers on a variety of topics related to strength and conditioning practices and their application to health, injury prevention and sports performance. These included strength training in high-performance sports and older adults, sleep and recovery in elite athletes, performance optimization of the female athlete, high-intensity interval training, velocity-based resistance training, and running and cycling biomechanics, among others. The Conference also included different practical workshops conducted by renowned academics and practitioners on post-competition recovery strategies, plyometric training, hamstring strain injuries in soccer, and resisted sprint training. Finally, the event disseminated up-to-date strength and conditioning research by providing practitioners and researchers with the opportunity to present their most recent findings. In this regard, all abstracts of the communications presented at the SCS 5th Annual Conference can be found in this Conference Report.
The study aim was to compare kinetics and kinematics of two, lower-body free-weight exercises, calculated from concentric and propulsion sub-phases, across multiple loads. Sixteen strength trained men performed back squat one-repetition maximum tests (1RM) (visit 1), followed by two incremental back squat and jump squat protocols (visit 2) (loads = 0% and 30-60%, back squat 1RM). Concentric and propulsion phase force-time-displacement characteristics were derived from force-plate-data and compared via analysis of variance and Hedges g effect sizes. Intra-session reliability was calculated via intraclass correlation coefficient (ICC) and coefficient of variation (CV). All dependent variables met acceptable reliability (ICC > 0.7; CV < 10%). Statistically significant three-way interactions (load phase exercise) and two-way main effects (phase exercise) were observed for mean force, velocity (30-60% 1RM), power, work, displacement, and duration (0%, 30-50% 1RM) (p < 0.05). A significant two-way interaction (load exercise) was observed for impulse (p < 0.001). Jump squat velocity (g = 0.94-3.80), impulse (g = 1.98-3.21), power (g = 0.84-2.93) and work (g = 1.09-3.56) were significantly larger across concentric and propulsion phases, as well as mean propulsion force (g = 0.30-1.06) performed over all loads (p < 0.001). No statistically significant differences were observed for mean concentric force. Statistically longer durations (g = 0.38-1.54) and larger displacements (g = 2.03-4.40) were evident for all loads and both sub-phases (p < 0.05). Ballistic, lower-body exercise produces greater kinetic and kinematic outputs than non-ballistic equivalents, irrespective of phase determination. Practitioners should therefore utilize ballistic methods when prescribing or testing lower-body exercises to maximize athlete’s force-time-displacement characteristics.
Purpose:
Neuromuscular fatigue is considered to be important in the etiology of hamstring strain injuries in football. Fatigue is assumed to lead to decreases in hamstring contractile strength and changes in sprinting kinematics, which would increase hamstring strain injury risk. Therefore, the aim was to examine the effects of football-specific fatigue on hamstring maximal voluntary torque (MVT) and rate of torque development (RTD), in relation to alterations in sprinting kinematics.
Methods:
Ten amateur football players executed a 90-minute running based football match simulation. Before and after every 15 minutes of simulated play MVT and RTD of the hamstrings were obtained in addition to the performance and lower body kinematics during a 20 m maximal sprint. Linear mixed models and repeated measurement correlations were used to assess changes over time and common within participant associations between hamstring contractile properties and peak knee extension during the final part of the swing phase, peak hip flexion, peak combined knee extension and hip flexion, and peak joint angular velocities, respectively.
Results:
Hamstring MVT and sprint performance were significantly reduced by 7.5% and 14.3% at the end of the football match simulation. Unexpectedly, there were no indications for reductions in RTD when MVT-decrease was considered. Decreases in hamstring MVT were significantly correlated to decreases in peak knee angle (R = 0.342) and to increases in the peak combined angle (R = -0.251).
Conclusions:
During a football match simulation, maximal voluntary isometric hamstring torque declines. This decline is related to greater peak knee extension and peak combined angle during sprint running, which indicates a reduced capacity of the hamstrings to decelerate the lower leg during sprint running with fatigue.
The aim of this study was to determine the architectural, eccentric strength and sprinting adaptations following a hip‐dominant flywheel (FLY) or Nordic hamstring exercise (NHE) intervention in Australian footballers. Twenty‐seven male athletes were randomised to FLY (n=13) or NHE (n=14) training across a 39‐week period (inclusive of pre‐season and in‐season). Biceps femoris long head (BFlh) architecture was assessed throughout. Eccentric hamstring strength and 40m sprint times (with force‐velocity profiling) were assessed at baseline, end of pre‐season and following the intervention. After the intervention, BFlh fascicle length was longer in both groups compared to baseline (FLY: 1.16cm, 95%CI: 0.66 to 1.66cm, d=1.99, p<0.001; NHE: 1.08cm, 95%CI: 95%CI 0.54 to 1.61cm, d=1.73, p<0.001). Both groups also increased their eccentric strength (FLY: mean change 82N, 95%CI 12 to 152N, d=1.34, p=0.026; NHE: mean change 97N, 95%CI 47 to 146N, d=1.77, p=0.001). After pre‐season, the NHE group improved their 5m sprint time by 3.5% (±1.2%) and were 3.7% (±1.4%) and 2.0% (±0.5%) faster than the FLY group across 5m and 10m, respectively. At the end of pre‐season, the FLY group improved maximal velocity by 3.4% (±1.4%) and improved horizontal force production by 9.7% in‐season (±2.2%). Both a FLY and NHE intervention increase BFlh fascicle length and eccentric strength in Australian Footballers. An NHE intervention led to enhanced acceleration capacity. FLY intervention was suggested to improve maximal sprint velocity and horizontal force production, without changes in sprint times. These findings have implications for hamstring injury prevention but also programs aimed at improving sprint performance.
Purpose
Neural drive and contractile properties are well-defined physiological determinants of explosive strength, the influence of muscle architecture and related morphology on explosive strength is poorly understood. The aim of this study was to examine the relationships between Quadriceps muscle architecture (pennation angle [Θ P ] and fascicle length [F L ]) and size (e.g., volume; Q VOL ), as well as patellar tendon moment arm (PT MA ) with voluntary and evoked explosive knee extension torque in 53 recreationally active young men.
Method
Following familiarisation, explosive voluntary torque at 50 ms intervals from torque onset (T 50 , T 100 , T 150 ), evoked octet at 50 ms (8 pulses at 300-Hz; evoked T 50 ), as well as maximum voluntary torque, were assessed on two occasions with isometric dynamometry. B-mode ultrasound was used to assess Θ P and F L at ten sites throughout the quadriceps (2–3 sites) per constituent muscle. Muscle size (Q VOL ) and PT MA were quantified using 1.5 T MRI.
Result
There were no relationships with absolute early phase explosive voluntary torque (≤ 50 ms), but θ P (weak), Q VOL (moderate to strong) and PT MA (weak) were related to late phase explosive voluntary torque (≥ 100 ms). Regression analysis revealed only Q VOL was an independent variable contributing to the variance in T 100 (34%) and T 150 (54%). Evoked T 50 was also related to Q VOL and θ P. When explosive strength was expressed relative to MVT there were no relationships observed.
Conclusion
It is likely that the weak associations of θ P and PT MA with late phase explosive voluntary torque was via their association with MVT/Q VOL rather than as a direct determinant.
Background
Sprint performance is an essential skill to target within soccer, which can be likely achieved with a variety of methods, including different on-field training options. One such method could be heavy resisted sprint training. However, the effects of such overload on sprint performance and the related kinetic changes are unknown in a professional setting. Another unknown factor is whether violating kinematic specificity via heavy resistance will lead to changes in unloaded sprinting kinematics. We investigated whether heavy resisted sled training (HS) affects sprint performance, kinetics, sagittal plane kinematics, and spatiotemporal parameters in professional male soccer players.
Methods
After familiarization, a nine-week training protocol and a two-week taper was completed with sprint performance and force-velocity (FV) profiles compared before and after. Out of the two recruited homogenous soccer teams ( N = 32, age: 24.1 ± 5.1 years: height: 180 ± 10 cm; body-mass: 76.7 ± 7.7 kg, 30-m split-time: 4.63 ± 0.13 s), one was used as a control group continuing training as normal with no systematic acceleration training (CON, N = 13), while the intervention team was matched into two HS subgroups based on their sprint performance. Subgroup one trained with a resistance that induced a 60% velocity decrement from maximal velocity ( N = 10, HS60%) and subgroup two used a 50% velocity decrement resistance ( N = 9, HS50%) based on individual load-velocity profiles.
Results
Both heavy resistance subgroups improved significantly all 10–30-m split times ( p < 0.05, d = − 1.25; −0.62). Post-hoc analysis showed that HS50% improved significantly more compared to CON in 0–10-m split-time ( d = 1.03) and peak power ( d = 1.16). Initial maximal theoretical horizontal force capacity (F0) and sprint FV-sprint profile properties showed a significant moderate relationship with F0 adaptation potential ( p < 0.05). No significant differences in sprinting kinematics or spatiotemporal variables were observed that remained under the between-session minimal detectable change.
Conclusion
With appropriate coaching, heavy resisted sprint training could be one pragmatic option to assist improvements in sprint performance without adverse changes in sprinting kinematics in professional soccer players. Assessing each player’s initial individual sprint FV-profile may assist in predicting adaptation potential. More studies are needed that compare heavy resisted sprinting in randomized conditions.
Background
Short-sprint (≤ 20 m) performance is an important quality for success in the football codes. Therefore, developing an evidence base for understanding training methods to enhance short-sprint performance is key for practitioners. However, current systematic reviews are limited by (1) a lack of focus on football code athletes, (2) a lack of consideration of all training modalities and (3) a failure to account for the normal training practices undertaken by intervention groups within their analysis. Therefore, this review aimed to (1) conduct a systematic review of the scientific literature evaluating training interventions upon short-sprint performance within football code athletes, (2) undertake a meta-analysis to assess the magnitude of change of sport-sprint performance following training interventions and (3) identify how moderator variables affect the training response.
Methods
A systematic search of electronic databases was conducted. A random-effects meta-analysis was performed to establish standardised mean difference with 95% confidence intervals. This identified the magnitude and direction of the individual training effects of intervention subgroups (primary, secondary, combined-specific, tertiary and combined training methods) on short-sprint performance while considering moderator variables (i.e., football code, sex, age, playing standard, phase of season).
Results
121 studies met the inclusion criteria, totalling 3419 athletes. Significant improvements (small-large) were found between pre- and post-training in short-sprint performance for the combined, secondary, tertiary and combined-specific training methods. No significant effect was found for primary or sport only training. No individual mode was found to be the most effective. Between-subgroup analysis identified that football code, age, playing standard and phase of season all moderated the overall magnitude of training effects.
Conclusions
This review provides the largest systematic review and meta-analysis of short-sprint performance development methods and the only one to assess football code athletes exclusively. Practitioners can apply combined, secondary and tertiary training methods to improve short-sprint performance within football code athletes. The application of sport only and primary methods does not appear to improve short-sprint performance. Regardless of the population characteristics, short-sprint performance can be enhanced by increasing either or both the magnitude and the orientation of force an athlete can generate in the sprinting action.
Acknowledgments We would like to acknowledge the help of the clubs and participants who took part in the current study. Abstract The purpose of this study was to investigate the interval in which male rugby union players reach maximum speed in a 50 m sprint according to age categories and playing positions. This study also aimed to establish the optimal distance for the assessment of sprint speed and to compare the differences in anthropometrics, sprint and sprint momentum according to the age and playing position. Three hundred amateur rugby players performed anthropometric and physical fitness tests (10, 20, 30, 40 and 50 m sprint times, acceleration, velocity, and sprint momentum) during the in-season period. Participants from different age categories (under 14's (U14), under 16's (U16), under 18's (U18) and Seniors) and positions (forwards and backs) volunteered to participate in this study. Results revealed that most of the U14 and U16 players (58.2% and 55.3%, respectively) reached maximum speed in the interval between 20 and 30 m with lower sprint speed than U18 players and Seniors (44% and 49%, respectively). Comparisons between each interval showed significant differences for all U14 and U16 forwards, suggesting the fastest interval was between 20-30 m. No significative differences were found for U16 backs, U18 and Seniors, between sprint times in the 20-30 m and 30-40 m intervals. In addition, between-group comparisons, demonstrated significant (p < 0.001) differences in U14 when compared to U16, U18 and Seniors in anthropometric variables, sprint times and sprint momentum. In conclusion, this study suggests that the optimal distance for the assessment of sprint speed of rugby players is 30 m and that body mass, sprint momentum and sprint speed clearly discriminate between players of different age categories and playing positions.
During high-speed running, lower limb vertical velocity at touchdown has been cited as a critical factor needed to generate large vertical forces. Additionally, greater leg angular velocity has also been correlated with increased running speeds. However, the association between these factors has not been comprehensively investigated across faster running speeds. Therefore, this investigation aimed to evaluate the relationship between running speed, thigh angular motion, and vertical force determinants. It was hypothesized that thigh angular velocity would demonstrate a positive linear relationship with both running speed and lower limb vertical velocity at touchdown. A total of 40 subjects (20 males, 20 females) from various athletic backgrounds volunteered and completed 40 m running trials across a range of sub-maximal and maximal running speeds during one test session. Linear and angular kinematic data were collected from 31-39 m. The results supported the hypotheses, as across all subjects and trials (range of speeds: 3.1-10.0 m s-1), measures of thigh angular velocity demonstrated a strong positive linear correlation to speed (all R
2
>0.70, p<0.0001) and lower limb vertical velocity at touchdown (all R
2
=0.75, p<0.0001). These findings suggest thigh angular velocity is strongly related to running speed and lower limb impact kinematics associated with vertical force application.
The study aimed to evaluate the effects of 1 vs. 2 sessions per week of equal-volume sprint training on explosive, high-intensity and endurance-intensive performances among young soccer players. Thirtysix young male soccer players were randomly divided into 2 experimental groups that performed either a single weekly sprint training session (ST1, n = 18, age: 17.2 ± 0.8 years) or two weekly sprint training sessions (ST2, n = 18; age: 17.1 ± 0.9 years) of equal weekly and total volume, in addition to their regular soccer training
regimen. Linear sprinting (10 m, 20 m, 30 m, and flying 10 m), T-test agility, countermovement jump (CMJ) and maximal oxygen consumption were assessed one week before (T1), in the middle (T2) and immediately after the 10 weeks of training (T3). A large magnitude and statistically significant main effect for time was found in all the assessed variables after both training interventions (all p < 0.001; ES ≥ 0.80). No main effect was observed between the 2 groups at any time in linear sprinting, T-test or CMJ test (p > 0.05; ES < 0.20). A significant interaction effect (F = 4.05; p = 0.04, ES = 0.21) was found for maximal oxygen consumption with ST2 inducing better performance than ST1 (p = 0.001; ES = 1.11). Our findings suggested that the two sprint training frequencies were effective in enhancing explosive, high-intensity and endurance-intensive performances. However, it is recommended for coaches and fitness coaches to use a biweekly sprint training modality as it was found to be more effective in improving endurance-intensive performance.
Cahill, MJ, Oliver, JL, Cronin, JB, Clark, K, Cross, MR, Lloyd, RS, and Lee, JE. Influence of resisted sled-pull training on the sprint force-velocity profile of male high-school athletes. J Strength Cond Res XX(X): 000-000, 2020-Although resisted sled towing is a commonly used method of sprint-specific training, little uniformity exists around training guidelines for practitioners. The aim of this study was to assess the effectiveness of unresisted and resisted sled-pull training across multiple loads. Fifty-three male high-school athletes were assigned to an unresisted (n 5 12) or 1 of 3 resisted groups: light (n 5 15), moderate (n 5 14), and heavy (n 5 12) corresponding to loads of 44 6 4 %BM, 89 6 8 %BM, and 133 6 12 %BM that caused a 25, 50, and 75% velocity decrement in maximum sprint speed, respectively. All subjects performed 2 sled-pull training sessions twice weekly for 8 weeks. Split times of 5, 10, and 20 m improved across all resisted groups (d 5 0.40-1.04, p , 0.01) but did not improve with unresisted sprinting. However, the magnitude of the gains increased most within the heavy group, with the greatest improvement observed over the first 10 m (d $ 1.04). Changes in preintervention to postintervention force-velocity profiles were specific to the loading prescribed during training. Specifically, F 0 increased most in moderate to heavy groups (d 5 1.08-1.19); Vmax significantly decreased in the heavy group but increased in the unresisted group (d 5 012-0.44); whereas, Pmax increased across all resisted groups (d 5 0.39-1.03). The results of this study suggest that the greatest gains in short distance sprint performance, especially initial acceleration, are achieved using much heavier sled loads than previously studied in young athletes.
The aims of this study were to compare the outcomes and provide reference data for a set of barbell mechanical parameters collected via a linear velocity transducer in 126 male sprinters (n=62), rugby (n=32), and soccer players (n=32). Bar-velocity, bar-force, and bar-power outputs were assessed in the jump-squat exercise with jump-squat height determined from bar-peak velocity. The test started at a load of 40% of the athletes’ body mass (BM) and a load of 10% of BM was gradually added until a clear decrement in the bar-power was observed. Comparisons of bar-variables among the three sports were performed using a one-way analysis of variance. Relative measures of bar-velocity, -force, and -power, and jump-squat height were significantly higher in sprinters than in rugby (difference ranging between 5 and 35%) and soccer (difference ranging between 5 and 60%) players across all loads (40-110% of BM). Rugby players exhibited higher absolute bar-power (mean difference = 22%) and bar-force (mean difference = 16%) values than soccer players, but these differences no longer existed when the data were adjusted for BM (mean difference = 2.5%). Sprinters optimized their bar-power production at significantly greater relative loads (% BM) than rugby (mean difference = 22%) and soccer players (mean difference = 25%); nonetheless, all groups generated their maximum bar-power outputs at similar bar-velocities. For the first time, we provided reference values for the jump-squat exercise for three different bar-velocity measures (i.e., mean, mean propulsive-, and peak-velocity) for sprinters, rugby, and soccer players, over a wide range of relative loads. Practitioners can use these reference values to monitor their athletes and compare them with top-level sprinters and team-sport players.
The purpose of this study was to identify the kinematic characteristics of resisted sled sprinting under different loading conditions (0%, 10%, 20% and 30% velocity decrement (Vdec)) and in different sporting populations. Thirty-three healthy athletes (Sprinters n=10; Invasion team sport athletes n=23) were recruited and completed 3 days of testing. Kinematics were captured with high-speed cameras and processed using Dartfish Software. Loads of 20% and 30% Vdec resulted in a significant increase in trunk lean relative to unloaded sprinting, during both acceleration and maximum velocity phases, with no difference between groups (sprint & team sport athletes). This increase in trunk lean with load (20% and 30% Vdec) appeared to prevent athletes transitioning into upright maximum velocity mechanics, and therefore extended the distance of the acceleration phase. The trunk lean increase was related to the heavy loads and athletes were not able to reach mechanics that were truly reflective of maximum velocity (maxV) sprinting. However, heavy loading extended the distance over which it is possible to train acceleration.
We tested the hypothesis that the degree of adaptation to highly focused sprint training at opposite ends of the sprint Force-Velocity (FV) spectrum would be
associated with initial sprint FV-profile in rugby athletes. Training-induced changes
in sprint FV-profiles were computed before and after an 8-week in-season resisted
or assisted sprint training protocol, including a 3-week taper. Professional male
rugby players (age: 18.9 ± 1.0 years; body-height: 1.9 ± 0.0 m; body-mass: 88.3 ±
10.0 kg) were divided into two groups based on their initial sprint FV-profiles: 1)
heavy sled training (RESISTED, N = 9, velocity loss 70-80%), and 2) assisted
acceleration training (ASSISTED, N = 12, velocity increase 5-10%). A total of 16
athletes were able to finish all required measurements and sessions. According to
the hypothesis, a significant correlation was found between initial sprint FV-profile
and relative change in sprint FV-profile (RESISTED: r = -0.95, p<0.01, ASSISTED:
r = -0.79, p<0.01). This study showed that initial FV-properties influence the degree
of mechanical response when training at different ends of the FV-spectrum.
Practitioners should consider utilizing the sprint FV-profile to improve the individual
effectiveness of resisted and assisted sprint training programs in high-level rugby
athletes.
Isolated injury to the long head of biceps femoris is the most common type of acute hamstring strain injury (HSI). However, the precise hamstring injury mechanism (i.e., sprint-type) is still not well understood, and research is inconclusive as to which phase in the running cycle HSI risk is the greatest. Since detailed information relating to hamstring muscle function during sprint running cannot be obtained in vivo in humans, the findings of studies investigating HSI mechanisms are based on modeling that requires assumptions to be made based on extrapolations from anatomical and biomechanical investigations. As it is extremely difficult to account for all aspects of muscle-tendon tissues that influence function during high-intensity running actions, much of this complexity is not included in these models. Furthermore, the majority of analyses do not consider the influence of prior activity or muscular fatigue on kinematics, kinetics and muscle activation during sprinting. Yet, it has been shown that fatigue can lead to alterations in neuromuscular coordination patterns that could potentially increase injury risk. The present critical review will evaluate the current evidence on hamstring injury mechanism(s) during high-intensity running and discuss the interactions between fatigue and hamstring muscle activation and function.
This study aimed to investigate the relationship between a specific isometric-strength sprint test (SIST) and unresisted maximum velocity (Vmax), sprint times across different loading conditions, and the velocity loss (Vloss) loads required to achieve each intended Vloss condition during resisted sprint training (RST) in rugby players. Additionally, the investigation examined the relationship between strength in the back-squat one-repetition maximum (1RM-SQ) as well as isometric squat (ISQT), jumps, and sprint performance variables. Twenty (n = 20) male amateur rugby players performed, on two separate occasions, a structural multiple-joint assessment of jumps, strength, and sprint performance. Interestingly, SIST revealed moderate correlations (r = 0.453 to 0.681; p < 0.05) between 1RM-SQ and ISQT. The SIST rel (relative to body mass), but not SIST, used in the present study showed moderate correlations (r = 0.508 to 0.675; p < 0.05) with the loads needed to reach 10%, 30%, and 50% of Vloss during RST. The SIST rel that measures resultant force application in a more sprint-related position explains much of the individual response of each athlete during sprinting towing a sled and can also be used to prescribe and quantify loads in the RST in a more objective and individual manner.
Despite a voluminous body of research devoted to sprint training, our understanding of the training process leading to world-class sprint performance is limited. The objective of this review is to integrate scientific and best practice literature regarding the training and development of elite sprint performance. Sprint performance is heavily dependent upon genetic traits, and the annual within-athlete performance differences are lower than the typical variation, the smallest worthwhile change and the influence of external conditions such as wind, monitoring methodologies, etc. Still, key underlying determinants (e.g., power, technique and sprint-specific endurance) are trainable. In this review, we describe how well-known training principles (progression, specificity, variation/periodization and individualization) and varying training methods (e.g., sprinting/running, technical training, strength/power, plyometric training) are used in a sprint-training context. Indeed, there is a considerable gap between science and best practice in how training principles and methods are applied. While the vast majority of sprint-related studies are performed on young team-sport athletes and focus on brief sprints with maximal intensity and short recoveries, elite sprinters perform sprinting/running over a broad range of distances and with varying intensity and recovery periods. Within best practice there is a stronger link between choice of training component (i.e., modality, duration, intensity, recovery, session rate) and the intended purpose of the training session compared to the “one-size-fits-all” approach in scientific literature. This review provides a point of departure for scientists and practitioners regarding the training and development of elite sprint performance and can serve as a position statement for outlining state-of-the-art sprint training recommendations and for generation of new hypotheses to be tested in future research.
The aim of the present study was to investigate the influence of maximum strength and power levels on change of direction (COD) ability and deficit in elite soccer and rugby players. Seventy-eight elite athletes (soccer, n = 46; rugby, n = 32) performed the following assessments: squat and countermovement jumps (SJ and CMJ), 1 repetition-maximum in the half-squat exercise (HS 1RM), peak power (PP) in the jump-squat exercise, and 20-m linear sprint and Zigzag COD tests. Utilizing the median split analysis, athletes were divided into two groups according to their HS 1RM and PP JS (e.g., higher and lower HS 1RM and higher and lower PP JS). The magnitude-based inference method was used to analyze the differences between groups in the physical performance tests. Athletes in the high strength and power groups outperformed their weaker and less powerful counterparts in all speed and power measurements (i.e., 5-, 10-, and 20-m sprint velocity, Zigzag COD speed, and CMJ and SJ height). In contrast, stronger and more powerful athletes displayed greater COD deficits. The present data indicate that players with superior strength-power capacity tend to be less efficient at changing direction, relative to maximum sprinting speed, despite being faster in linear trajectories. From these results, it appears that current strength and power training practices in team-sports are potentially not the “most appropriate” to increase the aptitude of a given athlete to efficiently utilize his/her neuromuscular abilities during COD maneuvers. Nevertheless, it remains unknown whether more multifaceted training programs are effective in decreasing COD deficits.
Resisted sprinting in the form of both sled pushing and pulling is a popular training method to improve speed capability, although research has been biased towards investigating the effects of sled pulling. Practitioners need to understand whether the sled push and pull offer differential training effects, and hence their utility in influencing sprint kinematics and kinetics for targeted adaptation. Furthermore, there are a number of recent developments in loading and assessment that warrant discussion, given the impact of these techniques on understanding the load-velocity relationship and optimizing horizontal power output. Finally, some thoughts regarding load prescription are shared with the reader.
This study analysed the acute mechanical and metabolic responses to a sprint training session focused on maintaining maximal speed until a given speed loss was reached. Nine male high-level sprinters performed 60 m running sprints up to a 3% in speed loss with 6 min rests between sets. Mechanical responses (countermovement jump (CMJ) height and speed loss) and metabolic responses (blood lactate and ammonia concentrations) were measured pre-exercise and after each set was performed. Jump height loss showed almost perfect relationships with both lactate (r = 0.91) and ammonia (r = 0.91) concentrations. In addition, nearly perfect relationships were observed for each athlete between CMJ height loss and lactate (r = 0.93–0.99) and ammonia (r = 0.94–0.99). Very large correlations were found between speed loss and lactate (r = 0.83), and ammonia (r = 0.86) concentrations. Furthermore, close relationships were observed for each athlete between speed loss and lactate (r = 0.86–0.99), and ammonia (r = 0.88–0.98). These results suggest that the CMJ test may allow more accurate setting of training loads in sprint training sessions, by using an individualised sprint dose based on mechanical and physiological responses rather than a standard fixed number of sprints for all athletes.
The initial steps of a sprint are important in team sports, such as rugby, where there is an inherent requirement to maximally accelerate over short distances. Current understanding of sprint acceleration technique is primarily based on data from track and field sprinters, although whether this information is transferable to athletes such as rugby players is unclear, due to differing ecological constraints. Sagittal plane video data were collected (240 Hz) and manually digitised to calculate the kinematics of professional rugby forwards (n = 15) and backs (n = 15), and sprinters (n = 18; 100 m personal best range = 9.96–11.33 s) during the first three steps of three maximal sprint accelerations. Using a between-group research design, differences between groups were determined using magnitude-based inferences, and within-group relationships between technique variables and initial sprint acceleration performance were established using correlation. Substantial between-group differences were observed in multiple variables. Only one variable, toe-off distance, differed between groups (d = −0.42 to −2.62) and also demonstrated meaningful relationships with sprint performance within all three groups (r = −0.44 to −0.58), whereby a stance foot position more posterior relative to the centre of mass at toe-off was associated with better sprint performance. While toe-off distance appears to be an important technical feature for sprint acceleration performance in both sprinters and rugby players, caution should be applied to the direct transfer of other kinematic information from sprinters to inform the technical development of acceleration in team sports athletes.
Background:
Sprinting is key in the development and final results of competitions in a range of sport disciplines, both individual (e.g., athletics) and team sports. Resisted sled training (RST) might provide an effective training method to improve sprinting, in both the acceleration and the maximum-velocity phases. However, substantial discrepancies exist in the literature regarding the influence of training status and sled load prescription in relation to the specific components of sprint performance to be developed and the phase of sprint.
Objectives:
Our objectives were to review the state of the current literature on intervention studies that have analyzed the effects of RST on sprint performance in both the acceleration and the maximum-velocity phases in healthy athletes and to establish which RST load characteristics produce the largest improvements in sprint performance.
Methods:
We performed a literature search in PubMed, SPORTDiscus, and Web of Science up to and including 9 January 2018. Peer-reviewed studies were included if they met all the following eligibility criteria: (1) published in a scientific journal; (2) original experimental and longitudinal study; (3) participants were at least recreationally active and towed or pulled the sled while running at maximum intensity; (4) RST was one of the main training methods used; (5) studies identified the load of the sled, distance covered, and sprint time and/or sprint velocity for both baseline and post-training results; (6) sprint performance was measured using timing gates, radar gun, or stopwatch; (7) published in the English language; and (8) had a quality assessment score > 6 points.
Results:
A total of 2376 articles were found. After filtering procedures, only 13 studies were included in this meta-analysis. In the included studies, 32 RST groups and 15 control groups were analyzed for sprint time in the different phases and full sprint. Significant improvements were found between baseline and post-training in sprint performance in the acceleration phase (effect size [ES] 0.61; p = 0.0001; standardized mean difference [SMD] 0.57; 95% confidence interval [CI] - 0.85 to - 0.28) and full sprint (ES 0.36; p = 0.009; SMD 0.38; 95% CI - 0.67 to - 0.10). However, non-significant improvements were observed between pre- and post-test in sprint time in the maximum-velocity phase (ES 0.27; p = 0.25; SMD 0.18; 95% CI - 0.49 to 0.13). Furthermore, studies that included a control group found a non-significant improvement in participants in the RST group compared with the control group, independent of the analyzed phase.
Conclusions:
RST is an effective method to improve sprint performance, specifically in the early acceleration phase. However, it cannot be said that this method is more effective than the same training without overload. The effect of RST is greatest in recreationally active or trained men who practice team sports such as football or rugby. Moreover, the intensity (load) is not a determinant of sprint performance improvement, but the recommended volume is > 160 m per session, and approximately 2680 m per week, with a training frequency of two to three times per week, for at least 6 weeks. Finally, rigid surfaces appear to enhance the effect of RST on sprint performance.
Aims
In the current study we investigated the effects of resisted sprint training on sprinting performance and underlying mechanical parameters (force-velocity-power profile) based on two different training protocols: (i) loads that represented maximum power output (Lopt) and a 50% decrease in maximum unresisted sprinting velocity and (ii) lighter loads that represented a 10% decrease in maximum unresisted sprinting velocity, as drawn from previous research (L10).
Methods
Soccer [n = 15 male] and rugby [n = 21; 9 male and 12 female] club-level athletes were individually assessed for horizontal force-velocity and load-velocity profiles using a battery of resisted sprints, sled or robotic resistance respectively. Athletes then performed a 12-session resisted (10 × 20-m; and pre- post-profiling) sprint training intervention following the L10 or Lopt protocol.
Results
Both L10 and Lopt training protocols had minor effects on sprinting performance (average of -1.4 to -2.3% split-times respectively), and provided trivial, small and unclear changes in mechanical sprinting parameters. Unexpectedly, Lopt impacted velocity dominant variables to a greater degree than L10 (trivial benefit in maximum velocity; small increase in slope of the force-velocity relationship), while L10 improved force and power dominant metrics (trivial benefit in maximal power; small benefit in maximal effectiveness of ground force orientation).
Conclusions
Both resisted-sprint training protocols were likely to improve performance after a short training intervention in already sprint trained athletes. However, widely varied individualised results indicated that adaptations may be dependent on pre-training force-velocity characteristics.
Limited research has compared the physical qualities of adolescent rugby union (RU) players across differing playing standards. This study therefore compared the physical qualities of academy and school Under-18 RU players. One-hundred and eighty-four (professional regional academy, n = 55 school, n = 129) male RU players underwent a physical testing battery to quantify height, body mass, strength (bench press and pull-up), speed (10, 20 and 40 m), 10 m momentum (calculated; 10 m velocity * body mass) and a proxy measure of aerobic fitness (Yo-Yo Intermittent Recovery Test Level 1; IRTL1). The practical significance of differences between playing levels were assessed using magnitude-based inferences. Academy players were taller (very likely small), heavier (likely moderate) and stronger (bench press possibly large; pull-up plus body mass likely small) than school players. Academy players were faster than school players over 20 and 40 m (possibly and likely small), although differences in 10 m speed were not apparent (possibly trivial). Academy players displayed greater 10 m momentum (likely moderate) and greater IRTL1 performance (likely small) than school players. These findings suggest that body size, strength, running momentum, 40 m speed and aerobic fitness contribute to a higher playing standard in adolescent rugby union.
Resisted sprint training consists of performing overloaded sprints, which may produce greater effects than traditional sprint training. We compared a resisted sprint training with overload control versus an unresisted sprint training program on performance in soccer players. Eighteen elite athletes were randomly assigned to resisted (RST) or unresisted sprint training protocol (UR). Before and after a 6-week training period, sprinting ability, change of direction speed (COD), vertical jumps (SJ and CMJ), mean power (MP) and mean propulsive power (MPP) at distinct loads were assessed. Both groups improved sprinting ability at all distances evaluated (5m: UR = 8%, RST = 7%; 10m: UR = 5%, RST = 5%; 15m: UR = 4%, RST = 4%; 20m: UR = 3%, RST = 3%; 25m: UR = 2%, RST = 3%;), COD (UR = 6%; RST = 6%), SJ (UR = 15%; RST = 13%) and CMJ (UR = 15%; RST = 15%). Additionally, both groups increased MP and MPP at all loads evaluated. The between-group magnitude-based inference analysis demonstrated comparable improvement ("trivial" effect) in all variables tested. Finally, our findings support the effectiveness of a short-term training program involving squat jump exercise plus sprinting exercises to improve the performance of soccer players.
THIS COLUMN DISCUSSES TWO RELATED, BUT IMPORTANTLY DIFFERENT, APPROACHES TO ENHANCING POWER; ASSISTED AND RESISTED TRAINING. UNDERSTANDING BOTH MODALITIES ALLOWS THE STRENGTH AND CONDITIONING PROFESSIONAL TO DISCERN THE ROLE OF EACH IN ENHANCING JUMP AND SPRINT PERFORMANCE.
The aim of this study was to compare the effects of two different mixed training programs (optimum power load [OPL] + resisted sprints [RS] and OPL + vertical/horizontal plyometrics [PL]) on neuromuscular performance of elite soccer players during a short-term training preseason. Eighteen male professional soccer players took part in this study. The athletes were pair-matched in two training groups: OPL + RS and OPL + PL. Unloaded and resisted sprinting speeds at 5-, 10-, 20-, and 30-m, change of direction (COD) speed, and performance in the squat jump (SJ), countermovement jump (CMJ), and horizontal jump (HJ) were assessed pre- and post- a 5-week training period. Magnitude based inference with the effect sizes were used for data analysis. A possible increase in the SJ and CMJ heights and a likely increase in the HJ distance were observed in the OPL + PL group. Meaningful improvements were observed in the COD speed test for both training groups comparing pre- and post-measures. In both unloaded and resisted sprints, meaningful decreases were observed in the sprinting times for all distances tested. This study shows that a mixed training approach which comprises exercises and workloads able to produce positive adaptations in different phases of sprinting can be a very effective strategy in professional soccer players. Moreover, the possibility of combining optimum power loads with resisted sprints and plyometrics emerges as a novel and suitable option for coaches and sport scientists, due to the applicability and efficiency of this strength-power training approach.
Background:
The aim of the present systematic review was to profile soccer players' anthropometric, physiological, and physical attributes relative to different competitive levels, playing positions and age groups.
Methods:
The systematic search was conducted using different databases and according to the Population/Intervention or Exposure/Comparison/Outcome(s) [PICO] criteria.
Results:
The present review shows that the somatotype characteristics, percentage (%) of body fat, maximal oxygen uptake (VO2max), repeated sprint ability (RSA), running speed, strength, and muscular power of the lower limbs were the most powerful discriminators between male soccer players of different competitive levels, playing positions, and age groups. Specifically, higher VO2max, muscle strength, muscular power (vertical jump height), running speed (10-30 m) and agility, and lower % of body fat were identified in elite soccer players (higher level) compared to all other competitive levels (i.e., lowerlevel: subelite, amateur, recreational). As for the competitive level differences, higher VO2max, mean anaerobic power, RSA and sprint performances (5 to 20 m), and lower % of body fat and lower limbs' explosive capabilities (countermovement jump (CMJ) and squat jump (SJ)) were found in outfielders (forwards, midfielders, and defenders) as compared to goalkeepers, from a very youth age (8 years old). Concerning age related performance, it appears that physical performance increased significantly with age.
Conclusions:
These data, together with the fact that each position, age category, and playing level has a different physiological background in male soccer players, demonstrate that training programs should be individualized to each position, playing level and age category, as is already done with goalkeepers.
Purpose:
To understand how training periodization influences sprint performance and key step characteristics over an extended training period in an elite sprint training group.
Methods:
Four sprinters were studied during five months of training. Step velocities, step lengths and step frequencies were measured from video of the maximum velocity phase of training sprints. Bootstrapped mean values were calculated for each athlete for each session and 139 within-athlete, between-session comparisons were made with a repeated measures ANOVA.
Results:
As training progressed, a link in the changes in velocity and step frequency was maintained. There were 71 between-session comparisons with a change in step velocity yielding at least a large effect size (>1.2), of which 73% had a correspondingly large change in step frequency in the same direction. Within-athlete mean session step length remained relatively constant throughout. Reductions in step velocity and frequency occurred during training phases of high volume lifting and running, with subsequent increases in step velocity and frequency happening during phases of low volume lifting and high intensity sprint work.
Conclusions:
The importance of step frequency over step length to the changes in performance within a training year was clearly evident for the sprinters studied. Understanding the magnitudes and timings of these changes in relation to the training program is important for coaches and athletes. The underpinning neuro-muscular mechanisms require further investigation, but are likely explained by an increase in force producing capability followed by an increase in the ability to produce that force rapidly.
This study aimed to investigate activation characteristics of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during the acceleration and maximum-speed phases of sprinting. Lower-extremity kinematics and electromyographic (EMG) activities of the BFlh and ST muscles were examined during the acceleration sprint and maximum-speed sprint in 13 male sprinters during an overground sprinting. Differences in hamstring activation during each divided phases and in the hip and knee joint angles and torques at each time point of the sprinting gait cycle were determined between two sprints. During the early stance of the acceleration sprint, the hip extension torque was significantly greater than during the maximum-speed sprint, and the relative EMG activation of the BFlh muscle was significantly higher than that of the ST muscle. During the late stance and terminal mid-swing of maximum-speed sprint, the knee was more extended and a higher knee flexion moment was observed compared to the acceleration sprint, and the ST muscle showed higher activation than that of the BFlh. These results indicate that the functional demands of the medial and lateral hamstring muscles differ between two different sprint performances.
This study aimed to analyze various fitness qualities in handball players of different ages, and to determine the relationships between these parameters and throwing velocity. Forty-four handball players participated, pooled by age groups: ELITE (n = 13); under-18 (U18, n = 16); under-16 (U16, n = 15). The following tests were completed: 20-m running sprints; countermovement jumps (CMJ); jump squat to determine the load that elicited ~20 cm jump height (JSLOAD-20cm); a progressive loading test in full-squat and bench-press to determine the load that elicited ~1 m[middle dot]s-1 (SQ-V1-LOAD and BP-V1-LOAD), and handball throwing (Jump Throw and 3-Step Throw). ELITE showed greater performance in almost all sprint distances, CMJ, JSLOAD-20cm and bench-press strength than U18 and U16. The differences between U18 and U16 were unclear for these variables. ELITE also showed greater (P < 0.001) performance for squat strength and throwing than U18 and U16, and U18 attained greater performance (P < 0.05) for these variables than U16. Throwing performance correlated (P < 0.05) with sprint times (r = -.31; -.51) and jump ability (CMJ: r = .39; .56 and JSLOAD-20cm: r = .57; .60). Muscle strength was also associated (P < 0.001) with both types of throw (SQ-V1-LOAD: r = .66; .76; and BP-V1-LOAD: r = .33; .70). These results indicate handball throwing velocity is strongly associated with lower-limb strength, although upper-limb strength, jumping and sprint capacities also play a relevant role in throwing performance, suggesting the need for coaches to include proper strength programs to improve handball players' throwing velocity.
Rugby league is a collision team sport played at junior and senior levels worldwide, whereby players require highly developed anthropometric and physical qualities (i.e. speed, change-of-direction speed, aerobic capacity, muscular strength and power). Within junior levels, professional clubs and national governing bodies implement talent identification and development programmes to support the development of youth (i.e. 13-20 years) rugby league players into professional athletes. This review presents and critically appraises the anthropometric and physical qualities of elite male youth rugby league players aged between 13 and 20 years, by age category, playing standard and playing position. Height, body mass, body composition, linear speed, change-of-direction speed, aerobic capacity, muscular strength and power characteristics are presented and demonstrate that qualities develop with age and differentiate between playing standard and playing position. This highlights the importance of anthropometric and physical qualities for the identification and development of youth rugby league players. However, factors such as maturity status, variability in development, longitudinal monitoring and career attainment should be considered to help understand, identify and develop the physical qualities of youth players. Further extensive research is required into the anthropometric and physical qualities of youth rugby league players, specifically considering national standardised testing batteries, links between physical qualities and match performance, together with intervention studies, to inform the physical development of youth rugby league players for talent identification and development purposes.
This study aimed to assess the within- and between-session reliability of the KiSprint system for determining force-velocity-power (FVP) profiling during sprint running. Thirty (23 males, 7 females; 18.7 ± 2.6 years;) young high-level sprinters performed maximal effort sprints in two sessions separated by one week. Split times (5, 10, 20 and 30 m), which were recorded with a laser distance meter (a component of the KiSprint system), were used to determine the horizontal FVP profile using the Samozino’s field-based method. This method assesses the FVP relationships through estimates of the step-averaged ground reaction forces in sagittal plane during sprint acceleration using only anthropometric and spatiotemporal (split times) data. We also calculated the maximal theoretical power, force and velocity capabilities and the slope of the FV relationship, the maximal ratio of horizontal-to-resultant force (RF), and the decrease in the RF (DRF). Overall, the results showed moderate or good to excellent within- and between-session reliability for all variables (ICC > 0.75; CV < 10 %), with the exception of FV slope and DRF that showed low relative reliability (ICC = 0.47-0.48 within session, 0.31-0.33 between-session) and unacceptable between-session absolute reliability values (CV = 10.9-11.1 %). Future studies are needed to optimize the protocol in order to maximize the reliability of the FVP variables, especially when practitioners are interested in the FV slope and DRF. In summary, our results question the utility of the sprint-based FVP profiling for individualized training prescription, since the reliability of the FV slope and D RF variables is highly questionable.
The acute physiological and perceptual responses to a single session of resisted sled sprint (RSS) training are largely unexplored, nor have differences, if any, between male and female athletes been compared. Team field sport athletes (n 5 27; male/female, 15/12; 21.1 6 2.7 years) were assessed for Maximal Resisted Sled Load (MRSL) from which light (L-RSS, 30%MRSL) and heavy (H-RSS, 80%MRSL) sled loads were prescribed. On separate occasions in random order, 2 training sessions of 12 3 20 m RSS repetitions at either L-or H-RSS were performed, and assessments of physiological and perceptual responses were performed before (PRE), during, after (POST) and 24 hours after (+24 hours POST) each session. Compared to unresisted sprints, velocity decrements of 7.5 6 2.2 and 22.7 6 8.1% were produced by L-RSS and H-RSS, respectively. Heart rate, blood lactate, and ratings of perceived exertion were higher in H-RSS compared to L-RSS. Decrements in 20 m sprint and countermovement jump performance observed at POST had returned to PRE values at +24 hours POST. Except for a higher heart rate (;7-12 b·min 21) in females during the respective sessions, responses to Land H-RSS were generally similar between males and females. A single session of heavy RSS training is more demanding than light RSS training when matched for sprint number and distance, but measures of lower limb power and sprint performance return to pre-training levels within 24 hours regardless of sled load. Males and females respond similarly to a single session of RSS training when individualized, relative intensity sled loads are prescribed.
This study determined the effects of two wearable resistance (WR) placements (i.e. thigh and shank) on horizontal force-velocity and impulse measures during sprint running acceleration. Eleven male athletes performed 50 m sprints either unloaded or with WR of 2% body mass attached to the thigh or shank. In-ground force platforms were used to measure ground reaction forces and determine dependent variables of interest. The main findings were: 1) increases in sprint times and reductions in maximum velocity were trivial to small when using thigh WR (0.00–1.93%) and small to moderate with shank WR (1.56–3.33%); 2) athletes maintained or significantly increased horizontal force-velocity mechanical variables with WR (effect size = 0.32–1.23), except for theoretical maximal velocity with thigh WR, and peak power, theoretical maximal velocity and maximal ratio of force with shank WR; 3) greater increases to braking and vertical impulses were observed with shank WR (2.72–26.3% compared to unloaded) than with thigh WR (2.17–12.1% compared to unloaded) when considering the entire acceleration phase; and, 4) no clear trends were observed in many of the individual responses. These findings highlight the velocity-specific nature of this resistance training method and provide insight into what mechanical components are overloaded by lower-limb WR.
Rodríguez-Rosell, D, Sáez de Villarreal, E, Mora-Custodio, R, Asián-Clemente, JA, Bachero-Mena, B, Loturco, I, and Pareja-Blanco, F. Effects of different loading conditions during resisted sprint training on sprint performance. J Strength Cond Res XX(X): 000-000, 2020-The aim of this study was to compare the effects of 5 loading conditions (0, 20, 40, 60, and 80% of body mass [BM]) during weighted sled sprint training on unresisted and resisted sprint performance and jump ability. Sixty physically active men were randomly assigned into 5 groups according to the overload used during sled sprint training: 0% (G0%, n = 12), 20% (G20%, n = 12), 40% (G40%, n = 12), 60% (G60%, n = 12), and 80% BM (G80%, n = 12). Pretraining and post-training assessments included: countermovement jump (CMJ), 30-m sprint without extra load, and 20-m sprint with 20, 40, 60, and 80% BM. All 5 experimental groups trained once a week for a period of 8 weeks completing the same training program (number of sessions, number of bouts, running distance in each sprint, rest intervals between repetitions, and total running distance), but with different sled loads (0, 20, 40, 60, and 80% BM). There was a significant "time × group" interaction for resisted sprint performance at 80% BM condition, where the G40% group attained improvements in performance and G80% worsened. Moreover, G40% increased performance in unresisted and the rest of loading conditions. In addition, G0% and G60% showed statistically significant increases in unresisted sprint performance. No relevant changes were observed in the other experimental groups. All groups showed significant improvements (p < 0.05-0.001) in CMJ height. Therefore, our findings suggest that resisted sprint training with moderate loads (i.e., 40% BM) may have a positive effect on unresisted and resisted sprint performance.
This study compared the kinematics (step and joint) and muscle activity of unresisted and active resisted 30 m sprints with different loads (10–40% body mass) in experienced male and female sprinters. Step kinematics were measured using a laser gun and contact mat in 28 male and female participants during unresisted 30 m sprint, and sprints with 10–40% of body mass (BM) active resistance, while peak angular velocities of lower limb was measured, together with muscle activation of nine muscles. Increased resisted loads resulted in slower 30 m times, as a result of lower step velocity mainly caused by shorter step lengths and frequencies, flight times and longer contact times, with a greater effect on women than on men. These step kinematic differences, due to increasing load were accompanied with lower peak joint movements. However, gender differences were only found for peak plantar flexion with unresisted and 10% BM resisted sprints. Furthermore, increasing load decreased calf and hamstring muscles activity, while medial vastus activity increased. Based upon these findings, it was concluded that when introducing active resisted sprints, women should sprint with approximately 10% less active loads than men to have equal step and joint kinematics development over the sprint distance.
Purpose:
To test the relationships between maximum and relative strength (MS and RS), absolute and relative peak force (PF and RPF), and strength deficit (SDef), with sprint and jump performance, and to compare these mechanical variables between elite sprinters and professional rugby union players.
Methods:
Thirty-five male rugby union players and 30 male sprinters performed vertical jumps, 30-m sprint, and half-squat 1-repetition maximum (1RM), where these force-related parameters were collected. Pearson correlation coefficients were used to test the relationships between the variables. An independent t test and magnitude-based inferences compared the mechanical variables between sprinters and rugby players.
Results:
Almost certain significant differences were observed for jump and sprint performance between groups (P < .0001). The rugby union players demonstrated a likely significant higher MS (P = .03) but a very likely lower RS (P = .007) than the sprinters. No significant differences were observed for PF between them. The sprinters exhibited an almost certain significant higher RPF than the rugby players (P < .0001). Furthermore, the rugby players demonstrated almost certain to likely significant higher SDef from 40% to 70% 1RM (P < .05) compared with the sprinters. Overall, all strength-derived parameters were significantly related to functional performance.
Conclusions:
Elite sprinters present higher levels of RS and RPF, lower levels of SDef, and better sprint and jump performance than professional rugby players. Relative strength-derived values (RS and RPF) and SDef are significantly associated with speed-power measures and may be used as effective and practical indicators of athletic performance.
This study investigated the effects of a 11-week moderate-to-heavy sled training intervention with different magnitudes of velocity loss on sprint and jump performance, mechanical muscle function, and body composition in professional soccer players. Seventeen players (age 25.8±4.3 years; height 180.0±8.6 cm; weight 77.7±9.7 kg) were randomly
allocated into two groups, based on different magnitudes of velocity loss: 10% of velocity decrease (G10, n=8) and 20% of velocity decrease (G20, n=9). The velocity-based sled
training consisted of 20m resisted sprints with a progressive loading increase from 45% to 65% of body-mass throughout the intervention. Pre- and post-intervention sprint and jump performance, hamstring and quadriceps peak torque and isometric rate of torque development, and lower-limb lean mass measured by dual X-ray absorptiometry were assessed and compared. Two-way repeated measures analysis of variance revealed a significant time-effect for decreases in 10m and 20m sprint times (p=0.018 and p=0.033, respectively), but without a time-group interaction. The G10 showed greater beneficial effects than G20 for both 10m (- 5.5±3.3%, magnitude-based inference [MBI]: possibly versus -1.7±5.9%, MBI: possibly trivial) and 20m (-2.5±2.1%, MBI: possibly versus -1.4±3.7%, MBI: likely trivial) sprint times. Moreover, there was a significant time effect for CMJ height and quadriceps isometric peak torque, which decreased significantly after training (p=0.019 and p=0.010, respectively), with no within-group effect of time versus group interaction for these respective outcomes. The novel velocity-based sled model proposed here, especially under lower magnitudes of velocity loss, was able to significantly improve linear sprint performance in professional soccer players.
Lizana, JA, Bachero-Mena, B, Calvo-Lluch, A, Sánchez-Moreno, M, Pereira, LA, Loturco, I, and Pareja-Blanco, F. Do faster, stronger, and more powerful athletes perform better in resisted sprints? J Strength Cond Res XX(X): 000-000, 2020-This study aimed to analyze the relationships between different strength, power, and speed abilities and resisted sprint performance across a wide range of sled loads (10, 30, and 50% body mass [BM]). Seventy-nine young physically active male sport science students (age: 22.8 ± 3.4 years, BM: 74.2 ± 9.1 kg, and height: 175.4 ± 8.5 cm) performed 2 testing sessions. Session 1 consisted of a 20 m sprint without any additional load and with 10, 30, and 50% BM. Session 2 consisted of countermovement jump and full squat (SQ) tests. The CMJ was performed without any additional load and with loads of 30 and 50% BM, and the SQ was performed with loads corresponding to 30, 50, 70, and 90% BM. Resisted sprint times were moderate to large correlated with unloaded sprint times (r = 0.79 to 0.89), unloaded and loaded jump height (r = -0.62 to -0.71), and SQ performance (r = -0.56 to -0.71). Negative relationships were observed between velocity loss induced by each sled load and jump and SQ performance. The magnitude of these relationships increased with increasing sled loads. In conclusion, differences in speed, strength, and power abilities may explain, at least partially, the individual response of each athlete during sprinting towing a sled, especially with heavier sled loads. Thus, faster, stronger, and more powerful athletes require heavier sled loads (relative to %BM) to experience similar exercise intensities.
This study aimed to compare muscle activity, leg stiffness, and kinematics (contact and flight time [FT], stride length and frequency, and trunk angle [TA]) of unloaded sprinting to resisted sprint (RST) using different loads. Twelve male rugby players (age: 23.5 ± 5.1 years; height: 1.79 ± 0.04 m; body mass 82.5 ± 13.1 kg) performed 30-m sprints using different loading conditions (0, 10, 30 and 50% of velocity loss-Vloss-from the maximum velocity reached under unloaded condition). Muscle activity from 4 muscles (biceps femoris long head, rectus femoris [RF], gluteus medius and gastrocnemius), leg stiffness (Kleg), and kinematics were measured during the acceleration and maximum velocity (Vmax) phases of each sprint. Heavier loads led to significantly lower biceps femoris long head activation and higher rectus femoris activity (p < 0.01-0.05). Significant reductions in Kleg were observed as loading increased (p < 0.001-0.05). Kinematic variables showed substantial changes with higher loads during the acceleration and Vmax phase. In conclusion, the heavier the sled load, the higher the disruptions in muscle activity, Kleg, and kinematics. When coaches and practitioners intend to conduct resisted sprint training sessions without provoking great disruptions in sprint technique, very-heavy sled loads (greater than 30% Vloss) should be avoided. However, heavy sled loads may allow athletes to keep specific positions of the early acceleration phase for longer time intervals (i.e., first 2-3 strides during unresisted sprints).
Purpose:
To analyze the acute and short-term physical and metabolic responses to resisted sprint training with 5 different loading conditions (0%, 20%, 40%, 60%, and 80% body mass).
Methods:
Fifteen male participants performed 8 × 20-m sprints with 2-minute rests between sprints with 5 different loading conditions. Subjects performed a battery of tests (creatine kinase and lactate concentrations, countermovement jump, 20-m sprint, and isokinetic knee extension and flexion contractions) at 3 different time points (preexercise [PRE], postexercise [POST], and 24-h postexercise [POST24H]).
Results:
Results revealed significant increases in blood lactate for all loading conditions; however, as sled loadings increased, higher blood lactate concentrations and increments in sprint times during the training session were observed. Significant increases in creatine kinase concentration were observed from PRE to POST24H for all loading conditions. Concerning physical performance, significant decreases in countermovement-jump height from PRE to POST were found for all loading conditions. In addition, significant decreases in 20-m sprint performance from PRE to POST were observed for 0% (P = .05) and 80% (P = .02). No significant differences with PRE were observed for the physical-performance variables at POST24H, except for 20% load, which induced a significant decrease in mean power during knee flexion (P = .03).
Conclusions:
These results suggest that the higher the load used during resisted sprint training, the higher the physical-performance impairments and metabolic response produced, although all loading conditions led to a complete recovery of sprint performance at POST24H.
We examined the effects of five loading conditions (0%, 20%, 40%, 60%, and 80% of body-mass [BM]), on resisted sprint performance and kinematics in male rugby players over different distances. Ten players from the Brazilian National Team (20.1±3.3 years; 88.7±18.8 kg; 178.3±6.2 cm) performed 20-m sprints under the five loading conditions. Sprint times in 5-, 10- and 20-m were recorded. Stride length (SL), and hip, knee and ankle angles were measured using an eight-sensor motion analysis system. The kinematic parameters were calculated over the different distances. Heavier loads led to significantly greater velocity loss (P < 0.001-0.05). Significant reductions in SL were also observed when comparing 0% BM and all resisted sprints in all assessed distances (P < 0.001-0.05, Effect Size, [ES]: 1.35-4.99). Very-heavy (80% BM) sled load provoked significantly greater decreases in SL than the rest of loading conditions (P < 0.01-0.05). Important kinematic alterations were observed for all loading conditions and sprint distances when compared to 0%BM (ES: 0.76-1.79, for hip-angle; 0.20-1.40, for knee-angle; and 0.73-1.88, for ankle-angle). Moreover, 80% BM induced significantly higher hip flexion, lower knee flexion and higher ankle dorsiflexion than 20% BM condition at 5-10- and 10-20-m distances (P < 0.05). Lighter sled loads (< 40% BM) seem to be more adequate to improve speed ability without provoking drastic changes in unloaded sprinting technique, whereas heavier loads might be more suitable for optimizing horizontal force production and thus, acceleration performance.
Purpose:
To analyze and compare the effects of 4 different resisted sprint training (RST) modalities on youth soccer players' performance after 8 weeks of training.
Methods:
Forty-eight youth soccer players were first randomly assigned to 4 groups and only then completed 8 weeks of RST: horizontal resisted sprint, vertical resisted sprint (VRS), combined resisted sprint, and unresisted sprint. Performance in horizontal and vertical jumps, sprint, and change of direction (COD) ability were assessed 1 week before and after the training intervention. Magnitude-based inference analysis was performed for calculating within-group pre-post differences. In addition, an analysis of covariance test was performed for between-group comparison, using the pretest values as covariates. After that, the analysis of covariance P values and the effect statistic were transformed to magnitude-based inference.
Results:
Within-group outcomes showed that all resisted training modalities experienced improvements in sprint (small to moderate) and COD (small to large) performance. Moreover, all groups, except unresisted sprint, enhanced the horizontal jump performance. However, only VRS improved on vertical jump. Between-group comparison outcomes revealed that only VRS improved the sprint time compared with horizontal resisted sprint (moderate) and COD performance compared with all groups (moderate to large). In addition, VRS enhanced the countermovement jump performance (small to large) compared with the other groups.
Conclusions:
Independent of the orientation of the resistance applied, RST is an effective training method for improving sprinting and COD performance. Nevertheless, VRS may promote greater improvements on sprint and COD ability and have a positive additional effect on countermovement jump performance and the reduction of COD deficit.
This study compared the kinematics of unresisted and active resisted 30 m sprints with different loads in male and female sprinters. Step kinematics were measured in 14 male and 14 female participants during an unresisted 30 m sprint, and sprints with 10%, 20%, 30%, and 40% of body mass active resistance. Increased resisted loads resulted in slower 30 m times, which was the result of a lower step velocity, mainly caused by shorter step lengths and frequencies, flight times, and longer contact times. In addition, the resisted loads had a larger effect on women than men, as shown by a larger increase in sprint times. These time differences were the result of an earlier and slower maximal step velocity, which was mainly caused by longer contact times, shorter step lengths, and frequencies in women compared with men. Based upon these findings, it was concluded that when introducing active resisted sprints, women should sprint a shorter distance and/or have a lower resistance load than men, to prevent too much fatigue, and thereby avoid training for more endurance rather than acceleration ability. Furthermore, women should focus on increasing relative leg muscle mass to increase leg stiffness and their horizontal force production capacity.
This study aimed to examine the effects of different sled overloads on maximum sprint velocity achieved by female soccer players with different strength, speed, and power levels. Twenty elite female soccer players from the same club participated. On the same day, athletes performed: linear and resisted-sprint tests with 30 and 60% of body-mass over 5-, 10-, and 20-m; half-squat one-repetition maximum assessment; and half-squat maximum bar-power output. A median split analysis was used to divide players into two groups according to their velocity, half-squat one-repetition maximum, and half-squat power. Differences in percentage decreases between unresisted- and resisted-sprints comparing higher and lower groups were analyzed using magnitude-based inferences. Overall, the stronger, faster, and more powerful players were less affected by both loads, as demonstrated by their lower decreases in velocity over the different distances. However, half-squat power appeared to be more sensitive for indicating impairments in resisted-sprint performance, due to meaningful differences in percentage decreases observed between higher and lower power groups. Notably, overloads of 30 and 60% body-mass provoked substantial reductions in resisted-sprint velocity (~22.9% for 30% and ~51.4% for 60% body-mass, relative to unresisted-sprint velocity). Athletes with superior power levels are less affected by the progressive sled overloading.
This study investigated the role of reactive and eccentric strength in stiffness regulation during maximum velocity sprinting (Vmax) in team sport athletes compared with highly trained sprinters. Thirteen team sport athletes and eleven highly trained sprinters were recruited. Vmax was measured using radar, and stiffness regulation was inferred from modelled vertical and leg spring stiffness. Reactive strength (RSI) was determined from a 0.50 m drop jump, and an eccentric back squat was used to assess maximum isoinertial eccentric force. Trained sprinters attained a higher Vmax than team sport athletes, partly due to a briefer contact time and higher vertical stiffness. Trained sprinters exhibited a moderately higher RSI via the attainment of a briefer and more forceful ground contact phase, while RSI also demonstrated large to very large associations with vertical stiffness and Vmax, respectively. Isoinertial eccentric force was largely correlated with Vmax, but only moderately correlated with vertical stiffness. Reactive and eccentric strength contribute to the ability to regulate leg spring stiffness at Vmax, and subsequently, the attainment of faster sprinting speeds in highly trained sprinters versus team sport athletes. However, stiffness regulation appears to be a task-specific neuromuscular skill, reinforcing the importance of specificity in the development of sprint performance.
Introduction: Hamstring strain injuries typically occur in the
proximal biceps femoris long head (BFlh) at high running speeds. Strain magnitude seems to be the primary determinant of strain injury,
and may be regulated by muscle activation. In running, BFlh strain is largest in the proximal region, especially at high speeds. However,
region-specific activity has not been examined. This study examined the proximal–distal and intermuscular activity of BFlh and semitendinosus (ST) as a function of increasing running speed. Methods: Thirteen participants ran at steady speeds of 4.1 (slow), 5.4 (moderate), and 6.8 m·s−1 (fast) on a treadmill. Region- and muscle-specific EMG activity were recorded at each speed using high-density EMG, and were normalized to maximal voluntary isometric activity. Muscle–tendon unit lengths were calculated from kinematic recordings. Speed effects, regional, and intermuscular differences were tested with Statistical Parametric Mapping. Results: With increasing running speed, EMG activity increased in all regions of both muscles to a similar extent in the clinically relevant late swing phase. Increases in muscle–tendon unit lengths in late swing as a function of running speed were comparatively small. In fast running, EMG activity was highest in late swing in all regions, and reached 115% ± 20% (proximal region, mean ± 95% confidence limit), 106% ± 11% (middle), and 124% ± 16% (distal) relative to maximal voluntary isometric activity in BFlh. Regional and intermuscular EMG patterns
were highly individual, but each individual maintained similar roximal–distal and intermuscular EMG activity patterns across running speeds. Conclusions: Running is associated with highly individual hamstring activity patterns, but these patterns are similar across speeds. It may thus be crucial to implement running at submaximal speeds early after hamstring injury for restoration of normal neuromuscular function.
As the effect of performance level on sprinting mechanics has not been fully studied, we examined mechanical differences at maximal running speed (MRS) over a straight-line 35 m sprint amongst sprinters of different performance levels. Fifty male track and field sprinters, divided in Slow, Medium and Fast groups (MRS: 7.67 ± 0.27 m∙s⁻¹, 8.44 ± 0.22 m∙s⁻¹, and 9.37 ± 0.41 m∙s⁻¹, respectively) were tested. A high-speed camera (250 Hz) recorded a full stride in the sagittal plane at 30–35 m. MRS was higher (p < 0.05) in Fast vs. Medium (+11.0%) and Slow (+22.1%) as well as in Medium vs. Slow (+10.0%). Twelve, eight and seven out of 21 variables significantly distinguished Fast from Slow, Fast from Medium and Medium from Slow sprinters, respectively. Propulsive phase was significantly shorter in Fast vs. Medium (−17.5%) and Slow (−29.4%) as well as in Medium vs. Slow (−14.4%). Fast sprinters had significantly higher vertical and leg stiffness values than Medium (+44.1% and +18.1%, respectively) and Slow (+25.4% and +22.0%, respectively). MRS at 30–35 m increased with performance level during a 35-m sprint and was achieved through shorter contact time, longer step length, faster step rate, and higher vertical and leg stiffness.
Pareja-Blanco, F, Asián-Clemente, JA, and Sáez de Villarreal, E. Combined squat and light-load resisted sprint training for improving athletic performance. J Strength Cond Res 35(9): 2457-2463, 2021-This study aimed to analyze the effects of 5 training methods: squat (SQ), light-load sled towing (LST), heavy-load sled towing (HST), squat combined with LST (SQ + LST), and squat combined with HST (SQ + HST) on physical performance. Ninety-one physically active men were randomly assigned to one of the aforementioned training methods or a control group. Before and after the training period, a battery of tests was completed: 30-m sprint; change of direction (COD); countermovement jump (CMJ) and Abalakov jump (ABK); and estimated 1 repetition maximum (1RM) in squat. Training took place once per week for 8 weeks. SQ trained the squat exercise, HST trained resisted sprints with 80% body mass (BM) load, LST trained resisted sprints with 12.5% BM load, SQ + HST combined squat with 80% BM load resisted sprint, and SQ + LST combined squat with 12.5% BM load resisted sprint. The loads used in squat ranged from 40 to 55% 1RM. After the training program, SQ + LST showed improvements in 0- to 30-, 10- to 20-, and 10- to 30-m sprint times, whereas SQ + HST did not achieve significant enhancements over any sprint time. LST and HST improved over 0-20 and 10-30 m, respectively. SQ showed improvements in 20- to 30-m sprint time. Change of direction and CMJ performance were increased for HST, SQ + HST, and SQ + LST, whereas only SQ + LST improved ABK height. SQ, HST, SQ + HST, and SQ + LST increased 1RM. Squat training with low/moderate loads combined with LST (12.5% BM) may be an effective stimulus for improving leg strength, jump ability, COD, and sprint performance.
Bentley, I, Sinclair, JK, Atkins, SJ, Metcalfe, J, and Edmundson, CJ. Effect of velocity-based loading on acceleration kinetics and kinematics during sled towing. J Strength Cond Res XX(X): 000-000, 2018-Sled towing (ST) provides an external load in the form of a sled towed using a shoulder or waist harness and cord behind the athlete. Loading strategies have varied greatly between studies, and despite many investigations, there is little agreement on the optimum sled loading to develop the acceleration phase. The aim of this study was to investigate the kinetics and kinematics of velocity-based ST during the acceleration phase of sprinting. Twelve academy rugby league players performed a series of 6-m sprints in different conditions; uninhibited, 10, 15, and 20% velocity decrement (VDec). Sagittal plane kinematics and kinetic measures were examined using 1-way repeated-measures analysis of variance. Results indicated that ST affected trunk, knee, and ankle joint kinematics (p < 0.05). Peak knee flexion increased as sled loads increased (p < 0.05), which may enable athletes to lower their center of mass and increase their horizontal force application. Net horizontal and propulsive impulse measures were greater in all sled conditions (p < 0.05), which increased significantly because sled loadings were heavier. In conclusion, this study highlights the effects of differential loads to help coaches understand acute kinetics and kinematic changes to improve the planning of sprint training.