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Does the Initial Level of Horizontal Force Determine the Magnitude of Improvement in Acceleration Performance in Rugby?
European Journal of Sport Science
Abstract
This study aimed to observe the effect of 8 weeks of resisted sled training (RST), with optimal loading for maximal power output production and initial levels of force, on the magnitude of improvement in sprint performance and individual sprint mechanical outputs in female amateur rugby union players. The study examined the horizontal Power-Force-Velocity profile (P-F-V profile), which provides a measure of the athlete’s individual balance between force and velocity capabilities (Sfv), theoretical maximum force (F0), theoretical maximum velocity (V0), maximum power (Pmax), the maximum ratio of force (Rfmax) and rate of decrease in ratio of force (Drf). Thirty-one participants (age=23.7 ± 3.3years, BM=69 ± 9Kg, height=167.5 ± 5.2 cm) were divided into a control group and two experimental groups; forwards (FG) and backs (BG). For 8 consecutive weeks (16 sessions), all groups performed the same training program: 2 sets of 5 × 30 m, but athletes assigned to FG and BG ran towing a resisted sled attached to their waists, with optimal loading for maximal power output production. Both FG and BG significantly improved (p≤0.05) in 5 m and 20 m sprint performance, and in the mechanical properties related to the horizontal P-F-V profile. The correlation between the initial level of horizontal strength and the magnitude of improvement in Pmax also suggests that higher levels of horizontal force may lead to greater adaptations in RST. The P-F-V profile is a useful field method for identifying the weakest mechanical variable in rugby players during sprinting and enabling the prescription of individualized training programs according to specific running performance.
... Of the 27 studies that passed the first filter, the full text of 1 could not be accessed, and of the remaining 26 studies, twelve were excluded due to wrong intervention (n = 5), wrong design (n = 2), wrong population (n = 3), wrong analysis (n = 1), and study replication (n = 1). Finally, fourteen studies (Escobar Álvarez et al., 2021;Grazioli et al., 2020Grazioli et al., , 2023Harrison and Bourke, 2009;Hasan et al., 2021;Kawamori et al., 2014;Lahti et al., 2020;Lahti et al., 2020;Loturco et al., 2017;Luteberget et al., 2015;McMorrow et al., 2019;Morin et al., 2017;Panascì et al., 2023;Sinclair et al., 2021) met the eligibility criteria for inclusion in this systematic review with meta-analysis ( Fig. 1). No additional studies were identified following the grey literature search and citation search. ...
... A total of 344 participants from ten randomized controlled trials were included (Escobar Álvarez et al., 2021;Grazioli et al., 2020Grazioli et al., , 2023Harrison and Bourke, 2009;Hasan et al., 2021;Kawamori et al., 2014;Loturco et al., 2017;Morin et al., 2017;Panascì et al., 2023;Sinclair et al., 2021), and four non-randomized controlled trial (Lahti et al., 2020;Lahti et al., 2020;Luteberget et al., 2015;McMorrow et al., 2019). The age of the participants varied between 18.7 ± 0.6 (Luteberget et al., 2015;Sinclair et al., 2021) to 27.7 ± 4.5 (Panascì et al., 2023). ...
... The age of the participants varied between 18.7 ± 0.6 (Luteberget et al., 2015;Sinclair et al., 2021) to 27.7 ± 4.5 (Panascì et al., 2023). Regarding sports modality, eight studies considered soccer (Grazioli et al., 2020(Grazioli et al., , 2023Hasan et al., 2021;Kawamori et al., 2014;Lahti et al., 2020;Loturco et al., 2017;McMorrow et al., 2019;Morin et al., 2017), five rugby (Escobar Álvarez et al., 2021;Harrison and Bourke, 2009;Lahti et al., 2020;Panascì et al., 2023;Sinclair et al., 2021), one handball (Luteberget et al., 2015), one basketball (Kawamori et al., 2014), and one field hockey (Kawamori et al., 2014). Training planning con-sidered from five (Loturco et al., 2017) up to eleven weeks (Grazioli et al., 2020), with frequencies from one (Grazioli et al., 2020;Lahti et al., 2020) to three weekly sessions (Loturco et al., 2017). ...
Objective
This systematic review and meta-analysis aimed to examine the effects of resistance sled training (RST) on sprint performance in team sport athletes.
Methods
A systematic search was conducted in the electronic databases MEDLINE, Sportdiscus, Scopus and Web of Science from inception until October, 2023. Randomized or non-randomized controlled clinical trials that included collective field sports athletes who were trained with sled drag were included to evaluate the effectiveness of the training on performance in speed tests. Independent reviewer selected the studies with www.rayyan.ai, extracted the data, performed the risk-of-bias assessment, and methodological quality. The sprint time at distances of 5, 10 and 20 m were included for the meta-analysis. A random-effects model, standardized mean difference, and standard deviation were used for meta-analysis.
Results
Fourteen studies involving 344 participants were selected (overall risk: high risk; methodological quality: moderate quality). Meta-analysis revealed statistically significant effects in favor of RST on 5 m (SMD = -0.87; 95% CI = -1.58 to -0.16; p = 0.02) and 10 m (SMD = -0.40; 95% CI = -0.78 to -0.03; p = 0.04). However, there are no significant effects on 20 m (SMD = -0.34; 95% CI = -0.73 to 0.06 p = 0.1).
Conclusion
These results indicate that RST improves performance mainly in the short distance, suggesting that RST is a viable training method to improve athletic performance in team sports.
... It was then adjusted for small sample bias (15,21). For studies in which the times for intervals were reported (12,24,27,28,32,34,37,42), the mean change was calculated by subtracting the post-training time from the pre-training time. In the remaining studies (2,20,22,26,38,40,43), speed (m/s) was reported and pre-training speed was subtracted from posttraining speed to find the mean change. ...
... body mass). While some studies consisted exclusively of men (n=7, 47%) (22,27,28,34,37,38,42), or women (n=5, 33%) (12,24,26,32,40), other samples were mixed (n=2, 13%) (2,20). One study (n=1, 7%) did not report biological sex of the participants included in their sample (43). ...
... In addition, nearly all studies (n=14, 93.3%) included training groups who were similar at baseline regarding most important characteristics. The one exception was a study of 31 rugby athletes who were allocated to a RS or UR group (12). However, the two experimental RS groups were stratified by player position including forwards and backs, whereas the UR group included a combined sample of players from both position groups (12). ...
Resisted sprint (RS) training, such as sled or parachute towing, is commonly used for sprint training among field sport athletes. While RS training is frequently employed by athletes and coaches, there is little research on its benefits, especially compared to unresisted running (UR) training programs with similar training volumes. This systematic review and meta-analysis compared the effectiveness of RS training on acceleration compared to UR training. Potential sources were limited to peer-reviewed articles published in English prior to June 12, 2022, and gathered from the EBSCOhost, PubMed, and Web of Science online databases identified using combinations of the following terms: towing, sled, “resisted sprint,” “sprint acceleration,” “sprint performance,” and “sprint speed.” The search returned 1,159 sources, from which 15 were eligible for inclusion. Fifty effects were used to estimate the impact of RS training on initial sprint speed. Based on the cumulative results from these studies, RS training yielded a small improvement in acceleration but was not different from same volume of UR training (Hedges’ d Effect Size=0.11, 95% CI: −0.01 to 0.23; p=0.08). These results do not support the use of RS training over UR training for improving initial sprint speed; however, further research should be conducted.
... The L 50%vdec is defined as a load, which corresponds to a decrement of v 0 of 50% (50%v dec ), based on the parabolic velocity-power relationship (7). EscobarÁlvarez et al. (11) examined the effect of 8 weeks of sled pulling with loads corresponding to 50%v dec on sprint acceleration performance, as well as on sprint mechanics. They found significant performance improvements in 5 and 20 m and in mechanical properties related to sprinting (F 0, v 0 , P max , RF max ). ...
... The sprinting performance did not improve in the 10% BM and URS groups, indicating the potential advantage of training with heavier loads in developing higher running velocities throughout the sprint acceleration phase in trained sprinters. Our findings are in line with previous studies that have revealed similar improvements in sprinting performance after RSS training with a load associated with the apex of the velocity-power relationship, which maximizes the horizontal power production during sled pulling (3,11,15). ...
... Accordingly, the increase of P max in the same group exhibits an increased ability to transfer higher amounts of horizontal force throughout the early and late acceleration phases posttraining (21). Our results confirm that heavy sled towing selectively improves F 0 , RF max (20), and P max (3,8,11,15,19). Conversely, no significant changes in v 0 and D rf were found postintervention in any of the groups. This indicates that the capability to produce horizontal force at high running velocities and the ability to maintain a net horizontal force production throughout the sprint acceleration phase did not differ after 6 weeks of RSS or URS training. ...
Stavridis, I, Ekizos, A, Zisi, M, Agilara, GO , Tsolakis, C, Terzis, G, and Paradisis, G. The effects of heavy resisted sled pulling on sprint mechanics and spatiotemporal parameters. J Strength Cond Res 37(12): 2346-2353, 2023-This study examines the effects of 2 resisted sled sprinting (RSS) training programs: with a load corresponding to the running velocity associated with the apex of the individual velocity-power relationship (50%vdec), with a load equal to 10% of body mass (10% BM), and of an unresisted sprint training (URS). We measured the 30-m sprint performance in intervals of 5 m examining sprint acceleration, mechanical properties (theoretical maximal horizontal power [Pmax], force [F0], velocity [v0], slope of the force-velocity relationship [SFv], maximal ratio of horizontal-to-resultant force [RFmax], rate of decrease in RF [Drf]), and spatiotemporal parameters (step frequency [SF], step length [SL], flight time [FT], and contact time [CT]). Twenty-seven sprinters were randomly assigned into the 50%vdec , 10% BM, and URS groups, performing 12 sessions over 6 consecutive weeks (2 sets of 5 sprints per session). The 50%vdec group significantly improved (p < 0.05) their performance in all 30-m intervals. Posttraining, the 50%vdec group showed significantly increased Pmax, F0, and RFmax (mean differences: 1.46 ± 1.70 W·kg−1, 0.51 ± 0.68 N·kg−1, and 0.17 ± 0.18%, respectively), compared with pretraining. The 50%vdec group achieved higher SF, whereas FT decreased postintervention. No significant changes (p > 0.05) were found in the performance and mechanical and spatiotemporal variables in the other groups. In conclusion, RSS training with a load of 50%vdec provides an effective loading stimulus to induce adaptations that improve sprint acceleration performance. The improvements are explained by greater amounts of force and power, efficient force application, and higher step frequencies.
... Therefore, it is apparent that there is a need to investigate the effectiveness and application of RST with a specific emphasis on the FITS player [18]. Additionally, since the published reviews of Petrakos et al. [28] and Alcaraz et al. [26], renewed interest in RST with heavier loads has seen five additional studies published in this area [37][38][39][40][41], with a further eight interventions utilising light and moderate loads [42][43][44][45][46][47][48][49]. Indeed, the recent narrative review by Zabaloy et al. [18] questions the need to use heavy (30-< 50% V dec ), and very heavy (≥ 50% V dec ) loads, with little evidence suggesting they provide any benefit above those found with lighter loads. ...
... Twenty-one studies [21,[37][38][39][40][41][42][43][44][45][46][47][48][49][62][63][64][65][66][67][68] met the inclusion criteria. In total, this sample included 31 study groups of which 12 studies included a non-exposed control group [21, 37, 39, 43, 44, 47-49, 62, 66-68], with the remaining studies eligible for inclusion owing to the presence of a comparison group. ...
... The age of the participants ranged from 16.6 (± 0.6) to 27.1 (± 4.8) years and training level ranged from trained to highly trained. Only three studies included female players [38,39,49]. Soccer (n = 14), rugby (n = 7), lacrosse (n = 2), field hockey (n = 1) and Australian Rules football (n = 2) were the recruited sports across the 21 studies (Table S2 of the ESM). ...
Developing the sprint performance of field-based invasion team sport (FITS) players is considered an essential training goal for FITS coaching practitioners, and thus numerous training methods are employed to elicit improvements. Although interest in resisted sprint training (RST) has grown considerably in recent times, there remains a lack of clarity around its utility in FITS, particularly regarding the use and effectiveness of heavier RST loads.
The aims of this review were to (1) compare RST to unresisted sprinting, (2) examine if RST can improve sprint performance and (3) investigate if external load and the method of load prescription influence the impact of RST in FITS players.
The systematic review and meta-analysis were conducted in compliance with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. The search strategy included terms for RST, RST modalities and FITS, and was applied to PubMed, SPORTDiscus, Web of Science and OpenGrey databases. Methodological quality and risk of bias associated with each study were assessed using the Physiotherapy Evidence Database scale (PEDro) and Cochrane Risk of Bias assessment tool respectively.
Twenty-one studies met the inclusion criteria for this review and were included in the final analysis. The primary between-group analysis revealed no differences between RST and unresisted sprinting for developing the early acceleration, late acceleration and maximum velocity sprint phases. Secondly, a within-group analysis found significant improvements for resisted sprint training in the early acceleration (standardised mean difference [SMD] − 0.80) and late acceleration (SMD − 0.28) sprint phases, with no change detected for the maximum velocity phase. Finally, significant moderate improvements were found for light (SMD − 0.69) and very heavy (SMD − 1.01) loads during early acceleration.
Resisted sprint training achieved similar improvements in sprint performance to those found for unresisted sprinting during the acceleration and maximum velocity sprint phases. Within-group findings show RST is an effective method for improving early acceleration and late acceleration performance of FITS players. Finally, a subgroup analysis supports the use of light and very heavy loads for increasing early acceleration performance, while also highlighting greater benefits associated with using the percentage velocity decrement loading method.
Open Science Framework, https://osf.io/thms7/.
... One of these studies was performed in rugby sevens with an international cohort (33% of 3 studies). 140 In comparison, the other two were performed in rugby union (67%) with amateur 141 and combined (club and international) 142 cohorts. In amateur women's rugby union, improvements in 5 m and 20 m sprint performance and mechanical properties related to the horizontal power-force-velocity profile were observed over the course of an 8-week sled training intervention. ...
... In amateur women's rugby union, improvements in 5 m and 20 m sprint performance and mechanical properties related to the horizontal power-force-velocity profile were observed over the course of an 8-week sled training intervention. 141 In international women's rugby sevens, asymmetry of running mechanical variables was investigated, and symmetry angle remained mostly constant across all kinetic, kinematic, spring-mass characteristics and horizontal force production variables. 140 Finally, machine scrummaging forces were described in club and international rugby union, and women's peak compressive force was 8.7 kN. ...
Objectives
In part 1, the objective was to undertake a systematic scoping review of applied sports science and sports medicine in women’s rugby, and in part 2 to develop a consensus statement on future research priorities.
Design
In part 1, a systematic search of PubMed (MEDLINE), Scopus and SPORTDiscus (EBSCOhost) was undertaken from the earliest records to January 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020, the PRISMA extension for Scoping Reviews, and the PRISMA extension protocols were followed. In part 2, 31 international experts in women’s rugby (ie, elite players, sports scientists, medical clinicians, sports administrators) participated in a three-round Delphi consensus method. These experts reviewed the findings from part 1 and subsequently provided a list of priority research topics in women’s rugby. Research topics were grouped into expert-based themes and expert-based subthemes via content analysis. Expert-based themes and expert-based subthemes were ranked from very low to very high research priority on a 1–5 Likert scale. Consensus was defined by ≥70% agreement. The median research priority agreement and IQR were calculated for each expert-based theme and subtheme.
Data sources
PubMed (MEDLINE), Scopus and SPORTDiscus (EBSCOhost).
Eligibility criteria for selecting studies
Studies were eligible for inclusion if they investigated applied sports science or sports medicine in women’s rugby.
Results
In part 1, the systematic scoping review identified 123 studies, which were categorised into six sports science and sports medicine evidence-based themes: injury (n=48), physical performance (n=32), match characteristics (n=26), fatigue and recovery (n=6), nutrition (n=6), and psychology (n=5). In part 2, the Delphi method resulted in three expert-based themes achieving consensus on future research priority in women’s rugby: injury (5.0 (1.0)), female health (4.0 (1.0)) and physical performance (4.0 (1.0)).
Summary/Conclusion
This two-part systematic scoping review and Delphi consensus is the first study to summarise the applied sports science and sports medicine evidence base in women’s rugby and establish future research priorities. The summary tables from part 1 provide valuable reference information for researchers and practitioners. The three expert-based themes that achieved consensus in part 2 (injury, female health and physical performance) provide clear direction and guidance on future research priorities in women’s rugby. The findings of this two-part study facilitate efficient and coordinated use of scientific resources towards high-priority research themes relevant to a wide range of stakeholders in women’s rugby.
... Sekine and Okoda's [25] study was not indexed in any of the databases that were used for the systematic search. Xu et al. are correct about the study by Escobar Alvarez et al. [26], unfortunately, this study appears to have been missed in the original search. Concerning Makaruk et al. [27], the study was neither indexed in the databases used nor did it qualify as part of our inclusion criteria since it investigated the effects of assisted sprint training (and not combined uphilldownhill sprinting or resisted sprinting). ...
... Recent research has shown an increase in sprint performance and horizontal force production capacities in lowlevel rugby and soccer players after specific training modalities (such as RST) [5,6]. Horizontally-oriented strength exercises may be similar to the spatial-temporal patterns associated with sprinting (e.g., RST, unilateral plyometrics, or both). ...
Background: The aim of this study was to investigate the effects of combined vertical and horizontal strength exercises on sprint mechanical parameters and sprint performance among amateur soccer players. Methods: The study followed a controlled experimental design. Twenty amateur soccer players were assigned to either an experimental group (EG, n = 11) or a control group (CG, n =9). In addition to the soccer training, the EG group conducted a sixweek training program involving combined horizontal and vertical strength exercises. Sprint performance and sprint mechanical parameters were computed using a field method based on velocity-time data pre- and post-intervention. The repeated measures ANOVA test was used for between-group comparisons. Results: The results suggest a significant (p < 0.05) improvement in sprint performance at 0-10 meter distance (p = 0.02), 0-15 meter distance (p = 0.01), 0-20 meter distance (p = 0.03), and the maximal value for the ratio of force - RFmax (p = 0.03) in EG compared to CG. Conclusions: The horizontal and vertical strength exercises can improve sprinting performance at distances longer than 5 m but do not improve the most of examined mechanical sprinting parameters in amateur soccer players.
... This relationship describes the mechanical properties of the body and can be based on several variables that can be calculated from velocity data measured by radar or laser devices [9]. The F-V profile (e.g., maximal theoretical force (F0), maximal theoretical velocity (V0), F-V slope, and maximal power (P max )) can be used to implement individualized training programs [10][11][12][13]. In female soccer players, sprint performance (time to run 20-m) was determined by V0 and P max [14]. ...
Aim: The purpose of the present study was to evaluate the relationships between sprint mechanical parameters and sprint performance among female soccer players at different skill levels. Materials and methods: Sixty-six female soccer players (age = 23.1 ± 5.1 years) performed a 30-m sprint to assess sprint performance and mechanical variables. Speed was measured by radar technology for 5, 10, 20, and 30 m and was used to calculate the theoretical maximal velocity (V0), theoretical maximal horizontal force (F0), maximal horizontal power (Pmax), decrease in the ratio of horizontal to resultant force (DRF), and p eak ratio of horizontal to resultant force (RFpeak). Results: Different force-velocity (F-V) profile parameters are determinants of sprint performance at various distances. RFpeak (r = -0.99), Pmax (r = -0.93), and F0 (r = 0.92) had the strongest associations with sprint performance at shorter (5-m) distances, while at longer (20-m) distances, V0 (r = -0.73), Pmax (r = -0.94), and RFpeak (r = -0.88) were largely associated with sprint performance. Conclusion: The results of this study show that as the skill level in female soccer players increases, an increase in maximal theoretical horizontal force during sprinting can be observed.
... This application provides easy low-cost measurements. Moreover, the My Jump app is used as a research tool in different athlete populations [3,5,7]. This device provides an accurate and reliable assessment of the level of muscles' mechanical parameters tested during the jump, i.e.: force (F), velocity (V), power (P), and height [6,8]. ...
Ensuring internal validity is the key procedure when planning the study design. Numerous systematic reviews have demonstrated that considerations for internal validity do not receive adequate attention in the primary research in sport sciences. Therefore, the purpose of this study was to review methodological procedures in current literature where the effects of resistance training on strength, speed, and endurance performance in athletes were analyzed. A computer-based literature searches of SPORTDiscus, Scopus, Medline, and Web of Science was conducted. The internal validity of individual studies was assessed using the PEDro scale. Peer-reviewed studies were accepted only if they met all the following eligibility criteria: (a) healthy male and female athletes between the ages of 18-65 years; (b) training program based on resistance exercises; (c) training program lasted for at least 4 weeks or 12 training sessions, with at least two sessions per week; (d) the study reported maximum strength, speed, or endurance outcomes; and (e) systematic reviews, cohort studies, case-control studies, cross-sectional studies were excluded. Of the 6,516 articles identified, 133 studies were selected for rating by the PEDro scale. Sixty-eight percent of the included studies used random allocation to groups, but only one reported concealed allocation. Baseline data are presented in almost 69% of the studies. Thirty-eight percent of studies demonstrated adequate follow-up of participants. The plan to follow the intention-to-treat or stating that all participants received training intervention or control conditions as allocated were reported in only 1.5% of studies. The procedure of blinding of assessors was also satisfied in only 1.5% of the studies. The current study highlights the gaps in designing and reporting research in the field of strength and conditioning. Randomization, blinding of assessors, reporting of attrition, and intention-to-treat analysis should be more fully addressed to reduce threats to internal validity in primary research.
The aim of this study was to test individual adaptation kinetics to a high-resistance sprint training program designed to improve maximal horizontal power (Pmax), and compare the group and individual results of a classical “pre-post” analysis, and a “pre-peak” approach. Thirteen male and 9 female trained sprinters had their 30-m sprint performance and mechanical outputs assessed 1 week before (PRE), and one (POST, W1), 2 (W2), 3 (W3) and 4 (W4) weeks after a 10-week training block (10 repetitions of 20-m resisted sprints at the load associated to the apex of their velocity-power relationship: i.e., 90 ± 10% body mass on average (range: 75–112%). We observed clearly different outcomes on all variables for the PRE-POST vs. PRE-PEAK analyses. The PRE-PEAK analysis showed a larger (almost double) increase in Pmax (9.98 ± 5.27% on average, p < 0.01) than the PRE-POST (5.39 ± 5.87%, p < 0.01). Individual kinetics of post-training adaptations show that peak values were not captured in the POST (W1) assessment (generally observed at W3 and W4). Finally, the week of greatest Pmax output differed strongly among subjects, with most subjects (7/22) peaking at W4. In conclusion, after a 10-week high-resistance sprint training block, a classical 1-week-PRE to 1-week-POST assessment could not capture peak adaptation, which differed among athletes. Adopting a similar approach in practice or research should improve insight into the true effects of training stimuli on athletic capabilities.
Aims
We analysed the changes in force-velocity-power variables and jump performance in response to an individualized training program based on the force-velocity imbalance (FVimb). In particular, we investigated (i) the individual adaptation kinetics to reach the optimal profile and (ii) de-training kinetics over the three weeks following the end of the training program.
Methods
Sixty subjects were assigned to four sub-groups according to their initial FVimb: high or low force-deficit (FD) and high or low velocity-deficit (VD). The duration of training intervention was set so that each individual reached their “Optimal force-velocity (F-v) profile”. Mechanical and performance variables were measured every 3 weeks during the program, and every week after the end of the individualized program.
Results
All subjects in the FD sub-groups showed extremely large increases in maximal theoretical force output (+30±16.6% Mean±SD; ES = 2.23±0.28), FVimb reduction (-74.3±54.7%; ES = 2.17±0.27) and large increases in jump height (+12.4±7.6%; ES = 1.45±0.23). For the VD sub-groups, we observed moderate to extremely large increases in maximal theoretical velocity (+15.8±5.1%; ES = 2.72±0.29), FVimb reduction (-19.2±6.9%; ES = 2.36±0.35) and increases in jump height (+10.1±2.7%; ES = 0.93±0.09). The number of weeks needed to reach the optimal F-v profile (12.6 ± 4.6) was correlated to the magnitude of initial FVimb (r = 0.82, p<0.01) for all participants regardless of their initial subgroup. No significant change in mechanical variables or jump performance was observed over the 3-week de-training period.
Conclusions
Collectively, these results provide useful insights into a more specific, individualized (i.e. based on the type and magnitude of FVimb) and accurate training prescription for jumping performance. Considering both training content and training duration together with FVimb may enable more individualized, specific and effective training monitoring and periodization.
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 total training program, 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.
Rugby union is a contact sport in which players require high levels of physical fitness, which is a composite of aerobic and anaerobic endurance, muscle strength and power, speed, agility and body composition. The aim of this study was to assess the physical fitness characteristics of elite female rugby union players. Thirty two elite female rugby players who were members of the South African Rugby Union High Performance Squad were assessed during the pre-season. The players were sub-divided into two positional categories consisting of 17 forwards and 15 backs. The players underwent a comprehensive physical fitness testing (height, body mass and sum of seven skinfolds, sit-and-reach, vertical jump, 10m and 40m speed, 1 RM bench press, pull-ups, one minute push-ups and multi-stage shuttle run test). Analysis of variance was used to examine the difference between forwards and back-line players with regards to physical fitness. There were statistical differences (p < 0.01) between positional groups, as forward players had a greater body mass, sum of skinfolds and body fat percentage than back-line players. In terms of explosive leg power, speed, muscular endurance, back-line players demonstrated superior performances. In contrast, no significant differences were detected between forward and back-line players in terms of flexibility, upper body strength (1 RM bench press and pull-ups) and estimated maximal aerobic power. These findings provide the coaches with a good understanding of the physical fitness of elite female rugby union players.
Keywords: Fitness, rugby, performance, positional groups.
Ballistic performances are determined by both the maximal lower limb power output (Pmax) and their individual force-velocity (F-v) mechanical profile, especially the F-v imbalance (FVimb): difference between the athlete's actual and optimal profile. An optimized training should aim to increase Pmax and/or reduce FVimb. The aim of this study was to test whether an individualized training program based on the individual F-v profile would decrease subjects' individual FVimb and in turn improve vertical jump performance. FVimb was used as the reference to assign participants to different training intervention groups. Eighty four subjects were assigned to three groups: an “optimized” group divided into velocity-deficit, force-deficit, and well-balanced sub-groups based on subjects' FVimb, a “non-optimized” group for which the training program was not specifically based on FVimb and a control group. All subjects underwent a 9-week specific resistance training program. The programs were designed to reduce FVimb for the optimized groups (with specific programs for sub-groups based on individual FVimb values), while the non-optimized group followed a classical program exactly similar for all subjects. All subjects in the three optimized training sub-groups (velocity-deficit, force-deficit, and well-balanced) increased their jumping performance (12.7 ± 5.7% ES = 0.93 ± 0.09, 14.2 ± 7.3% ES = 1.00 ± 0.17, and 7.2 ± 4.5% ES = 0.70 ± 0.36, respectively) with jump height improvement for all subjects, whereas the results were much more variable and unclear in the non-optimized group. This greater change in jump height was associated with a markedly reduced FVimb for both force-deficit (57.9 ± 34.7% decrease in FVimb) and velocity-deficit (20.1 ± 4.3%) subjects, and unclear or small changes in Pmax (−0.40 ± 8.4% and +10.5 ± 5.2%, respectively). An individualized training program specifically based on FVimb (gap between the actual and optimal F-v profiles of each individual) was more efficient at improving jumping performance (i.e., unloaded squat jump height) than a traditional resistance training common to all subjects regardless of their FVimb. Although improving both FVimb and Pmax has to be considered to improve ballistic performance, the present results showed that reducing FVimb without even increasing Pmax lead to clearly beneficial jump performance changes. Thus, FVimb could be considered as a potentially useful variable for prescribing optimal resistance training to improve ballistic performance.
Purpose:
To ascertain whether force-velocity-power relationships could be compiled from a battery of sled-resisted overground sprints and to clarify and compare the optimal loading conditions for maximizing power production for different athlete cohorts.
Methods:
Recreational mixed-sport athletes (n = 12) and sprinters (n = 15) performed multiple trials of maximal sprints unloaded and towing a selection of sled masses (20-120% body mass [BM]). Velocity data were collected by sports radar, and kinetics at peak velocity were quantified using friction coefficients and aerodynamic drag. Individual force-velocity and power-velocity relationships were generated using linear and quadratic relationships, respectively. Mechanical and optimal loading variables were subsequently calculated and test-retest reliability assessed.
Results:
Individual force-velocity and power-velocity relationships were accurately fitted with regression models (R2> .977, P < .001) and were reliable (ES = 0.05-0.50, ICC = .73-.97, CV = 1.0-5.4%). The normal loading that maximized peak power was 78% ± 6% and 82% ± 8% of BM, representing a resistance of 3.37 and 3.62 N/kg at 4.19 ± 0.19 and 4.90 ± 0.18 m/s (recreational athletes and sprinters, respectively). Optimal force and normal load did not clearly differentiate between cohorts, although sprinters developed greater maximal power (17.2-26.5%, ES = 0.97-2.13, P < .02) at much greater velocities (16.9%, ES = 3.73, P < .001).
Conclusions:
Mechanical relationships can be accurately profiled using common sled-training equipment. Notably, the optimal loading conditions determined in this study (69-96% of BM, dependent on friction conditions) represent much greater resistance than current guidelines (~7-20% of BM). This method has potential value in quantifying individualized training parameters for optimized development of horizontal power.
The ability of the human body to generate maximal power is linked to a host of performance outcomes and sporting success. Power-force-velocity relationships characterize limits of the neuromuscular system to produce power, and their measurement has been a common topic in research for the past century. Unfortunately, the narrative of the available literature is complex, with development occurring across a variety of methods and technology. This review focuses on the different equipment and methods used to determine mechanical characteristics of maximal exertion human sprinting. Stationary cycle ergometers have been the most common mode of assessment to date, followed by specialized treadmills used to profile the mechanical outputs of the limbs during sprint running. The most recent methods use complex multiple-force plate lengths in-ground to create a composite profile of over-ground sprint running kinetics across repeated sprints, and macroscopic inverse dynamic approaches to model mechanical variables
Background:
Sprint running acceleration is a key feature of physical performance in team sports, and recent literature shows that the ability to generate large magnitudes of horizontal ground-reaction force and mechanical effectiveness of force application are paramount. The authors tested the hypothesis that very-heavy loaded sled sprint training would induce an improvement in horizontal-force production, via an increased effectiveness of application.
Methods:
Training-induced changes in sprint performance and mechanical outputs were computed using a field method based on velocity-time data, before and after an 8-wk protocol (16 sessions of 10- × 20-m sprints). Sixteen male amateur soccer players were assigned to either a very-heavy sled (80% body mass sled load) or a control group (unresisted sprints).
Results:
The main outcome of this pilot study is that very-heavy sled-resisted sprint training, using much greater loads than traditionally recommended, clearly increased maximal horizontal-force production compared with standard unloaded sprint training (effect size of 0.80 vs 0.20 for controls, unclear between-groups difference) and mechanical effectiveness (ie, more horizontally applied force; effect size of 0.95 vs -0.11, moderate between-groups difference). In addition, 5-m and 20-m sprint performance improvements were moderate and small for the very-heavy sled group and small and trivial for the control group, respectively. Practical Applications: This brief report highlights the usefulness of very-heavy sled (80% body mass) training, which may suggest value for practical improvement of mechanical effectiveness and maximal horizontal-force capabilities in soccer players and other team-sport athletes.
Results:
This study may encourage further research to confirm the usefulness of very-heavy sled in this context.
The purpose of this study was to assess validity and reliability of sprint performance outcomes measured with an iPhone application (named: MySprint) and existing field methods (i.e. timing photocells and radar gun). To do this, 12 highly trained male sprinters performed 6 maximal 40-m sprints during a single session which were simultaneously timed using 7 pairs of timing photocells, a radar gun and a newly developed iPhone app based on high-speed video recording. Several split times as well as mechanical outputs computed from the model proposed by Samozino et al. [(2015). A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running. Scandinavian Journal of Medicine & Science in Sports. https://doi.org/10.1111/sms.12490] were then measured by each system, and values were compared for validity and reliability purposes. First, there was an almost perfect correlation between the values of time for each split of the 40-m sprint measured with MySprint and the timing photocells (r=0.989–0.999, standard error of estimate=0.007–0.015 s, intraclass correlation coefficient (ICC)=1.0). Second, almost perfect associations were observed for the maximal theoretical horizontal force (F0), the maximal theoretical velocity (V0), the maximal power (Pmax) and the mechanical effectiveness (DRF – decrease in the ratio of force over acceleration) measured with the app and the radar gun (r= 0.974–0.999, ICC=0.987–1.00). Finally, when analysing the performance outputs of the six different sprints of each athlete, almost identical levels of reliability were observed as revealed by the coefficient of variation (MySprint: CV=0.027–0.14%; reference systems: CV=0.028–0.11%). Results on the present study showed that sprint performance can be evaluated in a valid and reliable way using a novel iPhone app.
Purpose:
1) to analyze the reliability and validity of a simple computation method to evaluate force (F), velocity (v) and power (P) output during a countermovement jump (CMJ) suitable for use in field conditions; and 2) to verify the validity of this computation method to compute the CMJ Force-velocity (F-v) profile (including unloaded and loaded jumps) in trained athletes.
Methods:
Sixteen high-level male sprinters and jumpers performed maximal CMJs under six different load conditions (from 0 to 87 kg). A force-plate sampling at 1000 Hz was used to record vertical ground reaction force and derive vertical displacement data during CMJ trials. For each condition, mean F, v, and P of the push-off phase were determined from both force plate data (reference method) and simple computation measures based on body mass, jump height (from flight time), and push-off distance, and used to establish linear F-v relationship for each individual.
Results:
Mean absolute bias values were 0.9% (±1.6), 4.7% (±6.2), 3.7% (±4.8), and 5% (±6.8) for F, v, P and slope of the F-v relationship (SFv), respectively. Both methods showed high correlations for F-v profile related variables (r = 0.985 - 0.991). Finally, all variables computed from the simple method showed high reliability with ICC > 0.980 and CV < 1.0%.
Conclusions:
These results suggest that the simple method presented here is valid and reliable for computing CMJ force, velocity, power, and force-velocity profiles in athletes and could be used in practice under field conditions when body mass, push-off distance, and jump height are known.
This review article discusses previous literature that has examined the influence of muscular strength on various factors associated with athletic performance and the benefits of achieving greater muscular strength. Greater muscular strength is strongly associated with improved force-time characteristics that contribute to an athlete’s overall performance. Much research supports the notion that greater muscular strength can enhance the ability to perform general sport skills such as jumping, sprinting, and change of direction tasks. Further research indicates that stronger athletes produce superior performances during sport specific tasks. Greater muscular strength allows an individual to potentiate earlier and to a greater extent, but also decreases the risk of injury. Sport scientists and practitioners may monitor an individual’s strength characteristics using isometric, dynamic, and reactive strength tests and variables. Relative strength may be classified into strength deficit, strength association, or strength reserve phases. The phase an individual falls into may directly affect their level of performance or training emphasis. Based on the extant literature, it appears that there may be no substitute for greater muscular strength when it comes to improving an individual’s performance across a wide range of both general and sport specific skills while simultaneously reducing their risk of injury when performing these skills. Therefore, sport scientists and practitioners should implement long-term training strategies that promote the greatest muscular strength within the required context of each sport/event. Future research should examine how force-time characteristics, general and specific sport skills, potentiation ability, and injury rates change as individuals transition from certain standards or the suggested phases of strength to another.
Recent studies have brought new insights into the evaluation of power-force-velocity profiles in both ballistic push-offs (e.g. jumps) and sprint movements. These are major physical components of performance in many sports, and the methods we developed and validated are based on data that are now rather simple to obtain in field conditions (e.g. body mass, jump height, sprint times or velocity). The promising aspect of these approaches is that they allow for a more individualized and accurate evaluation, monitoring, and training practices; the success of which are highly dependent on the correct collection, generation and interpretation of athletes' mechanical outputs. We therefore wanted to provide a practical vade mecum to sports practitioners interested in implementing these power-force-velocity profiling approaches. After providing a summary of theoretical and practical definitions for the main variables, we have first detailed how vertical profiling can be used to manage ballistic push-off performance with emphasis on the concept of optimal force-velocity profile and the associated force-velocity imbalance. Further, we have discussed these same concepts with regards to horizontal profiling in the management of sprinting performance. These sections have been illustrated by typical examples from our own practice. Finally, we have provided a practical and operational synthesis, and outlined future challenges that will help in further developing these approaches.
Background:
Based on recent findings regarding the mechanical determinants of sprint performance, resisted sled sprint (RSS) training may provide an effective tool for the improvement of sprint acceleration and maximal velocity. However, the volume and intensity for effective RSS training in different populations is unclear.
Objectives:
The primary objective was to evaluate the effectiveness of RSS training compared with unresisted sprint (URS) training, and the differential effects of sled load on RSS training outcomes.
Data sources:
STUDY ELIGIBILITY AND APPRAISAL: A systematic review was performed primarily using PubMed and SPORTDiscus databases. Peer-reviewed studies were accepted only if the participants used a sled towing device for a longitudinal intervention of resisted sprint training, and if RSS training was the primary difference in training intervention between groups. Effect size (ES) reported using Cohen's d was presented to compare the magnitude of effect between both dependent and independent groups.
Results:
A total of 11 studies fulfilled the eligibility criteria. Sled loads were prescribed either as a percentage of body mass (%BM), a targeted reduction in velocity compared with unresisted sprint velocity (%V dec) or as an absolute load (kg). RSS training with 'light' (<10 %BM or <10 %V dec) loads provide 'small' decrements in acceleration (-1.5 %, ES = 0.50) to 'moderate' improvements in maximal sprint velocity (2.4 %, ES = 0.80) in sprint-trained individuals. 'Moderate' (10-19.9 %BM or 10-14.9 %V dec) to 'very heavy' (>30 %BM or >30 %V dec) sled loads provide 'trivial' to 'extremely large' improvements in acceleration performance (0.5-9.1 %, ES = 0.14-4.00) in strength-trained or team sport individuals. Whether RSS training is more effective than URS training in the improvement of acceleration or maximal sprint velocity remains equivocal.
Conclusions:
RSS training is a novel training method with potential for the improvement of sprint performance, but its performance benefits over URS training remain to be conclusively demonstrated. Between-study comparisons are limited primarily by discrepancies in the training status and phase of the participants, and sled load prescription. Future work is required to define the optimal load and volume for RSS depending on the specific components of sprint performance to be enhanced.
Linear sprinting speed is an essential physical quality for many athletes. There are a number of different training modalities that can be used to improve sprint performance. Strength and conditioning coaches must select the most appropriate modalities for their athletes, taking into consideration the sprint distances that typically occur during competition. The study purpose was to perform a brief review as to the effect of specific (free sprinting; resisted sprinting by sleds, bands, or incline running; assisted sprinting with a towing device or a downhill slope), non-specific (resistance and plyometric training) and combined (a combination of specific and non-specific) training methods on different sprint distances (0-10 m, 0-20 m, 0-30 m, and 31+ m). A total of 48 studies fulfilled the inclusion criteria, resulting in 1485 subjects from a range of athletic backgrounds. The training effects associated with specific sprint training were classified as moderate (effect size [ES] = -1.00; %change = -3.23). Generally, the effect of specific sprint training tended to decrease with distance, although the largest training effects were observed for the 31+ m distance. The greatest training effects (ES = -0.43; % change = -1.65) of non-specific training were observed for the 31+ m distance. The combined training revealed greatest effects (ES = -0.59; % change = -2.81) for the 0-10 m distance. Following this review, specific sprint training methods appear the most beneficial over the investigated distances. However, the implementation of non-specific training methods (e.g. strength and power training) could also benefit speed and athletic performance.
This study aimed to validate a simple field method for determining force- and power-velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatiotemporal data. Force- and power-velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force-velocity relationships; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running.
© 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
The objective of this study was to characterize the mechanics of maximal running sprint acceleration in high-level athletes. Four elite (100-m best time 9.95–10.29 s) and five sub-elite (10.40–10.60 s) sprinters performed seven sprints in overground conditions. A single virtual 40-m sprint was reconstructed and kinetics parameters were calculated for each step using a force platform system and video analyses. Anteroposterior force (FY), power (PY), and the ratio of the horizontal force component to the resultant (total) force (RF, which reflects the orientation of the resultant ground reaction force for each support phase) were computed as a function of velocity (V). FY-V, RF-V, and PY-V relationships were well described by significant linear (mean R2 of 0.892 ± 0.049 and 0.950 ± 0.023) and quadratic (mean R2 = 0.732 ± 0.114) models, respectively. The current study allows a better understanding of the mechanics of the sprint acceleration notably by modeling the relationships between the forward velocity and the main mechanical key variables of the sprint. As these findings partly concern world-class sprinters tested in overground conditions, they give new insights into some aspects of the biomechanical limits of human locomotion.
The purpose of this investigation was to analyze the concurrent validity and reliability of an iPhone app (called: My Jump) for measuring vertical jump performance. Twenty recreationally-active healthy men (age: 22.1 ± 3.6 years) completed five maximal countermovement jumps (CMJ), which were evaluated using a force platform (time in the air –TIA– method) and a specially designed iPhone app. My jump was developed to calculate the jump height from flight time using the high-speed video recording facility on the iPhone 5s. Jump heights of the 100 jumps measured, for both devices, were compared using the intraclass correlation coefficient (ICC), Pearson product-moment correlation coefficient (r), Cronbach’s alpha (α), coefficient of variation (CV) and Bland-Altman plots. There was an almost perfect agreement between the force platform and My Jump for the CMJ height (ICC = 0.997, p < 0.001; Bland-Altman bias= 1.1 ±0.5cm, p < 0.001). In comparison with the force platform, My Jump showed good validity for the CMJ height (r = 0.995, p < 0.001). The results of the present study show that CMJ height can be easily, accurately, and reliably evaluated using a specially developed iPhone 5s app.
The aim of the present study was to examine, in highly trained young soccer players, the mechanical horizontal determinants of acceleration (Acc) and maximal sprinting speed (MSS). Eighty-six players (14.1 ± 2.4 year) performed a 40-m sprint to assess Acc and MSS. Speed was measured with a 100-Hz radar, and theoretical maximal velocity (V 0), horizontal force (F 0) and horizontal power (P max) were calculated. Within each age group, players were classified as high Acc/fast MSS (>2% faster than group mean), medium (between −2% and +2%), and low/slow (>2% slower). Acc and MSS were very largely correlated (−0.79; 90% confidence limit [−0.85; −0.71]). The determinants (multiple regression r 2 = 0.84 [0.78; 0.89]) of Acc were V 0 (partial r: 0.80 [0.72; 0.86]) and F 0 (0.57 [0.44; 0.68]); those of MSS (r 2 = 0.96 [0.94; 0.97]) were V 0 (0.96 [0.94; 0.97]) and P max (0.73 [0.63; −0.80]). High/Med have likely greater F 0 (Cohen’s d: +0.8 [0.0; 1.5]), V 0 (+0.6 [−0.1; 1.3]) and P max (+0.9 [0.2; 1.7]) than Low/Med. High/Fast have an almost certainly faster V 0 (+2.1 [1.5; 2.7]) and a likely greater P max (+0.6 [−0.1; 1.3]) than High/Med, with no clear differences in F 0 (−0.0 [−0.7; 0.6]). Speed may be a generic quality, but the mechanical horizontal determinants of Acc and MSS differ. While maximal speed training may improve both Acc and MSS, improving horizontal force production capability may be efficient to enhance sprinting performance over short distances.
The aim of this study was to compare biomechanical and perceptual-cognitive variables between genders during an offensive and defensive agility protocol. Twelve male and female (n=24) recreational team sport athletes participated in this study, each performing 12 offensive and defensive agility trials (six left, six right) changing direction in response to movements of a human stimulus. Three-dimensional motion, ground reaction force (GRF) and impulse data was recorded across plant phase for dominant leg change of direction (COD) movements, while timing gates and high-speed video captured decision time, total running time and post COD stride velocity. Subjects also performed a unilateral isometric squat to determine lower-body strength, and limb dominance. Group (gender) by condition (2x2) MANOVA's with follow up ANOVA's were conducted to examine differences between groups (p ≤ 0.05). Male athletes demonstrated significantly greater lower body strength, vertical braking force and impulse application, knee and spine flexion, hip abduction, a faster decision time and post COD stride velocity during both agility conditions compared to females. Differences between offensive and defensive movements appear to be attributed to differences in decision time between genders. This study demonstrates that biomechanical and perceptual-cognitive differences exist between genders and within offensive and defensive agility movements.
This study sought to lend experimental support to the theoretical influence of force-velocity (F-v) mechanical profile on jumping performance independently from the effect of maximal power output (P max ). 48 high-level athletes (soccer players, sprinters, rugby players) performed maximal squat jumps with additional loads from 0 to 100% of body mass. During each jump, mean force, velocity and power output were obtained using a simple computation method based on flight time, and then used to determine individual linear F-v relationships and P max values. Actual and optimal F-v profiles were computed for each subject to quantify mechanical F-v imbalance. A multiple regression analysis showed, with a high-adjustment quality (r²=0.931, P<0.001, SEE=0.015 m), significant contributions of P max , F-v imbalance and lower limb extension range (h PO ) to explain interindividual differences in jumping performance (P<0.001) with positive regression coefficients for P max and h PO and a negative one for F-v imbalance. This experimentally supports that ballistic performance depends, in addition to P max , on the F-v profile of lower limbs. This adds support to the actual existence of an individual optimal F-v profile that maximizes jumping performance, a F-v imbalance being associated to a lower performance. These results have potential strong applications in the field of strength and conditioning.
This series of reviews focuses on the most important neuromuscular function in many sport performances, the ability to generate maximal muscular power. Part 1 focuses on the factors that affect maximal power production, while part 2, which will follow in a forthcoming edition of Sports Medicine, explores the practical application of these findings by reviewing the scientific literature relevant to the development of training programmes that most effectively enhance maximal power production. The ability of the neuromuscular system to generate maximal power is affected by a range of interrelated factors. Maximal muscular power is defined and limited by the force-velocity relationship and affected by the length-tension relationship. The ability to generate maximal power is influenced by the type of muscle action involved and, in particular, the time available to develop force, storage and utilization of elastic energy, interactions of contractile and elastic elements, potentiation of contractile and elastic filaments as well as stretch reflexes. Furthermore, maximal power production is influenced by morphological factors including fibre type contribution to whole muscle area, muscle architectural features and tendon properties as well as neural factors including motor unit recruitment, firing frequency, synchronization and inter-muscular coordination. In addition, acute changes in the muscle environment (i.e. alterations resulting from fatigue, changes in hormone milieu and muscle temperature) impact the ability to generate maximal power. Resistance training has been shown to impact each of these neuromuscular factors in quite specific ways. Therefore, an understanding of the biological basis of maximal power production is essential for developing training programmes that effectively enhance maximal power production in the human.
Sprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force-velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P < 0.01), as was the theoretical maximal velocity production capability (P < 0.011), whereas the theoretical maximal force production capability was not. The ability to apply the resultant force backward during acceleration was positively correlated to 100-m performance (r (s) > 0.683; P < 0.018), but the magnitude of resultant force was not (P = 0.16). Step frequency, contact and swing time were significantly correlated to acceleration and 100-m performance (positively for the former, negatively for the two latter, all P < 0.05), whereas aerial time and step length were not (all P > 0.21). Last, anthropometric data of body mass index and lower-limb-to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a "velocity-oriented" force-velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time.
The purpose of this study was to investigate the sprinting demands of National Rugby League (NRL) competition and characterize the sprinting patterns of different rugby league playing positions. Thirty-seven elite rugby league players (mean ± SE age: 23.6 ± 0.5 years) underwent global positioning satellite analysis during 104 NRL appearances. The majority (67.5%) of sprint efforts were across distances of <20 m. The most common sprint distance for hit-up forwards was 6-10 m (46.3%). Outside backs had a greater proportion (33.7%) of sprint efforts over distances of ≥21 m. The proportion of sprint efforts over 40 m or greater for hit-up forwards, wide running forwards, adjustables, and outside backs was 5.0, 7.4, 5.0, and 9.7%, respectively. Of the sprints performed, approximately 48.0% involved contact, approximately 58.0% were preceded by forward locomotion (forward walking, jogging, or striding), whereas over 24.0% occurred from a standing start. Hit-up forwards more commonly sprinted from a standing start, or after lateral movement, whereas forward striding activities more commonly preceded sprint efforts for the adjustables and outside backs. The majority of sprint efforts were performed without the ball (78.7 vs. 21.3%). Most sprint efforts (67.5%) were followed by a long recovery (i.e., ≥5 minutes). Outside backs had the greatest proportion (76.1%) of long duration recovery periods and the smallest proportion (1.8%) of short duration recovery periods (i.e., <60 seconds) between sprints. The results of this study demonstrate differences among rugby league playing positions for the nature of sprint efforts and the typical distances covered during these efforts. Furthermore, the activities preceding and the recovery periods after sprint efforts were different among playing positions. These findings suggest that rugby league sprint training should be tailored to meet the individual demands of specific playing positions.
The study's purpose was to determine the respective influences of the maximal power (Pmax) and the force-velocity (F-v) mechanical profile of the lower limb neuromuscular system on performance in ballistic movements.
A theoretical integrative approach was proposed to express ballistic performance as a mathematical function of Pmax and F-v profile. This equation was (i) validated from experimental data obtained on 14 subjects during lower limb ballistic inclined push-offs and (ii) simulated to quantify the respective influence of Pmax and F-v profile on performance.
The bias between performances predicted and obtained from experimental measurements was 4%-7%, confirming the validity of the proposed theoretical approach. Simulations showed that ballistic performance was mostly influenced not only by Pmax but also by the balance between force and velocity capabilities as described by the F-v profile. For each individual, there is an optimal F-v profile that maximizes performance, whereas unfavorable F-v balances lead to differences in performance up to 30% for a given Pmax. This optimal F-v profile, which can be accurately determined, depends on some individual characteristics (limb extension range, Pmax) and on the afterload involved in the movement (inertia, inclination). The lower the afterload, the more the optimal F-v profile is oriented toward velocity capabilities and the greater the limitation of performance imposed by the maximal velocity of lower limb extension.
High ballistic performances are determined by both maximization of the power output capabilities and optimization of the F-v mechanical profile of the lower limb neuromuscular system.
We transposed the concept of effectiveness of force application used in pedaling mechanics to calculate the ratio of forces (RF) during sprint running and tested the hypothesis that field sprint performance was related to the technical ability to produce high amounts of net positive horizontal force. This ability represents how effectively the total force developed by the lower limbs is applied onto the ground, despite increasing speed during the acceleration phase.
Twelve physically active male subjects (including two sprinters) performed 8-s sprints on a recently validated instrumented treadmill, and a 100-m sprint on an athletics track. Mean vertical (FV), net horizontal (FH), and total (FTot) ground reaction forces measured at each step during the acceleration allowed computation of the RF as FH/FTot and an index of force application technique (DRF) as the slope of the RF-speed linear relationship from the start until top speed. Correlations were tested between these mechanical variables and field sprint performance variables measured by radar: mean and top 100-m speeds and 4-s distance.
Significant (r > 0.731; P < 0.01) correlations were obtained between DRF and 100-m performance (mean and top speeds; 4-s distance). Further, FH was significantly correlated (P < 0.05) to field sprint performance, but FTot and FV were not.
Force application technique is a determinant factor of field 100-m sprint performance, which is not the case for the amount of total force subjects are able to apply onto the ground. It seems that the orientation of the total force applied onto the supporting ground during sprint acceleration is more important to performance than its amount.
Purpose:
Ballet dancers are required to achieve performance feats such as exciting and dramatic elevations. Dancers with a greater jump height can perform a wider range of skills during their flight time and implement more specific technical skills related to the aesthetic components of a dance choreography. New findings suggest the relationship between force and velocity mechanical capabilities (F-V profile) as an important variable for jumping performance. A new field method based on several series of loaded vertical jumps provides information on the theoretical maximal force, theoretical maximal velocity, theoretical maximal power, and the imbalance between force and velocity (F-VIMB). The purpose of this study was to observe the effects of 9 wk of individualized F-V profile-based training during countermovement jumps (CMJs) in female ballet dancers.
Methods:
CMJ and mechanical outputs of 46 dancers (age = 18.9 [1.1] y, body mass = 54.8 [6.1] kg, height = 163.7 [8.4] cm) were estimated in a pre-post intervention. The control group (10 participants) continued with the standardized training regimen (no resistance training), whereas the experimental group (36 participants) performed 2 sessions over 9 wk of a training plan based on their F-V profile.
Results:
The experimental group presented significant differences with large effect sizes in CMJ height (29.3 [3.2] cm vs 33.5 [3.72] cm), theoretical maximal force (24.1 [2.2] N/kg vs 29.9 [2.8] N/kg), and theoretical maximal velocity (4 [0.6] m/s vs 3.2 [0.5] m/s). Significant differences with a very large effect size were found in F-VIMB (43.8% [15.3%] vs 24.9% [8.7%]).
Conclusion:
A training program addressing F-VIMB is an effective way to improve CMJ height in female ballet dancers.
The purpose of this investigation was to determine if the magnitude of adaptation to integrated ballistic training is influenced by initial strength level. Such information is needed to inform resistance training guidelines for both higher- and lower-level athlete populations. To this end, two groups of distinctly different strength levels (stronger: one-repetition-maximum (1RM) squat = 2.01 ± 0.15 kg.BM⁻¹; weaker: 1.20 ± 0.20 kg.BM⁻¹) completed 10 weeks of resistance training incorporating weightlifting derivatives, plyometric actions and ballistic exercises. Testing occurred at pre-, mid- and post-training. Measures included variables derived from the incremental-load jump squat and the 1RM squat, alongside muscle activity (electromyography), and jump mechanics (force-time comparisons throughout the entire movement). The primary outcome variable was peak velocity derived from the unloaded jump squat. It was revealed that the stronger group displayed a greater (P = 0.05) change in peak velocity at midtest (baseline: 2.65±0.10 m∙s⁻¹, midtest: 2.80±0.17 m∙s⁻¹) but not posttest (2.85±0.18 m∙s⁻¹) when compared to the weaker participants (baseline 2.48 ±0.09, midtest. 2.47 ±0.11, posttest: 2.61 ±0.10 m∙s⁻¹). Different changes occurred between groups in the force-velocity relationship (P=0.001–0.04) and jump mechanics (P≤0.05), while only the stronger group displayed increases in muscle activation (P=0.05). In conclusion, the magnitude of improvement in peak velocity was significantly influenced by pre-existing strength level in the early stage of training. Changes in the mechanisms underpinning performance were less distinct.
There is limited published research on strength and conditioning (S&C) practices in elite Rugby Union (RU). Information regarding testing batteries and programme design would provide valuable information to both applied practitioners and researchers investigating the influence of training interventions or pre performance strategies. The aim of this study was to detail the current practices of S&C coaches and Sport Scientists working in RU. A questionnaire was developed that comprised 7 sections; personal details, physical testing, strength and power development, concurrent training, flexibility development, unique aspects of the programme and any further relevant information regarding prescribed training programmes. Forty-three (41 male, 2 female; 33.1 +/- 5.3y) of 52 (83%) coaches responded to the questionnaire. The majority of practitioners worked with international level and/or professional RU athletes. All respondents believed strength training benefits RU performance and reported their athletes regularly performed strength training. The clean and back squat were rated the most important prescribed exercises. Forty-one (95%) respondents reported prescribing plyometric exercises and 38 (88%) indicated periodisation strategies were employed. Forty-two (98%) practitioners reported conducting physical testing, with body composition being the most commonly tested phenotype. Thirty-three (77%) practitioners indicated that the potential muted strength development associated with concurrent training was considered when programming and 27 (63%) believed strength prior to aerobic training was more favourable for strength development than vice versa. This research represents the only published survey to date of S&C practices in Northern and Southern hemisphere RU. Copyright (C) 2016 by the National Strength & Conditioning Association.
An athletic profile should encompass the physiological, biomechanical, anthropometric and performance measures pertinent to the athlete's sport and discipline. The measurement systems and procedures used to create these profiles are constantly evolving and becoming more precise and practical. This is a review of strength and ballistic assessment methodologies used in sport, a critique of current maximum strength [one-repetition maximum (1RM) and isometric strength] and ballistic performance (bench throw and jump capabilities) assessments for the purpose of informing practitioners and evolving current assessment methodologies. The reliability of the various maximum strength and ballistic assessment methodologies were reported in the form of intra-class correlation coefficients (ICC) and coefficient of variation (%CV). Mean percent differences [Formula: see text] and effect size (ES = [X method2 - X method1] ÷ SDmethod1) calculations were used to assess the magnitude and spread of methodological differences for a given performance measure of the included studies. Studies were grouped and compared according to their respective performance measure and movement pattern. The various measurement systems (e.g. force plates, position transducers, accelerometers, jump mats, optical motion sensors and jump-and-reach apparatuses) and assessment procedures (i.e. warm-up strategies, loading schemes and rest periods) currently used to assess maximum isometric squat and mid-thigh pull strength (ICC > 0.95; CV < 2.0 %), 1RM bench press, back squat and clean strength (ICC > 0.91; CV < 4.3 %), and ballistic (vertical jump and bench throw) capabilities (ICC > 0.82; CV < 6.5 %) were deemed highly reliable. The measurement systems and assessment procedures employed to assess maximum isometric strength [M Diff = 2-71 %; effect size (ES) = 0.13-4.37], 1RM strength (M Diff = 1-58 %; ES = 0.01-5.43), vertical jump capabilities (M Diff = 2-57 %; ES = 0.02-4.67) and bench throw capabilities (M Diff = 7-27 %; ES = 0.49-2.77) varied greatly, producing trivial to very large effects on these respective measures. Recreational to highly trained athletes produced maximum isometric squat and mid-thigh pull forces of 1,000-4,000 N; and 1RM bench press, back squat and power clean values of 80-180 kg, 100-260 kg and 70-140 kg, respectively. Mean and peak power production across the various loads (body mass to 60 % 1RM) were between 300 and 1,500 W during the bench throw and between 1,500 and 9,000 W during the vertical jump. The large variations in maximum strength and power can be attributed to the wide range in physical characteristics between different sports and athletic disciplines, training and chronological age as well as the different measurement systems of the included studies. The reliability and validity outcomes suggest that a number of measurement systems and testing procedures can be implemented to accurately assess maximum strength and ballistic performance in recreational and elite athletes, alike. However, the reader needs to be cognisant of the inherent differences between measurement systems, as selection will inevitably affect the outcome measure. The strength and conditioning practitioner should also carefully consider the benefits and limitations of the different measurement systems, testing apparatuses, attachment sites, movement patterns (e.g. direction of movement, contraction type, depth), loading parameters (e.g. no load, single load, absolute load, relative load, incremental loading), warm-up strategies, inter-trial rest periods, dependent variables of interest (i.e. mean, peak and rate dependent variables) and data collection and processing techniques (i.e. sampling frequency, filtering and smoothing options).
A new method for encoding a videoconference image sequence, termed adaptive neural net vector quantisation (ANNVQ), has been derived. It is based on Kohonen's self-organised feature maps, a neural network type clustering algorithm. The new method differs from it, in that after training the initial codebook, a modified form of adaptation resumes, in order to respond to scene changes and motion. The main advantages are high image quality with modest bit rates and effective adaptation to motion and scene changes, with the capability to quickly adjust the instantaneous bit rate in order to keep the image quality constant. This is a good match to packet switched networks where variable bit rate and uniform image quality are highly desirable. Simulation experiments have been carried out with 4 × 4 blocks of pixels from an image sequence consisting of 20 frames of size 112 × 96 pixels each. With a codebook size of 512, ANNVQ results in high image quality upon image reconstruction, with peak signal-to-noise ratio (PSNR) of about 36 to 37 dB, at coding bit rates of about 0.50 bit/pixel. This compares quite favourably with classical vector quantisation at a similar bit rate. Moreover, this value of PSNR remains approximately constant, even when encoding image frames with considerable motion.
Weighted sled towing is used by athletes to improve sprint acceleration ability. The typical coaching recommendation is to use relatively light loads, as excessively heavy loads are hypothesized to disrupt running mechanics and be detrimental to sprint performance. However, this coaching recommendation has not been empirically tested. This study compared the effects of weighted sled towing with two different external loads on sprint acceleration ability. Twenty-one physically active men were randomly allocated to heavy- (n = 10) or light-load weighted sled towing (n = 11) groups. All subjects participated in two training sessions per week for 8 weeks. The subjects in the heavy and light groups performed weighted sled towing using external loads that reduced sprint velocity by ∼30% and ∼10%, respectively. Before and after the training, the subjects performed a 10-m sprint test, in which split time was measured at 5 and 10 m from the start. The heavy group significantly improved both the 5- and 10-m sprint time by 5.7 ± 5.7% and 5.0 ± 3.5%, respectively (P < 0.05), whereas only 10-m sprint time was improved significantly by 3.0 ± 3.5% (P < 0.05) in the light group. No significant differences were found between the groups in the changes in 5-m and 10-m sprint time from pre- to post-training. These results question the notion that training loads that induce greater than 10% reduction in sprint velocity would negatively affect sprint performance, and point out the potential benefit of using a heavier load for weighted sled towing.
Statistical guidelines and expert statements are now available to assist in the analysis and reporting of studies in some biomedical disciplines. We present here a more progressive resource for sample-based studies, meta-analyses, and case studies in sports medicine and exercise science. We offer forthright advice on the following controversial or novel issues: using precision of estimation for inferences about population effects in preference to null-hypothesis testing, which is inadequate for assessing clinical or practical importance; justifying sample size via acceptable precision or confidence for clinical decisions rather than via adequate power for statistical significance; showing SD rather than SEM, to better communicate the magnitude of differences in means and nonuniformity of error; avoiding purely nonparametric analyses, which cannot provide inferences about magnitude and are unnecessary; using regression statistics in validity studies, in preference to the impractical and biased limits of agreement; making greater use of qualitative methods to enrich sample-based quantitative projects; and seeking ethics approval for public access to the depersonalized raw data of a study, to address the need for more scrutiny of research and better meta-analyses. Advice on less contentious issues includes the following: using covariates in linear models to adjust for confounders, to account for individual differences, and to identify potential mechanisms of an effect; using log transformation to deal with nonuniformity of effects and error; identifying and deleting outliers; presenting descriptive, effect, and inferential statistics in appropriate formats; and contending with bias arising from problems with sampling, assignment, blinding, measurement error, and researchers' prejudices. This article should advance the field by stimulating debate, promoting innovative approaches, and serving as a useful checklist for authors, reviewers, and editors.
The purpose of this investigation was to examine the impact of training on the power-, force-, and velocity-time curves of the countermovement jump (CMJ) through both cross-sectional and longitudinal comparisons. The most novel aspect of this study was the analysis of these curves for the entire movement at a sampling frequency of 386-506 Hz averaged across 30 subjects. Thirty subjects, all men, participated in this investigation and included 12 athletes and 18 untrained men. Two major comparisons were conducted: 1) an acute, cross-sectional examination comparing experienced jumpers (jump height > 0.50 m; n = 12 men's athletes) with nonjumpers (jump height < 0.50 m; n = 14 untrained men), and 2) a longitudinal examination comparing performance before and after 12 weeks of power training (training group n = 10 untrained men; control group n = 8 untrained men). Data obtained from the baseline testing session of 14 subjects involved in the longitudinal study were used for the cross-sectional examination to represent the nonjumper group. The cross-sectional examination revealed significant (p <or= 0.05) differences between jumpers and nonjumpers in peak performance variables (i.e., peak power, force, velocity, displacement) as well as over a range of time points throughout the power-, force-, velocity-, and displacement-time curves of the CMJ. Similar results were observed in the longitudinal examination, with power training eliciting significant changes to peak performance variables as well as significant changes to the power-, force-, velocity-, and displacement-time curves over a range of time points throughout the CMJ. This study illustrates that training status not only influences the peak performance variables of the countermovement jump but also impacts the shape of the power-, force-, velocity-, and displacement-time curves throughout the movement. Because analysis of peak performance variables offers little insight into how adaptations have occurred after training, examination of the changes to the power-, force-, velocity-, and/or displacement-time curves offers a simple yet powerful monitoring technique that practitioners can use to gain insight into the precise nature and timing of adaptations to training.
The purpose of this study was to investigate the relationship of the 1 repetition maximum (1RM) squat to power output during countermovement and static weighted vertical squat jumps. The training experience of subjects (N = 22, 87.0 +/- 15.3 kg, 14.1 +/- 7.1% fat, 22.2 +/- 3.8 years) ranged from 7 weeks to 15+ years. Based on the 1RM squat, subjects were further divided into the 5 strongest and 5 weakest subjects (p <or= 0.05). Squat jumps were performed with a countermovement or statically at 2 different sessions spaced 1 week apart. Jumps were performed with weights ranging from 10 to 100% of the 1RM squat. A maximum effort was made for each trial; subjects performed jumps (feet left the floor) with weights up to approximately 90% of 1RM. Squat-jump power was determined using the V-scope 120. Results indicate strong correlations (r = 0.77-0.94) between the 1RM squat and both countermovement and static jump power up to 90% of 1RM. The highest power outputs for both jump conditions occurred at 10% of the 1RM and decreased as the relative intensity increased. Comparisons of weak and strong subjects indicate that as maximum strength increases the percentage of 1RM at which peak power occurs also increases (40 vs. 10% of 1RM). From a practical aspect, to improve jumping power output, these results suggest that improving maximum strength should be a primary component of training programs and that strength training should shift from lighter (10% 1RM) to heavier (40% 1RM) loads.
Power and maximum strength relationships during performance of dynamic and static weighted jumps
- M H Stone
- H S Bryant
- L Mccoy
- R Coglianese
- M Lehmkuhl
- B Schilling
Stone, M. H., O'Bryant, H. S., McCoy, L., Coglianese, R.,
Lehmkuhl, M., & Schilling, B. (2003). Power and maximum
strength relationships during performance of dynamic and
static weighted jumps. The Journal of Strength & Conditioning
Research, 17, 140-147. doi:10.1519/1533-4287(2003)017
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