A comparison between the force-velocity relationships of unloaded and sled-resisted sprinting: single vs. multiple trial methods

The relationship between load-velocity profiles and 50 m breaststroke performance in national-level male swimmers

This study investigated the relationships between load-velocity profiling and 50 m breaststroke performance. Twenty-seven male swimmers qualified for the national championship participated and performed a 50 m breaststroke trial with a multicamera system. The total race time (t50 m), forward velocity during surface swimming (v50 m), stroke length, and stroke frequency were obtained from the automatic post-processing of the system. Afterwards, the participants performed semi-tethered swimming with three external loads using a robotic resistance device. The average velocity from three stroke cycles was plotted as a function of the corresponding load. The theoretical maximum velocity (v0) and load (L0), L0 normalized to body mass, steepness of the regression line (slope), and active drag (AD) were calculated. The main findings were moderate to large correlations of two 50 m race variables (t50 m and v50 m) with v0, L0, and AD (t50 m range: r = -.444 to r = -.619, p = .020 to p = .001), (v50 m range: r = .451 to r = .568, p = .018 to p = .002). This shows the importance of applying maximum propulsive force to achieve high swimming performance and that load-velocity profiling is an indicator of 50 m breaststroke performance. Load-velocity measurements over time can also monitor velocity, strength, and drag-minimizing abilities, explaining performance changes and training effects.

Reliability and validity of sprint performance using the Alex7 motorized device

Introduction

Advancements in technology have recently made it possible to implement effective training solutions across different environmental conditions. This study evaluated the reliability and validity of measures obtained from the innovative motorized device, Alex7 (Inosportas, Lithuania), and differences in speed and kinematic characteristics between resisted and assisted sprinting in young football players.

Methods

Twenty-seven male athletes (mean age: 16.5 ± 0.8 years; height: 179.5 ± 6.9 cm; body weight: 67.7 ± 8.3 kg) each performed 30-m sprints twice under three different conditions: regular, resisted, and assisted sprinting. The Alex7 device provided the assistance and resistance during sprints. Results were compared with those from Witty timing gates. Ground contact time, flight time, stride length, and pace were measured using the OptoJump system. Reliability was assessed using two-way mixed intraclass correlation coefficients (ICCs) for single measures, the standard error of the mean (SEM), and the coefficient of variation (CV). Pearson's correlation coefficient determined the associations between Alex7 and Witty timing systems. Criterion-referenced validity was based on the mean difference and CV. Systematic bias was determined by limits of agreement using Bland-Altman analysis.

Results

Running times obtained using the Alex7 equipment exhibited good to excellent test-retest reliability between sessions (ICC, 0.83-0.94) and good to excellent correlation (Pearson's r = 0.88-0.98) between the Alex7 and Witty systems in both assisted and resisted running conditions. However, the Alex7 device consistently produced longer running times than the Witty device (up to 0.16 s difference, p < 0.001). The different running conditions produced substantial variations in kinematic variables, such as stride length, ground contact time, and running speed (p < 0.001 for all), but the effects on flight time and running pace were smaller.

Discussion

The Alex7 device shows high reliability for creating resisted and assisted running conditions for young football players. However, it tends to overestimate running time, necessitating caution when assessing the time parameters.

Does Resisted Sprint Training Improve the Sprint Performance of Field-Based Invasion Team Sport Players? A Systematic Review and Meta-analysis

BACKGROUND

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.

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

CLINICAL TRIAL REGISTRATION

Open Science Framework, https://osf.io/thms7/ .

Influence of horizontal resistance loads on spatiotemporal and ground reaction force variables during maximal sprint acceleration

This study aimed to elucidate the influence of horizontal resistance loads on the spatiotemporal and ground reaction force (GRF) variables during maximal sprint acceleration. Nine male sprinters (20.2 ± 1.2 years; 175.3 ± 4.5 cm, 69.7 ± 6.1 kg) performed sprint-running with six loading conditions of one unresisted and five resisted loads of 4, 6, 8, 10, and 12 kg using a resistance training device with intelligent drag technology. During the trials, the GRFs for all steps were determined using a 50-m force plate system. The spatiotemporal and GRF variables at running velocity of every 0.5 m/s were obtained and compared across the loading conditions. The maximal running velocity under 0, 4, 6, 8, 10, and 12 kg loading conditions were 9.84 ± 0.41, 8.55 ± 0.41, 8.09 ± 0.33, 7.62 ± 0.34, 7.11 ± 0.31, and 6.71 ± 0.29 m/s, respectively. ANOVA revealed significant main effects of load on the measured variables (η2 = 0.236-0.715, p < 0.05), except for stance-averaged anteroposterior GRF and braking impulse. However, the observed differences between the loading conditions were small, with approximately 4% (1.3-7.5%) for the GRF variables and approximately 9% (1.2-22.3%) for the spatiotemporal variables. The present study indicates that horizontal resistance load in sprint acceleration has little impact on the spatiotemporal and GRF variables at a given running velocity. In contrast to a general recommendation, one should adopt a heavy load in resisted sprint aiming to improve performance in the earlier stage of maximal sprint acceleration.

Practice to pitch: The relationship between force-velocity profiles and match-day performance of semi-professional rugby union players

Introduction

This exploratory study aimed to assess the relationship between athlete neuromuscular performance and rugby performance indicators. Specifically, the study looked at the force-velocity profiles (FVPs) derived from four common resistance exercises and their relationship with rugby performance indicators (RPIs).

Methods

The study recruited twenty-two semi-professional male rugby players (body mass 102.5 ± 12.6 kg, height 1.85 ± 0.74 m, age 24.4 ± 3.4 years) consisting of ten backs and twelve forwards. Prior to the first game of a Covid-impacted nine-match season, participants performed four common resistance exercises (barbell box squat, jammer push-press, sled pull, and sled push) at incremental loads to establish force-velocity profiles. During the season, rugby performance indicators (post-contact metres, tries, turnovers conceded, tackles, try assists, metres ran, defenders beaten, and tackle breaks) were collated from two trusted sources by a performance analyst. Correlational analyses were used to determine the relationship between the results of FVPs and RPIs.

Results

The study found a statistically significant, moderate, positive correlation between tackle-breaks and sled push V ₀ (r = .35, p = .048). Significant, large, positive correlations were also found between tackles and jammer push-press V ₀ (r = .53, p = .049) and tackle-breaks and sled pull F ₀ (r = .53, p = .03). There was a significant, negative relationship between sled pull V ₀ and tackle-breaks (r = -.49, p = .04). However, the largest, significant correlation reported was between metres ran and sled pull F ₀ (r = .66, p = .03).

Conclusion

The study suggests that a relationship may exist between FVPs of particular exercises and RPIs, but further research is required to confirm this. Specifically, the results suggest that horizontal resistance training may be best to enhance RPIs (tackle-breaks, tackles, and metres ran). The study also found that maximal power was not related to any rugby performance indicator, which suggests that a specified prescription of either force or velocity dominant exercises to enhance RPIs may be warranted.

Development, evaluation and application of a novel markerless motion analysis system to understand push-start technique in elite skeleton athletes

This study describes the development, evaluation and application of a computer vision and deep learning system capable of capturing sprinting and skeleton push start step characteristics and mass centre velocities (sled and athlete). Movement data were captured concurrently by a marker-based motion capture system and a custom markerless system. High levels of agreement were found between systems, particularly for spatial based variables (step length error 0.001 ± 0.012 m) while errors for temporal variables (ground contact time and flight time) were on average within ± 1.5 frames of the criterion measures. Comparisons of sprinting and pushing revealed decreased mass centre velocities as a result of pushing the sled but step characteristics were comparable to sprinting when aligned as a function of step velocity. There were large asymmetries between the inside and outside leg during pushing (e.g. 0.22 m mean step length asymmetry) which were not present during sprinting (0.01 m step length asymmetry). The observed asymmetries suggested that force production capabilities during ground contact were compromised for the outside leg. The computer vision based methods tested in this research provide a viable alternative to marker-based motion capture systems. Furthermore, they can be deployed into challenging, real world environments to non-invasively capture data where traditional approaches are infeasible.

Four Weeks of Power Optimized Sprint Training Improves Sprint Performance in Adolescent Soccer Players

PURPOSE

This study compared the effects of heavy resisted sprint training (RST) versus unresisted sprint training (UST) on sprint performance among adolescent soccer players.

METHODS

Twenty-four male soccer players (age: 15.7 [0.5] y; body height: 175.7 [9.4] cm; body mass: 62.5 [9.2] kg) were randomly assigned to the RST group (n = 8), the UST group (n = 10), or the control group (n = 6). The UST group performed 8 × 20 m unresisted sprints twice weekly for 4 weeks, whereas the RST group performed 5 × 20-m heavy resisted sprints with a resistance set to maximize the horizontal power output. The control group performed only ordinary soccer training and match play. Magnitude-based decision and linear regression were used to analyze the data.

RESULTS

The RST group improved sprint performances with moderate to large effect sizes (0.76-1.41) across all distances, both within and between groups (>92% beneficial effect likelihood). Conversely, there were no clear improvements in the UST and control groups. The RST evoked the largest improvements over short distances (6%-8%) and was strongly associated with increased maximum horizontal force capacities (r = .9). Players with a preintervention deficit in force capacity appeared to benefit the most from RST.

CONCLUSIONS

Four weeks of heavy RST led to superior improvements in short-sprint performance compared with UST among adolescent soccer players. Heavy RST, using a load individually selected to maximize horizontal power, is therefore highly recommended as a method to improve sprint acceleration in youth athletes.

Resisted Sled Sprint Kinematics: The Acute Effect of Load and Sporting Population

In this study, we assessed the acute kinematic effects of different sled load conditions (unloaded and at 10%, 20%, 30% decrement from maximum velocity (Vdec)) in different sporting populations. It is well-known that an athlete’s kinematics change with increasing sled load. However, to our knowledge, the relationship between the different loads in resisted sled sprinting (RSS) and kinematic characteristics is unknown. Thirty-three athletes (sprinters n = 10; team sport athletes n = 23) performed a familiarization session (day 1), and 12 sprints at different loads (day 2) over a distance of 40 m. Sprint time and average velocity were measured. Sagittal-plane high-speed video data was recorded for early acceleration and maximum velocity phase and joint angles computed. Loading introduced significant changes to hip, knee, ankle, and trunk angle for touch-down and toe-off for the acceleration and maximum velocity phase (p < 0.05). Knee, hip, and ankle angles became more flexed with increasing load for all groups and trunk lean increased linearly with increasing loading conditions. The results of this study provide coaches with important information that may influence how RSS is employed as a training tool to improve sprint performance for acceleration and maximal velocity running and that prescription may not change based on sporting population, as there were only minimal differences observed between groups. The trunk lean increase was related to the heavy loads and appeared to prevent athletes to reach mechanics that were truly reflective of maximum velocity sprinting. Lighter loads seem to be more adequate to not provoke changes in maxV kinematics. However, heavy loading extended the distance over which it is possible to train acceleration.

The Relationship Between Selected Load-Velocity Profile Parameters and 50 m Front Crawl Swimming Performance

The purpose of the present study was to establish relationships between sprint front crawl performance and a swimming load-velocity profile. Fourteen male national-level swimmers performed 50 m front crawl and semi-tethered swimming with three progressive loads. The 50 m performance was recorded with a multi-camera system, with which two-dimensional head displacement and the beginning of each arm-stroke motion were quantified. Forward velocity (V_50m), stroke length (SL) and frequency (SF) were quantified for each cycle, and the mean value of all cycles, excluding the first and last cycles, was used for the analysis. From the semi-tethered swimming test, the mean velocity during three stroke cycles in mid-pool was calculated and plotted as a function of the external load, and a linear regression line expressing the relationship between the load and velocity was established for each swimmer. The intercepts between the established line and the axes of the plot were defined as theoretical maximum velocity (V₀) and load (L₀). Large to very large correlations were observed between V_50m and all variables derived from the load-velocity profiling; L₀ (R = 0.632, p = 0.015), L₀ normalized by body mass (R = 0.743, p = 0.002), V₀ (R = 0.698, p = 0.006), and the slope (R = 0.541, p < 0.046). No significant relationships of SL and SL with V_50m and the load-velocity variables were observed, suggesting that each swimmer has his own strategy to achieve the highest swimming velocity. The findings suggest that load-velocity profiling can be used to assess swimming-specific strength and velocity capabilities related to sprint front crawl performance.

INFLUENCE OF MAXIMAL ISOMETRIC STRENGTH ON 20-METER SPRINT TIME

ABSTRACT Introduction The squat is an exercise that is widely used for the development of strength in sports. However, considering that not all sports gestures are vertical, it is important to investigate the effectiveness of propulsive force stimuli applied in different planes. Objective The main purpose of this study was to determine the influence of maximum isometric force (MIF) exerted on starting blocks over performance in 5, 10 and 20-meter sprints. Methods Seven high-level male sprinters (mean age ± SD = 28 ± 5.77 years) participated in this study. The variables were: a) MIF in squats and on starting blocks (measured using a functional electromechanical dynamometer [FEMD]), b) time in 5, 10 and 20-m sprints and c) jump height (measured by the squat jump test). For data analysis, a Pearson correlation was performed between the different variables. The criteria for interpreting the strength of the r coefficients were as follows: trivial (<0.1), small (0.1−0.3), moderate (0.3−0.5), high (0.5−0.7), very high (0.7−0.9), or practically perfect (>0.9). The level of significance was p < 0.05. Results There was very high correlation between MIF exerted on starting blocks and performance in the first meters of the sprint (5-m: r = -0.84, p = 0.01). However, there was small correlation between MIF in squats and performance in the first meters of the sprint (5-m: r = -0.22, p < 0.62). Conclusion The MIF applied on starting blocks correlates very high with time in the first meters of the sprint in high-level athletes. In addition, the use of the FEMD provides a wide range of possibilities for evaluation and development of strength with a controlled natural movement. Level of evidence IV; Prognostic Studies - Case series.

Reliability of Load-Velocity Profiling in Front Crawl Swimming

The purposes of this study were to establish test-retest reliability of calculating load-velocity profiles in front crawl swimming using five and three different external loads, and if outcome results were comparable between calculation methods for monitoring performance over time. Fifteen swimmers at either national or international competition level (seven females and eight males) participated in this study. The subjects performed 25 m of semi-tethered swimming with maximal effort with five progressive loads (females 1, 2, 3, 4, and 5 kg and males 1, 3, 5, 7, and 9 kg) as well as 50 m maximal front crawl on 2 different days. The mean velocity during three stroke cycles in mid-pool was calculated and plotted as a function of the external load. Relationship between the load and velocity was expressed by a linear regression line and established for each swimmer. The intercepts between the axes of the plot and the established regression line were defined as theoretical maximum velocity (V₀) and load (L₀). In addition, L₀ was also expressed as a percentage of body mass (rL₀). The coefficient of determination (R²) and the slope (S_lv) of the linear load-velocity relationship were calculated. The intra-class correlation coefficient (ICC) showed excellent agreement (ICC ≥0.902) for all variables. The coefficient of variation was ≤3.14% and typical error was rated as "good" in all variables. A difference was found between day 1 and 2 in V₀ for three- and five-load calculations and for 50 m front crawl time (p < 0.05). No difference was found between the load-velocity profile outcomes variables compared between the three- and five-trial protocols on neither day 1 nor 2. The Bland-Altman plots showed a small bias across all resistance conditions for five loads, L₀: 0.04 kg, rL₀: 0.13%, V₀: -0.03 m/s, and S_lv: 0.003 -m/s/kg and for three loads, L₀: -0.24 kg, rL₀: -0.27%, V₀: -0.04 m/s, S_lv: 0.002 -m/s/kg. In conclusion, the load-velocity profile for front crawl swimming can be calculated with high reliability from both five and three external loads and comparable results in outcome variables were established. These methods can be used to monitor performance parameters over time, and to investigate and compare swimmers' velocity and strength capabilities to allow for individualized training prescription to improve performance.

Do Faster, Stronger, and More Powerful Athletes Perform Better in Resisted Sprints?

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.

Sled-Push Load-Velocity Profiling and Implications for Sprint Training Prescription in Young Athletes

Cahill, MJ, Oliver, JL, Cronin, JB, Clark, KP, Cross, MR, and Lloyd, RS. Sled-push load-velocity profiling and implications for sprint training prescription in young athletes. J Strength Cond Res XX(X): 000-000, 2020-Resisted sled pushing is a popular method of sprint-specific training; however, little evidence exists to support the prescription of resistive loads in young athletes. The purpose of this study was to determine the reliability and linearity of the force-velocity relationship during sled pushing, as well as the amount of between-athlete variation in the load required to cause a decrement in maximal velocity (Vdec) of 25, 50, and 75%. Ninety (n = 90) high school, male athletes (age 16.9 ± 0.9 years) were recruited for the study. All subjects performed 1 unresisted and 3 sled-push sprints with increasing resistance. Maximal velocity was measured with a radar gun during each sprint and the load-velocity (LV) relationship established for each subject. A subset of 16 subjects examined the reliability of sled pushing on 3 separate occasions. For all individual subjects, the LV relationship was highly linear (r > 0.96). The slope of the LV relationship was found to be reliable (coefficient of variation [CV] = 3.1%), with the loads that cause a decrement in velocity of 25, 50, and 75% also found to be reliable (CVs = <5%). However, there was large between-subject variation (95% confidence interval) in the load that caused a given Vdec, with loads of 23-42% body mass (%BM) causing a Vdec of 25%, 45-85 %BM causing a Vdec of 50%, and 69-131 %BM causing a Vdec of 75%. The Vdec method can be reliably used to prescribe sled-push loads in young athletes, but practitioners should be aware that the load required to cause a given Vdec is highly individualized.

Influence of resisted sled-push training on the sprint force-velocity profile of male high school athletes

Sled pushing is a commonly used form of resisted sprint training; however, little empirical evidence exists, especially in youth populations. The aim of this study was to assess the effectiveness of unresisted and resisted sled pushing across multiple loads. Fifty high school athletes were assigned to an unresisted (n = 12), or 3 resisted groups; light (n = 14), moderate (n = 13), and heavy (n = 11) resistance that caused a 25%, 50%, and 75% velocity decrement in maximum sprint speed, respectively. All participants performed two sled-push training sessions twice weekly for 8 weeks. Before and after the training intervention, the participants performed a series of jump, strength, and sprint testing to assess athletic performance. Split times between 5 and 20 m improved significantly across all resisted groups (all P < .05, d = 0.34-1.16) but did not improve significantly with unresisted sprinting. For all resisted groups, gains were greatest over the first 5 m (d = 0.67-0.84) and then diminished over each subsequent 5 m split (d = 0.08-0.57). The magnitude of gains in split times was greatest within the heavy group. Small but non-significant within-group effects were found in pre to post force-velocity profiles. There was a main effect of time but no interaction effects as all groups increased force and power, although the greatest increases were observed with the heavy load (d = 0.50-0.51). The results of this study suggest that resisted sled pushing with any load was superior to unresisted sprint training and that heavy loads may elicit the greatest gains in sprint performance over short distances.

Sled-Pull Load-Velocity Profiling and Implications for Sprint Training Prescription in Young Male Athletes

The purpose of this study was to examine the usefulness of individual load–velocity profiles and the between-athlete variation using the decrement in maximal velocity (Vdec) approach to prescribe training loads in resisted sled pulling in young athletes. Seventy high school, team sport, male athletes (age 16.7 ± 0.8 years) were recruited for the study. All participants performed one un-resisted and four resisted sled-pull sprints with incremental resistance of 20% BM. Maximal velocity was measured with a radar gun during each sprint and the load–velocity relationship established for each participant. A subset of 15 participants was used to examine the reliability of sled pulling on three separate occasions. For all individual participants, the load–velocity relationship was highly linear (r > 0.95). The slope of the load–velocity relationship was found to be reliable (coefficient of variation (CV) = 3.1%), with the loads that caused a decrement in velocity of 10, 25, 50, and 75% also found to be reliable (CVs = <5%). However, there was a large between-participant variation (95% confidence intervals (CIs)) in the load that caused a given Vdec, with loads of 14–21% body mass (% BM) causing a Vdec of 10%, 36–53% BM causing a Vdec of 25%, 71–107% BM causing a Vdec of 50%, and 107–160% BM causing a Vdec of 75%. The Vdec method can be reliably used to prescribe sled-pulling loads in young athletes, but practitioners should be aware that the load required to cause a given Vdec is highly individualized.

Assessing Horizontal Force Production in Resisted Sprinting: Computation and Practical Interpretation

The assessment of horizontal force during overground sprinting is increasingly prevalent in practice and research, stemming from advances in technology and access to simplified yet valid field methods. As researchers search out optimal means of targeting the development of horizontal force, there is considerable interest in the effectiveness of external resistance. Increasing attention in research provides more information surrounding the biomechanics of sprinting in general and insight into the potential methods of developing determinant capacities. However, there is a general lack of consensus on the assessment and computation of horizontal force under resistance, which has resulted in a confusing narrative surrounding the practical applicability of loading parameters for performance enhancement. As such, the aim of this commentary was twofold: to provide a clear narrative of the assessment and computation of horizontal force in resisted sprinting and to clarify and discuss the impact of methodological approaches to subsequent training implementation. Horizontal force computation during resisted sleds, a common sprint-training apparatus in the field, is used as a test case to illustrate the risks associated with substandard methodological practices and improperly accounting for the effects of friction. A practical and operational synthesis is provided to help guide researchers and practitioners in selecting appropriate resistance methods. Finally, an outline of future challenges is presented to aid the development of these approaches.

Force-velocity profiling of sprinting athletes: single-run vs. multiple-run methods

PURPOSE

This study explored the agreement between a single-run and a multiple-run method for force-velocity (Fv) profiling of sprinting athletes; we evaluated both absolute values and changes over time caused by sprint training.

METHODS

Seventeen female handball players (23 ± 3 years, 177 ± 7 cm, 73 ± 6 kg) performed 30 m un-resisted and resisted sprints (50, 80 and 110 N resistance) before and after an 8-week sprint training intervention. Two approaches were used to calculate theoretical maximal velocity (v₀), horizontal force (F₀), power (P_max), and the force-velocity slope (S_Fv): (1) the single-run method, based on inverse dynamics applied to the centre-of-mass movement, was calculated from anthropometric and sprint split time data; and (2) the multiple-run method, where peak velocity from un-resisted and resisted sprints were plotted against the horizontal resistances.

RESULTS

Trivial differences in v₀ (0.7%) were observed between the two calculation methods. Corresponding differences for F₀, P_max and S_Fv were 16.4, 15.6 and 17.6%, respectively (most likely; very large effect size). F₀ showed poor agreement between the methods (r = 0.26 and 0.16 before and after the intervention). No substantial correlation between the changes (from pre- to post-training tests) in SFV calculated with the single-run and the multiple-run methods were observed (r = 0.03) [corrected].

CONCLUSIONS

This study revealed poor agreement between the Fv relationships of the investigated calculation methods. In practice, both methods may have a purpose, but the single-run and the multiple-run methods appear to measure somewhat different sprint properties and cannot be used interchangeably.

The addition of very light loads into the routine testing of the bench press increases the reliability of the force-velocity relationship

Background

The aim of this study was to examine whether the addition of very light loads for modeling the force–velocity (F–V) relationship during the bench press (BP) exercise can confirm its experimental linearity as well as to increase the reliability and concurrent validity of the F–V relationship parameters (maximum force (F₀), maximum velocity (V₀), F–V slope, and maximum power (P_max)).

Method

The F–V relationship of 19 healthy men were determined using three different methods: (I) 6-loads free method: six loads performed during the traditional free-weight BP exercise (≈ 1–8–29–39–49–59 kg), (II) 4-loads free method: four loads performed during the traditional free-weight BP exercise (≈ 29–39–49–59 kg), and (III) 4-loads Smith method: four loads performed during the ballistic bench press throw exercise in a Smith machine (≈ 29–39–49–59 kg).

Results

The linearity of the F–V relationship was very high and comparable for the three F–V methods (p = 0.204; median Pearson’s correlation coefficient (r) = 0.99). The three methods were ranked from the most to the least reliable as follows: 6-loads free (coefficient of variation (CV) range = 3.6–6.7%) > 4-loads Smith (CV range = 4.6–12.4%) > 4-loads free (CV range = 3.8–14.5%). The higher reliability of the 6-loads free method was especially pronounced for F–V slope (CV_ratio ≥ 1.85) and V₀ (CV_ratio ≥ 1.49) parameters, while the lowest difference in reliability was observed for F₀ (CV_ratio ≤ 1.27). The 6-loads free and 4-loads free methods showed a very high concurrent validity respect to the 4-loads Smith method for F₀ and P_max (r ≥ 0.89), a moderate validity for the F–V slope (r = 0.66–0.82), and a low validity for V₀ (r ≤ 0.37).

Discussion

The routine testing of the F–V relationship of upper-body muscles through the BP exercise should include trials with very light loading conditions to enhance the reliability of the F–V relationship.

Training at maximal power in resisted sprinting: Optimal load determination methodology and pilot results in team sport athletes

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.