Maximal Sprint Research Articles

A Novel Approach of Modelling and Predicting Track Cycling Sprint Performance

In cycling, performance models are used to investigate factors that determine performance and to optimise competition results. We present an innovative and easily applicable mathematical model describing time-resolved approaches for both the physical aspects of tractional resistance and the physiological side of propelling force generated by muscular activity and test its validity to reproduce and forecast time trials in track cycling. Six elite track cyclists completed a special preparation and two sprint time trials in an official velodrome under continuous measurement of crank force and cadence. Fatigue-free force-velocity profiles were calculated, and their fatigue-induced changes were determined by non-linear regression analysis using a monoexponential equation at a constant slope. Model parameters were calibrated based on pre-exercise performance testing and the first of the two time-trials and then used to predict the performance of the second sprint. Measured values for power output and cycling velocity were compared to the modelled data. The modelled results were highly correlated to the measured values (R2>0.99) without any difference between runs (p>0.05; d<0.1). Our mathematical model can accurately describe sprint track cycling time trial performance. It is simple enough to be used in practice yet sufficiently accurate to predict highly dynamic maximal sprint performances. It can be employed for the evaluation of completed runs, to forecast expected results with different setups, and to study various contributing factors and quantify their effect on sprint cycling performance.

Fast and dark: The case of Mezquite lizards at extreme altitude.

Sprint speed is a major performance trait in animal fitness involved in escaping from predators, obtaining food, and defending territory. Biotic and abiotic factors may influence sprint speed in lizards. Temperature decreases at higher altitude. Therefore, lizards at high elevations may require longer basking times to reach optimal body temperatures, increasing their vulnerability to predation and decreasing their time for other activities such as foraging or reproduction. Here, we tested whether the maximum sprint speed of a lizard that shows conservative thermal ecology varied along an altitudinal gradient comprising low (2500m), middle (3400m) and high-altitude (4300m) populations. We also tested whether sprint speed was related to dorsal reflectance at different ecologically relevant temperatures. Given that the lizard Sceloporus grammicus shows conservative thermal ecology with altitude, we expected that overall average sprint speed would not vary with altitude. However, given that darker lizards heat up quicker, we expected that darker lizards would be faster than lighter lizards. Our results suggest that S. grammicus at high altitude are faster and darker at 30°C, while lizards from low and middle altitude are faster and lighter in color at 20°C than high altitude lizards. Also, our results suggest a positive relationship between sprint speed and dorsal skin reflectance at 10 and 20°C. Sprint speed was also affected by snout-vent length, leg length, and leg thickness at 10°C. These results suggest that, even though predation pressure is lower at extreme altitudes, other factors such as vegetation cover or foraging mode have influenced sprint speed.

Increased air temperature during repeated-sprint training in hypoxia amplifies changes in muscle oxygenation without decreasing cycling performance

ABSTRACT The present study aims to investigate the acute performance and physiological responses, with specific reference to muscle oxygenation, to ambient air temperature manipulation during repeated-sprint training in hypoxia (RSH). Thirteen male team-sport players completed one familiarisation and three experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144). Air temperatures utilised across the three experimental sessions were: 20°C, 35°C and 40°C (all 50% relative humidity). Participants performed 3 × 5 × 10-s maximal cycle sprints, with 20-s passive recovery between sprints, and 5 min active recovery between sets. There were no differences between conditions for cycling peak power, mean power, and total work (p>0.05). Peak core temperature (Tc) was not different between conditions (38.11 ± 0.36°C). Vastus lateralis muscle deoxygenation during exercise and reoxygenation during recovery was of greater magnitude in 35°C and 40°C than 20°C (p<0.001 for all). There was no condition × time interaction for Tc, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion and thermal sensation (P>0.05). Exercise-induced increases in blood lactate concentration were higher in 35°C and 40°C than 20°C (p=0.010 and p=0.001, respectively). Integrating ambient temperatures up to 40°C into a typical RSH session had no detrimental effect on performance. Additionally, the augmented muscle oxygenation changes experienced during exercise and recovery in temperatures ≥35°C may indicate that the potency of RSH training is increased with additional heat. However, alterations to the training session may be required to generate a sufficient rise in Tc for heat training purposes. Highlights Heat exposure (35-40°C) did not affect mechanical performance during a typical RSH session. This indicates hot ambient temperature can be implemented during RSH, without negative consequence to training output. Hotter ambient conditions (35-40°C) likely result in greater muscle oxygenation changes during both exercise and recovery compared to temperate conditions. Although hotter sessions were perceived as more difficult and more thermally challenging, they did not further elevate Tc beyond that of temperate conditions. Accordingly, if intended to be used for heat acclimation purposes, alterations to the session may be required to increase heat load.

Association and Predictive Ability of Jump Performance with Sprint Profile of Collegiate Track and Field Athletes

ABSTRACT This study examined the relationship between broad jump (BJ), countermovement jump (CMJ) and light load countermovement jump (LL-CMJ) performance and sprint performance and Sprint Profile measures in athletes. Additionally, this study aimed to determine the predictive ability of jump measures on Sprint Profile components. Twenty-five athletes performed BJ, CMJ, LL-CMJ, 30-metre acceleration and 30-metre maximal speed fly-by sprints. Results revealed moderate to very large correlations between BJ, CMJ and LL-CMJ performance with acceleration sprint completion times (r = −0.423 to −0.807; p < 0.05), fly-by sprint completion times (r = −0.452 to −0.838; p < 0.05) and maximal sprint speed (r = 0.424 to 0.794; p < 0.05). Additionally, associations were observed with multiple jumping measures and components of the Sprint Profile (r = 0.431 to 0.777; p < 0.05) during acceleration sprints. Furthermore, the BJ distance was the best predictor of Sprint Profile components during acceleration sprints (R2 = 0.57–0.76; p < 0.01) and maximal speed fly-by sprints (R2 = 0.775; p < 0.001). The forces and the manner of force application during the BJ to propel the athlete forwards and upwards are similar to those necessary to exhibit superior sprint performance. This may be due to the rapid generation of forces and orientation of force application during both movements.

Effect of concurrent strength and endurance training on run performance and biomechanics: A randomized controlled trial.

This parallel-group randomized controlled trial investigated the effect of concurrent strength and endurance (CSE) training on running performance, biomechanics, and muscle activity during overground running. Thirty moderately trained distance runners were randomly assigned to 10-week CSE training (n=15; 33.1±7.5years) or a control group (n=15; 34.2±8.2years). Participants ran ≥30km per week and had no experience with strength training. The primary outcome measure was 2-km run time. Secondary outcome measures included lower limb sagittal plane biomechanics and muscle activity during running (3.89ms-1 and maximal sprinting); maximal aerobic capacity (V̇O2 max); running economy; and body composition. CSE training improved 2-km run time (mean difference (MD): -11.3s [95% CI -3.7, -19.0]; p=0.006) and time to exhaustion during the V̇O2 max running test (MD 59.1s [95% CI 8.58, 109.62]; p=0.024). The CSE training group also reduced total body fat (MD: -1.05kg [95% CI -0.21, -1.88]; p=0.016) while total body mass and lean body mass were unchanged. Hip joint angular velocity during the early swing phase of running at 3.89ms-1 was the only biomechanical or muscle activity variable that significantly changed following CSE training. CSE training is beneficial for running performance, but changes in running biomechanics and muscle activity may not be contributing factors to the performance improvement. Future research should consider other possible mechanisms and the effect of CSE training on biomechanics and muscle activity during prolonged running under fatigued conditions.

Uphill sprinting load– and force–velocity profiling: Assessment and potential applications

ABSTRACT This study aimed to quantify the validity and reliability of load–velocity (LV) relationship of hill sprinting using a range of different hill gradients and to describe the effect of hill gradient on sprint performance. Twenty-four collegiate-level athletes performed a series of maximal sprints on either flat terrain or hills of gradients 5.2, 8.8 and 17.6%. Velocity–time curves were recorded using a radar device. LV relationships were established using the maximal velocity achieved in each sprinting condition, whilst force–velocity–power (FVP) profiles were established using only the flat terrain sprint. LV profiles were shown to be valid (R2 = 0.99) and reliable (TE < 4.4%). For every 1-degree increase in slope, subjects’ velocity decreased by 1.7 ± 0.1% on average. All the slopes used represented low resistance relative to the entire LV spectrum (<25% velocity loss). Subjects who exhibited greater horizontal force output at higher velocities on flat terrain were most affected by the gradient of the hill. Hills of gradients up to 17.6% do not provide sufficient resistance to optimize power development. However, such hills could be used to develop late-stage technical ability, due to the prolonged horizontally oriented body position that occurs as subjects attempt to overcome the acceleration due to gravity.

Transcranial Direct Current Stimulation Does Not Affect Sprint Performance or the Horizontal Force-Velocity Profile

ABSTRACT Purpose: The aim of this study was to explore the effects of transcranial direct current stimulation (tDCS) on sprint performance and the horizontal force-velocity (F-v) profile. Method: Thirty-two healthy subjects (25 men and 7 women; age = 21.8 ± 2.4 years) completed three sessions separated by 1 week following a double-blinded crossover design. Each session consisted of two maximal sprints of 30 meters that were performed after applying ANODAL, CATHODAL or SHAM tDCS over the left dorsolateral prefrontal cortex (DLPFC) for 15 minutes at 2 mA. The 30-m time and the horizontal F-v profile variables (theoretical maximal force [F 0], theoretical maximal velocity, Fv slope, maximal power [Pmax], decrease in the ratio of horizontal-to-resultant force, and maximal ratio of horizontal-to-resultant force) were compared between the tDCS conditions. Results: No significant differences between the tDCS conditions were observed for any variable (p range = 0.061 to 0.842). The magnitude of the differences was negligible for most of the comparisons (effect size [ES] < 0.20) with the only exception of Pmax and F 0 which were greater for the ANODAL compared to the SHAM condition (both ES = 0.20). Conclusions: The application of tDCS over the DLPFC is not effective to increase non-fatigued sprint performance.

Exploration of the Age-Category Soccer Performance Effects During Ball Possession Small-Sided Games.

Small-sided games have been adopted as an integral part of soccer training, however, the use of task constraints by the coach and the action capabilities of both players and teams require further investigation. The aim of this investigation was to explore the age-category effects (under-11: U11, under-15: U15 and under-23: U23) on external training workloads (total distance covered, distance covered while walking, running and sprinting, number of sprints and maximum sprint speed), internal training load metrics (rate of perceived exertion, RPE) and tactical individual actions (passing number with dominant and non-dominant foot, and max passing speed) during 4 vs. 4 ball possession small-sided game constrained within three different playing areas (small: 20 x 15 m, medium: 25 x 20 m, and large: 30 x 25 m). Results revealed substantial differences (all p < .001) for each specific playing area observed across many of the external workload measures. For every area analysed, U23 players covered more distance walking, whereas U11 and U15 players covered more distances at higher intensities. Additionally, significant differences were found for the RPE (small playing area: p = .001; large playing area: p < .001) with U23 and U15 players showing higher scores compared with U11 ones. It can be concluded that a 4 vs. 4 ball possession small-sided game can provide different performance related stimuli to players, depending on age category and the playing surface area. Therefore, coaches and individuals involved with training and development of soccer players across all age groups should be aware of the key variables highlighted in this study before planning training drills.

Deceleration Training in Team Sports: Another Potential \u2018Vaccine\u2019 for Sports-Related Injury?

High-intensity horizontal decelerations occur frequently in team sports and are typically performed to facilitate a reduction in momentum preceding a change of direction manoeuvre or following a sprinting action. The mechanical underpinnings of horizontal deceleration are unique compared to other high-intensity locomotive patterns (e.g., acceleration, maximal sprinting speed), and are characterised by a ground reaction force profile of high impact peaks and loading rates. The high mechanical loading conditions observed when performing rapid horizontal decelerations can lead to tissue damage and neuromuscular fatigue, which may diminish co-ordinative proficiency and an individual’s ability to skilfully dissipate braking loads. Furthermore, repetitive long-term deceleration loading cycles if not managed appropriately may propagate damage accumulation and offer an explanation for chronic aetiological consequences of the ‘mechanical fatigue failure’ phenomenon. Training strategies should look to enhance an athlete’s ability to skilfully dissipate braking loads, develop mechanically robust musculoskeletal structures, and ensure frequent high-intensity horizontal deceleration exposure in order to accustom individuals to the potentially damaging effects of intense decelerations that athletes will frequently perform in competition. Given the apparent importance of horizontal decelerations, in this Current Opinion article we provide considerations for sport science and medicine practitioners around the assessment, training and monitoring of horizontal deceleration. We feel these considerations could lead to new developments in injury-mitigation and physical development strategies in team sports.

Reliability and Minimal Detectable Change of Sprint Times and Force-Velocity-Power Characteristics.

Edwards, T, Banyard, HG, Piggott, B, Haff, GG, and Joyce, C. The reliability and minimal detectable change of sprint times and force-velocity-power characteristics. J Strength Cond Res 36(1): 268-272, 2022-Research has not yet provided critical information for practitioners to determine the minimal detectable change (MDC) in sprint times or force-velocity-power characteristics. Therefore, the aim of this study was to establish the interday reliability and MDC of sprint times and sprint force-velocity-power characteristics in junior Australian football (AF) players. Seventeen players were assessed using a radar device that recorded instantaneous velocity during 3 maximal 30-m sprint accelerations performed on 2 nonconsecutive days. Sprint force, velocity, and power characteristics were derived through inverse dynamics applied to the raw velocity-time data. Relative and absolute reliability was determined by calculating the intraclass correlation coefficient (ICC), coefficient of variation (CV), and MDC. Data analysis was assessed for (a) the first trial, (b) the best trial (the fastest 30-m split time), (c) the average of the first 2 trials, and (d) the average of all 3 trials from each testing session. The main findings were (a) absolute theoretical maximum force (F0), theoretical maximal velocity (V0), absolute and relative maximum power (Pmax), maximum ratio of force (RFmax), maximum velocity (Vmax), and all sprint distance times (5-30 m) displayed acceptable reliability (CV < 10% and ICC >0.75) and 2) the average of 2 and 3 trials was the best method of establishing reliable sprint times and force-velocity-power characteristics between sessions. This study provides important information for practitioners to determine the MDC in sprint times and force-velocity-power characteristics that allow coaches to identify true changes in performance.

Anthropometric traits and physical performance of amateur rugby players within specific playing positions

BACKGROUND: This study examined the differences in physical and anthropometric traits between specific playing positions (i.e., forwards: front row, second row, back row; backs: half backs, centers, wings/fullbacks) in amateur rugby players and analyzed the magnitude of correlations among jump, sprint, and strength measures in forwards and backs. METHOD: Sixty-four male rugby players were assessed in anthropometrics, a variety of vertical jumps, 10- and 30-m sprint, and strength tests (i.e., squat and bench press). RESULTS: Front row forwards (FFR) demonstrated significantly higher body mass (BM) than second row (FSR) and back row (FBR) (107.4 ± 12.8, 99.1 ± 9.9 and 91.6 ± 7.6 kg respectively; p&lt; 0.001). FFR showed greater absolute strength in bench press and squat, although no differences were found in relative strength. Regarding the differences in jump performance, FBR and FSR showed significantly (p&lt; 0.05) and significant to non-significant (p= 0.042–0.078, ES = 0.90–1.55) higher jumps in all tasks compared to FFR. Moreover, FBR demonstrated lower sprint times and greater maximum sprinting speed (MSS) than FFR (p&lt; 0.01). For the backs, centers (BCEN) were significantly heavier (p&lt; 0.05) and exhibited a non-significantly moderate larger sprint momentum (p= 0.068, ES = 0.75) compared to half backs (BHB). MSS values were small to moderately greater in favor of wings/fullbacks [BWFB] (p= 0.188–0.059, ES = 0.50–0.71). Finally, statistically significant correlations were found between drop jump (flight time) and jump height across all jump tasks, sprint times and speed for both forwards (r= 0.541 to 0.996, p&lt; 0.001) and backs (r= 0.422 to 0.995, p&lt; 0.05). CONCLUSIONS: In conclusion, FFR demonstrated significant, small to very large differences, when compared to their specific peers, whereas the backs were more similar. Additionally, our results indicated moderate to strong associations between explosive tasks such as sprinting and jumping in both playing positions.

Relationship Between Explosive Strength Capacity of the Knee Muscles and Deceleration Performance in Female Professional Soccer Players.

The present study aimed to investigate the relationship between linear deceleration performance and explosive strength capacity of the knee muscles. Fourteen female professional soccer players completed the maximal sprint deceleration tests and knee flexor (KF) and knee extensor (KE) isokinetic concentric (240° and 60°.s−1) and eccentric contractions (30°.s−1). Linear deceleration performance was evaluated from horizontal breaking force (FH), power (PH), and impulse (IH) during a maximal linear deceleration. The peak torque (PT) of KF and KE, PT ratio between KF and KE (conventional and functional H/Q ratio), rate of torque development (RTD) for each muscle group, and RTD between KF and KE (RTD H/Q) were extracted from the isokinetic contractions. Pearson’s correlation coefficients revealed that the eccentric (30°.s−1) and concentric (60°.s−1, 240°.s−1) KE peak torque, and the concentric KF peak torque (240°.s−1) were significantly correlated with FH, PH, and IH (−0.75<r<−0.54). Moreover, a significant correlation was found between KE RTD during eccentric contraction and FH, PH, and IH (−0.63<r<−0.54). Besides, a significant correlation was observed between RTD H/Q at 60°.s−1 and PH, IH (−0.61<r<−0.57). No significant relationship was observed between the H/Q ratio, KF RTD and deceleration performance. These main findings indicated the importance of the ability to quickly produce high KE eccentric torque, contributing to braking force production. Meanwhile, RTD H/Q should be assessed for its essential role in knee joint dynamic stability and can be a relevant index to determine deceleration performance.

Maturation Stage Does Not Affect Change of Direction Asymmetries in Young Soccer Players.

Asimakidis, ND, Dalamitros, AA, Ribeiro, J, Lola, AC, and Manou, V. Μaturation stage does not affect change of direction asymmetries in young soccer players. J Strength Cond Res 36(12): 3440-3445, 2022-This study examined whether the stage of biological maturation can affect interlimb asymmetries during a change of direction (COD) test. Seventy-six young soccer players were divided into 2 different groups according to their peak height velocity stage (PHV): pre-PHV (n = 45, age = 11.8 ± 1.2 years, height = 149.8 ± 9.3 cm, body mass = 43.9 ± 11.2 kg) and post-PHV (n = 31, age = 14.4 ± 0.9 years, height = 170.0 ± 4.9 cm, body mass = 61.5 ± 8.9 kg). Subjects performed a 505 test to measure the completion time in both directions and a 20-m maximum sprint test. Change of direction deficit (CODD) was used as a measure for isolating COD ability. An independent sample t-test detected no significant differences between the asymmetry index values for the 505 test completion time when the pre-PHV group and the post-PHV group were compared (-3.49 ± 2.49% vs. -3.45 ± 2.47%, effect size [ES] = 0.02, p = 0.923). Similarly, the CODD asymmetry index indicated no differences between the 2 groups (-8.21 ± 5.95% vs. -7.37 ± 5.12%, ES = 0.15, p = 0.457). A paired sample t-test revealed that the values of the CODD asymmetry index were larger than those of the 505 asymmetry index (-7.88 ± 5.61% vs. -3.49 ± 2.46%, ES = 1.09, p < 0.001). According to these results, maturational status has no influence on the interlimb asymmetries of COD ability. Furthermore, subjects showed greater asymmetry values in CODD compared with the 505 test completion time, reinforcing that the evaluation of COD asymmetries should be based on CODD. As interlimb asymmetries are not altered during the maturation process, practitioners should address abnormal COD asymmetries early on during athletes' development processes.

Concentric not eccentric cycling sprint intervals acutely impair balance and jump performance in healthy active young adults: A randomized controlled cross-over study.

Moderate aerobic, high-intensity and sprint running or cycling training can transiently impair postural control. However, the acute effects of modified sprint interval training (mSIT) at different muscle working modes have not yet been examined. Thus, this study aimed at investigating acute effects of time-matched eccentric (ECC) versus concentric mSIT cycling session (CON) on jumping and functional balance performance. Twenty-five healthy and active males (30.0 ± 6.0 years; 80.1 ± 9.1 kg; V̇O2max: 64.2 ± 7.9 mL kg-1 min-1) were enrolled in this acute randomized controlled crossover trial. Counter-Movement-Jump (CMJ) and functional balance testing (Y-Balance-Test composite score [YBTCS]; Posturomed total distance: PosturomedTD) were assessed as primary outcomes before, and immediately after cessation of ECC and CON (10 × 10 s maximum sprints and 50 s of active recovery). A significant mode × time interaction effect for CMJ (F = 9.620, p = 0.005, ηp2 = 0.29) was observed. Subsequent post-hoc testing revealed significant moderate reductions in jumping height after CON (0.31 ± 0.06 vs. 0.27 ± 0.06m; p = 0.004, SMD = 0.59), whilst ECC remained unchanged. YBTCS (mode × time interaction: F = 6.880, p = 0.015, ηp2 = 0.22) showed small but significant balance impairments after CON (0.964 ± 0.068 vs. 0.960 ± 0.063 AU; p = 0.009, SMD = 0.28) and did not significantly change after ECC. Although large significant interaction effects (p = 0.029, ηp2 = 0.18) were observed for PosturomedTD, follow up post-hoc testing did not reveal relevant pre-post differences, neither for ECC nor CON. Both functional balance and jumping performance are deteriorated after acute concentric but not eccentric mSIT cycling. Although higher pedal forces at lower perceived efforts and heart rates during eccentric mSIT were observed, it seems that the cardiocirculatory demanding CON session elicited more pronounced balance and jump performance impairments than eccentric cycling.

The Inclusion of Sprints in Low-Intensity Sessions During the Transition Period of Elite Cyclists Improves Endurance Performance 6 Weeks Into the Subsequent Preparatory Period.

To investigate the effects of including repeated sprints in a weekly low-intensity (LIT) session during a 3-week transition period on cycling performance 6 weeks into the subsequent preparatory period (PREP) in elite cyclists. Eleven elite male cyclists (age = 22.0 [3.8]y, body mass = 73.0 [5.8]kg, height = 186 [7]cm, maximal oxygen uptake [VO2max] = 5469 [384]mL·min-1) reduced their training load by 64% and performed only LIT sessions (CON, n = 6) or included 3 sets of 3 × 30-second maximal sprints in a weekly LIT session (SPR, n = 5) during a 3-week transition period. There was no difference in the reduction in training load during the transition period between groups. Physiological and performance measures were compared between the end of the competitive period and 6 weeks into the PREP. SPR demonstrated a 7.3% (7.2%) improvement in mean power output during a 20-minute all-out test at PREP, which was greater than CON (-1.3% [4.6%]) (P = .048). SPR had a corresponding 7.0% (3.6%) improvement in average VO2 during the 20-minute all-out test, which was larger than the 0.7% (6.0%) change in CON (P = .042). No change in VO2max, gross efficiency, or power output at blood lactate concentration of 4mmol·L-1 from competitive period to PREP occurred in either group. Including sprints in a weekly LIT session during the transition period of elite cyclists provided a performance advantage 6 weeks into the subsequent PREP, which coincided with a higher performance VO2.

The Current Implementation of an Evidence-Based Hamstring Injury Prevention Exercise (Nordic Hamstring Exercise) among Athletes Globally

Purpose. The Nordic hamstring exercise (NHE) has been shown to be successful in reducing hamstring muscle injury (HMI), which is one of the most common non-contact injuries of the lower limbs. This is especially pertinent in sports that require acceleration, maximal sprints, and sudden changes in the direction of running and sprinting, such as soccer and rugby. This study aimed to evaluate the awareness, implementation, and opinions of athletes worldwide regarding the effectiveness of NHE in preventing hamstring injury.&#x0D; Materials and methods. A self-administered questionnaire was distributed to 1500 athletes from different sports. The survey consisted of six questions covering country, gender, type of sport, awareness, implementation, and opinions of athletes worldwide regarding the effectiveness of NHE in preventing hamstring injury. The survey was available in ten different languages.&#x0D; Results. A total of 1142 male and female athletes from different sports participated in the survey. More than half of the athletes 641 (56%) were aware of NHE, and only 519 (45.4 %) were implementing NHE in their current training routines. Athletes who implemented NHE reported a positive opinion regarding the program’s effectiveness with a score of 8.4 ± 1 out of 10.&#x0D; Conclusions. Many athletes were aware of NHE and implemented it in their training routine since they found it to be effective in decreasing hamstring injury rates. However, additional work must be done to educate athletes about the importance of implementing this exercise and its effectiveness in preventing hamstring injury.

Sprinting technique and hamstring strain injuries: A concept mapping study

ObjectiveThe aim of this study was to explore expert opinion to identify the components of sprinting technique they believed to be risk factors for hamstring strain injuries (HSI). DesignMixed-method research design. MethodsThe Concept Systems groupwisdom™ web platform was used to analyse and collect data. Participants brainstormed, sorted and rated the components of sprinting technique to consider in a HSI prevention strategy. ResultsTwenty-three experts (academic/researcher, physiotherapist, strength and conditioning coaches and sprint coaches) brainstormed 66 statements that were synthesised and edited to 60 statements. Nineteen participants sorted the statements into clusters and rated them for relative importance and confidence they could be addressed in a hamstring injury prevention program. Multidimensional scaling and cluster analysis identified a 8-cluster solution modified to a 5-cluster solution by the research team: Training prescription (10 statements, mean importance: 3.79 out of 5 and mean confidence: 3.79); Neuromuscular and tendon properties (9, 3.09, 3.08); Kinematics parameters/Technical skills (27, 2.99, 2.98); Kinetics parameters (10, 2.85, 2.92); and Hip mechanics (4, 2.70, 2.63). The statement: “low exposure to maximal sprint running” located in the cluster “Training prescription” received the highest mean importance (4.55) and confidence ratings (4.42) of all statements. ConclusionThe five clusters of components of sprinting technique believed to be risk factors for HSIs in order of most to least important were: training prescription, neuromuscular and tendon properties, kinematics parameters/technical drills, kinetics parameters and hip mechanics.

Validity and reliability of Polar Team Pro GPS units for assessing maximum sprint speed in soccer players

Previous research has reported inconsistencies in the validity and reliability of different brands of global positioning systems (GPS). Therefore, it should be questioned whether GPS units measure the maximum speed measurements validly and reliably. The current study aimed to analyze the validity and reliability of Polar Team Pro GPS units (10 Hz) when used to measure maximum sprint speed. Sixteen amateur soccer players (age: 27.22 ± 4.70 years; height: 177 ± 6.05 cm; body mass: 73.66 ± 5.63 kg) were tested in the 40 m sprint. Two Polar Team Pro GPS units were positioned on each player, while the radar was placed on a 1 m high tripod placed 10 m behind the starting point. The data obtained from the Polar Team Pro GPS units were compared to determine inter-unit reliability. The data obtained from one of the Polar Team Pro GPS units and radar gun (gold standard) were compared to determine validity. Good inter-unit reliability between the Polar Team Pro GPS units was reported for maximum sprint speed, with low coefficients of variation (5%–6%) and low smallest worthwhile changes (0.4 for all systems). Regarding validity, the coefficient of correlation was extremely high for maximum sprint speed ( r = 0.938, p &lt; 0.001). Moreover, measurement differences between both systems were statistically insignificant (Mean Bias error = 0.144, R2 = 0.879, MAPE = 1.6%, MAE = 0.688, and RMSE = 0.697). Consequently, good reliability and perfect validity were observed, indicating that the Polar Team Pro GPS unit is suitable for maximum sprint speed measurements.

A Combined Hot and Hypoxic Environment during Maximal Cycling Sprints Reduced Muscle Oxygen Saturation: A Pilot Study

The present study investigated the effects of a combined hot and hypoxic environment on muscle oxygenation during repeated 15-s maximal cycling sprints. In a single-blind, cross-over study, nine trained sprinters performed three 15-s maximal cycling sprints interspersed with 7-min passive recovery in normoxic (NOR; 23℃, 50%, FiO2 20.9%), normobaric hypoxic (HYP; 23℃, FiO2 14.5%), and hot normobaric hypoxic (HH; 35℃, FiO2 14.5%) environments. Relative humidity was set to 50% in all trials. The vastus lateralis muscle oxygenation was evaluated during exercise using near-infrared spectroscopy. The oxygen uptake (VO2) and arterial oxygen saturation (SpO2) were also monitored. There was no significant difference in peak or mean power output among the three conditions. The reduction in tissue saturation index was significantly greater in the HH (-17.0 ± 2.7%) than in the HYP (-10.4 ± 2.8%) condition during the second sprint (p < 0.05). The average VO2 and SpO2 were significantly lower in the HYP (VO2 = 980 ± 52 mL/min, SpO2 = 82.9 ± 0.8%) and HH (VO2 = 965 ± 42 mL/min, SpO2 = 83.2 ± 1.2%) than in the NOR (VO2 = 1149 ± 40 mL/min, SpO2 = 90.6 ± 1.4%; p < 0.05) condition. In conclusion, muscle oxygen saturation was reduced to a greater extent in the HH than in the HYP condition during the second bout of three 15-s maximal cycling sprints, despite the equivalent hypoxic stress between HH and HYP.

50 m freestyle in 21, 22 and 23 s: What differentiates the speed curve of world-class and elite male swimmers?

ABSTRACT We examined the association between 50 m freestyle performance (50FS) and average speed (AS), peak speed (PS), minimum speed (MS) and intracyclic speed variation (ISV) and compared the speed curves from swimmers with different performance levels using functional analysis of variance (FANOVA). Fourteen male swimmers (50FS: 22.50 ± 0.58 s) performed a maximal sprint with a speedometer and AS, PS, MS, and IVV were assessed for correlational analysis. 50FS were obtained in official competitions. Swimmers were assigned to three groups based on actual 50FS: G21 (n = 2, 21.99 ± 0.04 s), G22 (n = 6, 22.82 ± 0.10 s) or G23 (n = 6, 23.55 ± 0.18 s). FANOVA compared the average curves. 50FS correlated to AS (r = −0.781, p = 0.001) and PS (ρ = −0.766, p = 0.001), but not to MS (r = −0.185, p = 0.527) or IVV (r = −0.323, p = 0.259). FANOVA showed that faster swimmers achieved higher PS and stayed longer at the upper part of the curve. 50FS performance is related to average and peak speed assessed with the speedometer. Swimmers should seek techniques to maintain the speed at the upper part of the curve as long as possible.