Sprint Duration Research Articles

Physiological and Metabolic Responses to Low-Volume Sprint Interval Exercises: Influence of Sprint Duration and Repetitions.

This study aimed to determine physiological and metabolic responses to two different sprint interval exercises (SIE) matched for total sprint duration and sprint-rest ratio. After having measured peak oxygen uptake (V̇O 2peak ), 14 healthy males (27.1 ± 4.8 yr, 169.6 ± 6.0 cm, 64.5 ± 8.4 kg, V̇O 2peak : 47.2 ± 7.7 mL·kg -1 ·min -1 ) performed four 10-s sprints with 80-s recovery (SIE10) and two 20-s sprints with 160-s recovery (SIE20) on different occasions in a counterbalanced crossover manner. Pulmonary V̇O 2 and changes in tissue oxygenation index (∆TOI) at vastus lateralis (VL) and rectus femoris (RF) were measured during the SIE. Furthermore, T2-weighted magnetic resonance imaging was taken immediately before and after the SIE to determine the activation levels of VL, RF, vastus medialis, vastus intermedius, adductor magnus, biceps femoris long head, semitendinosus, and semimembranosus at 50% of right thigh length. In SIE10, increases in V̇O 2 and ∆TOI at VL and RF plateaued after the second sprint, whereas session-averaged ∆TOI was greater in SIE20 than SIE10 in both muscles (VL: 20.9 ± 7.4 vs 14.2% ± 5.9%, RF: 22.8 ± 9.3 vs 12.9% ± 6.6%, P = 0.00). Although both SIE significantly increased T2 values in all eight muscles, those magnitudes were similar between the conditions (SIE10 vs SIE20: 5%-16% vs 8%-16%). This study showed blunted responses of whole-body (V̇O 2 ) and peripheral (∆TOI) oxidative responses with successive sprints (sprint 1 < sprints 2-4) in SIE10, suggesting that increasing sprint repetitions does not necessarily induce greater oxidative metabolism or stimulus. Moreover, greater peripheral oxygen extraction (∆TOI) was achieved with SIE20, whereas %changes of T2 indicates that the thigh muscles were similarly activated between the SIE conditions.

Lamax: determining the optimal test duration for maximal lactate formation rate during all-out sprint cycle ergometry.

This study aimed to ascertain the optimal test duration to elicit the highest maximal lactate formation rate ( Lamax), whilst exploring the underpinning energetics, and identifying the optimal blood lactate sampling period. Fifteen trained to well-trained males (age 27 ± 6years; peak power: 1134 ± 174W) participated in a randomised cross-over design completing three all-out sprint cycling tests of differing test durations (10, 15, and 30s). Peak and mean power output (W and W.kg-1), oxygen uptake, and blood lactate concentrations were measured. Lamax and energetic contributions (phosphagen, glycolytic, and oxidative) were determined using these parameters. The shortest test duration of 10s elicited a significantly (p = 0.003; p < 0.001) higher Lamax (0.86 ± 0.17mmol.L-1.s-1; 95% CI 0.802-0.974) compared with both 15s (0.68 ± 0.18mmol.L-1.s-1; 95% CI 0.596-0.794) and 30s (0.45 ± 0.07mmol.L-1.s-1; 95% CI 0.410-0.487). Differences in Lamax were associated with large effect sizes (d = 1.07, d = 3.15). We observed 81% of the PCr and 53% of the glycolytic work completed over the 30s sprint duration was attained after 10s. BLamaxpost were achieved at 5 ± 2min (ttest 10s), 6 ± 2min (ttest 15s), and 7 ± 2min (ttest 30s), respectively. Our findings demonstrated a 10s test duration elicited the highest Lamax. Furthermore, the 10s test duration mitigated the influence of the oxidative metabolism during all-out cycling. The optimal sample time to determine peak blood lactate concentration following 10s was 5 ± 2min.

Effects of 2 Different Protocols of Repeated-Sprint Training in Hypoxia in Elite Female Rugby Sevens Players During an Altitude Training Camp.

Repeated-sprint training in hypoxia (RSH) is an effective way of improving physical performance compared with similar training in normoxia. RSH efficiency relies on hypoxia severity, but also on the oxidative-glycolytic balance determined by both sprint duration and exercise-to-rest ratio. This study investigated the effect of 2 types of RSH sessions during a classic altitude camp in world-class female rugby sevens players. Sixteen players performed 5 RSH sessions on a cycle ergometer (simulated altitude: 3000m above sea level [asl]) during a 3-week natural altitude camp (1850m asl). Players were assigned to 2 different protocols with either a high (RSH1:3, sprint duration: 8-10s; exercise-to-rest ratios: 1:2-1:3; n = 7) or a low exercise-to-rest ratio (RSH1:5, sprint duration: 5-15s; exercise-to-rest ratios: 1:2-1:5; n = 9). Repeated-sprint performances (maximal and mean power outputs [PPOmax, and PPOmean]) were measured before and after the intervention, along with physiological responses. PPOmax (962 [100] to 1020 [143]W, P = .008, Cohen d = 0.47) and PPOmean (733 [71] to 773 [91]W, P = .008, d = 0.50) increased from before to after. A significant interaction effect (P = .048, d = 0.50) was observed for PPOmean, with a larger increase observed in RSH1:3 (P = .003). No interaction effects were observed (P > .05) for the other variables. A classic altitude camp with 5 RSH sessions superimposed on rugby-sevens-specific training led to an improved repeated-sprint performance, suggesting that RSH effects are not blunted by prolonged hypoxic exposure. Interestingly, using a higher exercise-to-rest ratio during RSH appears to be more effective than when applying a lower exercise-to-rest ratio.

Sprint Cycling

Abstract: The time between races varies in the track cycling competition known as the Match Sprint but can be as little as 10–15 min. Both physiological and motivational factors could affect performance recovery. This study investigated how the between-sprint recovery activity, and an alteration in the duration of the second sprint, affected performance. Twenty-four strength-trained men (age: 26 ± 5 years; height: 180.3 ± 6.1 cm; body mass: 82.3 ± 6.9 kg) participated. During each of the four experimental trials, two sprints were performed 12 min apart. The first was always 18 s and the second was either 9 s or 18 s. Between sprints, passive rest or a mixture of active and passive recovery was undertaken. Peak power output (PPO), as well as mean power output over 9 s (MPO9) and 18 s (MPO18), was recorded. Lactate concentration, ratings of sprint preparation and performance, as well as perceptions of recovery, were also measured. Post-trial and post-study questionnaires explored factors that may have influenced performance. A sprint number × recovery method interaction, F(1, 23) = 28.791, p &lt; .001, ηp2 = .556, was found for PPO, with a significantly lower PPO in sprint 2 following passive recovery. Sprint number × second sprint duration interactions were found for PPO, F(1, 23) = 9.867, p = .005, ηp2 = .300, and MPO9, F(1, 23) = 8.922, p = .007, ηp2 = .279. A significant time × condition interaction was also found for lactate concentration, F(6.082, 97.320) = 2.982, p = .010, ηp2 = .157, although post hoc tests were unable to identify the cause of any of these effects. Typically, the participants were satisfied with their sprint performances and expressed positive views about the recovery activity undertaken. The main finding was, therefore, that PPO was lower following passive recovery, but the effects on MPO were not apparent.

Long recovery induced by short exercise-to-rest ratio and effort duration determine the influence of hypoxia during repeated cycling sprints to exhaustion

Introduction&#x0D; Repeated sprints exercise (RSE) performed in hypoxia (RSH) induce greater performance improvement than in normoxia (Brocherie et al., 2017). It has been previously argued that RSH efficiency depend on the oxidative-glycolytic balance which is influenced by sprint duration and exercise-to-rest-ratio (E:R). Indeed, we recently showed that long sprint duration (e.g. 20 s vs 10 s or 5 s) blunts the additional impact of hypoxia on RSH with a constant large E:R of 1:22. However, E:R also influence acute response to RSH. Therefore, this study aims to compare acute responses during RSE to exhaustion with a short E:R (1:6) in normoxia (RSN) and hypoxia (FiO2 = 0.13) and the same sprint durations (5, 10 or 20 s) previously used.&#x0D; Methods&#x0D; On separate visits, 10 active participants completed in random order three RSH and three RSN sessions to exhaustion on a cycle-ergometer (Excalibur Sport, Lode) with three sprint durations and a constant short E:R of 1:6 (5:30; 10:60 and 20:120). Vastus lateralis muscle de-reoxygenation (Oxymon, Artinis Medical Systems) and power output were continuously recorded. Lower limb and breathing discomfort, blood lactate, and ratings of perceived exertion were evaluated immediately after exhaustion.&#x0D; Results&#x0D; Number of sprints and peak power output were higher while blood lactate was lower (all p &lt; 0.001) during 5:30 compared to 10:60 or 20:120. No condition or interaction effects were reported for blood lactate and exercise-related sensation. Blood lactate and muscle deoxyhemoglobin increase (p &lt; 0.001) and total hemoglobin decrease (p = 0.002) during sprint were more pronounced when sprint duration increased (no hypoxia effect).&#x0D; Discussion&#x0D; Similar deoxygenation changes during recovery were reported in hypoxia compared to normoxia suggesting that 1:6 ratio and the associated long recovery period seemed to allow myoglobin O2 store restauration, even with a FiO2 = 13%. Sprint effort should be interspersed by incomplete recovery making impossible the full O2 reloading myoglobin and PCr resynthesis. The increase in blood lactate and the concomitant decrease in muscle oxygenation during sprint with longer duration confirmed a switch in the oxidative-glycolytic balance for energy supply. Since short exercise-to-rest ratio blunt hypoxic effect during RSH due to too long recovery period, hypoxia did not participate to the switch from oxidative to glycolytic energy supply.&#x0D; Conclusion&#x0D; During RSE to exhaustion, a short exercise-to-rest ratio (i.e., 1:6) blunts the specific psychophysiological responses induced by hypoxia, probably due to too long of recovery period. Manipulating effort duration rather than hypoxic exposure is preferable to alter both anaerobic energy system solicitation and power produced during repeated cycling sprints to exhaustion using a short exercise-to-rest ratio.&#x0D; References&#x0D; Brocherie, F., Girard, O., Faiss, R., &amp; Millet, G. P. (2017). Effects of repeated-sprint training in hypoxia on sea-level performance: A meta-analysis. Sports Medicine, 47, 1651-1660. https://doi.org/10.1007/s40279-017-0685-3

Hypoxia Does Not Change Performance and Psychophysiological Responses During Repeated Cycling Sprints to Exhaustion With Short Exercise-to-Rest Ratio.

To compare the acute performance and psychophysiological responses of repeated cycling sprints to exhaustion with a short exercise-to-rest ratio (1:6), between different effort durations and inspired oxygen fractions. On separate visits, 10 active participants completed 6 repeated cycling sprint exercises to exhaustion with 3 different effort durations (5, 10, and 20s) and 2 conditions of inspired oxygen (20.9% and 13.6%). Exercise-to-rest ratio was 1:6 for all trials (ie,5:30, 10:60, and 20:120). Vastus lateralis muscle oxygenation (near-infrared spectroscopy), blood lactate concentration, and lower-limb and breathing discomfort, using ratings of perceived exertion, were measured. Number of sprints and peak power output decreased while blood lactate increased (all P < .001) during 5:30 compared with 10:60 or 20:120. No condition or interaction effects were reported for blood lactate and exercise-related sensation. Muscle deoxyhemoglobin increased (P < .001) and total hemoglobin decreased (P = .002) during sprint with increasing sprint duration (no condition or interaction). During repeated-sprint exercise to exhaustion with a short exercise-to-rest ratio, the psychophysiological responses did not differ between normoxia and moderate hypoxia, probably due to an extended recovery period. It means that hypoxia did not modify repeated-sprint exercise performance with a short exercise-to-rest ratio. The sprint duration was the primary underlying factor of the observed differences in performance and muscle oxygenation reported between the repeated-sprint exercise sessions.

Different pitch configurations constrain the external and internal loads of young professional soccer players during transition games.

The aims of this study were to compare the influence of transition game (TG) size on the external and internal loads of young professional soccer players and to describe the high-speed profile of these drills in response to pitch dimensions. Eighteen young professional soccer players (age: 16.1 ± 0.3 years; height: 178.3 ± 5.4 cm; weight: 70.1 ± 6.2 kg) performed a 3vs2 TG on pitches measuring 40 × 30 m (TG30), 40 × 50 m (TG50) and 40 × 70 m (TG70) m. Distance covered (DC); accelerations-decelerations above 1.0 m · s-2 and 2.5 m · s-2; rate of perceived exertion (RPE); maximal heart rate and time above 90%; DC at 18.0 to 21.0 km · h-1 (DC 18-20.9 km · h-1); DC at 21.0 to 23.9 km · h-1 (DC 21-23.9 km · h-1); DC above 24.0 km · h-1 (DC > 24 km · h-1); and peak speed and sprint profile (duration, distance and maximal speed) were measured. TG30 achieved lower DC, DC above 18 km · h-1, peak speed, sprint distance and RPE than TG50 and TG70 (p < 0.01 and p < 0.05) and lower sprint duration and maximal speed sprint than TG70 (p < 0.01). TG30 and TG50 achieved higher Acc > 1.0 and > 2.5 m · s-2 respectively than TG70 (p < 0.05). TG70 showed greater DC above 21 km · h-1, peak speed, sprint distance and maximal speed sprint than TG50 (p < 0.01). Soccer coaches should use larger TGs to overload variables related to high speed and sprint demands during training and smaller TG formats to stimulate the accelerations of the soccer players.

Short-Term Creatine Supplementation and Repeated Sprint Ability-A Systematic Review and Meta-Analysis.

The aim of this study was to conduct a systematic review and meta-analysis of the effects of short-term creatine supplementation on repeated sprint ability. Fourteen studies met the inclusion criteria of adopting double-blind randomized placebo-controlled designs in which participants (age: 18-60years) completed a repeated sprint test (number of sprints: 4 < n ≤ 20; sprint duration: ≤10s; recovery duration: ≤90s) before and after supplementing with creatine or placebo for 3-7days in a dose of ∼20g/day. No exclusion restrictions were placed on the mode of exercise. Meta-analyses were completed using random-effects models, with effects on measures of peak power output, mean power output, and fatigue (performance decline) during each repeated sprint test presented as standardized mean difference (δ), and with effects on body mass and posttest blood lactate concentration presented as raw mean difference (D). Relative to placebo, creatine resulted in a significant increase in body mass (D = 0.79kg; p < .00001) and mean power output (δ = 0.61; p = .002). However, there was no effect of creatine on measures of peak power (δ = 0.41; p = .10), fatigue (δ = 0.08; p = .61), or posttest blood lactate concentration (D = 0.22L/min; p = .60). In conclusion, creatine supplementation may increase mean power output during repeated sprint tests, although the absence of corresponding effects on peak power and fatigue means that more research, with measurements of intramuscular creatine content, is necessary to confirm.

The Oxidative-Glycolytic Balance Influenced by Sprint Duration Is Key during Repeated Sprint in Hypoxia.

This study investigates the effects of normobaric hypoxia on repeated sprint exercise (RSE) with different balance between oxidative (phosphocreatine and oxidative pathway) and glycolytic contributions. Therefore, performance and psychophysiological responses were compared during RSE to exhaustion with the same exercise-to-rest ratio (1:2) but different sprint durations (5, 10, or 20 s) either in normoxic (RSN) or hypoxic (RSH; F io2 = 0.13) conditions. On separate visits, 10 active participants completed in random order three cycling RSN (5:10; 10:20 and 20:40) and three similar RSH sessions to exhaustion. Vastus lateralis muscle oxygenation was recorded by near-infrared spectroscopy. Blood lactate concentration, limb and breathing discomfort, and ratings of perceived exertion were measured. Total sprint number was smaller in hypoxia than in normoxia for 5:10 (20.8 ± 8.6 vs 14.7 ± 3.4; P = 0.014) and 10:20 (13.7 ± 6.3 vs 8.8 ± 2.5; P = 0.018) but not 20:40 (5.6 ± 1.9 vs 5.6 ± 2.5). The fatigue index was larger in hypoxia only for 5:10 (-43.5%, P < 0.001). Irrespective of condition, blood lactate concentration increased with the sprint duration with higher values for 20:40 than 5:10 (13.1 ± 2.7 vs 11.5 ± 2.2 mmoL·L -1 ; P = 0.027). Limb and breathing discomfort and ratings of perceived exertion did not differ in all RSE. Muscle oxygenation was mainly impacted by sprint duration (i.e., main effect of sprint duration on [HHb] min, [tHb] max, Δ[HHb], and Δ[tHb]) but not by hypoxia. The normoxia-to-hypoxia percentage decrease for total sprint number for 5:10 was correlated with the highest power output over 5 s ( R2 = 0.55; P = 0.013) and 10 s ( R2 = 0.53; P = 0.016). Hypoxia impairs repeated sprint ability when the oxidative but not the glycolytic contribution is substantial. The oxidative-glycolytic balance, influenced partly by sprint duration, is key during repeated sprint in hypoxia.

The Effects of Sprint Interval Training on Physical Performance: A Systematic Review and Meta-Analysis.

Hall, AJ, Aspe, RR, Craig, TP, Kavaliauskas, M, Babraj, J, and Swinton, PA. The effects of sprint interval training on physical performance: a systematic review and meta-analysis. J Strength Cond Res 37(2): 457-481, 2023-The present study aimed to synthesize findings from published research and through meta-analysis quantify the effect of sprint interval training (SIT) and potential moderators on physical performance outcomes (categorized as aerobic, anaerobic, mixed aerobic-anaerobic, or muscular force) with healthy adults, in addition to assessing the methodological quality of included studies and the existence of small study effects. Fifty-five studies were included (50% moderate methodological quality, 42% low methodological quality), with 58% comprising an intervention duration of ≤4 weeks and an array of different training protocols. Bayesian's meta-analysis of standardized mean differences (SMD) identified a medium effect of improved physical performance with SIT (ES 0.5 = 0.52; 95% credible intervals [CrI]: 0.42-0.62). Moderator analyses identified overlap between outcome types with the largest effects estimated for anaerobic outcomes (ES 0.5 = 0.61; 95% CrI: 0.48-0.75). Moderator effects were identified for intervention duration, sprint length, and number of sprints performed per session, with larger effects obtained for greater values of each moderator. A substantive number of very large effect sizes (41 SMDs > 2) were identified with additional evidence of extensive small study effects. This meta-analysis demonstrates that short-term SIT interventions are effective for developing moderate improvements in physical performance outcomes. However, extensive small study effects, likely influenced by researchers analyzing many outcomes, suggest potential overestimation of reported effects. Future research should analyze fewer a priori selected outcomes and investigate models to progress SIT interventions for longer-term performance improvements.

Anthropometrics And Body Composition Predict Performance During A Direct-fire Engagement Simulation.

Heavy load carriage is linked to lower performance in direct-fire engagements and higher physiological strain (higher O2 cost, lower cerebral blood flow); which have potential tactical consequences (impaired mobility, marksmanship, cognitive ability). However, performance may also deteriorate with other nonfunctional loads (i.e, excess body fat). PURPOSE: To determine the association between anthropometric and body composition measures and performance during a direct-fire engagement simulation. METHODS: Thirty three healthy male (n = 25) and female (n = 8) volunteers (age 25.7 ± 7.0 yr) underwent a direct-fire engagement simulation. Anthropometric and body composition measures were taken prior to the simulation using a stadiometer and bioelectrical impedance analysis. Marksmanship with cognitive workload and a fire and move drill (16 x 6 m sprints) were completed under combat load (25 kg) during the direct-fire engagement simulation. Marksmanship accuracy and reaction time were assessed as the number of target hits and the time between target callout and engagement, respectively. Cognitive performance was assessed as the number of correct arithmetic problems answered between target engagements. Susceptibility to enemy fire was modeled on sprint duration during the fire and move drill. Partial correlation and multiple linear regression were conducted to establish the relationship between anthropometric and body composition measures and performance outcomes, controlling for age and sex. RESULTS: Higher percent body fat and fat mass predicted greater susceptibility to enemy fire (r = 0.42, p = 0.03 and r = 0.38, p = 0.02, respectively), and worse cognitive performance (r = -0.49, p = 0.01 and r = -0.45, p = 0.01, respectively). Higher body mass index also predicted worse cognitive performance (r = -0.49, p = 0.01). Taller stature predicted worse marksmanship accuracy (r = -0.40, p = 0.02) and higher fat-free mass predicted slower marksmanship reaction times (r = 0.41, p = 0.02). CONCLUSIONS: Anthropometric and body composition measures were predictive of survivability (i.e., susceptibility to enemy fire) and lethality (i.e., marksmanship, cognitive performance) during the direct-fire engagement simulation. These data suggest anthropometrics and body composition modulate combat effectiveness.

Anthropometrics and body composition predict performance during a simulated direct-fire engagement

ABSTRACT This study determined anthropometric and body composition predictors of performance during a simulated direct-fire engagement. Healthy subjects (N = 33, age =25.7 ± 7.0yr) underwent anthropometric and body composition assessments before completing a simulated direct-fire engagement – consisting of marksmanship with cognitive workload assessment and a fire-and-move drill (16x6-m sprints) while wearing combat load. Susceptibility to enemy fire was modeled on sprint duration. Partial correlations and multiple linear regressions established relationships between predictors and performance outcomes, controlling for age and sex. Significance was p ≤ 0.05. Higher percent body fat, fat mass, fight load index predicted greater susceptibility to enemy fire (r = 0.40 to 0.42) and lower cognitive performance (r=-0.45 to -0.49). Higher BMI predicted lower cognitive performance (r=-0.49). Shorter stature/hand length predicted higher marksmanship accuracy (r=-0.40), while higher fat-free mass/fat-free mass index predicted slower reaction times (r = 0.36 to 0.41). These data suggest anthropometric and body composition measures modulate combat effectiveness and reinforce body composition standards in military organizations.

When and how do professional soccer players experience maximal intensity sprints in LaLiga?

ABSTRACT Objectives To 1) examine the periods in which maximal intensity sprints occurred during professional soccer matches and 2) analyze the maximal intensity sprints registered in match play considering the effect of playing position and other contextual variables. Methods A total of 1252 match observations were collected from 277 male professional players. Sprinting actions at maximal intensity were analyzed during 30 matches, and both contextual and performance variables were collected using performance tracking systems. Results Maximal intensity sprints were more frequent in the first and last periods of the match (0’-15’; 75’-90’), regardless of the playing position (χ2=23.01; p=0.29; ES=0.07). These sprints were usually non-linear actions without possession of the ball and had different tactical purposes depending on the position. The mean sprint duration ranged from ~4.9 s to ~9 s, the mean distance covered ranged from ~30 m to ~55 m, while the mean maximum velocity was between ~30.12 and ~32.80 km/h depending on the tactical purpose and playing position. Conclusion Professional soccer players need to be prepared during warm-ups for maximal intensity sprints in the first period of the match as well as maximal intensity sprints under high fatigue conditions given the frequency of sprints in the last period of the match. Also, training drills should be designed with a special focus on non-linear sprints without possession of the ball, based on the main tactical purpose of each position (e.g., CD: interceptions; MF: recovery runs; FB, WMF and FW: run the channel).

Assessing the rate of torque development in sprint cycling: a methodological study

ABSTRACT The present study examined (i) the magnitude of the rate of torque development (RTD) and (ii) the between-day reliability of RTD at the start of a cycling sprint when sprint resistance, sprint duration, and the pedal downstroke were altered. Nineteen well-trained cyclists completed one familiarisation and three testing sessions. Each session involved one set of 1-s sprints and one set of 5-s sprints. Each set contained one moderate (0.3 N m kg−1), one heavy (0.6 N m kg−1), and one very heavy (1.0 N m kg−1) resistance sprint. RTD measures (average and peak RTD, RTD 0–100 ms, and RTD 0–200 ms) were calculated for downstroke 1 in the 1-s sprint. For the 5-s sprints, RTD measures were calculated for each of the first three downstrokes, as an average of downstrokes 1 and 2, and as an average of downstrokes 2 and 3. Whilst RTDs were greatest in downstroke 3 at all resistances, the greatest number of reliable RTD measures were obtained using the average of downstrokes 2 and 3 with heavy or very heavy resistances, where average and peak RTD, and RTD 0–200 ms were deemed reliable (ICC ≥ 0.8, CV ≤ 10%). Since only 1–2 downstrokes can be completed within 1 s, the greatest RTD reliability cannot be achieved using a 1-s sprint; therefore, the average of downstrokes 2 and 3 during a >2-s cycling sprint (e.g. 5-s test) with heavy or very heavy resistance is recommended for the assessment of RTD in sprint cyclists. Highlights Whilst RTD measures were greatest in pedal downstroke 3 at all resistances, the greatest number of reliable RTD measures were obtained using the average of pedal downstrokes 2 and 3 with heavy or very heavy resistances, with average and peak RTD, and RTD 0–200 ms having acceptable reliability. RTD 0–100 ms and all RTD measurements for downstroke 1 were not reliable and should not be used. As only 1–2 downstrokes can be performed in 1 s, the greatest RTD reliability cannot be achieved using a 1-s sprint. Instead, RTD may be evaluated using a 5-s sprint.

Inter-Unit Consistency and Validity of 10-Hz GNSS Units in Straight-Line Sprint Running.

The present study aimed to investigate the inter-unit consistency and validity of multiple 10-Hz Catapult Global Navigation Satellite System (GNSS) units in measuring straight-line sprint distances and speeds. A total of 13 participants performed one 45.72-m linear sprint at maximum effort while wearing all eight GNSS units at once. Total run distance and peak speed recorded using GNSS units during the sprint duration were extracted for analysis. Sprint time and peak speed were also obtained from video recordings as reference values. Inter-unit consistency was assessed using intraclass correlation coefficients (ICC) and standard errors of measurements (SEM). For a validity test, one-sample t-tests were performed to compare each GNSS unit’s distance with the known distance. Additionally, Wilcoxon signed-rank tests were performed to compare each unit’s peak speed with the reference peak speed measured using video analysis. Results showed poor inter-unit consistency for both distance (ICC = 0.131; SEM = 8.8 m) and speed (ICC = 0.323; SEM 1.3 m/s) measurements. For validity, most units recorded a total distance (44.50 m to 52.69 m) greater than the known distance of 45.72 m and a lower peak speed (7.25 (0.51) m/s) than the video-based reference values (7.78 (0.90) m/s). The present findings demonstrate that there exist variations in distance and speed measurements among different units of the same GNSS system during straight-line sprint running. Practitioners should be aware of the window of errors associated with GNSS measurements and interpret the results with caution. When making comparisons over a season, players should wear the same unit every time if logistically possible.

Lower-body muscular power and exercise tolerance predict susceptibility to enemy fire during a tactical combat movement simulation

This study examined if field-expedient physical fitness/performance assessments predicted performance during a simulated direct-fire engagement. Healthy subjects (n = 33, age = 25.7 ± 7.0 years) completed upper- and lower-body strength and power assessments and a 3-min all-out running test to determine critical velocity. Subjects completed a simulated direct-fire engagement that consisted of marksmanship with cognitive workload assessment and a fire-and-move drill (16 × 6-m sprints) while wearing a combat load. Susceptibility to enemy fire was modelled on average sprint duration during the fire-and-move drill. Stepwise linear regression identified predictors for the performance during the simulated direct-fire engagement. Critical velocity (β = −0.30, p < 0.01) and standing broad jump (β = −0.67, p < 0.001) predicted susceptibility to enemy fire (R 2 = 0.74, p < 0.001). All predictors demonstrated poor relationships with marksmanship accuracy and cognitive performance. These data demonstrate the importance of exercise tolerance and lower-body power during simulated direct-fire engagements and provide potential targets for interventions to monitor and enhance performance and support soldier survivability. Practitioner Summary: This study identified field-expedient physical fitness/performance predictors of a simulated direct-fire engagement which evaluated susceptibility to enemy fire, marksmanship, and cognitive performance. Our findings suggest that high-intensity exercise tolerance and lower-body power are key determinants of performance that predicted susceptibility to enemy fire.

Behavioural plasticity of motor personality traits in the common vole under three-day continual observation in a test box

In animals, behavioural personality traits have been well-documented in a wide array of species. However, these traits, different between individuals, are not completely stable in individuals. They show behavioural plasticity like many other phenotypic traits. This plasticity is able to overcome some weak aspects of personality trait behavioural strategy. In the present study, we examined the relationship between motor personality traits and behavioural plasticity in the common vole (Microtus arvalis) using a PhenoTyper (PT) box (Noldus). During a three-day test, four behavioural motor activity parameters were monitored in 47 voles: distance moved, (loco)motion duration, motion change frequency, sprint duration. Consistency repeatability (RC) of the parameters from the PT test was very high, with all values ≥ 0.91. To select the best linear mixed-effect models (LMMs), several predictors (test day, sex, body weight) were tested. Only test day had a significant effect on the dependent variables and other predictors did not improve the LMMs. Further, we found significant effects of random intercepts (motor personality traits) and slopes (behavioural plasticity), as well as significant negative correlations between them for all behavioural parameters. Our results indicate that motor personality traits were connected with behavioural plasticity. Moreover, we revealed a significant positive correlation between the random slopes of (loco)motion duration and motion change frequency. This relationship could indicate some central plasticity of motor personality traits. In conclusion, negative correlations between the motor personality traits and the behavioural plasticity demonstrate expression of convergent tendency from both opposite trait values. This corresponds with different ideas on ability to compensate personality effects or to prepare for potential future conditions. In the laboratory, plasticity of personality traits take place whenever an animal is placed e. g. in a breeding box for the first time or is left for a long time in an experimental apparatus.

Influence of Sprint Duration during Minimal Volume Exercise on Aerobic Capacity and Affect.

The aims of this study were to investigate the influence of reduced-exertion, high-intensity interval training (REHIT), comparing a novel shortened-sprint protocol (SSREHIT) against a traditional protocol (TREHIT), on perceptual responses and to determine if changes in peak oxygen uptake (V˙O2peak) are attenuated with shorter sprints. Twenty-four healthy men undertook 15 sessions of SSREHIT or TREHIT. V˙O2peak was determined at baseline and after completion of each exercise condition. Affective (pleasure-displeasure) responses and perceived exertion were assessed during exercise to capture peak responses. Enjoyment was recorded 5-min after cessation of exercise. Compared to baseline, V˙O2peak increased in both groups (6% for SSREHIT [d=- 0.36] and 9% for TREHIT [d=- 0.53], p=0.01). Affective responses were more favourable for SSREHIT (p=0.001, d=1.62), but both protocols avoided large negative peaks of displeasure. Peak ratings of perceived exertion were lower for SSREHIT (p=0.001, d=- 1.71), although there were no differences in enjoyment (d=0.25). The results demonstrate both exercise conditions can increase V˙O2peak without overly compromising perceptual responses. Decreased sprint duration might further circumvent negative perceptual responses but might also attenuate physiological adaptations.

A Sensor Fusion Approach to the Estimation of Instantaneous Velocity Using Single Wearable Sensor During Sprint.

Power-Force-Velocity profile obtained during a sprint test is crucial for designing personalized training and evaluating injury risks. Estimation of instantaneous velocity is requisite for developing these profiles and the predominant method for this estimation assumes it to have a first order exponential behavior. While this method remains appropriate for maximal sprints, the sprint velocity profile may not always show a first-order exponential behavior. Alternately, velocity profile has been estimated using inertial sensors, with a speed radar, or a smartphone application. Existing methods either relied on the exponential behavior or timing gates for drift removal, or estimated only the mean velocity. Thus, there is a need for a more flexible and appropriate approach, allowing for instantaneous velocity estimation during sprint tests. The proposed method aims to solve this problem using a sensor fusion approach, by combining the signals from wearable Global Navigation Satellite System (GNSS) and inertial measurement unit (IMU) sensors. We collected data from nine elite sprinters, equipped with a wearable GNSS-IMU sensor, who ran two trials each of 60 and 30/40 m sprints. We developed an algorithm using a gradient descent-based orientation filter, which simplified our model to a linear one-dimensional model, thus allowing us to use a simple Kalman filter (KF) for velocity estimation. We used two cascaded KFs, to segment the sprint data precisely, and to estimate the velocity and the sprint duration, respectively. We validated the estimated velocity and duration with speed radar and photocell data as reference. The median RMS error for the estimated velocity ranged from 6 to 8%, while that for the estimated sprint duration lied between 0.1 and −6.0%. The Bland–Altman plot showed close agreement between the estimated and the reference values of maximum velocity. Examination of fitting errors indicated a second order exponential behavior for the sprint velocity profile, unlike the first order behavior previously suggested in literature. The proposed sensor-fusion algorithm is valid to compute an accurate velocity profile with respect to the radar; it can compensate for and improve upon the accuracy of the individual IMU and GNSS velocities. This method thus enables the use of wearable sensors in the analysis of sprint test.

Acceleration and sprint profiles of professional male football players in relation to playing position.

The study aims were to describe positional differences in the acceleration and sprint profiles of professional football players in match-play, and analyse start speeds required based on the intensity of accelerations and decelerations. This longitudinal study was conducted over thirteen competitive microcycles in a professional football team from LaLiga 123. Data were collected through electronic performance tracking systems. Every player was categorised based on the playing position: central defender (CD), full-back (FB), forward (FW), midfielder (MF), and wide midfielder (WMF). In respect of acceleration profile, positional differences were found for all variables (p < 0.05), except average magnitude of accelerations (ACCAVG, p = 0.56) and decelerations (DECAVG, p = 0.76). The sprint profile also showed positional differences for all variables (p < 0.05), apart from sprint duration (p = 0.07). In addition, although low-intensity accelerations required significantly greater start speeds (Vo) than high-intensity accelerations in WMF (0.4 ± 0.2 km/h; p < 0.05) and FW (0.4 ± 0.2 km/h; p < 0.05), no significant differences (p > 0.05) were found in CD, FB, and MF. However, high-intensity decelerations were performed at significantly higher Vo than low-intensity decelerations in MF (2.65 ± 0.1 km/h; p < 0.05), FW (3.3 ± 0.1 km/h; p < 0.05), FB (3.9 ± 0.4 km/h; p < 0.05), WMF (4.3 ± 0.3 km/h; p < 0.05), and CD (4.1 ± 0.7 km/h; p < 0.05). Therefore, positional differences exist for most variables of the acceleration and sprint profiles. In addition, different Vo were observed between high-intensity and low-intensity accelerations as well as high-intensity and low-intensity decelerations.