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Mehdi Kordi, Campbell Menzies and Andy Galbraith

Purpose: The hyperbolic distance–time relationship can be used to profile running performance and establish critical speed (CS) and D′ (the curvature constant of the speed–time relationship). Typically, to establish these parameters, multiple (3+) performance trials are required, which can be highly fatiguing and limit the usability of such protocols in a single training session. This study aimed to compare CS and D′ calculated from a 2-trial (2-point model) and a 3-trial (3-point model) method. Methods: A total of 14 male distance runners completed 3 fixed-distance (3600, 2400, and 1200 m) time trials on a 400-m outdoor running track, separated by 30-min recoveries. Participants completed the protocol 9 times across a 12-mo period, with approximately 42 d between tests. CS and D′ were calculated using all 3 distances (3-point model) and also using the 3600- and 1200-m distances only (2-point model). Results : Mean (SD) CS for both 3-point and 2-point models was 4.94 (0.32) m·s−1, whereas the values for D′ were 123.3 (57.70) and 127.4 (57.34) m for the 3-point and 2-point models, respectively. Overall bias for both CS and D′ between 3-point and 2-point model was classed as trivial. Conclusion: A 2-point time-trial model can be used to calculate CS and D′ as proficiently as a 3-point model, making it a less fatiguing, inexpensive, and applicable method for coaches, practitioners, and athletes for monitoring running performance in 1 training session.

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Laura Pomportes, Jeanick Brisswalter, Arnaud Hays and Karen Davranche

Purpose: To investigate the effect of ingesting carbohydrate (CHO), caffeine  (CAF), and a guarana complex (GUAc) during a running exercise on cognitive performance, rating of perceived exertion (RPE), and shooting performance in high-level modern pentathlon athletes. Methods: A total of 10 athletes completed 4 counterbalanced sessions within a 2-wk period, corresponding to ingestions of CHO (30 g), GUAc (300 mg), CAF (200 mg), or placebo. The exercise involved a 40-min run on a treadmill at a steady speed, previously determined as a “somewhat hard” exercise (RPE 13). Shooting and cognitive performance (Simon task) were assessed in 3 phases: before exercise and ingestion, before exercise and after half ingestion, and after exercise and full ingestion. Drinks were consumed 40 min (250 mL) and 5 min (125 mL) prior to exercise and after 20 min of running (125 mL). RPE was assessed at 10-min intervals during exercise. Results: There was an interaction between drink and exercise on mean reaction time (P = .01, ηp2=.41) and a drink effect on RPE (P = .01, ηp2=.15). CHO, CAF, and GUAc enhanced the speed of information processing after exercise (P = .003, P = .004, and P = .04, respectively), but only CAF and GUAc decreased RPE (P = .002 and P = .02, respectively). Conclusion: The results highlight a beneficial effect of nutritional supplements on information processing and RPE. This finding is particularly interesting as decision-making processes are crucial in the performance of many sports.

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Olaf Prieske, Helmi Chaabene, Christian Puta, David G. Behm, Dirk Büsch and Urs Granacher

Purpose: To examine the effects of drop height on drop-jump (DJ) performance and on associations between DJ and horizontal-jump/sprint performances in adolescent athletes. Methods: Male (n = 119, 2.5 [0.6] y post-peak-height velocity) and female (n = 120, 2.5 [0.5] y post-peak-height velocity) adolescent handball players (national level) performed DJs in randomized order using 3 drop heights (20, 35, and 50 cm). DJ performance (jump height, reactive strength index [RSI]) was analyzed using the Optojump Next system. In addition, correlations were computed between DJ height and RSI with standing-long-jump and 20-m linear-sprint performances. Results: Statistical analyses revealed medium-size main effects of drop height for DJ height and RSI (P < .001, 0.63 ≤ d ≤ 0.71). Post hoc tests indicated larger DJ heights from 20 to 35 and 35 to 50 cm (P ≤ .031, 0.33 ≤ d ≤ 0.71) and better RSI from 20- to 35-cm drop height (P < .001, d = 0.77). No significant difference was found for RSI between 35- and 50-cm drop height. Irrespective of drop height, associations of DJ height and RSI were small with 5-m-split time (−.27 ≤ r ≤ .05), medium with 10-m-split time (−.44 ≤ r ≤ .14), and medium to large with 20-m sprint time and standing-long-jump distance (−.57 ≤ r ≤ .22). Conclusions: The present findings indicate that, irrespective of sex, 35-cm drop heights are best suited to induce rapid and powerful DJ performance (ie, RSI) during reactive strength training in elite adolescent handball players. Moreover, training-related gains in DJ performance may at least partly translate to gains in horizontal jump and longer sprint distances (ie, ≥20-m) and/or vice versa in male and female elite adolescent athletes, irrespective of drop height.

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Martin J. Barwood, Joe Kupusarevic and Stuart Goodall

Purpose: Exercise performance is impaired in the heat, and a contributing factor to this decrement is thermal discomfort. Menthol spraying of skin is one means of alleviating thermal discomfort but has yet to be shown to be ergogenic using single-spray applications. The authors examined whether repeated menthol spraying could relieve thermal discomfort, reduce perception of exertion, and improve exercise performance in hot (35°C), dry (22% relative humidity) conditions, hypothesizing that it would. Methods: A total of 8 trained cyclists completed 2 separate conditions of fixed-intensity cycling (50% maximal power output) for 45 min before a test to exhaustion (TTE; 70% maximal power output) with 100 mL of menthol spray (0.20% menthol) or control spray applied to the torso after 20 and 40 min. Perceptual (thermal sensation, thermal comfort, and rating of perceived exertion) performance (TTE duration), thermal variables (skin temperature, rectal temperature, and cardiac frequency), and sweating were measured. Data were compared using analysis of variance to .05 alpha level. Results: Menthol spray improved thermal sensation (cold sensation cf warm/hot after first spraying; P = .008) but only descriptively altered thermal comfort (comfortable cf uncomfortable; P = .173). Sweat production (994 [380] mL cf 1180 [380] mL; P = .020) and sweat rate (827 [327] mL·h−1 cf 941 [319] mL·h−1; P = .048) lowered. TTE performance improved (4.6 [1.74] cf 2.4 [1.55] min; P = .004). Menthol-spray effects diminished despite repeated applications, indicating increased contribution of visceral thermoreceptors to thermal perception. Conclusion: Repeated menthol spraying improves exercise capacity but alters thermoregulation, potentially conflicting behavioral and thermoregulatory drivers; care should be taken with its use. Carrying and deploying menthol spray would impose a logistical burden that needs consideration against performance benefit.

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Erin L. McCleave, Katie M. Slattery, Rob Duffield, Philo U. Saunders, Avish P. Sharma, Stephen Crowcroft and Aaron J. Coutts

Purpose: To determine whether combining training in heat with “Live High, Train Low” hypoxia (LHTL) further improves thermoregulatory and cardiovascular responses to a heat-tolerance test compared with independent heat training. Methods: A total of 25 trained runners (peak oxygen uptake = 64.1 [8.0] mL·min−1·kg−1) completed 3-wk training in 1 of 3 conditions: (1) heat training combined with “LHTL” hypoxia (H+H; FiO2 = 14.4% [3000 m], 13 h·d−1; train at <600 m, 33°C, 55% relative humidity [RH]), (2) heat training (HOT; live and train <600 m, 33°C, 55% RH), and (3) temperate training (CONT; live and train <600 m, 13°C, 55% RH). Heat adaptations were determined from a 45-min heat-response test (33°C, 55% RH, 65% velocity corresponding to the peak oxygen uptake) at baseline and immediately and 1 and 3 wk postexposure (baseline, post, 1 wkP, and 3 wkP, respectively). Core temperature, heart rate, sweat rate, sodium concentration, plasma volume, and perceptual responses were analyzed using magnitude-based inferences. Results: Submaximal heart rate (effect size [ES] = −0.60 [−0.89; −0.32]) and core temperature (ES = −0.55 [−0.99; −0.10]) were reduced in HOT until 1 wkP. Sweat rate (ES = 0.36 [0.12; 0.59]) and sweat sodium concentration (ES = −0.82 [−1.48; −0.16]) were, respectively, increased and decreased until 3 wkP in HOT. Submaximal heart rate (ES = −0.38 [−0.85; 0.08]) was likely reduced in H+H at 3 wkP, whereas CONT had unclear physiological changes. Perceived exertion and thermal sensation were reduced across all groups. Conclusions: Despite greater physiological stress from combined heat training and “LHTL” hypoxia, thermoregulatory adaptations are limited in comparison with independent heat training. The combined stimuli provide no additional physiological benefit during exercise in hot environments.

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Ilkka Heinonen, Jukka Kemppainen, Toshihiko Fujimoto, Juhani Knuuti and Kari K. Kalliokoski

Human bone marrow is a metabolically active tissue that responds to acute low-intensity exercise by having increased glucose uptake (GU). Here, the authors studied whether bone marrow GU increases more with increased exercise intensities. Femoral bone marrow GU was measured using positron emission tomography and [18F]-fluorodeoxyglucose in six healthy young men during cycling at intensities of 30% (low), 55% (moderate), and 75% (high) of maximal oxygen consumption on three separate days. Bone marrow GU at low was 17.2 µmol·kg−1·min−1 (range 9.0–25.4) and increased significantly (p = .003) at moderate (31.2 µmol·kg−1·min−1, 22.9–39.4) but was not significant from moderate to high (37.4 µmol·kg−1·min−1, 29.0–45.7, p = .26). Furthermore, the ratio between bone and muscle GU decreased from low to moderate exercise intensity (p < .01) but not (p = .99) from moderate to high exercise intensity. In conclusion, these results show that although the increase is not as large as observed in exercising skeletal muscle, GU in femoral bone marrow increases with increasing exercise intensity at least from low- to moderate-intensity effort, which may be important for bone and whole-body metabolic health.

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Mitchell J. Henderson, Job Fransen, Jed J. McGrath, Simon K. Harries, Nick Poulos and Aaron J. Coutts

Purpose: To examine the collective independent influence of a range of individual characteristics on physical and technical match performance during international rugby sevens matches. Methods: Data were collected from 20 international rugby sevens players from 1 team across 1 season. Activity profiles were measured using wearable microtechnology devices, and technical performance measures were collected from match video analysis. Subjective well-being measures were collected using a well-being questionnaire completed on the morning of main training days, and groin-squeeze assessments at 0° and 60° knee flexion were also conducted using a sphygmomanometer. Assessments of aerobic fitness were completed periodically across the season, including time to complete a 2-km run and final velocity during the 30:15 Intermittent Fitness Test (V IFT). A principal-components analysis was conducted to reduce the dimensionality of the physical and technical variables into single-factor values. Linear mixed models were then constructed to examine the collective influence of a range of individual contextual variables on physical and technical performance factors. Results: Increased muscle soreness, stress, and VIFT were associated with trivial to small increases in physical and technical performance values, whereas trivial to small decreases were associated with higher perceived recovery, body weight, and groin squeeze (0° knee flexion). Conclusions: A range of well-being metrics are required to account for a significant portion of the variance in physical and technical performance. These factors may be manipulated by coaches or practitioners to achieve favorable physiological readiness that may lead to improved match performance.

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Lasse Ishøi, Per Aagaard, Mathias F. Nielsen, Kasper B. Thornton, Kasper K. Krommes, Per Hölmich and Kristian Thorborg

Purpose: To investigate the association between hamstring muscle peak torque and rapid force capacity (rate of torque development, RTD) vs sprint performance in elite youth football players. Methods: Thirty elite academy youth football players (16.75 [1.1] y, 176.9 [6.7] cm, 67.1 [6.9] kg) were included. Isometric peak torque (in Newton meters per kilogram) and early- (0–100 ms) and late- (0–200 ms) phase RTD (RTD100, RTD200) (in Newton meters per second per kilogram) of the hamstring muscles were obtained as independent predictor variables. Sprint performance was assessed during a 30-m-sprint trial. Mechanical sprint variables (maximal horizontal force production [F H0, in Newtons per kilogram], maximal theoretical velocity [V 0, in meters per second], maximal horizontal power output [Pmax, in watts per kilogram]) and sprint split times (0–5, 0–15, 0–30, and 15–30 m, in seconds) were derived as dependent variables. Subsequently, linear-regression analysis was conducted for each pair of dependent and independent variables. Results: Positive associations were observed between hamstring RTD100 and F H0 (r 2 = .241, P = .006) and Pmax (r 2 = .227, P = .008). Furthermore, negative associations were observed between hamstring RTD100 and 0- to 5-m (r 2 = .206, P = .012), 0- to 15-m (r 2 = .217, P = .009), and 0- to 30-m sprint time (r 2 = .169, P = .024). No other associations were observed. Conclusions: The present data indicate that early-phase (0–100 ms) rapid force capacity of the hamstring muscles plays an important role for acceleration capacity in elite youth football players. In contrast, no associations were observed between hamstring muscle function and maximal sprint velocity. This indicates that strength training focusing on improving early-phase hamstring rate of force development may contribute to enhance sprint acceleration performance in this athlete population.

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Jason D. Stone, Adam C. King, Shiho Goto, John D. Mata, Joseph Hannon, James C. Garrison, James Bothwell, Andrew R. Jagim, Margaret T. Jones and Jonathan M. Oliver

Purpose: To provide a joint-level analysis of traditional (TS) and cluster (CS) set structure during the back-squat exercise. Methods: Eight men (24 [3] y, 177.3 [7.9] cm, 82.7 [11.0] kg, 11.9 [3.5] % body fat, and 150.3 [23.0] kg 1-repetition maximum [1RM]) performed the back-squat exercise (80%1RM) using TS (4 × 6, 2-min interset rest) and CS (4 × [2 × 3], 30-s intraset rest, 90-s interset rest), randomly. Lower-limb kinematics were collected by motion capture, as well as kinetic data by bilateral force platforms. Results: CS attenuated the loss in mean power (TS −21.6% [3.9%]; CS −12.4% [7.5%]; P = .042), although no differences in gross movement pattern (sagittal-plane joint angles) within and between conditions were observed (P ≥ .05). However, joint power produced at the hip increased from repetition (REP) 1 through REP 6 during TS, while a decrease was noted at the knee. A similar pattern was observed in the CS condition but was limited to the hip. Joint power produced at the hip increased from REP 1 through REP 3 but returned to REP 1 values before a similar increase through REP 6, resulting in differences between conditions (REP 4, P = .018; REP 5, P = .022). Conclusions: Sagittal-plane joint angles did not change in either condition, although CS elicited greater power. Differing joint power contributions (hip and knee) suggest potential central mechanism that may contribute to enhanced power output during CS and warrant further study. Practitioners should consider incorporating CS into training to promote greater power adaptations and to mitigate fatigue.

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Matthew Ellis, Mark Noon, Tony Myers and Neil Clarke

Context: High doses of ∼6 mg·kg−1 body mass have improved performance during intermittent running, jumping, and agility protocols. However, there are sparse data on low doses of caffeine, especially in elite adolescent soccer players. Methods: A total of 15 elite youth soccer players (177.3 [4.8] cm, 66.9 [7.9] kg, and 16 [1] y) participated in the study, consuming 1, 2, or 3 mg·kg−1 caffeine in a gelatin capsule or a 2-mg·kg−1 placebo in a single-blind, randomized, crossover study design. Testing consisted of a 20-m sprint, arrowhead agility (change of direction [CoD] right or left), countermovement jump (CMJ), and Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1). Postexercise CMJ performance was assessed as participants exited the Yo-Yo IR1. Data were analyzed using a Bayesian multilevel regression model to provide explained variance and probabilities of improvement (P = %). Results: Compared with placebo, 3 mg·kg−1 caffeine presented the highest probabilities of change across a range of tests (mean [SD], P = %). Times for 20-m sprint were 3.15 (0.10) s vs 3.18 (0.09) s (P = 73%), CoD-right times were 8.43 (0.24) s vs 8.55 (0.25) s (P = 99%), CoD-left times were 8.44 (0.22) s vs 8.52 (0.18) s (P = 85%), Yo-Yo IR1 distance was 2440 (531) m vs 2308 (540) m (P = 15%), and preexercise CMJ height was 41.6 (7.2) cm vs 38 (8.5) cm (P = 96%). Postexercise CMJ was higher with 3 mg·kg−1 than with placebo (42.3 [8] cm vs 36.6 [8] cm; P = 100%). Doses of 1 or 2 mg·kg−1 caffeine also demonstrated the ability to enhance performance but were task dependent. Conclusion: Low doses of caffeine improve performance but are dose and task dependent. A dose of 3 mg·kg−1 caffeine improved performance across the majority of tests with potential to further improve postexercise CMJ height.