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Bjarne Rud, Eivind Øygard, Even B. Dahl, Gøran Paulsen, and Thomas Losnegard

Purpose: We tested whether a single session of heavy-load resistance priming conducted in the morning improved double-poling (DP) performance in the afternoon. Methods: Eight national-level male cross-country skiers (mean [SD]: 23 [3] y, 184 [6] cm, 73 [7] kg, maximum oxygen consumption = 69 [6] mL·kg−1·min−1) carried out 2 days of afternoon performance tests. In the morning, 5 hours before tests, subjects were counterbalanced to either a session of 3 × 3 repetitions (approximately 85%–90% 1-repetition maximum) of squat and sitting pullover exercises or no exercise. The performance was evaluated in DP as time to exhaustion (TTE) (approximately 3 min) on a treadmill and 30-m indoor sprints before and after TTE (30-m DP pre/post). Furthermore, submaximal DP oxygen cost, countermovement jump, and isometric knee-extension force during electrical stimulation were conducted. Participants reported perceived readiness on test days. Results: Resistance exercise session versus no exercise did not differ for TTE (approximately 3 min above) (mean ± 95% confidence interval = 3.6% ± 6.0%; P = .29; effect size [ES], Cohen d = 0.27), 30-m DP pre (−0.56% ± 0.80%; P = .21; ES = 0.20), 30-m DP post (−0.18% ± 1.13%; P = .76; ES = 0.03), countermovement jump (−2.0% ± 2.8%; P = .21; ES = 0.12), DP oxygen cost (−0.13% ± 2.04%; P = .91; ES = 0.02), or perceived readiness (P ≥ .11). Electrical stimulation force was not different in contraction or relaxation time but revealed low-frequency fatigue in the afternoon for the resistance exercise session only (−12% [7%]; P = .01; ES = 1.3). Conclusion: A single session of heavy-load, low-volume resistance exercise in the morning did not increase afternoon DP performance of short duration in high-level skiers. However, leg low-frequency fatigue after resistance priming, together with the presence of small positive effects in 2 out of 3 DP tests, may indicate that the preconditioning was too strenuous.

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Megan A. Kuikman, Margo Mountjoy, Trent Stellingwerff, and Jamie F. Burr

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Maria Misailidi, Konstantinos Mantzios, Christos Papakonstantinou, Leonidas G. Ioannou, and Andreas D. Flouris

Purpose: We investigated the environmental conditions in which all outdoor International Tennis Federation (ITF) junior tournaments (athlete ages: <18 y) were held during 2010–2019. Thereafter, we performed a crossover trial ( NCT04197375) assessing the efficacy of head–neck precooling for mitigating the heat-induced psychophysical and performance impacts on junior athletes during tennis match play. Methods: ITF junior tournament information was collected. We identified meteorological data from nearby (13.6 [20.3] km) weather stations for 3056 (76%) tournaments. Results: Overall, 30.1% of tournaments were held in hot (25°C–30°C wet-bulb globe temperature [WBGT]; 25.9%), very hot (30°C–35°C WBGT; 4.1%), or extremely hot (>35°C WBGT; 0.1%) conditions. Thereafter, 8 acclimatized male junior tennis athletes (age = 16.0 [0.9] y; height = 1.82 [0.04] m; weight = 71.3 [11.1] kg) were evaluated during 2 matches: one with head–neck precooling (27.7°C [2.2°C] WBGT) and one without (27.9°C [1.8°C] WBGT). Head–neck precooling reduced athletes’ core temperature from 36.9°C (0.2°C) to 36.4°C (0.2°C) (P = .001; d = 2.4), an effect reduced by warm-up. Head–neck precooling reduced skin temperature (by 0.3°C [1.3°C]) for the majority of the match and led to improved (P < .05) perceived exertion (by 13%), thermal comfort (by 14%), and thermal sensation (by 15%). Muscle temperature, heart rate, body weight, and urine specific gravity remained unaffected (P ≥ .05; d < 0.2). Small or moderate improvements were observed in most performance parameters assessed (d = 0.20–0.79). Conclusions: Thirty percent of the last decade’s ITF junior tournaments were held in hot, very hot, or extremely hot conditions (25°C–36°C WBGT). In such conditions, head–neck precooling may somewhat lessen the physiological and perceptual heat strain and lead to small to moderate improvements in the match-play performance of adolescent athletes.

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Charli Sargent, Michele Lastella, Shona L. Halson, and Gregory D. Roach

Purpose: Anecdotal reports indicate that many elite athletes are dissatisfied with their sleep, but little is known about their actual sleep requirements. Therefore, the aim of this study was to compare the self-assessed sleep need of elite athletes with an objective measure of their habitual sleep duration. Methods: Participants were 175 elite athletes (n = 30 females), age 22.2 (3.8) years (mean [SD]) from 12 individual and team sports. The athletes answered the question “how many hours of sleep do you need to feel rested?” and they kept a self-report sleep diary and wore a wrist activity monitor for ∼12 nights during a normal phase of training. For each athlete, a sleep deficit index was calculated by subtracting their average sleep duration from their self-assessed sleep need. Results: The athletes needed 8.3 (0.9) hours of sleep to feel rested, their average sleep duration was 6.7 (0.8) hours, and they had a sleep deficit index of 96.0 (60.6) minutes. Only 3% of athletes obtained enough sleep to satisfy their self-assessed sleep need, and 71% of athletes fell short by an hour or more. Specifically, habitual sleep duration was shorter in athletes from individual sports than in athletes from team sports (F1,173 = 13.1, P < .001; d = 0.6, medium), despite their similar sleep need (F1,173 = 1.40, P = .24; d = 0.2, small). Conclusions: The majority of elite athletes obtain substantially less than their self-assessed sleep need. This is a critical finding, given that insufficient sleep may compromise an athlete’s capacity to train effectively and/or compete optimally.

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Alexandra Martin, Hande Hofmann, Clemens Drenowatz, Birgit Wallmann-Sperlich, Billy Sperlich, and Karsten Koehler

Energy availability describes the amount of dietary energy remaining for physiological functionality after the energy cost of exercise is deducted. The physiological and hormonal consequences of low energy availability (LEA) are well established, but the impact of LEA on physical activity behavior outside of exercise and, specifically, nonexercise activity thermogenesis (NEAT) has not been systematically examined. The authors conducted a secondary analysis of a repeated-measures crossover study in which recreationally trained young men (n = 6, 25 ± 1.0 years) underwent two 4-day conditions of LEA (15 kcal·kg fat-free mass−1 ·day−1) with and without endurance exercise (LEA + EX and LEA EX) and two energy-balanced control conditions (CON + EX and CON EX). The duration and intensity of physical activity outside of prescribed exercise were assessed using the SenseWear Pro3 armband. LEA did not alter NEAT (p = .41), nor time spent in moderate to vigorous (p = .20) and low-intensity physical activity (p = .17). However, time spent in low-intensity physical activity was lower in LEA + EX than LEA − EX (13.7 ± 0.3 vs. 15.2 ± 0.3 hr/day; p = .002). Short-term LEA does not seem to impact NEAT per se, but the way it is attained may impact physical activity behavior outside of exercise. As the participants expended similar amounts of energy during NEAT (900–1,300 kcal/day = 12.5–18.0 kcal·kg fat-free mass−1·day−1) and prescribed exercise bouts (15.0 kcal·kg fat-free mass−1·day−1), excluding it as a component of energy expenditure may skew the true energy available for physiological functionality in active populations.

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Stephanie J. Shell, Brad Clark, James R. Broatch, Katie Slattery, Shona L. Halson, and Aaron J. Coutts

Purpose: This study aimed to independently validate a wearable inertial sensor designed to monitor training and performance metrics in swimmers. Methods: A total of 4 male (21 [4] y, 1 national and 3 international) and 6 female (22 [3] y, 1 national and 5 international) swimmers completed 15 training sessions in an outdoor 50-m pool. Swimmers were fitted with a wearable device (TritonWear, 9-axis inertial measurement unit with triaxial accelerometer, gyroscope, and magnetometer), placed under the swim cap on top of the occipital protuberance. Video footage was captured for each session to establish criterion values. Absolute error, standardized effect, and Pearson correlation coefficient were used to determine the validity of the wearable device against video footage for total swim distance, total stroke count, mean stroke count, and mean velocity. A Fisher exact test was used to analyze the accuracy of stroke-type identification. Results: Total swim distance was underestimated by the device relative to video analysis. Absolute error was consistently higher for total and mean stroke count, and mean velocity, relative to video analysis. Across all sessions, the device incorrectly detected total time spent in backstroke, breaststroke, butterfly, and freestyle by 51% (15%). The device did not detect time spent in drill. Intraclass correlation coefficient results demonstrated excellent intrarater reliability between repeated measures across all swimming metrics. Conclusions: The wearable device investigated in this study does not accurately measure distance, stroke count, and velocity swimming metrics or detect stroke type. Its use as a training monitoring tool in swimming is limited.

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Mitchell J. Henderson, Bryna C.R. Chrismas, Christopher J. Stevens, Job Fransen, Aaron J. Coutts, and Lee Taylor

Purpose: To determine the effect of wearing a phase-change cooling vest in elite female rugby sevens athletes during (1) a simulated match-day warm-up in hot conditions prior to a training session and (2) a prematch warm-up during a tournament in cool conditions. Methods: This study consisted of 2 randomized independent group designs (separated by 16 d) where athletes completed the same 23- to 25-minute match-day warm-up (1) in hot conditions (range = 28.0°C to 35.1°C wet bulb globe temperature [WBGT]) prior to training and (2) in cool conditions (range = 18.8°C to 20.1°C WBGT) prior to a World Rugby Women’s Sevens Series match. In both conditions, athletes were randomly assigned to wearing either (1) the standardized training/playing ensemble (synthetic rugby shorts and training tee/jersey) or (2) the standardized training/playing ensemble plus a commercial phase-change athletic cooling vest. Group-wise differences in core temperature rise from baseline, global positioning system–measured external locomotive output, and perceptual thermal load were compared. Results: Core temperature rise during a match warm-up was lower in the hot condition only (−0.65°C [95% confidence interval = −1.22°C to −0.08°C], ηp2=.23 [95% confidence interval = .00 to .51], P = .028). No differences in various external-load variables were observed. Conclusions: Phase-change cooling vests can be worn by athletes prior to, and during, a prematch warm-up in hot conditions to limit excess core temperature rise without adverse effects on thermal perceptions or external locomotion output.

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Iva Obrusnikova, Albert R. Cavalier, Richard R. Suminski, Ashleigh E. Blair, Cora J. Firkin, and Ashley M. Steinbrecher

Adults with an intellectual disability have significantly lower levels of fitness compared with the general population. This study examined the effects of a 13-week theoretically guided, community-based, multicomponent resistance training intervention, resistance training for empowerment, on muscular strength and independent functional performance in 24 adults with an intellectual disability, aged 18–44 years. Twelve participants were randomly allocated to an experimental group and 12 to an active control group. An analysis of covariance revealed that the experimental group had significantly greater increases (p < .05) on the chest press and leg press one-repetition maximum tests and the 6-min walk test from the baseline to postintervention compared with the control group. The experimental group correctly and independently performed a significantly greater number of steps of resistance training exercise tasks than the control group. Marginal significance and large effect sizes were found for the prone plank test and the stair climb test. The resistance training for empowerment was effective in promoting muscular strength and independent functional performance among adults with an intellectual disability.

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Julia Kathrin Baumgart, Espen Tønnessen, Morten Eklund, and Øyvind Sandbakk

Purpose: To describe the training volume, intensity distribution, and use of swimming styles during a Paralympic cycle in a multiple swimming champion with paraplegia. Methods: The female Paralympic swimmer was 23–26 years of age and had a body mass of 60 to 62 kg and a body height of 174 cm. She has a spinal cord injury at the Th6 level, competed in the S5/SB4 Para swimming classes, and uses a wheelchair for mobility. Training time, as well as distance in the different intensity zones and swimming styles, was registered with the “workouts for swim coaches” software throughout a full Paralympic cycle. Results: The Para swimmer performed a total of 388, 524, 471, and 656 annual hours of swimming, corresponding to 1126, 1504, 1463, and 1993 km, in the 2012–13, 2013–14, 2014–15, and 2015–16 seasons, respectively. In addition, she performed 1 to 3 weekly dry-land strength sessions and 4 to 6 weekly dry-land basic skill sessions. She conducted 91% to 94% of the swimming distance in each macrocycle at low intensity, 2% to 4% at moderate intensity, and 3% to 6% at high intensity. She performed 78% to 84% of the swimming distance in each macrocycle in the freestyle swimming technique and the remaining 16% to 22% in the backstroke, breaststroke, and butterfly techniques. Conclusion: This case study exemplifies how a female Paralympic swimmer with paraplegia progressed her training in the seasons leading up to the Paralympic Games, reaching an annual training distance of 2000 km, which is similar to that of able-bodied swimmers.

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Fredrik Tonstad Vårvik, Thomas Bjørnsen, and Adam M. Gonzalez

Citrulline malate (CitMal) is a dietary supplement that is suggested to enhance strength training performance. However, there is conflicting evidence on this matter. Thus, the purpose of this meta-analysis was to determine whether supplementing with CitMal prior to strength training could increase the total number of repetitions performed before reaching voluntary muscular failure. A systematic search was conducted wherein the inclusion criteria were double-blind, placebo-controlled studies in healthy participants that examined the effect of CitMal on repetitions to failure during upper body and lower body resistance exercises. The Hedges’s g standardized mean differences (SMD) between the placebo and CitMal trials were calculated and used in a random effect model. Two separate subanalyses were performed for upper body and lower body exercises. Eight studies, including 137 participants who consisted of strength-trained men (n = 101) and women (n = 26) in addition to untrained men (n = 9), fulfilled the inclusion criteria. Across the studies, 14 single-joint and multijoint exercises were performed with an average of 51 ± 23 total repetitions during 5 ± 3 sets per exercise at ∼70% of one-repetition maximum. Supplementing with 6–8 g of CitMal 40–60 min before exercise increased repetitions by 3 ± 5 (6.4 ± 7.9%) compared with placebo (p = .022) with a small SMD (0.196). The subanalysis for the lower body resulted in a tendency for an effect of the supplement (8.1 ± 8.4%, SMD: 0.27, p = .051) with no significant effect for the upper body (5.7 ± 8.4%, SMD: 0.16, p = .131). The current analysis observed a small ergogenic effect of CitMal compared with placebo. Acute CitMal supplementation may, therefore, delay fatigue and enhance muscle endurance during high-intensity strength training.