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Håvard Wiig, Thor Einar Andersen, Live S. Luteberget, and Matt Spencer

variables. The magnitude of the individual response to external load has, however, not been previously investigated. In this study we aimed, first, to model the within-player and the between-player effects of different external load variables on sRPE-TL in elite football. Second, to model the magnitude of

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Mary O. Whipple, Erica N. Schorr, Kristine M.C. Talley, Ruth Lindquist, Ulf G. Bronas, and Diane Treat-Jacobson

headings in the article). “adj3” denotes a search in which the first term is within three words of the second term (e.g., “differ* adj3 respon*” would capture the phrase “difference in individual response”). Selection of Studies To be eligible for inclusion in this review, articles had to meet the

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Thimo Wiewelhove, Constantin Thase, Marcel Glahn, Anthony Hessel, Christoph Schneider, Laura Hottenrott, Tim Meyer, Michael Kellmann, Mark Pfeiffer, and Alexander Ferrauti

interventions is commonly reported by recovery studies, including individuals who fail to show any changes in the expected direction (ie, “nonresponders”) 9 or even show a change in the opposite direction (ie, “negative-responders”). 6 This phenomenon, frequently referred to as an individual response to a

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Neil D. Clarke and Darren L. Richardson

users regardless of any withdrawal period. Therefore, consuming coffee providing 3 mg/kg 60 min prior to exercise is a practical source of caffeine prior to exercise in habitual low- and high-caffeine users. However, given the individual response to caffeine, athletes should experiment with various

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Heidi R. Thornton, Jace A. Delaney, Grant M. Duthie, and Ben J. Dascombe

compensate for large measurement errors. 10 Means and SDs should be reported, as these depict the variation in the responses, reflecting the effect of the treatment between individuals. The SD at baseline may be used to assess the magnitudes of effects and individual responses by standardization. 10 These

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Christian Cook, C. Martyn Beaven, Liam P. Kilduff, and Scott Drawer

Introduction:

This study aimed to determine whether caffeine ingestion would increase the workload voluntarily chosen by athletes in a limited-sleep state.

Methods:

In a double-blind, crossover study, 16 professional rugby players ingested either a placebo or 4 mg/kg caffeine 1 hr before exercise. Athletes classified themselves into nondeprived (8 hr+) or sleep-deprived states (6 hr or less). Exercise comprised 4 sets of bench press, squats, and bent rows at 85% 1-repetition maximum. Athletes were asked to perform as many repetitions on each set as possible without failure. Saliva was collected before administration of placebo or caffeine and again before and immediately after exercise and assayed for testosterone and cortisol.

Results:

Sleep deprivation produced a very large decrease in total load (p = 1.98 × 10−7). Caffeine ingestion in the nondeprived state resulted in a moderate increase in total load, with a larger effect in the sleep-deprived state, resulting in total load similar to those observed in the nondeprived placebo condition. Eight of the 16 athletes were identified as caffeine responders. Baseline testosterone was higher (p < .05) and cortisol trended lower in non-sleep-deprived athletes. Changes in hormones from predose to preexercise correlated to individual workload responses to caffeine. Testosterone response to exercise increased with caffeine compared with placebo, as did cortisol response.

Conclusions:

Caffeine increased voluntary workload in professional athletes, even more so under conditions of self-reported limited sleep. Caffeine may prove worthwhile when athletes are tired, especially in those identified as responders.

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Olli-Pekka Nuuttila, Santtu Seipäjärvi, Heikki Kyröläinen, and Ari Nummela

Purpose: To assess the reliability of nocturnal heart rate (HR) and HR variability (HRV) and to analyze the sensitivity of these markers to maximal endurance exercise. Methods: Recreational runners recorded nocturnal HR and HRV on nights after 2 identical low-intensity training sessions (n = 15) and on nights before and after a 3000-m running test (n = 23). Average HR, the natural logarithm of the root mean square of successive differences (LnRMSSD), and the natural logarithm of the high-frequency power (LnHF) were analyzed from a full night (FULL), a 4-hour (4H) segment starting 30 minutes after going to sleep, and morning value (MOR) based on the endpoint of the linear fit through all 5-minute averages during the night. Differences between the nights were analyzed with a general linear model, and intraclass correlation coefficient (ICC) was used for internight reliability assessments. Results: All indices were similar between the nights followed by low-intensity training sessions. A very high ICC (P < .001) was observed in all analysis segments with a range of .97 to .98 for HR, .92 to .97 for LnRMSSD, and .91 to .96 for LnHF. HR increased (P < .001), whereas LnRMSSD (P < .01) and LnHF (P < .05) decreased after the 3000-m test compared with previous night only in 4H and FULL. Increments in HR (P < .01) and decrements in LnRMSSD (P < .05) were greater in 4H compared with FULL and MOR. Conclusions: Nocturnal HR and HRV indices are highly reliable. Demanding maximal exercise increases HR and decreases HRV most systematically in 4H and FULL segments.

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Kristy Martin, Kevin G. Thompson, Richard Keegan, and Ben Rattray

 < .01). Physical Endurance Test There was no significant difference in the mean time to exhaustion between the control and mental exertion conditions (control: 628 ± 247 s vs. mental exertion: 601 ± 245 s, p  = .074, d  = 0.110). The individual responses were highly varied with 14 participants

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Cindy Lee, Hyejin Bang, and David J. Shonk

how its CSR activity is received by consumers. H1 : Existing corporate image will have an influence on individualsresponses toward the PTSO’s CSR activity in terms of perceived motive and change of attitude when controlled for their level of identification with the PTSO. Consumer-Specific Factor

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Filippo Dolci, Andrew E. Kilding, Tania Spiteri, Paola Chivers, Ben Piggott, Andrew Maiorana, and Nicolas H. Hart

influential factors that impact a change-of-direction economy during shuttle runs (SRE) after repeated bouts of intense sprint activity. Overall, SRE scores of the pooled group did not fluctuate significantly following RSAs; however, this was due to varied individual responses in SRE CHANGE . Specifically