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Combining Heat and Altitude Training to Enhance Temperate, Sea-Level Performance

Olivier Girard, Peter Peeling, Sébastien Racinais, and Julien D. Périard

Background: Repeated exposure to heat (ie, plasma volume expansion) or altitude (ie, increase in total hemoglobin mass), in conjunction with exercise, induces hematological adaptations that enhance endurance performance in each respective environment. Recently, combining heat and altitude training has become increasingly common for athletes preparing to compete in temperate, sea-level conditions. Purpose: To review the physiological adaptations to training interventions combining thermal and hypoxic stimuli and summarize the implications for temperate, sea-level performance. Current Evidence: To date, research on combining heat and hypoxia has employed 2 main approaches: simultaneously combining the stressors during training or concurrently training in the heat and sleeping at altitude, sometimes with additional training in hypoxia. When environmental stimuli are combined in a training session, improvements in aerobic fitness and time-trial performance in temperate, sea-level conditions are generally similar in magnitude to those observed with heat, or altitude, training alone. Similarly, training in the heat and sleeping at altitude does not appear to provide any additional hematological or nonhematological benefits for temperate; sea-level performance relative to training in hot, hypoxic, or control conditions. Conclusions: Current research regarding combined heat and altitude interventions does not seem to indicate that it enhances temperate, sea-level performance to a greater extent than “traditional” (heat or hypoxia alone) training approaches. A major challenge in implementing combined-stressor approaches lies in the uncertainty surrounding the prescription of dosing regimens (ie, exercise and environmental stress). The potential benefits of conducting heat and altitude exposure sequentially (ie, one after the other) warrants further investigation.

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Effects of In-Exercise Carbohydrate Supplementation on Prolonged High-Intensity Exercise Performance in Oral Contraceptive Users

Serene J.L. Lee, Fleur E.C.A. Van Rens, and Jeremiah J. Peiffer

Purpose: To examine the impact of oral contraceptive (OC) phases on performance, physiological, and subjective responses to prolonged, intensive exercise when carbohydrate (CHO) stores are reduced. Methods: Ten well-trained female cyclists using monophasic OC completed 4 identical trials (>150 min) under conditions of in-trial 60-g·h−1 CHO supplementation (CHO+) or placebo (CHO−) during the sugar- (SUG) and active-pill (ACT) phases of their OC cycle. Each trial comprised two 400-kcal time trials (TT) separated by 1 hour of submaximal cycling at first ventilatory threshold. Results: Change in completion time from TT1 to TT2 was minimized in CHO+ compared with CHO− (4.06 [2.55] vs 6.08 [5.33] min; P = .019, effect size = −0.36). An interaction effect of OC and CHO was observed for time to complete TT (P = .006), mean TT power (P = .002), mean TT heart rate (P = .002), and posttrial emotional balance (P = .020) and negative emotional state (P = .033). In ACT, mean TT power and heart rate were higher in CHO+ when compared with CHO−, resulting in faster TTs in CHO+ and improved posttrial emotional well-being. When CHO was not supplemented, TT power and heart rate were higher in SUG when compared with ACT, resulting in faster TTs in SUG and improved posttrial emotional balance. Conclusion: CHO depletion during ACT negatively influenced TT performance and emotional well-being when compared with SUG. Irrespective of OC pill phase, CHO supplementation should be prioritized to sustain performance and improve postexercise recovery–stress balance.

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From Mentorship to Sponsorship in Sport Science

Iñigo Mujika and Peter Leo

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Individualizing Basketball-Specific Interval Training Using Anaerobic Speed Reserve: Effects on Physiological and Hormonal Adaptations

Chenhang Wang and Mingliang Ye

Purpose : We compared the adaptive responses to supramaximal high-intensity interval training (HIIT) individualized according to anaerobic speed reserve (ASR), the 30-15 Intermittent Fitness Test (V IFT), and velocity associated with maximum oxygen uptake (MAS) to determine which approach facilitates more identical adaptations across athletes with different profiles. Methods : Thirty national-level basketball players (age = 28.4 [5] y; body mass = 88.9 [6.3] kg; height = 190 [4.8] cm) were randomly assigned to 3 training groups performing 2 sets of 4, 6, 8, 6, 8, and 10-minute runs (from first to sixth week, respectively), consisting of 15-second running at Δ%20ASR (MAS + 0.2 × ASR), 95%V IFT, and 120%MAS, with 15 seconds recovery between efforts and a 3-minute relief between sets. Results : All 3 interval interventions significantly (P < .05) enhanced maximum oxygen uptake ( V ˙ O 2 max ), oxygen pulse ( V ˙ O 2 / HR ), first and second ventilatory threshold (VT1 and VT2), cardiac output ( Q ˙ max ), stroke volume, peak and average power output, testosterone levels, and testosterone-to-cortisol ratio following the training period. Different values of interindividual variability (coefficient of variation) for the percentage changes of the measured variables were observed in response to HIITASR, HIITv IFT, and HIITMAS for V ˙ O 2 max (8.7%, 18.8%, 34.6%, respectively), V ˙ O 2 / HR (9.5%, 15.0%, 28.6%), VT1 (9.6%, 19.6%, 34.6%), VT2 (21.8%, 32.4%, 56.7%), Q ˙ max (8.2%, 16.9%, 28.8%), stroke volume (7.9%, 15.2%, 23.5%), peak power output (20%, 22%, 37.3%), average power output (21.1%, 21.3%, 32.5%), testosterone (52.9%, 61.6%, 59.9%), and testosterone-to-cortisol ratio (55.1%, 59.5%, 57.8%). Conclusions : Supramaximal HIIT performed at Δ%20ASR resulted in more uniform physiological adaptations than HIIT interventions prescribed using V IFT or MAS. Although hormonal changes do not follow this approach, all the approaches induced an anabolic effect.

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Why Should Athletes Brake Fast? Influence of Eccentric Velocity on Concentric Performance During Countermovement Jumps at Different Loads

Jose L. Hernández-Davó, Rafael Sabido, Manuel Omar-García, and Daniel Boullosa

Purpose: The aim of the present study was to analyze the effect of different eccentric tempos on eccentric kinetics and kinematics and the subsequent concentric performance when performing countermovement jumps against different loads. Methods: After 1-repetition-maximum assessment and 2 familiarization sessions, 13 well-trained participants performed, in randomized order, 12 sets (4 tempos × 3 loads) of 4 repetitions of the loaded countermovement-jump exercise. The eccentric tempos analyzed were 5 and 2 seconds, as fast as possible, and accelerated (ie, without pause between repetitions), while the loads used were 30%, 50%, and 70% of 1-repetition maximum. Several kinetic and kinematic variables during both phases were recorded by linking a linear position transducer to the barbell. Results: The eccentric work was greater in the accelerated condition despite no changes in the eccentric depth. The peak and mean propulsive velocities were greater in the as-fast-as-possible and accelerated conditions. Correlation analysis showed that, compared with the 5-second condition, the increased concentric performance in the accelerated condition was related to the difference in eccentric work performed in the last 100 milliseconds of the eccentric phase (r > .770). Conclusions: Contrary to current practices, the current study highlights the need for performing the eccentric phase of loaded countermovement jumps, a common exercise performed by athletes for both training and evaluation purposes, as fast as possible. This allows not only a greater eccentric work but also improved concentric performance.

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Characteristics of Physical Activity Interventions for People With Visual Impairments: A Scoping Review

Soyoung Choi and JJ Pionke

This study evaluated physical activity interventions designed for individuals with visual impairments and sought to guide health intervention scientists aiming to promote physical activity in this demographic. We delved into the specifics of participants’ visual impairments, intervention features, accommodation approaches, and replicability prospects. The search spanned four databases, namely PubMed, CINAHL, SportDiscus, and Scopus, providing a wide scope and diversity of potential studies. There were no restrictions on publication years. We reviewed 13 studies, totaling 15 interventions. A consensus on visual-impairment definitions remains elusive, and the intervention dosages displayed variability. Notably, 66.7% (n = 7) integrated behavior-change techniques to amplify physical activity levels. Multiple studies employed audio descriptions as an accommodation method. While most studies provided adequate information for potential replication, detailed study protocols were frequently absent. It is essential for developed interventions to be persistently evaluated and fine-tuned to optimize results.

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Effects of High-Intensity Inspiratory Muscle Warm-Up on High-Intensity Exercise Performance and Muscle Oxygenation

Jun Koizumi and Toshiyuki Ohya

Purpose: An inspiratory muscle warm-up (IMW) improves inspiratory muscle function, but the effects of high-intensity exercise are inconsistent. We aimed to determine the effects of high-intensity IMW on high-intensity exercise performance and muscle oxygenation. Methods: Ten healthy men (maximal oxygen uptake [ V ˙ O 2 max ] 52.2 [5.0] mL·kg–1·min–1) performed constant-load exercise to exhaustion on a cycle ergometer at V ˙ O 2 max under 2 IMW conditions: a placebo condition (PLA) and a high-intensity IMW condition (HIGH). The inspiratory loads were set at 15% and 80% of maximal inspiratory pressure, respectively. Maximal inspiratory pressure was measured before and after IMW. Oxyhemoglobin was measured in the vastus lateralis by near-infrared spectroscopy during exercise. Rating of perceived exertion (RPE) for a leg was measured after 1 and 2 minutes of exercise. Results: Exercise tolerance was significantly higher under HIGH than PLA (228 [49] s vs 218 [49] s, P = .003). Maximal inspiratory pressure was significantly increased by IMW under HIGH (from 125 [20] to 136 [25] cm H2O, P = .031). Oxyhemoglobin was significantly higher under HIGH than PLA at 80% of the total duration of exercise (P = .048). RPE for the leg was significantly lower under HIGH than PLA after 2 minutes of exercise (P = .019). Conclusions: Given that oxyhemoglobin is an index of local oxygen supply, the results of this study suggest that high-intensity IMW increases the oxygen supply to active limbs. It may also reflect a reduction in RPE in the leg. In addition, high-intensity IMW may improve exercise performance.

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Effects of Hypoxia Severity on Muscle Oxygenation Kinetics Using Statistical Parametric Mapping During Repeated Treadmill Sprints

Clint Hansen, Franck Brocherie, Grégoire P. Millet, and Olivier Girard

Purpose: We examined the effects of increasing hypoxia severity on oxygenation kinetics in the vastus lateralis muscle during repeated treadmill sprints, using statistical parametric mapping (SPM). Methods: Ten physically active males completed 8 sprints of 5 seconds each (recovery = 25 s) on a motorized sprint treadmill in normoxia (sea level; inspired oxygen fraction = 0.21), moderate hypoxia (inspired oxygen fraction = 0.17), and severe hypoxia (SH; inspired oxygen fraction = 0.13). Continuous assessment of tissue saturation index (TSI) in the vastus lateralis muscle was conducted using near-infrared spectroscopy. Subsequently, TSI data were averaged for the sprint–recovery cycle of all sprints and compared between conditions. Results: The SPM analysis revealed no discernible difference in TSI signal amplitude between conditions during the actual 5-second sprint phase. However, during the latter portion of the 25-second recovery phase, TSI values were lower in SH compared with both sea level (from 22 to 30 s; P = .003) and moderate hypoxia (from 16 to 30 s; P = .001). The mean distance covered at sea level (22.9 [1.0] m) was greater than for both moderate hypoxia (22.5 [1.2] m; P = .045) and SH (22.3 [1.4] m; P = .043). Conclusions: The application of SPM demonstrated that only SH reduced muscle oxygenation levels during the late portion of the passive (recovery) phase and not the active (sprint) phase during repeated treadmill sprints. These findings underscore the usefulness of SPM for assessing muscle oxygenation differences due to hypoxic exposure and the importance of the duration of the between-sprints recovery period.

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Pharmacokinetic Profile of Caffeine and Its Two Main Metabolites in Dried Blood Spots After Five Different Oral Caffeine Administration Forms—A Randomized Crossover Study

Chiara Tuma, Andreas Thomas, Lasse Trede, Hans Braun, and Mario Thevis

Caffeine is an ergogenic substance that is consumed globally in many forms. The use of buccally absorbable formulations instead of gastrointestinal uptake has become increasingly popular over the years, especially when accelerated absorption with minimal gastrointestinal stress is desired. This study investigated the impact of five different formulations and administration routes of caffeine on the whole blood concentrations of caffeine, paraxanthine, and theobromine: caffeinated capsules, tablets, shots, pouches, and chewing gums. A uniform dose of caffeine (200 mg) was administered to 16 healthy recreational athletes (26.0 ± 2.1 years) using a randomized crossover design. Samples were taken in the form of dried blood spots at 16 different time points in a 2-hr timeframe after drug administration. The samples were analyzed using a validated liquid chromatography–tandem mass spectrometry method. The results for caffeine showed no significant differences in the overall bioavailability (area under the concentration–time curve), maximal concentration, and time to maximum concentration. However, when analyzing the bioavailability of caffeine in the first 5, 10, and 15 min, the liquid caffeine formulation was superior to other administered forms (p < .05). This indicates that caffeine solubility has a major influence on its absorption rate. In sports, the rate of caffeine absorption must be considered, not only when ingesting anhydrous caffeine, but also when choosing buccal absorption. These findings imply that general guidelines for ergogenic caffeine use should consider the formulation used and, accordingly, the corresponding route of absorption.

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Sex Differences in Hydration Biomarkers and Test–Retest Reliability Following Passive Dehydration

Colin S. Doherty, Lauren V. Fortington, and Oliver R. Barley

This study investigated (a) differences between males and females for changes in serum, tear, and urine osmolality, hematocrit, and urine specific gravity following acute passive dehydration and (b) assessed the reliability of these biomarkers separately for each sex. Fifteen males (age: 26.3 ± 3.5 years, body mass: 76 ± 7 kg) and 15 females (age: 28.8 ± 6.4 years, body mass: 63 ± 7 kg) completed a sauna protocol twice (5–28 days apart), aiming for 4% body mass loss (BML). Urine, blood, and tear markers were collected pre- and postdehydration, and change scores were calculated. Male BML was significantly greater than that of females in Trial 1 (3.53% ± 0.55% vs. 2.53% ± 0.43%, p < .001) and Trial 2 (3.36% ± 0.66% vs. 2.53% ± 0.44%, p = .01). Despite significant differences in BML, change in hematocrit was the only change marker that displayed a significant difference in Trial 1 (males: 3% ± 1%, females: 2% ± 1%, p = .004) and Trial 2 (males: 3% ± 1%, females: 1% ± 1%, p = .008). Regression analysis showed a significant effect for sex (male) predicting change in hematocrit (β = 0.8, p = .032) and change in serum osmolality (β = −3.3, p = .005) when controlling for BML but not for urinary or tear measures. The intraclass correlation coefficients for females (ICC 2, 1) were highest for change in urine specific gravity (ICC = .62, p = .006) and lowest for change in tear osmolarity (ICC = −.14, p = .689), whereas for males, it was posthematocrit (ICC = .65, p = .003) and post tear osmolarity (ICC = .18, p = .256). Generally, biomarkers showed lower test–retest reliability in males compared with females but, overall, were classified as poor–moderate in both sexes. These findings suggest that the response and reliability of hydration biomarkers are sex specific and highlight the importance of accounting for BML differences.