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Kayla B. Henslin Harris, Carl Foster, Jos J. de Koning, Christopher Dodge, Glenn A. Wright and John P. Porcari

Previous studies have found decreases in arterial oxygen saturation to be temporally linked to reductions in power output (PO) during time-trial (TT) exercise. The purpose of this study was to determine whether preexercise desaturation (estimated from pulse oximetry [SpO2]), via normobaric hypoxia, would change the pattern of PO during a TT.

Purpose:

The authors tested the hypothesis that the starting PO of a TT would be reduced in the EARLY trial secondary to a reduced SpO2 but would not be reduced in LATE until ~30 s after the start of the TT.

Methods:

Eight trained cyclists/triathletes (4 male, 4 female) performed 3 randomly ordered 3-km TTs while breathing either room air (CONTROL) or hypoxic air administered 3 min before the start of the TT (EARLY) or at the beginning of the TT (LATE).

Results:

There was no effect of hypoxia on PO during the first 0.3 km of either the EARLY or the LATE trial compared with CONTROL, although there was a significant decrease in pre-TT SpO2 in EARLY vs CONTROL and LATE. The time for PO to decrease was ~40 s after the start of the TT in both EARLY and LATE.

Conclusions:

The results support the strong effect of the preexercise template on the pattern of PO during simulated competition and suggest that reductions in SpO2 are not direct signals to decrease PO.

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Akinobu Nishimura, Masaaki Sugita, Ko Kato, Aki Fukuda, Akihiro Sudo and Atsumasa Uchida

Purpose:

Recent studies have shown that low-intensity resistance training with vascular occlusion (kaatsu training) induces muscle hypertrophy. A local hypoxic environment facilitates muscle hypertrophy during kaatsu training. We postulated that muscle hypertrophy can be more efficiently induced by placing the entire body in a hypoxic environment to induce muscle hypoxia followed by resistance training.

Methods:

Fourteen male university students were randomly assigned to hypoxia (Hyp) and normoxia (Norm) groups (n = 7 per group). Each training session proceeded at an exercise intensity of 70% of 1 repetition maximum (RM), and comprised four sets of 10 repetitions of elbow extension and fexion. Students exercised twice weekly for 6 wk and then muscle hypertrophy was assessed by magnetic resonance imaging and muscle strength was evaluated based on 1RM.

Results:

Muscle hypertrophy was significantly greater for the Hyp-Ex (exercised fexor of the hypoxia group) than for the Hyp-N (nonexercised fexor of the hypoxia group) or Norm-Ex fexor (P < .05, Bonferroni correction). Muscle hypertrophy was significantly greater for the Hyp-Ex than the Hyp-N extensor. Muscle strength was significantly increased early (by week 3) in the Hyp-Ex, but not in the Norm-Ex group.

Conclusion:

This study suggests that resistance training under hypoxic conditions improves muscle strength and induces muscle hypertrophy faster than under normoxic conditions, thus representing a promising new training technique.

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David Montero and Carsten Lundby

Context:

Few recent studies indicate that short-term repeated-sprint (RS) training in hypoxia (RSH) improves RS performance compared with identical training under normoxic conditions (RSN) in endurance-trained subjects.

Purpose:

To determine the effects of RSH against RSN on RS performance under normoxic and moderate hypoxic conditions, using a randomized, doubleblind, crossover experimental design.

Methods:

Fifteen endurance-trained male subjects (age 25 ± 4 y) performed 4 wk of RS training (3 sessions/wk) in normobaric hypoxia (RSH, FiO2 = 13.8%) and normoxia (RSN, FiO2 = 20.9%) in a crossover manner. Before and after completion of training, RS tests were performed on a cycle ergometer with no prior exercise (RSNE), after an incremental exercise test (RSIE), and after a time-trial test (RSTT) in normoxia and hypoxia.

Results:

Peak power outputs at the incremental exercise test and time-trial performance were unaltered by RSH in normoxia and hypoxia. RS performance was generally enhanced by RSH, as well as RSN, but there were no additional effects of RSH over RSN on peak and mean sprint power output and the number of repeated sprints performed in the RSNE, RSIE, and RSTT trials under normoxic and hypoxic conditions.

Conclusions:

The present double-blind crossover study indicates that RSH does not improve RS performance compared with RSN in normoxic and hypoxic conditions in endurance-trained subjects. Therefore, caution should be exercised when proposing RSH as an advantageous method to improve exercise performance.

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Stacie L. Wing-Gaia, Andrew W. Subudhi and Eldon W. Askew

The purpose of this study was to assess the effects of purified oxygenated water on exercise performance under hypoxic conditions. Nine recreational male cyclists (age = 26.6 ± 5.2 y, weight = 87.6 ± 19.5 kg, VO2peak = 46.5 ± 5.9 mL · kg−1 · min−1) completed two 600 kJ cycling time trials under hypoxic conditions (FIO2 = 13.6% O2, Pbar = 641 mmHg) separated by 2 wk. Trials were completed following 3 d ingestion of 35 mL · kg−1 · d−1 of control (CON) or experimental (EXP) water. Time to completion, heart rate (HR), rate of perceived exertion (RPE), pulse oximetry (SaO2), blood gases (PcO2 and PcCO2), and lactate were measured during the trials. Hydration was assessed with pre- and post-exercise body weight and 24-h urine specific gravity. Performance, hydration, and blood oxygenation were unaffected by EXP water. Results of this study suggest that purified oxygenated water does not improve exercise performance in moderately active males.

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Christian Mariacher, Hannes Gatterer, Joachim Greilberger, Radoslav Djukic, Michaela Greilberger, Marc Philippe and Martin Burtscher

Background/Objectives:

To compare the effects of a 3-week supplementation between two different mixtures of antioxidants and placebo on aerobic exercise performance in acute normobaric hypoxia.

Subjects/Methods:

Seventeen subjects were randomly assigned in a double-blind fashion to receive a broad-based antioxidants supplement containing beta-carotene, ascorbic acid, d-alpha-tocopherol-succinate, N-acetylcysteine, riboflavin, zinc, and selenium (antioxidant capsule group [AO group]), or a combination of alpha-ketoglutaric acid (α-KG) and 5-hydroxymethylfurfural (5-HMF; CYL concentrate supplementation group [CS group]), or placebo (PL group). Before and after supplementation, subjects performed two incremental cycle-exercise tests until exhaustion. The first test was conducted under normoxic conditions (LA, FiO2 of 20.9%, ~547 m) and the second after the 3-week supplementation period under normobaric hypoxic conditions (AHA, FiO2 of 12.9%, ~4300m).

Results:

In CS peak cycling performance (peak power) declined from LA to AHA 7.3% (90% CI: 2.2–12.4) less compared with PL (p = .04) and 6.7% (90%CI: 3.2–10.2) less compared with AO (p = .03). Better maintenance of aerobic exercise capacity in CS was associated with an attenuated reduction in maximal heart rate in hypoxia.

Conclusions:

Aerobic exercise performance was less impaired in acute normobaric hypoxia after 3 weeks with supplementation of α-KG and 5-HMF compared with a broad-based antioxidants supplement or PL.

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Ben J. Lee and Charles Douglas Thake

known reductions in aerobic power associated with exercise at altitude, 12 – 14 a given intensity of work represents a greater relative intensity (higher percentage of V ˙ O 2 max ) when exercise is performed under hypoxic conditions. Therefore, greater physiological and metabolic adjustments are

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Pedro L. Valenzuela, Guillermo Sánchez-Martínez, Elaia Torrontegi, Javier Vázquez-Carrión, Manuela González, Zigor Montalvo and Grégoire P. Millet

) have been observed when performed under hypoxic conditions, which can be achieved both systemically (RSH) 3 or locally (RS-BFR). 8 – 10 However, to our knowledge, no previous study has compared the acute response to an RS session performed in hypoxia (RSH) versus with BFR (RS-BFR) in elite athletes

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Matthew J. Barlow, Antonis Elia, Oliver M. Shannon, Angeliki Zacharogianni and Angelica Lodin-Sundstrom

either the efficiency of mitochondrial respiration ( Larsen et al., 2011 ) and/or a reduced oxygen cost of muscle force generation ( Bailey et al., 2010 ). The reduction of NO 2 − into NO is enhanced in hypoxic conditions, yet oxygen-dependent generation of NO via the l -arginine NO synthase pathway

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Kristin L. Jonvik, Jan-Willem van Dijk, Joan M.G. Senden, Luc J.C. van Loon and Lex B. Verdijk

function—for example, by regulating blood flow and muscle contractility ( Stamler & Meissner, 2001 ). Hypoxic conditions with low oxygen availability and a low pH environment can stimulate the nitrate–nitrite–nitric oxide pathway ( Jones, 2014 ). Several studies have found ergogenic effects of nitrate

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Emma M. Crum, Matthew J. Barnes and Stephen R. Stannard

subsequent study by Crum et al. ( 2017a ) in highly trained cyclists (maximal oxygen uptake, VO 2 max = 74 ml·min −1 ·kg −1 ) using a similar supplementation protocol failed to replicate any performance benefits in a cycling TTE (100% VO 2 max), in either normoxic or hypoxic conditions. In addition, despite