Impact of Three Consecutive Days of Endurance Training Under Hypoxia on Muscle Damage and Inflammatory Responses

Abstract

Purpose: The purpose of this study was to determine the effect of 3 consecutive days of endurance training under hypoxia on muscle damage, inflammation, and performance responses.Methods: Nine active healthy males completed two trials in different periods, consisting of either 3 consecutive days of endurance training under hypoxia [fraction of inspired oxygen (Fio2): 14.5%, HYP] or normoxia (Fio2: 20.9%, NOR). They performed daily 90-min sessions of endurance training consisting of high-intensity endurance interval pedaling [10 × 4-min pedaling at 80% of maximal oxygen uptake (V˙o2max) with 2 min of active rest at 30% of V˙o2max] followed by 30-min continuous pedaling at 60% of V˙o2max during 3 consecutive days (days 1–3). Venous blood sample, muscular performance of lower limb, and score of subjective feelings were determined every morning (days 1–4) to evaluate muscle damage and inflammation. On day 4, subjects performed an incremental exercise test (IET) to evaluate the performance response.Results: Pedaling workload during daily endurance training was significantly lower in the HYP trial (interval exercise: 166 ± 4 W) than in the NOR trial (194 ± 8 W; P < 0.0001). Serum creatine kinase (CK) and high-sensitivity C-reactive protein (hsCRP) concentrations did not significantly change during days 1–4 in either trial. Maximal voluntary contraction (MVC) of knee extension (P < 0.0001) and drop jump (DJ) index (P = 0.004) were significantly decreased with training in both trials, with no significant difference between trials. The muscle soreness and fatigue scores significantly increased in both trials (P < 0.0001). However, the HYP trial showed a significantly lower score of fatigue on day 4 compared with the NOR trial (P = 0.004). Maximal aerobic power output during IET on day 4 did not significantly differ between trials.Conclusion: Three consecutive days of endurance training under hypoxia induced comparable levels of muscle damage, inflammation, and performance responses compared with the same training under normoxia.

Acute physiological responses and muscle recovery in females: a randomised controlled trial of muscle damaging exercise in hypoxia

“…Interestingly, a direct performance output benefit, arising from exercise under hypoxia, is rarely observed in the literature [54]. Similarly, high-intensity exercise under hypoxia did not induce a more severe inflammatory response than the same exercise load, performed under normoxia [55,56]. However, compared to normoxic training, hypoxic training has the potential to elicit specific molecular adaptations [57,58], but these are not necessarily associated with improved physical performance [54].…”

Metabolic and immune/inflammatory alterations induced by a triathlon under extreme conditions

“…By the way, it is paramount to mention that, at an appropriate level, the physical stress generated by exercise training sessions are triggers of the physiological adaptation process, promoting improved physical performance. However, when this stress promoted by training is poorly managed, it can result in temporary decreased performance, with high levels of fatigue, commonly associated with increased muscle damage (Sumi et al, 2021 ), imbalance in immune cells (Cosgrove et al, 2012 ), modulation of anabolic and catabolic hormones (Urhausen et al, 1995 ), and mood change (Comotto et al, 2015 ), which can evolve to overtraining, promoting the loss of performance that can last for months to be reestablished. In order to mitigate this negative status, a strategy often used is, after the period of the intensification of training loads to induce greater levels of adaptation and performance improvement, the athletes use the weeks prior to competition to reduce training loads and enhance supercompensation, a process known as polishing or taper (Clemente-Suárez and Ramos-Campo, 2019 ).…”