A Combined Hot and Hypoxic Environment during Maximal Cycling Sprints Reduced Muscle Oxygen Saturation: A Pilot Study

Abstract

The present study investigated the effects of a combined hot and hypoxic environment on muscle oxygenation during repeated 15-s maximal cycling sprints. In a single-blind, cross-over study, nine trained sprinters performed three 15-s maximal cycling sprints interspersed with 7-min passive recovery in normoxic (NOR; 23℃, 50%, FiO2 20.9%), normobaric hypoxic (HYP; 23℃, FiO2 14.5%), and hot normobaric hypoxic (HH; 35℃, FiO2 14.5%) environments. Relative humidity was set to 50% in all trials. The vastus lateralis muscle oxygenation was evaluated during exercise using near-infrared spectroscopy. The oxygen uptake (VO2) and arterial oxygen saturation (SpO2) were also monitored. There was no significant difference in peak or mean power output among the three conditions. The reduction in tissue saturation index was significantly greater in the HH (-17.0 ± 2.7%) than in the HYP (-10.4 ± 2.8%) condition during the second sprint (p < 0.05). The average VO2 and SpO2 were significantly lower in the HYP (VO2 = 980 ± 52 mL/min, SpO2 = 82.9 ± 0.8%) and HH (VO2 = 965 ± 42 mL/min, SpO2 = 83.2 ± 1.2%) than in the NOR (VO2 = 1149 ± 40 mL/min, SpO2 = 90.6 ± 1.4%; p < 0.05) condition. In conclusion, muscle oxygen saturation was reduced to a greater extent in the HH than in the HYP condition during the second bout of three 15-s maximal cycling sprints, despite the equivalent hypoxic stress between HH and HYP.

Effects of Acute Moderate Hypoxia versus Normoxia on Metabolic and Cardiac Function and Skeletal Muscle Oxygenation during Endurance Exercise at the Same Heart Rate Level

“…Endurance exercise under hypoxia decreases skeletal muscle oxygenation, such as decreased oxhb and StO 2 , and increased dxhb compared with that under normoxia. Skeletal muscle oxygenation during endurance exercise under hypoxia can decrease due to increased skeletal muscle extraction and a reduction in oxygen supply to the skeletal muscle tissue compared with that under normoxia [ 11 , 12 , 13 , 28 ]. Therefore, we examined changes in skeletal muscle oxygenation during endurance exercise at the same relative exercise intensity under hypoxia and normoxia.…”

“…In addition, exercise under hypoxia has been shown to have some adverse effects on skeletal muscle oxygen profiles [ 10 , 11 , 12 , 13 ]. Acute exposure to hypoxia induces systemic hypoxia, which can compromise skeletal muscle oxygenation and subsequently, skeletal muscle ability [ 14 , 15 ].…”

“…The majority of previous studies comparing the acute response during exercise under hypoxia and normoxia examined the changes in various physiological parameters in response to the same load or relative intensity during submaximal exercise and maximal exercise [ 3 , 4 , 5 , 6 , 7 , 8 , 10 , 12 , 13 , 17 , 20 ]. However, studies on metabolic function, skeletal muscle oxygenation, and cardiac function responses during exercise with the same HR level under hypoxia and normoxia are limited [ 21 ].…”

Variability in Perception of Dyspnea in the Context of Additional Respiratory Resistance: Cross-Sectional Observational Exploratory Study

“…Легочные функциональные тесты проводились с помощью компьютеризированного спирометра Spipolab III SpО 2 (Италия). Мы регистрировали ФЖЕЛ, ОФВ1 и отношение ОФВ1/ФЖЕЛ в трех пробах, и для анализа выбирали лучшую из трех [20]. Все параметры фиксировались в процентах от должных значений для заданного возраста, конституции и пола.…”