Tent versus Mask-On Acute Effects during Repeated-Sprint Training in Normobaric Hypoxia and Normoxia

Abstract

Repeated sprint in hypoxia (RSH) is used to improve supramaximal cycling capacity, but little is known about the potential differences between different systems for creating normobaric hypoxia, such as a chamber, tent, or mask. This study aimed to compare the environmental (carbon dioxide (CO₂) and wet-globe bulb temperature (WGBT)), perceptual (pain, respiratory difficulty, and rate of perceived exertion (RPE)), and external (peak and mean power output) and internal (peak heart rate (HRpeak), muscle oxygen saturation (SmO₂), arterial oxygen saturation (SpO₂), blood lactate and glucose) workload acute effects of an RSH session when performed inside a tent versus using a mask. Twelve well-trained cyclists (age = 29 ± 9.8 years, VO₂max = 70.3 ± 5.9 mL/kg/min) participated in this single-blind, randomized, crossover trial. Participants completed four sessions of three sets of five repetitions × 10 s:20 s (180 s rest between series) of all-out in different conditions: normoxia in a tent (RSNTent) and mask-on (RSNMask), and normobaric hypoxia in a tent (RSHTent) and mask-on (RSHMask). CO₂ and WGBT levels increased steadily in all conditions (p < 0.01) and were lower when using a mask (RSNMask and RSHMask) than when inside a tent (RSHTent and RSNTent) (p < 0.01). RSHTent presented lower SpO₂ than the other three conditions (p < 0.05), and hypoxic conditions presented lower SpO₂ than normoxic ones (p < 0.05). HRpeak, RPE, blood lactate, and blood glucose increased throughout the training, as expected. RSH could lead to acute conditions such as hypoxemia, which may be exacerbated when using a tent to simulate hypoxia compared to a mask-based system.

Keywords: CO2; carbon dioxide; cycling; endurance; hypercapnia; hypercarbia; hypoxemia; oxygen saturation; toxicity.

Figure 1

Schematic design of the test. (A) Randomization (R) of participants in each condition and flowchart of sessions. (B) Repeated-sprint test and chronological assessment of variables. RSH_Tent = repeated-sprint in normobaric hypoxia using a tent, RSH_Mask = repeated-sprint in normobaric hypoxia using a mask, RSN_Tent = repeated-sprint in normoxia using a tent, RSN_Mask = repeated-sprint in normoxia using a mask, FiO₂ = inspired fraction of oxygen, SmO₂ = muscle oxygen saturation, SpO₂ = oxygen saturation, RPE = rate of perceived exertion.

Figure 2

Training systems in normobaric hypoxia. (A) System setting for RSH_Mask = repeated-sprint in normobaric hypoxia using a mask and RSN_Mask = repeated-sprint in normoxia using a mask. (B) System setting for RSH_Tent = repeated-sprint in normobaric hypoxia and RSN_Tent= repeated-sprint in normoxia using a tent.

Figure 3

Changes in environmental conditions (A): CO₂ and (B): WGBT); by time and conditions during a repeated-sprint workout in normoxia and hypoxia. Statistical difference between ^§ RSNMask and * RSH_Mask. RSHTent = repeated-sprint in normobaric hypoxia using a tent, RSHMask = repeated-sprint in normobaric hypoxia using a mask, RSNTent = repeated-sprint in normoxia using a tent, RSNMask = repeated-sprint in normoxia using a mask.

Figure 4

Changes in pain, exertion, and respiratory difficulty perception during a repeated-sprint workout in hypoxia and normoxia. RSH_Tent = repeated-sprint in normobaric hypoxia using a tent, RSH_Mask = repeated-sprint in normobaric hypoxia using a mask, RSN_Tent = repeated-sprint in normoxia using a tent, RSN_Mask = repeated-sprint in normoxia using a mask.