Inter-set rest configuration effect on acute physiological and performance-related responses to a resistance training session in terrestrial vs simulated hypoxia

Abstract

Background Metabolic stress is considered a key factor in the activation of hypertrophy mechanisms which seems to be potentiated under hypoxic conditions.This study aimed to analyze the combined effect of the type of acute hypoxia (terrestrial vs simulated) and of the inter-set rest configuration (60 vs 120 s) during a hypertrophic resistance training (RT) session on physiological, perceptual and muscle performance markers. Methods Sixteen active men were randomized into two groups based on the type of hypoxia (hypobaric hypoxia, HH: 2,320 m asl; vs normobaric hypoxia, NH: FiO2 of 15.9%). Each participant completed in a randomly counterbalanced order the same RT session in four separated occasions: two under normoxia and two under the corresponding hypoxia condition at each prescribed inter-set rest period. Volume-load (load × set × repetition) was calculated for each training session. Muscle oxygenation (SmO2) of the vastus lateralis was quantified during the back squat exercise. Heart rate (HR) was monitored during training and over the ensuing 30-min post-exercise period. Maximal blood lactate concentration (maxLac) and rating of perceived exertion (RPE) were determined after the exercise and at the end of the recovery period. Results Volume-load achieved was similar in all environmental conditions and inter-set rest period length did not appreciably affect it. Shorter inter-set rest periods displayed moderate increases in maxLac, HR and RPE responses in all conditions. Compared to HH, NH showed a moderate reduction in the inter-set rest-HR (ES > 0.80), maxLac (ES > 1.01) and SmO2 (ES > 0.79) at both rest intervals. Conclusions Results suggest that the reduction in inter-set rest intervals from 120 s to 60 s provide a more potent perceptual, cardiovascular and metabolic stimulus in all environmental conditions, which could maximize hypertrophic adaptations in longer periods of training. The abrupt exposure to a reduced FiO2 at NH seems to reduce the inter-set recovery capacity during a traditional hypertrophy RT session, at least during a single acute exposition. These results cannot be extrapolated to longer training periods.

Analysis of Muscle Oxygenation after a Normobaric Hypoxia Tolerance Test

“…In both groups, there was a decrease in SmO 2 that was independent of gender, aged and body composition. During the test, we monitored HR and SpO 2 using a pulse oximeter in the earlobe and the NIRS device on the right thigh, while other studies, on one hand, obtained the HR through a wireless Polar heart rate monitor [ 18 , 19 ] or a the-lead ECG [ 20 ], or, on the other hand, assessed SpO 2 using a digital pulse oximeter on the right index finger [ 18 ]. The continuous evaluation of both variables allows us to analyze their evolution, observing that, while SpO 2 and SmO 2 decreased, HR increased in compensation.…”

“…The measurement of SmO 2 , using the Humon Hex ® device, made it possible to obtain saturation values in both groups of subjects, allowing an observation of the expected changes after the inhalation of oxygen-depleted air. Placement on the vastus lateralis of the right quadriceps is the most common in work performed with this type of technology, regardless of the model or brand used [ 12 , 19 ]. We can see that the decrease in SmO 2 , because of normobaric hypoxia, is like that which occurs with intense exercise, such as a treadmill stress test [ 17 ].…”

Acute effect of different rest interval on muscle performance and perceived exertion in young women

“…Inúmeros mecanismos fisiológicos podem explicar a redução do desempenho muscular ao realizar múltiplas séries até a falha muscular concêntrica em sessões de exercícios com pesos, por exemplo, alterações na ativação central e periférica, modificações no metabolismo energético intracelular e nas funções contráteis [24][25][26] . Convencionalmente, o uso de menores IR entre as séries promove maiores aumentos em parâmetros metabólicos, cardiovasculares, perceptivos, no dano do tecido muscular com uma maior duração dos processos inflamatórios, bem como melhoras no controle inibitório cognitivo após o exercício quando comparado a IR mais longos [27][28][29][30][31] . Por outro lado, o uso do IR-3 parece promover maiores índices de fadiga, avaliados por meio do espectro eletromiográfico de superfície, quando comparado a um IR-1 32 .…”