Neuroendocrine Responses and Body Composition Changes Following Resistance Training Under Normobaric Hypoxia

Abstract

The aim of the present study was to evaluate the effects of a 6 week resistance training protocol under hypoxic conditions (FiO2 = 12.9%, 4000 m) on muscle hypertrophy. The project included 12 resistance trained male subjects, randomly divided into two experimental groups. Group 1 (n = 6; age 21 ± 2.4 years; body height [BH] 178.8 ± 7.3 cm; body mass [BM] 80.6 ± 12.3 kg) and group 2 (n = 6; age 22 ± 1.5 years; BH 177.8 ± 3.7cm; BM 81.1 ± 7.5 kg). Each group performed resistance exercises alternately under normoxic and hypoxic conditions (4000 m) for 6 weeks. All subjects followed a training protocol that comprised two training sessions per week at an exercise intensity of 70% of 1RM; each training session consisted of eight sets of 10 repetitions of the bench press and barbell squat, with 3 min rest periods. The results indicated that strength training in normobaric hypoxia caused a significant increase in BM (p < 0.01) and fat free mass (FFM) (p < 0.05) in both groups. Additionally, a significant increase (p < 0.05) was observed in IGF-1 concentrations at rest after 6 weeks of hypoxic resistance training in both groups. The results of this study allow to conclude that resistance training (6 weeks) under normobaric hypoxic conditions induces greater muscle hypertrophy compared to training in normoxic conditions.

Effect of Resistance Training Under Normobaric Hypoxia on Physical Performance, Hematological Parameters, and Body Composition in Young and Older People

“…Even though the exposure to hypoxia as well as exercise under hypoxia is positively associated with the loss of body fat (Netzer et al, 2008(Netzer et al, , 2015, no changes of the FM were achieved in the current study. This result is in line with previous RTH studies that also did not find any effects on body fat (Ho et al, 2014b;Chycki et al, 2016;Martínez-Guardado et al, 2019). There are two RTH studies by Kon et al (2014) and Yan et al (2016) showing a significantly reduced FM between −1 and −2%, but without significant differences to the group who performed resistance training under normoxia.…”

“…Body composition, and in particular the FFM or lean body mass, was analyzed in previous RTH studies to indirectly research the effect of this type of intervention on muscle mass/muscular hypertrophy (Ho et al, 2014b;Kon et al, 2014;Chycki et al, 2016;Yan et al, 2016;Martínez-Guardado et al, 2019). We did not observe any changes regarding the FFM which is in line with the insights from the meta-analysis by Ramos-Campo et al (2018b) stating that there is only a small to non-significant effect regarding the increase of the muscle size with RTH compared to RT under normoxia.…”

“…This assumption is reasoned by higher metabolic stress (Scott et al, 2014(Scott et al, , 2015a(Scott et al, , 2017 triggering functional and structural muscular adaptations (Schoenfeld, 2010(Schoenfeld, , 2013. Even though the exact physiological adaptation processes for RTH are not yet precisely known and understood, it is currently known from 18 international publications on RTH-interventions that this special type of resistance training appears to be partially more effective than resistance training under normoxia regarding the improvement of (i) muscle physiological parameter, (ii) neuromuscular adaptation, (iii) hormonal response, (iv) blood parameter, (v) body composition/body mass, (vi) sprint ability, and (vii) endurance performance/cardiovascular health and fitness (Friedmann et al, 2003;Nishimura et al, 2010;Álvarez-Herms et al, 2012;Manimmanakorn et al, 2013a,b;Álvarez-Herms et al, 2014Álvarez-Herms et al, , 2016Ho et al, 2014b;Kon et al, 2014;Kurobe et al, 2015;Chycki et al, 2016;Inness et al, 2016;Yan et al, 2016;de Smet et al, 2017;Mayo et al, 2018;Morales-Artacho et al, 2018;Ramos-Campo et al, 2018a;Martínez-Guardado et al, 2019).…”

Intermittent hypoxic training improves anaerobic performance in competitive swimmers when implemented into a direct competition mesocycle

“…This data indicates that the chronic exposure to high altitude through a reduction in overall exercise activity may have a harmful effect on muscle tissue as a result of decreased synthesis of muscle proteins [ 21 , 56 ], leading to atrophic changes in skeletal muscles. On the other hand, our latest reports [ 57 ] and the studies of other researchers [ 58 , 59 ] suggest that acute short-term exposure (one to two hours), especially if combined with resistance exercise has a contrary effect on muscle tissue by stimulation of muscle protein synthesis.…”

Acute environmental hypoxia potentiates satellite cell‐dependent myogenesis in response to resistance exercise through the inflammation pathway in human

“…7 At a molecular level, resistance training promotes insulin-like growth factor-1(IGF1), interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3), and Hippo cellular pathways, which are known to foster myogenesis through the direct regulation of MRF. 15,16 Based on these observations, several studies have demonstrated that intermittent hypoxia potentiates muscle hypertrophy and/or strength induced by resistance training [17][18][19][20] (even if other authors showed equivocal results 21 ); however, the mechanisms involved in this process are largely unknown. 15,16 Based on these observations, several studies have demonstrated that intermittent hypoxia potentiates muscle hypertrophy and/or strength induced by resistance training [17][18][19][20] (even if other authors showed equivocal results 21 ); however, the mechanisms involved in this process are largely unknown.…”