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Separate and Combined Effects of Local and Systemic Hypoxia In European Journal of Applied Physiology (2019) 119:2313–2325 https://doi.org/10.1007/s00421-019-04217-3 ORIGINAL ARTICLE Separate and combined efects of local and systemic hypoxia in resistance exercise Olivier Girard1,2 · Sarah J. Willis2 · Marin Purnelle2 · Brendan R. Scott1 · Grégoire P. Millet2 Received: 8 May 2019 / Accepted: 21 August 2019 / Published online: 29 August 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Purposes This study quantifed performance, physiological, and perceptual responses during resistance exercise to task failure with blood fow restriction (BFR), in systemic hypoxia, and with these stimuli combined. Methods Fourteen young men were tested for 1-repetition maximum (1RM) in the barbell biceps curl and lying triceps extension exercises. On separate visits, subjects performed exercise trials (4 sets to failure at 70% 1RM with 90 s between sets) in six separate randomized conditions, i.e., in normoxia or hypoxia (fraction of inspired oxygen = 20.9% and 12.9%, respectively) combined with three diferent levels of BFR (0%, 45%, or 60% of resting arterial occlusion pressure). Muscle activation and oxygenation were monitored via surface electromyography and near-infrared spectroscopy, respectively. Arte- rial oxygen saturation, heart rate, and perceptual responses were assessed following each set. Results Compared to set 1, the number of repetitions before failure decreased in sets 2, 3, and 4 for both exercises (all P < 0.001), independently of the condition (P > 0.065). Arterial oxygen saturation was lower with systemic hypoxia (P < 0.001), but not BFR, while heart rate did not difer between conditions (P > 0.341). Muscle oxygenation and activa- tion during exercise trials remained unafected by the diferent conditions (all P ≥ 0.206). A signifcant main efect of time, but not condition, was observed for overall perceived discomfort, difculty breathing, and limb discomfort (all P < 0.001). Conclusion Local and systemic hypoxic stimuli, or a combination of both, did not modify the fatigue-induced change in performance, trends of muscle activation or oxygenation, nor exercise-related sensations during a multi-set resistance exer- cise to task failure. Keywords Vascular occlusion · Systemic hypoxia · Muscle activation · Muscle oxygenation · Strength training · Task failure Abbreviations RTH Resistance training in systemic hypoxia 1RM 1-Repetition maximum TSI Tissue saturation index BFR Blood fow restriction [FiO2] Fraction of inspired oxygen HR Heart rate Introduction NIRS Near-infrared spectroscopy SpO2 Pulse oxygen saturation Resistance exercise with loads over 60% of an individual’s RSH Repeated sprints in hypoxia 1-repetition maximum (1RM) is commonly used for improv- ing strength and skeletal muscle mass (Chodzko-Zajko et al. 2009) as well as subsequent athletic performance. In recent years, scientists have begun to implement hypoxic stimuli Communicated by Philip D. Chilibeck. during resistance exercise training in an attempt to augment * Olivier Girard these responses (Scott et al. 2014). This was initially studied [email protected] via blood fow restriction (BFR) techniques, involving the application of an infatable cuf around the proximal end 1 Murdoch Applied Sports Science (MASS) Laboratory, of a limb to occlude venous return while partially preserv- Murdoch University, Perth, Australia ing arterial infow (Loenneke et al. 2014). The resulting 2 Faculty of Biology and Medicine, Institute of Sport Sciences, alteration in limb hemodynamics causes a localized hypoxic University of Lausanne, Lausanne, Switzerland Vol.:(0123456789)1 3 2314 European Journal of Applied Physiology (2019) 119:2313–2325 intramuscular environment during exercise (Ganesan et al. oxygen [FiO2] = 16%) compared to normoxic air (Scott 2015). This ischemia facilitates increased production of et al. 2017). Similar fndings have been reported for high- metabolites, due to a greater reliance on anaerobic metabo- load resistance exercise circuits, whereby blood oxygena- lism, which may impact on several downstream processes tion and markers of metabolic stress were increased when (i.e., muscle cell swelling, intramuscular anabolic/anti-cat- undertaking exercise in more severe (FiO2 = 13%), but not abolic signaling, and muscle fber recruitment) thought to in moderate (FiO2 = 16%), levels of hypoxia vs. normoxia contribute to hypertrophy (Schoenfeld 2013). In addition, (Ramos-Campo et al. 2017a). the hypoxic environment may increase the activation and To date, only one study has directly compared resistance proliferation of satellite cells (Nielsen et al. 2012), which training using BFR and systemic hypoxia (Manimmanakorn would further enhance muscle growth. et al. 2013). These authors observed that both strategies were While exercise with BFR has been demonstrated to be more efective for improving muscular strength, hypertro- feasible and efective in training the limb muscles, trunk and phy, and performance in several running-based assessments hip muscles (i.e., not under fow restriction) are unlikely to than the same training without any additional hypoxia stimu- adapt to the same extent (Yasuda et al. 2011). Considering lus. An interesting question that remains unanswered, how- this, researchers have recently begun to investigate the use- ever, is whether the addition of local to systemic hypoxia fulness of performing resistance exercise under normobaric during resistance exercise provides a means to further aug- hypoxic conditions to magnify the metabolic responses in ment the muscle adaptation for a given physical training an attempt to augment subsequent muscle mass development dose. Practically, it is, therefore, important to verify that this (Ramos-Campo et al. 2018a). Systemic hypoxic environ- resistance training strategy does not adversely afect physical ments are created via nitrogen dilution or oxygen reduction performance and the potential training dose by a too large and exercise is performed in an environmental chamber or magnitude. breathing a gas mixture through a face mask (Millet et al. Due to increased fatigability, BFR limits the number of 2010). Participants can, therefore, undertake multi-joint repetitions that can be performed in a set of resistance exer- compound exercises with the same hypoxic stimulus being cise (Wernbom et al. 2009; Loenneke et al. 2014). Previ- applied to all contributing musculature. Although the picture ous researchers have reported no efect of systemic hypoxia is still emerging and debated (Scott et al. 2014), several stud- (FiO2 = 13–16%) on performance during high-load (Scott ies have reported that resistance training in systemic hypoxia et al. 2015) or moderate-load resistance exercises (Scott et al. (RTH) ofers greater hypertrophic and strength benefts than 2018a) and on the time course of recovery for neuromuscular the equivalent normoxic exercise (Nishimura et al. 2010; performance following training (Scott et al. 2018b). How- Manimmanakorn et al. 2013), in conjunction with improved ever, other researchers have shown that when performing muscular endurance (Kon et al. 2014). These benefts may high-load resistance exercise in a circuit style, adding severe improve physical performance, for instance, aerobic capac- hypoxia (FiO2 = 13%) can be detrimental for force and power ity and repeated-sprint ability (Ramos-Campo et al. 2018b). production during exercise (Ramos-Campo et al. 2017a). These augmented adaptations to RTH are likely driven partly These divergent fndings may arise from the diferences in by similar mechanisms to those underpinning BFR exercise exercise type and intensity between these research groups; but diferences are also possible. some authors (Scott et al. 2015, 2018a) implemented sub- In systemic hypoxia, the limited oxygen availability maximal exercise by prescribing pre-determined sets and induces vasodilation for increasing blood fow and oxygen repetitions, while others (Ramos-Campo et al. 2017a, 2018b) delivery, while when external pressure is applied (vascular employed circuits comprising of exercises performed for 6 occlusion, BFR), blood fow is impaired via vascular resist- repetitions each with 100% of 6RM. It is, therefore, pos- ance and venous return is nearly eliminated (Casey and sible that performance decrements resulting from breathing Joyner 2011). Both of these local and systemic methods hypoxic air during resistance exercise are only realized when create diferent intrinsic mechanisms (metabolic vasodila- each set is performed to failure. tion and vascular resistance) for a hypoxic environment, Therefore, our aim was to assess the separate and com- which may alter conductance and blood fow (Scott et al. bined acute efects of BFR and systemic hypoxia (both com- 2014). Specifcally, with repeated sprints during BFR con- pared with controls) during resistance exercise to task failure ditions, there is limited oxygen delivery, but also increased on exercise capacity, muscle oxygenation/activation levels, vascular resistance due to nearly no venous return, thereby and exercise-related sensations. It was hypothesized that increasing local blood volume (Willis et al. 2018). Previous resistance exercise with BFR would cause higher metabolic/ research has observed signifcantly elevated blood lactate neuromuscular stress than systemic hypoxia, yet with no concentrations (a marker of metabolic stress) in conjunc- measurable efect on performance (i.e., the number of rep- tion with increased motor unit recruitment during resist-
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