Author(s): PEREZ REGALADO, S., LEON, J., BENAVENTE, C., BONITCH-GONGORA, J., ALMEIDA, F., PADIAL, P., DE LA FUENTE, B., GIL-GUTIERREZ, R., FERICHE, B., Institution: UNIVERSITY OF GRANADA, Country: SPAIN, Abstract-ID: 724

INTRODUCTION:
Hypobaric hypoxia (HH) exposure is characterized by an elevation of the sympathetic nervous system that could impact on metabolic-related myokines in human adipocytes, such as interleukin 15 (IL-15), involved mainly in the promotion of lipolysis (1). Additionally, resistance training (RT) programs have been associated with weight loss while preserving muscle mass. However, there are no previous studies undertaken long-term RT regimens under terrestrial HH conditions describing the molecular mechanisms linked to modulation of subcutaneous adipose tissue (SAT) thickness. In this sense, the present study aims to analyse the influence of HH exposure on SAT and circulating IL-15 response after an 8-week RT program.
METHODS:
Twenty men (22.75±3.73 years; 176.4±5.93 cm; 73.01±10.97 kg) participated in an 8-week program (3 sessions/week) of a traditional hypertrophy training under intermittent terrestrial HH (2320 m) or normoxia (N, 690 m). Seventy-two hours before and after the RT program, vastus lateralis (VL) thickness and SAT were measured by ultrasound (GE-LOGICQ-E portable, UK) and blood samples were taken to analyse serum IL-15 by immunology multiplex assay (Sigma-Aldrich; Darmstadt, Germany).
RESULTS:
Circulating IL-15 revealed an environmental effect following 8 weeks of RT program (F1,18 = 4.399; p = 0.050; n2p = 0.196). The pairwise comparison test revealed that HH after RT tend to be favour IL-15 increase (ES = 0.890; p = 0.062) compared to N. Moreover, SAT displayed a very large decrease in HH after the RT period (11.56 % vs -17.69 % in N and HH; p < 0.001 [ES = -1.92]) with no remarkable change in VL between conditions (p > 0.05).
CONCLUSION:
These results evidence the effect of RT in HH on SAT and serum IL-15 with respect to the same training in N. This effect could be attributed to the IL-15 upregulation-induced muscle promotion of the fibber switching to type II and in the overall increase of lean mass ratio by the stress of the HH combined with RT. (2). Surprisingly, VL values were maintained without significant changes between conditions. Nonetheless, this outcome may not represent the entire effect on muscle growth on muscle due to a potential heterogeneous growth of the vastus quadriceps due to the orientation of the feet during squat training (3). Thus, taking all results together, it appears that the stressors factors linked to RT in HH may play a key role in the overall body composition. Further research targeting this potential non-pharmacological approach for adipose regulation is needed to determine the implication on sport performance and control of obesity-related disorders.

References
1. Duan Y, et al. 2017; PMID: 28752527.
2. Nielsen AR, et al. 2007; PMID: 17690139.
3. Murray N, Cipriani D, O’RAND D, Reed-Jones R. 2013; PMID: 27293497.