New insights into the integrative effects of resistance training at moderate altitude on systemic inflammation.

Purpose: To determine the effect of intermittent terrestrial hypobaric hypoxia (HH) exposure on stress and inflammatory biomarkers following a resistance training (R_T) program.

Methods: Twenty trained males completed an 8-week R_T program (3 sessions/week) under HH (2320 m asl) or normoxia (N, 690 m asl). Before and after the R_T, circulating stress biomarkers (calcium, inorganic phosphate, creatine kinase [CK], total antioxidant capacity [TAC]), inflammation (tumour necrosis factor-alpha [TNF-α]), interleukin 10 (IL-10), vascular endothelial growth factor and heat shock protein 70 (HSP70) were analyzed by immunology multiplex assay and ELISA. Moreover, maximal strength to back squat (1RM-SQ) and squat jump (SJ) performance were measured.

Results: The results revealed that, compared with N, the HH group exhibited a large increase in 1RM-SQ and SJ (all ES > 0.99; p < 0.041) outcomes. IL-10 and TNF-α levels increased in HH more and faster than N (all ES > 1.35; p < 0.003), returning to baseline following the R_T. Circulating HSP70 revealed a similar trend, although remaining elevated in HH after the program (all ES > 1.106; p < 0.029). HSP70 in HH explained ~ 44% of TNF-α variance (p < 0.001). In addition, the R_T program in HH induced greater decreases in TAC and CK than N (all ES < - 0.95; p < 0.05).

Conclusions: Findings highlight the potential role of moderate altitude in long-term R_T for inducing greater stress while maintaining the inflammatory balance, crucial for muscle adaptations in young males. Consequently, HH condition revealed an additional benefit in the contractile and explosive muscle strength development.