Hypoxic training is superior to protein supplementation during resistance exercise in team-sport athletes

Abstract

Background: Team sport athletes require optimal muscle strength and endurance, but traditional high-load resistance training may increase injury risk. Exercise performed under hypoxia or combined with protein supplementation may offer viable alternatives. Methods: Thirty male team-sport athletes completed low-load knee extension and flexion exercises at 50% of one-repetition maximum three times weekly for five weeks. Participants were randomly assigned to normoxic resistance training (RT), resistance training under hypoxia (RTH; FiO2 = 13.6%), or resistance training with protein supplementation (RTP). Pre- and post-intervention assessments included muscle strength and endurance, muscle thickness, superoxide dismutase, growth hormone, blood lactate, and athletic performance. Results: RTH athletes exhibited the highest gain in knee extension maximal strength (33.11 ± 15.81 kg), which was significantly greater than that of the RT group (18.38 ± 7.26 kg, p = 0.044). For knee extension muscular endurance, the RTH group improved significantly more than the RT group (7.33 ± 2.45 vs. 4.22 ± 2.73 reps, P = 0.038). Both RTH and RTP significantly increased muscle thickness from baseline: rectus femoris (RTH: 0.35 ± 0.29 cm, P = 0.015; RTP: 0.32 ± 0.35 cm, P = 0.027) and biceps femoris (RTH: 0.54 ± 0.36 cm, P = 0.001; RTP: 0.47 ± 0.52 cm, P = 0.027). Only RTH elevated superoxide dismutase level by 1.10 U/mL (p = 0.029). In the RTH group, immediate post-training blood lactate increased significantly more from the first to final session (2.45 ± 1.14 mmol·L⁻¹) compared to both the RT (0.74 ± 1.17 mmol·L⁻¹) and RTP groups (0.78 ± 1.61 mmol·L⁻¹; P < 0.05). Discussion: The RTH group's superior adaptations likely stem from amplified metabolic stress evidenced by higher blood lactate where hypoxia and mechanical tension boost local anabolic signaling and antioxidant pathways via reactive oxygen species. In contrast, while protein supplementation supplied enough substrate for muscle hypertrophy, it lacked the systemic metabolic and neuromuscular stimuli needed to translate these structural gains into improved performance within five weeks. Conclusions: Low-load hypoxic resistance training comprehensively boosts muscle strength, endurance, hypertrophy, and antioxidant defenses. While protein supplementation supports hypertrophy, it adds no functional or antioxidant gains over training alone, making hypoxia a far more effective, multifaceted strategy for athletes.