High-Intensity Functional Training Improves Cardiorespiratory Fitness and Neuromuscular Performance Without Inflammation or Muscle Damage

Abstract

Posnakidis, G, Aphamis, G, Giannaki, CD, Mougios, V, Aristotelous, P, Samoutis, G, and Bogdanis, GC. High-intensity functional training improves cardiorespiratory fitness and neuromuscular performance without inflammation or muscle damage. J Strength Cond Res 36(3): 615-623, 2022-We examined the effects of high-intensity functional training (HIFT) on cardiorespiratory and neuromuscular performance, as well as on inflammatory and muscle damage markers. Thirteen physically active healthy volunteers (aged 28.3 ± 3.8 years, 5 men and 8 women) underwent 8 weeks of a group HIFT program performed 3 times per week. Each session consisted of 4 rounds of a 9-exercise circuit (30-second exercise and 15-second recovery). During the first and last weeks of training, venous blood was sampled daily to monitor changes in serum C-reactive protein (CRP) and creatine kinase (CK). After 8 weeks of HIFT, body fat decreased by 0.64 ± 1.01 kg (p = 0.041), maximal oxygen uptake improved by 1.9 ± 2.2 ml·kg-1·min-1 (p = 0.009), countermovement jump by 2.6 ± 1.5 cm (p = 0.001), bench press 1-repetition maximum (1RM) by 4.5 ± 3.8 kg (p = 0.001), maximum number of bench press repetitions at 65% 1RM by 4 ± 5 repetitions (p = 0.03), and abdominal muscle endurance by 6 ± 4 repetitions (p < 0.001). In both week 1 and week 8 of training, CK increased mildly in the morning after the first session of the week (main effect for day, p = 0.008), whereas no significant changes were observed in CRP (p = 0.31). During week 8, CK on all days was ∼32% lower compared with week 1 (160 vs. 235 U·L-1; main effect of week 1 vs. week 8, p = 0.027), whereas CRP remained unchanged (p = 0.225). This HIFT program was effective in improving cardiorespiratory and neuromuscular physical fitness without causing significant inflammation or muscle damage in physically active subjects.