Far-Infrared-Emitting Fabric Improves Neuromuscular Parameters in Humans: Unexpected Result from Eccentric Exercise-Induced Muscle Damage Countermeasure Strategy

The present study examined the prophylactic effects of far-infrared-emitting fabric (FIR) on exercise-induced muscle damage and investigated its influence on neuromuscular parameters during eccentric exercise. FIR and placebo garments were worn for 1 h prior to and throughout a knee extension eccentric exercise protocol consisting of 10 sets of 15 maximal contractions performed at 210°·s−1, using a randomized, counterbalanced, double-blind, placebo-controlled crossover design. Twenty-one physically active individuals (age: 24 ± 1 years; body mass: 69.7 ± 2.3 kg; height: 1.73 ± 0.02 m) participated in this two-phase study. In the first phase (FIR effects on muscle damage; n = 9), eccentric peak torque (EPT) and total work (TW) were assessed during exercise, while maximal voluntary isometric contraction (MVIC) and creatine kinase (CK) were measured before and 24, 48, and 96 h after the protocol. No fabric × time interaction was observed for MVIC or CK. However, FIR use suggested an increased EPT and TW during exercise. To further investigate this effect and explore potential neuromuscular mechanisms, a second phase was conducted (FIR effects on eccentric exercise; n = 12) using the same exercise protocol. EPT, TW, and electromyographic root mean square (EMG-RMS) activity of the vastus lateralis (VL) and vastus medialis (VM) were assessed. Combined results from both phases (n = 21) demonstrated significant increases of 11% in mean EPT and 18.6% in mean TW, along with greater VL and VM EMG-RMS activity (n = 12), under FIR compared with placebo conditions. These findings indicate that FIR use enhances neuromuscular performance during eccentric exercise.