Immediate impacts of low-temperature exposure on cardiac autonomic modulation, neuromuscular efficiency, and postural stability in older adults Yangko dancers – a randomized controlled trial

Introduction To investigate the immediate effects of different cold environments on heart rate variability (HRV), surface electromyography (sEMG), and balance in older adults Yangko dance (a traditional Chinese folk dance) participants, and to elucidate the mechanisms underlying increased injury risks during the early exercise phase (10–20 minutes) in cold conditions. This study aims to provide scientific evidence for targeted protective measures. Methods A randomized controlled trial was conducted with 120 regular Yangko dancers (age>60 years) from Changchun, China. Participants were stratified into four temperature groups (15 °C, -5 °C, -10 °C, -15 °C; 30 cases in each group) using computer-generated randomization. All participants completed Yangko dance sessions under their assigned temperature conditions. HRV time-domain and frequency-domain indices (SDNN, RMSSD, PNN500, LogLF, LogHF, LF/HF), sEMG signals of the biceps femoris, rectus femoris, and medial gastrocnemius (RMS, IEMG), and balance parameters (RT, MVL, EPE) were measured using heart rate monitors, surface EMG devices, and a balance testing system. The impacts of different cold environments on cardiovascular and motor functions were analyzed. Results Compared to 15 °C, the cold groups (-5 °C, -10 °C, -15 °C) showed significant reductions in SDNN, RMSSD, PNN500, LogLF, and LogHF (P<0.05) after the experiment, while LF/HF increased significantly (P<0.05). Progressive hypothermia induced dose-dependent decreases in SDNN (15 °C: 65.4 ± 1.47 vs. -15 °C: 51.21 ± 13.41, P<0.001) and RMSSD, alongside increased LF/HF ratios (P<0.05). sEMG analysis demonstrated temperature-dependent neuromuscular adaptations, with -15 °C exposure eliciting 23.6% RMS elevation but 29.4% IEMG reduction versus controls (P<0.05), indicating enhanced muscle activation but decreased output efficiency. The conclusion of the balance ability test shows that RT is prolonged and DCL is reduced. Discussion Cold environments reduce HRV, increase muscle stiffness, and impair balance in the older adults, significantly raise injury risks during the early exercise phase. Recommendations include adequate warm-up, wearing thermal protective gear, and performing joint mobility exercises to enhance exercise safety in cold conditions.