Cutting Weight, Gaining Stress: The Hidden Battle That Outweighs Fight Day Tension in Kickboxing

Abstract

Background: This study investigated the effects of rapid weight-cutting on stress in elite kickboxers by analyzing Heart Rate Variability (HRV) and subjective stress levels using a Visual Analog Scale (VAS). Methods: Data were collected across seven standardized time points: Weigh-in Morning, PreWeigh-in, Post-Weigh-in, Post–Weigh-in Meal, Match Day Morning, Pre-Match, and Post-Match. Participants were divided into a weight-cutting group (n = 12), who reduced at least 5% of their body weight within 48 hours before competition, and a control group (n = 13), who maintained regular training and nutrition. HRV was measured using a chest-strap electrocardiography-based heart rate sensor (Polar H10) to obtain high-accuracy R–R interval data under real-world competition conditions. Results: The weight-cutting group showed consistently lower RMSSD values, indicating sustained physiological stress. Subjective stress levels were also higher in this group, peaking before the weigh-in and exceeding pre-match levels. A marked reduction in perceived stress was observed immediately after the weigh-in, suggesting psychological relief. However, despite post–weigh-in rehydration and feeding, RMSSD values remained suppressed on match day, indicating incomplete physiological recovery despite stabilized subjective stress. The control group demonstrated relatively stable HRV and VAS values across all time points. Conclusions: These findings highlight the prolonged autonomic strain associated with rapid weight-cutting and demonstrate a dissociation between subjective and physiological recovery. Monitoring both autonomic and perceptual stress responses may be essential for safeguarding athlete health and optimizing performance in weight-category sports. Trial Registration: ClinicalTrials.gov NCT06860204, 5 March 2025.