Mechanical Punch Intensity and Its Relationship with Oxygen Uptake and Heart Rate During Repeated Efforts in Elite and Amateur Boxers

The ability to generate and sustain high punch intensity is a key determinant of boxing performance. However, the relationship between mechanical output and physiological responses during intermittent high-intensity efforts remains insufficiently understood. This pilot study explored associations between mechanical punch intensity and physiological responses in elite and amateur boxers, considering sex and competitive level. Twenty boxers (10 elite and 10 amateurs; 5 males and 5 females per group) were assessed using the inertial sensor-derived Intensity Score to quantify mechanical punch intensity, alongside physiological measurements of heart rate (HR) and oxygen uptake (VO2) during a Repeated Punch Ability Test (RPAT). Data were analyzed using repeated-measures ANOVA and Spearman correlations (p < 0.05). A significant main effect of round was observed for all variables (p < 0.001), with a progressive decline in mechanical punch intensity and stabilization of physiological responses after the first round. Elite boxers showed descriptively higher mechanical punch intensity values than amateurs, particularly in later rounds, but subgroup comparisons should be considered preliminary. Correlation analyses indicated a positive association between mechanical punch intensity and VO2 that appeared to increase from the first to the third round (ρ = 0.398–0.563; p < 0.05), whereas the relationship with HR was weak or negative. No significant correlations were found between HR and VO2. Overall, the findings suggest preliminary patterns in which fatigue and competitive level may be associated with mechanical punch intensity, while VO2 may become more closely related to mechanical output under fatigue. These results should be interpreted as exploratory and non-causal.