Heart Rate Responses During Official Kick Light Competition and Their Associations with Ventilatory Thresholds and VO2max: An Exploratory Study

Kickboxing is a hybrid striking combat sport characterized by intermittent, acyclic activity that taxes both aerobic and anaerobic energy systems. Yet, physiological data from tatami disciplines such as Kick Light (KL) remain scarce. This exploratory study examined ventilatory thresholds and heart rate (HR) responses in a university kickboxing team comprising eight athletes (six males, two females) across 15 official bouts, focusing on intensity relative to the first and second ventilatory thresholds (VT1, VT2). One week before competition, athletes completed an incremental treadmill test to determine VT1, VT2, and maximum oxygen consumption (VO2max). During competition, HR was continuously monitored to quantify time spent below VT1, between VT1 and VT2, and above VT2, as well as maximal HR during rounds and HR recovery during breaks. VT1 and VT2 occurred at approximately 49% and 90% of VO2max, respectively, with VO2max averaging 52.46 ± 5.14 mL·kg−1·min−1. In competition, athletes spent most of Round 1 between VT1 and VT2, whereas Round 2 showed a shift towards intensities above VT2 (increase in 7 of 8 athletes; p = 0.018). Associations were examined at the athlete level (n = 8) after averaging repeated bout observations within each athlete. Higher VO2max was associated with greater time below VT1 in Round 1 and lower average in-competition HR. These exploratory findings provide preliminary information on cardiovascular responses during official university Kick Light competition and may inform future, larger studies.