The effect of sex on the cardiopulmonary and neuromuscular response to high-intensity interval exercise: Sex differences in the response to interval exercise

Sex differences exist in the integrative response to exercise, however, these are typically researched during incremental and constant-load exercise. Interval exercise involves high intensity efforts interspersed with recovery periods to repeatedly stress physiological systems, and it is currently unknown whether the response to this form of exercise differs between sexes.

Ten males and ten females (age: 25±3 years) completed two experimental visits. First, an incremental treadmill exercise test was performed to obtain submaximal (lactate threshold) and maximal (V̇O2peak) data. Thereafter, visit two involved 4 × 3-min running intervals at 90% of the final incremental test velocity (vV̇O2peak), with 90 secs rest between intervals. Before exercise and after each interval, maximal voluntary contraction (MVC), quadriceps potentiated twitch (Qtw.pot), and voluntary activation (VA) were recorded. The rates of oxygen uptake (V̇O2), carbon dioxide production (V̇CO2) and ventilation (V̇E) were continuously recorded throughout.

There was no sex difference in relative V̇O2peak (males: 47.2±6.0 vs. females: 44.4±5.8 ml.kg- 1.min-1, p=0.292). When expressed relative to peak values, there were no sex differences in the V̇O2 or V̇CO2 response to the interval task (p≥0.781). Females had greater V̇E/V̇O2, and V̇E/V̇CO2 values during the first (p≤0.034) and second (V̇E/V̇CO2, p=0.006) intervals, with a sex × time interaction effect (p≤0.046). There were no sex differences in the reductions in MVC, Qtw.pot, and VA during the interval task (p≥0.150), however females had lesser reductions in Qtw.pot values post-exercise (-24±9 vs. -15±8%, p=0.044).

Sex differences exist in the physiological response to interval exercise. Compared to males, females experienced greater hyperpnoea during the initial stages, and had lesser decreases in contractile function post-exercise.