Bernert, L. | Search bioRxiv

bioRxiv2024

Sex differences in the cardiopulmonary and neuromuscular response to high-intensity interval exercise

Sex differences exist in the integrative response to exercise, however, these are typically researched during 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 ([Formula] O2peak) data. Thereafter, visit two involved 4 x 3-min running intervals at 90% of the final incremental test velocity (v[Formula] O2peak), 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 ([Formula] O2), carbon dioxide production ([Formula] CO2) and ventilation ([Formula] E) were continuously recorded throughout. There was no sex difference in relative [Formula] O2peak (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 [Formula] O2 or [Formula] CO2 response to the interval task (p[≥]0.781). Females had greater [Formula] E, [Formula] E/[Formula] O2, and [Formula] E/[Formula] CO2 values during the first two intervals (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.

physiology↗

bioRxiv2023

No sex differences in oxygen uptake or extraction kinetics in the moderate or heavy exercise intensity domains

The integrative response to exercise differs between sexes, with oxidative energy contribution purported as a potential mechanism. The present study investigated whether this difference was evident in the kinetics of oxygen uptake (V{square}O2) and extraction (HHb+Mb) during exercise. Sixteen adults (8 males, 8 females, age: 27{+/-}5 years) completed three experimental visits. Incremental exercise testing was performed to obtain lactate threshold and V{square}O2peak. Subsequent visits involved three six-minute cycling bouts at 80% of lactate threshold and one 30-minute bout at a work rate 30% between the lactate threshold and power at V{square}O2peak. Pulmonary gas exchange and near-infrared spectroscopy of the vastus lateralis were used to continuously sample V{square}O2 and HHb+Mb, respectively. The phase II V{square}O2 kinetics were quantified using mono-exponential curves during moderate and heavy exercise. Slow component amplitudes were also quantified for the heavy intensity domain. Relative V{square}O2peak values were not different between sexes (p=0.111). Males achieved [~]30% greater power outputs (p=0.002). In the moderate and heavy intensity domains, the relative amplitude of the phase II transition was not different between sexes for V{square}O2 ([~]24 and [~]40% V{square}O2peak, p[≥]0.179) and HHb+Mb ([~]20 and [~]32% ischemia, p[≥]0.193). Similarly, there were no sex differences in the time constants for V{square}O2 ([~]28 s, p[≥]0.385) or HHb+Mb ([~]10s, p[≥]0.274). In the heavy intensity domain, neither V{square}O2 (p[≥]0.686) or HHb+Mb (p[≥]0.432) slow component amplitudes were different between sexes. The oxidative response to moderate and heavy intensity exercise did not differ between males and females, suggesting similar dynamic responses of oxidative metabolism during intensity-matched exercise. New and NoteworthyThis study demonstrated no sex differences in the oxidative response to moderate and heavy intensity cycling exercise. The change in oxygen uptake and deoxyhaemoglobin were modelled with mono-exponential curve fitting, which revealed no differences in the rate of oxidative energy provision between sexes. This provides insight into previously reported sex differences in the integrative response to exercise.

physiology↗