P-92 Different oxygen consumption kinetics elicits the same oxygen deficit in normalised intensity exercise

Abstract

<h3>Introduction</h3> Exercise tolerance is an important factor regarding quality of life. The maximal oxygen uptake (VO₂<i>max</i>) is a good indicator of pulmonary, cardiovascular and muscular functional integration during exercise. Oxygen uptake (VO₂) kinetics is a reliable determinant of sports performance, in terms of oxygen (O₂) transport adjustment, muscular metabolism during exercise, and exercise intensity. The time constant (τ) and the amplitude of the VO₂ response (ΔVO₂) are parameters of the VO₂ kinetics, and allow the determination of the O₂deficit, calculated as τ × Δ VO₂. For a given work rate in the moderate intensity domain, τ is lowest in subjects with the highest VO₂<i>max</i>. <h3>Methods</h3> To determine the effect of different training backgrounds on VO₂ kinetics parameters, six endurance-trained (T) and six sedentary (S) healthy males, aged 30–53 years, were recruited to perform 3-bouts of constant-work-rate (CWR) exercise in moderate intensity domain, in a treadmill ergometer. The selected work rate for each subject was previously determined from a maximal incremental stress test in a treadmill ergometer with gas-exchange analysis, as 10% below their individual first ventilatory threshold (VT1), also known as anaerobic threshold. Level of fitness and body composition were also determined. <h3>Results</h3> VO₂<i>max</i> was higher in T than in S (median T 60, 90 vs. S 42, 45 mL Kg-1 min-1, p=0.002). Body weight was lower in T than in S (median T 72.6 vs. S 77.15 Kg, p = 0.015), and muscle mass percentage was higher (median T 62% vs. S, 47%, p=0.009). During the CWR exercise, VO₂<i>rest</i> was not different between groups (median T, 5.75 vs. S, 5.07 mL Kg-1 min-1, p = 0.132), and work rate selected for each subject was higher in T than in S (median T 174 vs. S 101 Watt, p = 0.002), as was ΔVO₂(median T 32.63 vs. S 24.75 mL Kg-1 min-1, p=0.002). The time constant was not significantly different between groups (median T, 31.75 vs. S, 37.00 seconds, p = 0.240) nor was the O₂<i>cost</i> (median T, 0.20 vs. S 0.22 mL Kg-1.min-1, p = 0.485), or the O₂<i>deficit</i> (median T 17.30 vs. S 14.46 mL Kg-1, p = 0.132). <h3>Discussion</h3> Given that trained individuals performed CWR exercise at higher work rates and attained greater ΔVO₂ than those in the sedentary group, and that τ was not significantly different between groups, we were also expecting differences in the O₂<i> deficit</i>. However, at this normalized exercise intensity, the O₂<i>deficit</i> was not significantly different between groups. This is due to bigger τ values in the sedentary group, that despite not being significantly different, once multiplied by the ΔVO₂, elicited similar O₂<i>deficit</i>. <h3>Conclusion</h3> Our data suggests that individuals with different aerobic capacities, performing normalized CWR exercise, develop similar O₂<i>deficit</i>