Effects of Low-Intensity Exercise in the Morning on Physiological Responses During Unsteady Workload Exercise in the...

This study examined the effects of low-intensity morning exercise (ME) on physiological response during unsteady workload evening exercise. Nine healthy men participated in the following 2 experimental conditions: 15 minutes of bicycle exercise at 40% maximum oxygen consumption (V[Combining Dot Above]O2max) in the morning (the ME condition) and rest (control [C] condition). Heart rate (HR), blood pressure (BP), temperature, oxygen uptake, and natural logarithm of high frequency, an index of cardiac parasympathetic modulation, were measured before evening exercises, which were performed for 32 minutes in 2 parts: The steady-state exercise test included three 4-min bouts of exercise at 20, 60, and 40% V[Combining Dot Above]O2max. The unsteady exercise test consisted of 4-min bouts of exercise with gradual increases and decreases in workload at 20 and 60% V[Combining Dot Above]O2max. Heart rate, BP, and oxygen uptake were measured in both experiments. Maximal and minimal values, amplitude, and phase lags were measured with each cycle of unsteady workload exercise. With steady-state exercise, HR and systolic BP at 60 and 40% V[Combining Dot Above]O2max were significantly lower in the ME condition than in the C condition. However, oxygen uptake was not significantly different between the 2 conditions. With unsteady exercise, the HR and oxygen uptake phase lags were significantly shorter and the amplitude of oxygen intake was significantly larger in the ME condition than in the C condition. There were no significant differences in physiological parameters between the conditions at rest or during recovery. The physiological response during evening exercise is enhanced by low-intensity ME, which might be an effective conditioning method on a sporting event day.