Enhanced cerebro-cardiovascular responses before starting voluntary exercise in young men with higher peak aerobic capacity

We recently reported that countdown (CD) before voluntary exercise induced cerebral activation and pressor responses, resulting in muscle vasodilation (Manabe et al. <i>J Appl Physiol</i> 128: 1196-1206, 2020). We examined whether responses were enhanced as peak aerobic capacity (V̇o_2peak) increased. We studied 27 young men with V̇o_2peak from 25.2 to 61.4 mL·kg^-1·min^-1. We evaluated CD responses before initiating voluntary cycling at 50% of V̇o_2peak for 1 min in a semirecumbent position while measuring middle cerebral artery blood flow velocity (V_MCA; Doppler ultrasonography), heart rate, mean arterial pressure (MAP; finger photoplethysmography), oxygen consumption rate (V̇o₂), cardiac output (Q_c; ModelFlow), total peripheral resistance (MAP/Q_c), and oxygen saturation in thigh muscle (near-infrared spectrometry). All subjects performed eight trials, intermitted by ≥5-min rest, and were either given a 30-s countdown (CD+) or immediately signaled to begin exercise (CD-), with the order randomized and counterbalanced. We classified subjects with both V_MCA and MAP increases by CD as "responders" (Resp, <i>n</i> = 11) and those with either V_MCA or MAP increase, or an increase of neither, as "minimal responders" (MinResp, <i>n</i> = 16). We found that cerebro-cardiovascular and V̇o₂ responses to CD before starting exercise were all significantly greater in Resp than in MinResp (all <i>P</i> < 0.017), and cerebro-cardiovascular responses were significantly correlated with individual V̇o_2peak in data pooled from both groups (all <i>P</i> < 0.034). The increase in V̇o₂ by CD in Resp continued for a few seconds after starting exercise. Thus, cerebro-cardiovascular responses to CD before starting voluntary exercise were enhanced, as individual V̇o_2peak increased in young men, which might accelerate V̇o₂ response at starting exercise.<b>NEW & NOTEWORTHY</b> The delay of oxygen transport to muscle at the onset of exercise by the cardio-respiratory system increases anaerobic energy production and oxygen deficit, which can disturb a smooth start of exercise. We found that the anticipatory cerebro-cardiovascular responses evoked by a countdown before starting voluntary exercise were enhanced as peak aerobic capacity increased, suggesting that the central as well as peripheral mechanisms contribute to increasing aerobic energy production at the onset of exercise.