Meeting Abstract
Exercise performance depends on both physiological abilities (e.g. muscle strength) and behavioral characteristics (e.g. motivation). We tested the hypothesis that evolution of increased aerobic exercise performance can be triggered by evolution of motivation to undertake physical activity. We used a unique model system: four lines of bank voles (Myodes glareolus) selected for high swimming-induced aerobic metabolism (“aerobic” A-lines). In generation 21, voles from the A-lines achieved 61% higher aerobic metabolism during swimming (VO2swim) than voles from four unselected, “control” C-lines. Because the voles could vigorously swim or float on the water surface, the level of VO2swim depended both on aerobic capacity and motivation to undertake intensive activity. The level of metabolism achieved during an exercise that depends mainly on aerobic capacity (forced running, VO2run) was higher than VO2swim in the C-lines (mass-adjusted LSM±SE [mlO2/min]; run: 4.73±0.13, swim: 4.31±0.13; p=0.008), while the A-lines achieved similar VO2run and VO2swim (run: 6.09±0.13, swim: 6.31±0.13, p=0.13). Thus, we hypothesized that selection changed both aerobic capacity and neuronal mechanisms behind motivation to undertake activity. We investigated the influence of reuptake inhibitors of dopamine (vanoxerine), serotonin (fluoxetine) and noradrenaline (reboxetine) on VO2swim and VO2run. All drugs caused decreased VO2swim, but VO2run was decreased only by vanoxerine. The results indicate different neuronal processes underlying voluntary and forced activity. Because there were no differences in response to the drugs between A and C-lines, we are as yet unable to reach firm conclusions concerning the role of these monoamines in the evolution of increased aerobic exercise performance.
