Transfer effects of endurance training to exercise with untrained limbs

Summary

There has been a controversy over whether the increases in maximal oxygen uptake ($\dot V$O_{2 max}) and reductions in heart rate at a given submaximal workload after endurance training are limited to exercise with trained limbs or also may be observed during exercise with untrained limbs. In the present study five initially very sedentary young men trained by leg cycling (LT) and five by arm cranking (AT) 30 min per day on 4 days a week for 11 weeks at an intensity ≥75–80% $\dot V$O_{2 max}. Before and after training the subjects performed submaximal and maximal arm cranking and leg cycling tests. Leg cycling and arm cranking $\dot V$O_{2 max} increased 15% and 9% after LT and 12% and 35% after AT, respectively. Heart rate at a given submaximal workload was lower (p<0.05) during trained and untrained limb exercise following LT and AT. However, subjective ratings of perceived exertion (RPE) at a given submaximal workload were lower (p<0.01) only during exercise with trained limbs after LT and AT. In light of previous findings, the present increases in $\dot V$O_{2 max} and reductions in submaximal exercise heart rate with untrained limbs suggest that the initial fitness of the subjects as well as the intensity, frequency, and duration of training may be important factors in determining the extent to which transfer effects of endurance training can be observed. Although the present data suggest that reductions in RPE after endurance training may be the result of local changes in trained muscles, the possible contribution of central nervous adaptations cannot be excluded.