Differential cardiorespiratory response to combined exercise with different combinations of forearm and calf exercise

The purpose of this study was to examine whether cardiorespiratory responses to combined rhythmic exercise (60 contractions.min-1) was affected by different combinations of upper and lower limb exercise in seven healthy women. Six different rhythmic exercises were compared: 6-min rhythmic handgrip at 10% of isometric maximal voluntary contraction (MVC) (H10); 6-min rhythmic plantar flexion at 10% MVC (P10); exhausting rhythmic handgrip at 50% MVC (H50); exhausting rhythmic plantar flexion at 50% MVC (P50); H50 was added to P10 (P10H50); and P50 was added to H10 (H10P50). Exercise duration, after handgrip was combined with plantar flexion (P10H50), was shorter than that of H50, although the exercise duration of H10P50 was not significantly different from P50. No significant difference was found between the difference from rest in oxygen uptake (delta VO2) during H10P50 and the sum of delta VO2 during H10 and P50. Also, the differences from rest in forearm blood flow (delta FBF) and calf blood flow (delta CBF) during H10P50 were not significantly different from delta FBF in H10 and from delta CBF in P50. In contrast, delta VO2 in P10H50 was lower than the sum of delta VO2 in P10 and H50 (P < 0.05), and delta FBF in P10H50 was lower than that in H50 (P < 0.05), while delta CBF was not significantly different between P10H50 and P10. The changes in heart rate from rest (delta HR) during the combined exercises were lower than the sums of delta HR in the corresponding single exercises (P < 0.05). These results demonstrated an inhibitory summation of several cardiorespiratory responses to combined exercise resulting in a reduction in exercise performance which would seem to occur easily when upperlimb exercise is added to lower limb exercise.