Maximal strength training (MST) improves submaximal work efficiency (WE) in the arms. However, since assessment of muscle oxygen uptake (V[Combining Dot Above]O2) during exercise is lacking, the behavior of MST-induced adaptations is unknown, and it remains elusive if metabolic and vascular responses in arms may contrast what has been observed in legs.
PURPOUSE: To investigate responses in arm blood flow and arteriovenous oxygen difference (a-vO2diff) during steady state exercise following MST.
METHODS: Thus, utilizing Doppler-ultrasound and a catheter placed in the subclavian vein for measurements of blood flow and a-vO2diff, we assessed steady state WE and peak responses in seven young males (24±2(SD) years) following a six-week handgrip MST intervention.
RESULTS: As expected, MST improved maximal strength (49±9 to 62±10kg) and rate of force development (923±224 to 1086±238N·s−1), resulting in a reduced submaximal V[Combining Dot Above]O2 (31±9 to 25±10mL·min−1) and concomitantly increased WE (8.8±2.3 to 11.7±3.6%) (all p<0.05). In turn, the WE-improvement led to a reduced blood flow (486±102 to 395±114mL·min−1), mediated by a lower heart rate (66±4 to 59±7beats·min−1) and blood velocity (43±8 to 32±6cm·s−1) (all p<0.05). Conduit artery diameter and a-vO2diff remained unaltered. The peak test revealed increased time to exhaustion (948 to 1104 seconds; p<0.05), and a tendency towards increased peak work rate (p=0.06), but no change in peak oxygen uptake.
CONCLUSION: Despite arguments of metabolic and vascular limb-specific differences, these results reveal that the mechanisms responsible for WE adaptations following small muscle mass MST in the upper extremities is a direct reflection of what has been documented for lower extremities. Additionally, our data show that the advantageous reductions in blood flow is regulated through conduit artery blood velocity.