During static muscle activity, mechanical compression of blood vessels increases due to the muscle tension developed. However, there is still controversy concerning oxygen supply changes.
In order to identify the regional difference of oxygen supply and consumption, we measured the upper-limb blood flow and oxygenation level during static handgrip exercise.
Diameter and mean blood velocity in brachial and ulnaris arteries were measured by a Doppler ultrasound device. Oxygen saturation in biceps brachial and carpi ulnaris muscles were determined by near infrared spectroscopy. Eight healthy male subjects performed the 2min-sustained isometric handgrip at 30% of maximal voluntary contraction and 2min-recovery.
The diameter of brachial artery did not change throughout trial. In ulnaris artery, however, diameter decreased significantly during contraction and returned to resting levels after contraction (2.2 to 1.7mm). When compared to rest, mean velocity was significantly higher during contraction and faster yet during recovery. In ulnaris artery, mean velocity during recovery was significantly faster than in brachial artery (0.18 vs 0.08m/sec). Larger deoxygenation (optical density) in carpi ulnaris muscle was also found compared with biceps muscle during contraction (0.28 vs 0.12).
During forearm exercise the ulnaris area produced greater changes in blood flow and oxygen consumption than the biceps brachial area. This could result from differences in mechanical compression of blood vessels in the forearm area, and is consistent with previous results in exercising calf muscles.