The influence of strength-endurance training on the oxygenation of isometrically contracted forearm muscles

Ice-climbers frequently use the squeezing of a rubber rings for increasing their isometric strength-endurance in the forearm muscles. The aim of this study was to ascertain whether such training influences oxygenation and endurance of forearm muscles at higher as well as lower testing intensities. Fourteen healthy young ice-climbers were divided and randomized into two groups. Group A performed a specific ice-climbing test, an ice-axe-grasping (axe weight 750 g) until fatigue. Group B performed 150 N isometric hand-squeezing of dynamometer until fatigue. Both groups performed similar training of squeezing a rubber ring at 30% of Maximal Voluntary Contraction (MVC) for 6 weeks. The forearm oxygenation was assessed by relative saturation of oxygen (RSO₂), total hemoglobin concentration (RTOTHb), the concentration of oxygenated hemoglobin (ROXYHb) and concentration of deoxygenated hemoglobin (RDEOXYHb). The results revealed that muscle strength-endurance training increased performance of forearm muscles during 150 N contraction with an accompanied increase in oxygenation of the exercising muscles. In contrast, the same training did not influence the performance of forearm muscles during ice-axe-grasping in spite of increased oxygenation. Muscle oxygenation during intense isometric contraction is low in spite of an increase observed in training. This may be due to oxygenation levels that were below the limit where oxygenation may influence the duration of the contraction. Increased oxygenation may have occurred due to an increased blood flow and perfusion through superficial muscles or layers may not have contributed to the generation of the force of the contraction, as would be the case in deeper muscle layers.