Oxygenation kinetics of forearm muscles as a function of handle diameter during a repetitive power grip force task

Handle diameter was manipulated to evaluate the affect on muscle oxygenation and blood volume in the extensor carpi radialis and the flexor digitorum superficialis during rhythmic isometric gripping tasks. Power grip contractions were performed at 15% of maximum voluntary contraction (MVC) at a work:rest cycle of 10:5-s, with three different handles (30. 40, and 50 mm) for a period of 15-min by 19 participants. MVC was significantly greater for the 30 and 40 mm handle than for the 50 mm handle. TOI, the average hemoglobin saturation, and cHb, total hemoglobin (blood volume) were significantly different when working with the 30 and 40 mm handles than with the 50 mm handle, with a decreasing TOI and increasing cHb observed with the larger handle. This finding suggests that the two smaller handles had similar tissue oxygenation and blood volume requirements during repetitive gripping, and less oxygenated hemoglobin was available when gripping the larger handle. Significant interactions between handle diameter and muscle groups in TOI and cHb, were also observed, implying differential contributions of the flexor and extensor muscles. The results suggest that for the hand-handle interface it is not only important to consider handle diameter, but also perfusion of both flexor and extensor muscles. Relevance to industry: job requirements often dictate tool configuration. Based on an evaluation using a low-level cyclic power grip, for the general population cylindrical handles of 30-40 mm diameter may be superior to a 50 mm handle, not only in grip force capacity, but also because of the improved tissue perfusion characteristics. (c) 2008 Elsevier B.V. All rights reserved.