Temperature Effects on the Contractile Characteristics and Sub-maximal Voluntary Isometric Force Production of the First Dorsal Interosseus Muscle

Cooling of a muscle has a detrimental effect on its force, power and contraction velocity, but may improve force control during precision movements by reducing physiological tremor. We investigated if the contractile characteristics of the first dorsal interosseus muscle (FDI) were linked to voluntary force control in warm and hypothermic conditions. Evoked peak twitch force, force at repetitive stimulation of 10 and 20 Hz, and submaximal force control at 25 and 50% maximal voluntary contraction (MVC) of the FDI were measured with cooled [mean (SD); 17.7 (1.3) degrees C] and warm [27.9 (2.3) degrees C] local skin temperatures in six males and four females. With evoked twitches, the time to peak tension was increased after cooling from 161 (38) ms to 219 (34) ms ( P=0.001) and half-relaxation time increased from 94 (24) ms to 157 (46) ms ( P=0.013). Peak force evoked from the repetitive stimulation contraction (10 Hz) increased significantly after cooling from 13.1 (10.2) N to 19.9 (12.1) N ( P=0.026). The coefficient of variation (CV)-representative of the degree of fusion-for evoked repetitive stimulation force (10 Hz) was significantly higher in the warm [3.6 (2.7)%] versus hypothermic condition [2.2 (3.6)%] ( P<0.05). At 25% and 50% MVC, there were no differences in the CV between warm and hypothermic conditions. FDI contractile characteristics change with local cooling, but have little effect upon voluntary submaximal isometric force control. Results are given as mean (SD).