Effects of Cooling and Heating Treatments on Isometric Contraction and EMG Activity of the Upper Arm

This study examined the effects of cooling treatment (CT) and heating treatment (HT) on shoulder muscle isometric contraction. Sixteen college students (14 males, 2 females; age 21.9 ± 2.7 years; height 173.4 ± 7.0 cm; weight 74.9 ± 14.5 kg) participated. Participants abstained from high-intensity activity and medication for 7 days before testing. Maximum voluntary isometric contraction (MVIC) was measured at 65° shoulder abduction using a dynamometer. The order of CT and HT was randomized, with a 5-min recovery between treatments. Following 3-min of either CT or HT, isometric strength and electromyography (EMG) of the anterior deltoid (AD), lateral deltoid (LD), and posterior deltoid (PD) were recorded in the same position. Isometric endurance at 90° abduction was also assessed. There were no significant differences in Peak Torque (PT) and Average Torque (AT) during 5-second isometric contractions between CT and HT ( p > .05). EMG during thermal application showed significantly higher activation in the AD with CT compared to HT ( p < .05). Endurance was greater following CT ( p < .05). EMG during endurance tasks indicated significant increases in muscle activity in AD ( p < .001), LD ( p < .001), and PD ( p < .05). Cooling treatment significantly improves muscle endurance and EMG activity during isometric contraction compared to heating treatment. These findings suggest that CT can enhance sustained shoulder muscle performance.