Effects of a Thermal Agent and Physical Activity on Muscle Tendon Stiffness, as Well as the Effects Combined With Static Stretching

Abstract

Context: A recent review or article reported that thermal agents (TA) or physical activity (PA) can increase range of motion (ROM) and that the combination of TA with stretching is superior to performing stretching only. However, since ROM is affected by the psychological factors, it is questionable whether these studies measured the effect of these interventions on muscle flexibility. By measuring muscle stiffness, the authors attempted to evaluate the effect these interventions on muscle flexibility. Objective: To compare the individual effects of TA and PA on muscle flexibility, as well as their effectiveness when combined with static stretching (SS). Design: Crossover trial. Setting: University research laboratory. Participants: 15 healthy men without a history of orthopedic disease in their lower limbs. Interventions: 15 minutes of 3 different conditions: hot pack as TA, pedaling exercise as PA, and the control group with no TA or PA intervention, followed by 3 min of SS for the hamstrings. Main Outcome Measures: Joint angle and passive torque of the knee during passive elongation were obtained prior to interventions, after 3 kinds of intervention, and after SS. From these data, muscle-tendon-unit (MTU) stiffness of the hamstrings was calculated. Results: Although knee-joint ROM increased with both TA and PA (P < .05), there were no significant differences in MTU stiffness between pre- and postintervention measurements for either of the interventions (TA, P = .477; PA, P = .377; control, P = .388). However, there were similar significant decreases in MTU stiffness between postintervention and post-SS for all conditions (P < .01). Conclusions: TA and PA did not decrease MTU stiffness, and combining these interventions with SS did not provide additional decreases in MTU stiffness compared with performing SS alone.