Assessing Effectiveness of Using a Moist Heat Pack Prior to Single Leg Vertical Jump Performance

Context: Thermotherapy techniques, such as moist heat pack (MHP), produce increased circulation and metabolism, decreased pain, decreased muscle spasm, and decreased tissue stiffness. An increase in muscle elasticity causes an increase in flexibility, which can lead to an increase in range of motion. However, there is limited research directly related to the effect of MHP on functional performance since much of the research is indirectly associated with flexibility and range of motion. Therefore, the purpose of this study was to explore and assess the effectiveness of a moist heat pack on single leg vertical jump performance. Methods: A convenience sample of five healthy, college-aged students were selected for this study (2 females, 3 males; average age 23 + 4 years, height 68 ±4 inches, and weight 198 + 4 lbs). A repeated measures design was used whereby subjects completed two separate trials with a week between each trial. The two trials included a 10-minute treatment of MHP on the subject’s dominant limb or a 10- minute control trial consisting of laying prone on a treatment table for 10 minutes. Single leg vertical jump on the subject’s dominant leg was recorded using the Just Jump! Just Run! Mat before and after each trial. Three measurements were obtained and an average was recorded. Treatment order was randomized and spaced out a week apart. Microsoft Excel was used to calculate descriptive statistics for each participant’s height, weight, and age along with their vertical jump measurements. A 2 x 2 (trial x time) repeated measures ANOVA using SPSS v26.0 was used to calculate mean difference between the control and moist heat pack trial. Significance was set a priori at p = 0.05. Results: The 2 x 2 repeated measures ANOVA revealed no statistical difference between the moist heat pack and control groups on vertical jump performance (p = 0.15). While there was a trend for both groups\u27 vertical jump to slightly improve after both interventions, a main effect for time was not demonstrated. Conclusion: Applying MHP on hamstrings prior to vertical jump does not significantly improve performance. The results of this study suggest that a passive warm up may not be the best modality of choice when preparing for power production movements. Athletes who regularly apply a MHP to soft tissue in an effort to boost performance may want to consider engaging in a more active warm up or alternative modality to warm the tissue prior to performance. Word Count: 40