Abstract

Background: The hamstring is a biarticular postural muscle that flexes the knee, extends the hip, and plays a role in activities, such as walking, running, climbing stairs, and jumping. Hamstring shortening is associated with a high incidence of muscle strain, patellofemoral pain, and poor gait. Precooling and static stretching have been used to increase connective tissue viscoelasticity and improve muscle flexibility. Studies have shown that the application of ice may provide improvements in hamstring flexibility over heat or stretching alone. However, insufficient scientific data exist regarding the effectiveness of different durations of cooling combined with static stretching on muscle flexibility.

Methods: To help explore the effects of different durations of cryotherapy and stretching on muscle flexibility, four experimental conditions of cold pack applications were compared on different days with two days in between the experimental conditions. The purpose of this study was to compare 5, 10, 15, and 20 minutes of cold pack application followed by hamstring stretching on muscle flexibility in 25 healthy subjects. A randomized withinsubjects design was used to compare the changes before and immediately after cold pack application and stretching in popliteal angle measurement. Stretching was conducted for 30 seconds and repeated three times.

Results: Analysis of variance revealed a significant main effect for time demonstrated in an increased popliteal angle measurement. All groups showed significant differences in the popliteal angle measurement before and after cold pack administration. Additionally, although 15 minutes resulted in the highest measured popliteal angle among the four conditions, the post hoc test showed that this change was statistically significant from 5 and 10 minutes but not from 20 minutes.

Conclusion: The results infer that short cold pack application has limited effectiveness in altering muscle flexibility and that durations of 15 and 20 minutes are better employed for superior outcomes.

Keywords: Cold pack; Popliteal angle; Static stretch; Treatment duration