Immediate and short-term effect of hamstring static stretching on active mouth opening

Human body is an integrated unit that acts as a whole in such a way that the function of every part may influence the other parts. In this study the effect of hamstring muscle stretching on the amount of mouth opening in healthy people was investigated as a component of this integrated body. Eighty volunteers, 54 men and 26 women, aged 18 to 30 years old, participated in this study. Subjects were divided randomly into two groups. Group 1 underwent a single 60-second hamstring muscle static stretching for dominant leg. The control group received passive patellar mobilization as a placebo intervention for dominant leg. Outcome measure was maximum active mouth opening and popliteal angle which were measured by a digital caliper and a hand goniometer respectively. These measurements were done at baseline, 5 minutes, 1 hour and 24 hours, post intervention by an examiner blinded to the intervention allocated to each subject. Repeated measures ANOVA revealed significant decrease in mouth opening in group 1 (p<0.05); that was also significant when compared to control group (p<0.05). Popliteal angle was not significantly changed in both groups. In addition positive correlation was found between the active mouth opening and popliteal angle. The present study demonstrated an decrease in active mouth opening in response to the static stretching of hamstring muscles which confirms the hypothesis of a functional relationship between the masticatory and hamstring muscle. This relationship can be explained through myofascial meredians, nervous system, muscle chains and biomechanical linkage