The acute effect of static muscle stretching on knee joint repositioning error

Despite the fact that muscle stretching plays an important role in sport, therapeutic exercises and rehabilitation of musculoskeletal disorders, few studies have considered the effect of muscle stretching on joint proprioception. In addition, the studies report paradoxical results. Therefore, the aim of this study was to assess the effects of extensor and flexor muscles stretching on knee joint position sense in 15, 30 and 60 degrees of flexion angels. This quasi-experimental study with pre-test post-test control group design was done over 37 young healthy subjects in age range between 18-25 years.The subjects were randomly assigned to 3 conditions of extensor stretching, flexor stretching and control. Angular error was evaluated in 3 angles including 15, 30 and 60 degrees of knee flexion using digital photography, non-reflective markers and analysis with AutoCAD software. The results showed that when evaluating the proprioception during knee extention, the absolute angular error rate is significantly increased in flexor stretching condition in 15, 30 and 60 degrees of knee flexion (p<0.02), but in the extensor stretching condition, there was not any significant change. The results show that the minimum error occurs in 15 degrees and maximum error occurs in 60 degrees of knee. It seems that static stretching of antagonist muscles increases joint repositioning error.Also it seems that due to the stretching of soft tissues around the joints at the end of the range, there is less position sense error at the end range and more error at the middle range of motion. So in designing the stretching exercises for athletes and rehabilitation programs, the interference of stretching exercise with proprioception should be considered carefully.