Optimal position of PNF stretching for improving flexibility: Knee flexion in prone position versus hip extension in supine position

Background In clinical practice, knee flexion in the prone position is proposed for manual muscle testing (MMT) of the hamstrings, while hip extension in a supine position is suggested for hamstring stretching. Since the effect of proprioceptive neuromuscular facilitation (PNF) stretching on flexibility is greater during maximal isometric contractions, the MMT position exhibiting greater muscle activity may be more effective. The purpose of this study was to determine the effects of PNF stretching performed in the straight leg raise (SLR) and MMT positions on lower extremity flexibility. Methods Thirty healthy young adults participated in this study. Lower extremity flexibilities of the hip, knee, and ankle were measured before and after PNF stretching. PNF stretching was performed in one leg in the SLR position and the other leg in the MMT position. Results PNF stretching on both SLR and MMT positions significantly increased hip, knee, and ankle flexibilities. The increase in flexibility was higher for the SLR position compared to the MMT position, especially in knee and ankle flexibility. Conclusions PNF stretching in the SLR position exhibited significantly higher flexibility, especially in the knee and ankle. The SLR position can be recommended in most clinical settings. MMT position using knee flexion could be beneficial when hip joint motion is limited.