Proprioceptive Neuromuscular Facilitation Decreases Muscle Activity during the Stretch Reflex in Selected Posterior Thigh Muscles
Context:Proprioceptive neuromuscular facilitation (PNF) is commonly used before competition to increase range of motion. It is not known how it changes muscle response to rapid length changes.Objective:To determine whether PNF alters hamstring muscle activity during response to rapid elongation.Design:2 X 2 factorial.Setting:Laboratory.Participants:Twenty-four women; means: 167.27 cm, 58.92 kg, 21.42 y, 18.41% body fat, 21.06 kg/m2BMI.intervention:Measurements before and after either rest or PNF were compared.Main Outcome Measures:Average muscle activity immediately after a rapid and unexpected stretch, 3 times pretreatment and posttreatment, averaged into 2 pre-and post- measures.Results:PNF caused decreased activity in the biceps femoris during response to a sudden stretch (P= .04). No differences were found in semitendinosus activity (P= .35).Conclusions:Decreased muscle activity likely results from acute desensitization of the muscle spindle, which might increase risk of muscle and tendon injury.