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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.
To determine whether PNF alters hamstring muscle activity during response to rapid elongation.
2 X 2 factorial.
Twenty-four women; means: 167.27 cm, 58.92 kg, 21.42 y, 18.41% body fat, 21.06 kg/m2 BMI.
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.
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).
Decreased muscle activity likely results from acute desensitization of the muscle spindle, which might increase risk of muscle and tendon injury.
Allyson M. Carter is with the Department of Physical Education at Gordon College in Barnesville, GA 30204. Stephen J. Kinzey and Judith L. Cole are with the Applied Biomechanics and Motor Performance Laboratory, and Linda F. Chitwood, the Department of Exercise Science and Leisure Management, at The University of Mississippi, University, MS 38677.