Feland, J. B., & Marin, H. N. (2004). Effect of submaximal contraction intensity in contract-relax proprioceptive neuromuscular facilitation stretching. British Journal of Sports Medicine, 38, E18.

This investigation determined if submaximal contractions used in contract-relax proprioceptive neuromuscular facilitation (PNF) stretching of the hamstrings yield comparable gains in hamstring flexibility to maximal voluntary isometric contractions. Males (N = 72) with demonstrated tight hamstrings served as Ss. Sixty Ss were randomly assigned to one of three treatment groups that employed different levels of contraction force: 1, 20% of maximal voluntary isometric contractions; 2, 60% of maximal voluntary isometric contractions; 3, 100% maximal voluntary isometric contractions. Twelve Ss were randomly assigned to a control group (no stretching). Subjects in the stretching groups performed three separate 6-second CRPNF stretches at the respective intensity with a 10-second rest between contractions, once a day for five days.

Significant changes in flexibility were recorded for all treatment groups with no intergroup differences. Treatment groups were significantly altered when compared to the control group.

Implication. PNF stretching using submaximal contractions is as effective as when maximal contractions are used.

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