Mahieu NN, Cools A, De Wilde B, Boon M, Witvrouw E
The objective of this study was to examine the mechanism of effect of PNF stretching on changes in the ROM. Sixty-two healthy subjects were randomized into two groups: a PNF stretching group and a control group. The PNF group performed a 6-week stretching program for the calf muscles. The results of the study revealed that the dorsiflexion ROM was significantly increased in the PNF group. The PRT of the plantar flexors and the stiffness of the Achilles tendon did not change significantly after 6 weeks of PNF stretching.
These findings provide evidence that PNF stretching results in an increased ankle dorsiflexion. However, this increase in ROM could not be explained by a decrease of the PRT or by a change in stiffness of the Achilles tendon, and therefore can be explained by an increase in stretch tolerance.
Scandanavian Journal of Medicine and Science in Sports, 2008 Jun 17, online article ahead of print