Effect of PNF stretching
training on the properties of human muscle and tendon structures.

Konrad A,
Gad M, and Tilp M.
Scand J Med Sci Sports. 2014 [epub ahead of print].

Home Message: Following a 6 week
proprioceptive neuromuscular facilitation stretching program ankle dorsiflexion was increased and tendon
stiffness decreased.

Despite the common use of proprioceptive neuromuscular facilitation
(PNF) stretching we have limited information about how it affects range of
motion, maximal isometric torque, passive resistive torque, muscle stiffness or
tendon stiffness. By better understanding the effect of PNF stretching on musculotendinous
performance and structure, clinicians may be able to optimize rehabilitation
and pre-participation warm-ups to minimize injury without inhibiting
performance. Therefore, Konrad, Gad, and Tilp completed a randomized trial to
analyze the effects of a 6-week PNF stretching program on the functional and
structural parameter of the ankle joint compared with individuals assigned to a
control group. Researchers randomly assigned 49 police cadets (31 male, 18
female) to either a PNF stretching group (25 cadets) or control group (24
cadets). Prior to any intervention, participants’ range of motion (ROM),
passive resistive torque, maximum voluntary contraction, and parameters of the
muscle and tendon structure (for example, fascicle length, pennation angle, tendon
stiffness) were measured. Participants in the PNF group performed a PNF
stretching program 5 times per week over a 6 week period. The stretching
program consisted of a standing wall stretch of the plantar flexors for 15
seconds, followed by an isometric contraction of the plantar flexors for 6
seconds, and then contract the dorsiflexor muscles for another 15 seconds. This
cycle was repeated four times per session. Following the 6-period, the control
group had not noticeable changes but the cadets who performed PNF stretching had
greater ankle dorsiflexion ROM and pennation angle at rest as well as less
active and passive tendon stiffness. Fascicle length, pennation angle in
stretching position, passive resistance torque, and maximum voluntary
contraction torque did not change among cadets in either group.

Overall, the present study supports the use of PNF stretching as an
effective method of increasing dorsiflexion range of motion. Also interesting
is the finding that while ankle dorsiflexion increased, the authors only
observed changes in the tendon stiffness and pennation angle at rest. This is
interesting as it may indicate that while the ROM increases, the muscle may
maintain many of its characteristics needed for optimal performance. To better
understand the relationship between PNF stretching and its benefits to physical
performance, future studies should compare PNF stretching to static and
ballistic stretching, as well as measure a more sport-specific movements.
Ultimately, this study should aid encourage clinicians in incorporating more
PNF stretching into their rehabilitation and conditioning programs.

Questions for Discussion:
How often do you prescribe PNF stretching in your rehabilitation or
conditioning programs? Have you found PNF stretching to be particularly
beneficial to ROM and or overall performance?

Written by: Kyle Harris
Reviewed by: Jeffrey Driban

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Konrad, A., Gad, M., & Tilp, M. (2014). Effect of PNF stretching training on the properties of human muscle and tendon structures Scandinavian Journal of Medicine & Science in Sports DOI: 10.1111/sms.12228