Effect of proprioceptive neuromuscular facilitation stretching on the plantar flexor muscle-tendon tissue properties.

Proprioceptive neuromuscular facilitation (PNF) stretching programs have been shown to be the most effective stretching technique to increase the range of motion (ROM). 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. Before and after this period, all subjects were evaluated for dorsiflexion ROM, passive resistive torque (PRT) of the plantar flexors and stiffness of the Achilles tendon. The results of the study revealed that the dorsiflexion ROM was significantly increased in the PNF group (DeltaROMext: 5.97+/-0.671 degrees ; DeltaROMflex: 5.697+/-0.788 degrees ). 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.

Trapezius activity and intramuscular balance during isokinetic exercise in overhead athletes with impingement symptoms.

We compared normalized trapezius muscle activity and intramuscular balance ratios between overhead athletes with impingement symptoms and non-injured athletes during isokinetic abduction and external rotation movements. Thirty-nine overhead athletes with chronic impingement symptoms and 30 non-injured athletes participated in the study. Electromyographic activity of upper, middle, and lower trapezius was measured during isokinetic abduction and external rotation, using surface electrodes. The results show a significant increase of upper trapezius activity during both movements in the patient group, with decreased activity in the lower trapezius during abduction, and in the middle trapezius during external rotation. Analysis of the intramuscular activity ratios revealed muscle imbalance on the injured side of the patient group for upper/middle trapezius and upper/lower trapezius during abduction, and for all three muscle activity ratios during external rotation. These results confirm the presence of scapular muscle imbalances in patients with impingement symptoms and emphasize the relevance of restoration of scapular muscle balance in shoulder rehabilitation.