Effect Of Proprioceptive Neuromuscular Facilitation Stretching And Static Stretching On Maximal Voluntary Contraction

Abstract

One of the purposes of stretching is to increase range of motion (ROM). However, recent studies have shown that acute static stretching decreases maximal voluntary contraction (MVC) and that the deficits may be due to neurological and/or mechanical factors which increase ROM. Proprioceptive neuromuscular facilitation (PNF) stretching is one of the most effective procedures to increase ROM. If the mechanism of the MVC deficit induced by static stretching is also applicable to PNF stretching, PNF stretching may induce a greater decrease in MVC than static stretching. PURPOSE We tested if PNF stretching would decrease MVC more than static stretching. METHODS Fourteen male students participated in this study. They completed three different conditions of stretching; the control (CON; non-stretching), the static stretch (SS; 45s-passive stretching of hamstrings and 15s-relaxation), and the modified PNF stretch (PNF) that consisted of hold-relax with agonist contraction method (10s-passive stretching of hamstrings, 6s-maximal isometric contraction of hamstrings, and 30s-concentic contraction of quadriceps with passive stretching of hamstrings, 14s-relaxation). Each stretch was repeated 5 times and then MVC of knee flexion was measured with the iEMG of biceps femoris muscle. The flexibility of hip flexion (hamstrings) with supine position was evaluated by Leighton flexometer before and immediately after stretching. Measurement for each condition was performed on 3 non-consecutive days. RESULTS Although the flexibility was significantly improved by both SS (5.3±4.5%, p < 0.001) and PNF (15.0±8.4%, p < 0.001), the improvement was significantly greater in PNF (7.3±9.8%, p < 0.05) [CON: pre; 86±15, post; 86±15, SS: pre; 85±15, post; 90±16, PNF: pre; 83±14, post; 95±13 degrees]. MVC in SS significantly decreased as compared with CON (−7.5%, p < 0.05), however MVC in PNF was not significantly different from CON (−6.2%, P = 0.09) [CON; 32.7±4.8, SS; 30.2±5.3, PNF; 30.6±6.0 kg]. iEMG in SS significantly decreased by 9.9% (p < 0.05) as compared with CON but iEMG in PNF was not significantly different from CON [CON; 420±185, SS; 366±140, PNF; 396±161 μV.sec.sec−1]. iEMG/MVC was not significantly different among each condition [CON; 13±5, SS; 12±4, PNF; 13±4 μV.sec.sec−1.kg−1]. CONCLUSION Improvement of flexibility is greater in PNF stretching more than static stretching but deficit of MVC with the decrease of iEMG may be only caused by static stretching.