The Relationship between Hip Extension Force Measured by Using a Hand-held Dynamometer and the Effect of Proprioceptive Neuromuscular Facilitation Stretching on Hamstring Flexibility

Abstract

The purpose of this study was to investigate the relationship between hip extension force measured by using a hand-held dynamometer (HHD) and the effect of proprioceptive neuromuscular facilitation (PNF) stretching on hamstring flexibility. Many athletes try to avoid strains by excessive stress while maintaining or improving performance. It has been widely demonstrated that PNF stretching increases hamstring flexibility by decreasing active resistance. Thirty-four young men and women participated in the study. Active knee extension (AKE) was measured with a goniometer before and after hold-relax PNF stretching. Additionally, AKE data were collected at 2, 6, 10, 20, and 30 min. The maximal isometric contraction force of the hamstring was measured by using a HHD during a single set of PNF stretches (6 trials×5 s/trial). The mean forces measured by using the hand-held dynamometer were not significantly different between the trials; however, the averages of the maximum and minimum values obtained for each trial were significantly different. Hamstring flexibility at pre-stretch differed between men and women, but the immediate and sustained effects of stretching did not differ between the sexes. The isometric contraction force of the hip extensor during hold-relax PNF stretching was successfully measured and quantified with the use of a HHD. The inconsistencies in the isometric contraction force between trials might diminish the effect of stretching. The use of a HHD to monitor the effort applied by a subject and provide real-time feedback might enhance the effectiveness of stretching in the clinical field or in sports physiotherapy.