Acute Effect Of Static And PNF Stretching On Hip Adductor Isometric Strength

Abstract

Stretching exercises are commonly recommended as part of a routine preceding strength training, intending to avoid muscle injury and soreness or improve performance. However, the most appropriate method to conciliate these two kinds of training is still poorly understood. PURPOSE To examine the acute effect of static (STA) and PNF stretching on the dominant hip adductor isometric strength. METHODS Eighteen males (26 ± 5 yr; 83.6 ± 16.7 kg) volunteered to participate in 2 adaptation sessions and 3 randomly assigned test visits involving: 1) flexibility measures before and after STA followed by an isometric strength test (IST); 2) flexibility measures before and after PNF, followed by IST; 3) control (CON): IST with no previous stretching. Stretching exercises were passive and held for 4 sets of 30 s (STA) or 10 s blocks (contract-relax PNF). Hip adductor isometric strength was measured on an isokinetic dynamometer. Peak torque (PT) was determined on 3 different angles (45°, 30° and 15°). RESULTS PT values for CON, STA and PNF were 175.3 ± 46.8 N, 159.8 ± 48.1 N and 153.8 ± 38.9 N, respectively, at 45°; 169.1 ± 54.8 N, 151.6 ± 44.7 N and 150.7 ± 34.0 N at 30°; and 153.8 ± 47.1 N, 146.3 ± 42.5 N and 142.0 ± 35.4 N at 15°. Repeated measures ANOVA followed by LSD post hoc test showed significant differences from CON at 45° and 30°, for both STA (p=0.026 and p=0.031, respectively) and PNF (p=0.003 and p=0,018, respectively), with no differences between methods. CONCLUSIONS Relatively short duration (120 s) stretching exercises results in decreases in isometric strength. Stretching routines preceding strength training should be avoided due to the possibility of impairing strength performance.