Effect of Stance on Postural Sway During Bilateral Maximal Isometric Handgrip Testing

Abstract

Minimal postural sway while standing is indicative of good balance. The most prevalent method for evaluating postural sway is monitoring center of pressure (COP) motion for a specified duration as an individual stands on a force platform under several pre-planned conditions. Despite the potential need to generate upper body force bilaterally, previous research has focused primarily on COP motion during unilateral handgrip (HG) strength testing PURPOSE: To examine the effect of various stances on COP while performing maximal bilateral HG strength testing. METHODS: Twenty-six recreationally active male and female volunteers (19 males, 7 females; 21.9 ± 3.1 y; 75.6 ± 12.9 kg; 171.2 ± 7.9 cm) participated in this study and performed nine randomly assigned experimental trials. Each trial consisted of bilateral maximal HG strength assessments measured simultaneously with a HG dynamometer, three times with a neutral (N), dominant foot forward (D), and non-dominant (ND) foot forward stance. All trials were completed while standing on a portable force platform, which was used, in conjunction with corresponding software, to track COP motion while gripping the dynamometer. Subjects were instructed to grasp the dynamometer as forcefully as possible for ~5-sec during each trial. All trials were separated by a recovery period of 60-sec. A Waterloo Footedness Questionnaire was used to determine subject foot dominance, while maximal HG strength during the neutral stance was used to determine hand dominance. Repeated measures analysis of variance was used to detect COP displacements along the anterior/posterior (A/P) and mediolateral (M/L) axes and differences in bilateral HG strength among the three stances. RESULTS: Testing results showed that the shift in M/L COP during the D (0.67 ± 0.27 cm; p<0.001) and ND foot forward stances (0.65 ± 0.28 cm; p<0.001) were significantly greater than that during the N (0.38 ± 0.24 cm; p=0.674) stance. No significant interactions were reported for HG strength (D: 26-61 kg, ND: 26-54 kg) across the different stance conditions. CONCLUSION: Results indicated that M/L postural sway is increased when standing in both D and ND foot forward stances during maximal HG testing. Additionally, this data indicated that stance has no influence on maximal bilateral HG strength.