Effect of orthotics on postural sway after fatigue of the plantar flexors and dorsiflexors.

OBJECTIVE

To examine the effects of orthotic intervention on unilateral postural sway after fatigue of the plantar flexor and dorsiflexor muscle groups.

DESIGN AND SETTING

Subjects were assigned to both orthotic and nonorthotic testing conditions in a counterbalanced order, then assessed for postural sway before and after isokinetic fatiguing contractions of the plantar flexors and dorsiflexors. Postural stability was measured on the motor-dominant extremity. (Motor dominance was assessed as the foot the subject used to kick a ball.)

SUBJECTS

Eleven active, healthy male subjects (mean age = 24 +/- 2.0 years, wt = 74.5 +/- 8.8 kg, ht = 180.3 +/- 8.4 cm) volunteered to participate in the study.

MEASUREMENTS

Center-of-pressure postural sway was assessed via the force platforms of a Chattecx Dynamic Balance System and transformed via 4 transducers as values indicative of sway in the anterior-posterior and medial-lateral directions. The dependent measure was postural sway in centimeters. Fatigue was induced by consecutive concentric plantar flexiondorsiflexion contractions on a Kin-Com II isokinetic dynamometer.

RESULTS

A repeated-measures analysis of variance revealed a significant orthotic-by-test interaction. Post hoc analysis with the Tukey honestly significant difference method revealed that postural sway values of the postfatigue nonorthotic condition were significantly greater when compared with the prefatigue orthotic, prefatigue nonorthotic, and postfatigue orthotic conditions.

CONCLUSIONS

Our results suggest that molded orthotics may be an effective means of decreasing postural sway after an isokinetic fatigue protocol. Further research is needed to determine the exact mechanism of this improvement and whether orthotics are an effective means of preventing ankle injury.