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Difference in Response Latency of the Peroneus Longus Between the Dominant and Nondominant Legs

Adam C. Knight and Wendi H. Weimar

Context:

The latency of the peroneus longus in response to an inversion perturbation is a key component in the prevention of lateral ankle sprains. In addition, the dominant ankle is sprained more frequently than the nondominant ankle, but the cause of this has not been examined.

Objective:

To investigate the combination of these 2 research-supported statements, the purpose of this study was to use an inversion perturbation that replicates the mechanism of a lateral ankle sprain to determine whether there is a difference in the latency of the peroneus longus between the dominant and nondominant legs.

Design:

Repeated-measures single-group design.

Setting:

University laboratory.

Participants:

15 physically active healthy volunteers with no previous history of an ankle sprain or lower extremity surgery or fracture.

Interventions:

Outer sole with fulcrum was used to cause 25° of inversion at the subtalar joint on landing from a 27-cm step-down task. Participants performed 10 trials on both the dominant and nondominant leg.

Main Outcome Measures:

2 latency measures of the peroneus longus of both the dominant and nondominant leg, calculated as the amount of time from the moment of touchdown of the fulcrum until muscle activity exceeded 5 and 10 SD above baseline muscle activity.

Results:

The latency of the peroneus longus of the nondominant leg was significantly shorter when using both 5 SD (F 1,14 = 9.34, P = .009, d = .895) and 10 SD (F 1,14 = 18.56, P = .001, d = .920) above baseline muscle activity.

Conclusions:

This difference in latency may be a result of the different demands placed on the dominant and nondominant legs during activity and may predispose the dominant ankle to a greater number of ankle sprains than the nondominant ankle.

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Difference in Ratio of Evertor to Invertor Activity Between the Dominant and Nondominant Legs During Simulated Lateral Ankle Sprain

Adam C. Knight and Wendi H. Weimar

Context:

The dominant and nondominant legs respond asymmetrically during landing tasks, and this difference may occur during an inversion perturbation and provide insight into the role of ankle-evertor and -invertor muscle activity.

Objective:

To determine if there is a difference in the ratio of evertor to invertor activity between the dominant and nondominant legs and outer-sole conditions when the ankle is forced into inversion.

Design:

Repeated-measures single-group design.

Setting:

University laboratory.

Participants:

15 physically active healthy volunteers with no previous history of an ankle sprain or lower extremity surgery or fracture.

Interventions:

An outer sole with fulcrum was used to cause 25° of inversion at the subtalar joint after landing from a 27-cm step-down task. Participants performed 10 fulcrum trials on both the dominant and nondominant leg.

Main Outcome Measures:

The ratio of evertor to invertor muscle activity 200 ms before and 200 ms after the inversion perturbation was measured using electromyography. This ratio was the dependent variable. Independent variables included outer-sole condition (fulcrum, flat), leg (dominant, nondominant), and time (prelanding, postlanding). The data were analyzed with separate 2-way repeated-measures ANOVA, 1 for the prelanding ratios and 1 for the postlanding ratios.

Results:

For the postlanding ratios, the fulcrum outer sole had a significantly greater (P < .05) ratio than the flat outer sole, and the nondominant leg had a significantly greater (P < .05) ratio than the dominant leg.

Conclusions:

These results indicate that a greater evertor response is produced when the ankle is forced into inversion, and a greater response is produced for the nondominant leg, which may function better during a postural-stabilizing task than the dominant leg.

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Closed-Loop Reflex Responses of the Lateral Ankle Musculature From Various Thresholds During a Lateral Ankle Sprain Perturbation

Jeffrey D. Simpson, Ludmila Cosio Lima, Youngil Lee, Harish Chander, and Adam C. Knight

Context: Latency is a reliable temporal metric used to evaluate sensorimotor integration of the fibularis longus (FL) and fibularis brevis (FB) during lateral ankle sprain perturbations. Currently, no clinical recommendations exist to select appropriate thresholds to evaluate the closed-loop reflex response of the lateral ankle musculature. The purpose of this study was to assess threshold value on latency of the FL and FB during an unanticipated inversion perturbation that simulates the mechanism of a lateral ankle sprain. Design: Descriptive laboratory study. Methods: Twenty healthy adults with no history of lateral ankle sprain injury completed an unanticipated single-leg drop landing onto a 25° laterally inclined force platform from a height of 30 cm. Surface electromyography recorded muscle activity data from the FL and FB during the inversion perturbation. Latency was identified at points where muscle activity exceeded 2, 5, and 10 SD above the average muscle activity 200 milliseconds prior to foot contact, and compared across threshold value using a 1-way analysis of variance (P < .05). Results: The 2 SD threshold was significantly shorter than both 5 SD and 10 SD thresholds for the FL (P < .01) and FB (P < .01). Likewise, the 5 SD threshold was significantly shorter than the 10 SD thresholds for FL (P = .004) and FB (P = .003). Conclusions: More sensitive thresholds results in a shorter closed-loop reflexive response compared to the more rigorous thresholds. We recommend that selection of the appropriate threshold to identify latency of the lateral ankle musculature should be based on the device used to simulate a lateral ankle sprain and the ankle inversion velocity produced during the ankle inversion perturbation.