The effect of visual perturbation upon femoral acceleration during the single and bilateral squat.

OBJECTIVES: Record femoral accelerations using a smartphone accelerometer attached to the distal thigh during single-legged (SLS) and bilateral squats, and each squat condition occurred under two visual conditions: 1) normal vision and 2) visual perturbation with stroboscopic glasses.

DESIGN: Repeated-measures cross-over with counter-balanced order for four total conditions.

SETTING: Laboratory.

PARTICIPANTS: 22 females and 16 males without lower extremity pathologies.

MAIN OUTCOME MEASURES: 2D video assessment of frontal plane projection angle, composite amplitude index of smartphone accelerometer measurements, and bivariate correlations between these two outcomes.

RESULTS: A significant interaction was found for stance x vision as the difference occurred within the SLS stance condition between the visual conditions (Normal: 9.85 ± 0.06; Stroboscopic: 9.86 ± 0.07; p = 0.008 with an adjusted alpha of 0.25). Femoral accelerations were not associated (r = -0.07) with 2D video assessment of frontal plane projection angle.

CONCLUSIONS: Similar to other studies using smartphone accelerometry to assess movement quality, we found that the device could detect movement variation via femoral accelerations during SLS with visual perturbation in healthy individuals.