Relationship between Take-Off Force Profiles and Single Leg Hop Distance

Abstract

The anterior single leg hop for distance test (SLHOP) is a functional performance task that is often used to assess return to play criteria following ACL reconstruction. Clinicians primarily assess SLHOP distance, but the way an individual completes the task may be important when determining return to play status. Recent research has indicated that non-uniformity in vertical ground reaction force (VGRF) profiles may be related to pathomechanics during a vertical jump, but little research has been done to explore the relationship between force profiles and SLHOP distance. PURPOSE: To determine the correlation between a force profile ratio and SLHOP distance. METHODS: Twenty-three female collegiate soccer players (19.1±1.5 years; 166.9±7.1 cm; 62.6±8.3 kg) performed three SLHOP tests for maximal distance off a tri-axial force plate. The SLHOP was performed on the dominant limb. Ground reaction force (GRF) data were collected during SLHOP take-off phase to produce force-time curves that were used to calculate the ratio between the instantaneous and average force profile between three events. Force profile ratios were calculated between: A) the minimum GRF after initiation of the countermovement and the peak GRF prior to takeoff, and B) the point during the countermovement when body weight is reached and peak GRF. Ratio A and B where calculated in both the vertical (z) and anterior-posterior (y) axes. All forces were normalized to body weight, and SLHOP distances were normalized to leg length (cm/cm). The strength of the association between each of the aforementioned force profile ratios and maximum SLHOP distance were calculated using Pearson correlation coefficients with an alpha level set a priori at p<0.05. RESULTS: There were no significant correlations between any combination of force profile ratios and SLHOP distance (p-value range:0.19 to 0.62, r range: -0.11 to -0.26). CONCLUSION: Force profile ratios between straight-line and trace-line distance are not significantly related to average or maximum SLHOP distance. Further research should explore the relationship between other phases within the force-time curve, pathomechanics, and SLHOP distance.