Ground Reaction Force Analysis of the Anterior and Crossover Single Leg Hop Tests

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Medicine & Science in Sports & Exercise






In contrast to the landing phase, less research has examined the propulsion phase of the single leg anterior (AHT) and cross over (COHT) hop tests. Additionally, there appears to be a void regarding objective support for using 15cm for the COHT.

PURPOSE: To compare propulsive vertical, anterior, and lateral ground reaction forces (GRF) between AHT and COHT.

METHODS: Thirty-eight healthy, Division I male basketball, football, baseball, and soccer athletes (88.3 ± 12.3 kg; 183.9 ± 6.0 cm; 20.6 ± 1.4 years) completed AHT and COHT in a counterbalanced order using their dominant limb. One week prior to data collection, participants completed a practice session of the two tests until performance (hop distance) plateaued. GRF data was collected during the propulsive phase of four trials for each test variation. The propulsive phase was defined as the interval between the end of counter-movement and ground off. Vertical, anterior and lateral peak force and impulse were computed. The composite impulse was computed as the sum of the vertical, anterior and lateral impulses. Acceptable trials were defined as being within ±5% of the distances established during practice session. Paired t-tests were conducted to statistically compare respective dependent variables between the variations.

RESULTS: There was no significant difference in the distance hopped (P=.550) or in the composite impulse (P=.348) between the variations. In contrast to the lateral impulse being significantly greater for the COHT (P<.001), there was no significant difference for either the vertical impulse (P=.890) or the anterior impulse (P=.176). Both the vertical (P<.001) and anterior (P<.001) peak forces were significantly greater for the AHT, whereas the lateral peak force (P=.045) was significantly greater for the COHT.

CONCLUSION: Despite peak force and impulse differences, the total propulsive effort was equal between the two variations as evidenced by the hop distances and composite impulses. These data support the traditional use of 15cm crossover distance to stimulate greater lateral force production demands. Future research is recommended to consider different crossover distances as well as the impacts on ankle, knee and hip contributions.