A comparison of methods to determine bilateral asymmetries in vertical leg stiffness

ABSTRACT

Whilst the measurement and quantification of vertical leg stiffness (K_vert) asymmetry is of important practical relevance to athletic performance, literature investigating bilateral asymmetry in K_vert is limited. Moreover, how the type of task used to assess K_vert may affect the expression of asymmetry has not been properly determined. Twelve healthy males performed three types of performance tasks on a dual force plate system to determine K_vert asymmetries; the tasks were (a) bilateral hopping, (b) bilateral drop jumping and (c) unilateral drop jumping. Across all the three methods, K_vert was significantly different between compliant and stiff limbs (P < 0.001) with a significant interaction effect between limb and method (P = 0.005). Differences in K_vert between compliant and stiff limbs were −5.3% (P < 0.001), −21.8% (P = 0.007) and −15.1% (P < 0.001) for the bilateral hopping, bilateral drop jumping and unilateral drop jumping methods, respectively. All the three methods were able to detect significant differences between compliant and stiff limbs, and could be used as a diagnostic tool to assess K_vert asymmetry. Drop jumping tasks detected larger K_vert asymmetries than hopping, suggesting that asymmetries may be expressed to a greater extent in acyclic, maximal performance tasks.

KEYWORDS:

• Leg-spring behaviour
• centre of mass displacement
• spring-mass model

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

No benefits in any form have been or will be received from any commercial party or grant body related directly or indirectly in relation to this manuscript. The results of the current study do not constitute the endorsement of any product by the authors.