The lower extremity dexterity test as a measure of lower extremity dynamical capability

The capability of the lower extremity to dynamically interact with the ground is important for skilled locomotor performance. However, there is currently no test method designed to specifically quantify this sensorimotor ability, which we refer to as lower extremity dexterity. We describe a new method to quantify lower extremity dexterity, examine its reliability (n=10), and evaluate the extent to which it is associated with lower extremity strength and anthropometry in healthy young adults (n=38). The lower extremity dexterity test (LED-test)-an adaptation of the Strength-Dexterity test for the fingers-consists of using the isolated lower extremity to compress a slender spring prone to buckling at low forces. The goal of the LED-test is to sustain the highest compression force possible. Applying higher forces makes the spring increasingly unstable, thus achieving higher compression forces represents better ability to dynamically control instability at low force levels. As such, the LED-test provides a novel way to quantify the capability of the lower extremity to regulate dynamic and unstable foot-ground interactions at submaximal forces. LED-test performance ranged between 88.6 and 119.6 N, test-retest reliability was excellent (ICC(2,3)=0.94), and the minimal detectable difference was 5.5 N. Performance was not correlated with strength or height (r2≤0.053, p>0.05), and only weakly with body mass (r2=0.116, p=0.04). We propose that the unique lower extremity capability quantified by the LED-test could be informative of skilled locomotor performance and injury risk.