Relationship of knee extensor strength and hopping test performance in the assessment of lower extremity function.

Traditionally, open kinetic chain rehabilitation and evaluation have been used as the primary tool to assess a patient's strength and readiness to progress to a higher functional level. More recently, closed kinetic chain activities have been developed and well documented as an alternate means to prepare and evaluate a patient's ability to return to a higher functional level. However, a dearth in recent literature comparing the correlation between an open kinetic chain isokinetic strength test and performance on a functional performance test exists. Therefore, the purpose of this study was to examine the relationship between a knee extensor strength and functional performance test, specifically the one-legged hop for distance. Twenty subjects (mean = 20.7 years), with no prior history of lower extremity injury, participated in the study consisting of isokinetic evaluation of the quadriceps muscle using a Kinetic Communicator and a one-legged hop for distance. Isokinetic testing was performed at 240 degrees/sec. All tests were performed on the dominant and nondominant limbs. Pearson product moment correlation coefficients for peak torque and distance hopped were .78 for the dominant leg and .65 for the nondominant leg (p < .05). These results support the belief that isokinetic strength does not correlate strongly with functional tasks.