Suboptimal muscular performance: Measuring isokinetic strength of knee extensors with new testing protocol

Objective: To analyze the relevance of several isokinetics-based variables for the differentiation of suboptimal from optimal knee extension efforts. Design: Three experimental conditions using 4 intermittent-reciprocal concentric (Con) and eccentric (Ecc) efforts at 30/sec and 180/sec. The first condition (MAX) served as the baseline; subjects were instructed to exert maximal Con and Ecc effort. In the second condition (50%MAX), subjects were asked to exert 50% of the strength measured in the first condition based on the initial use of visual feedback. In the third condition (BREP), subjects repeated the second condition but were asked to exert what they thought was a reproducible level of strength. Setting: A motor performance laboratory in rehabilitation department of a major hospital. Participants: 16 healthy men, ages 21 to 30. Results: Among several parameters that included variability of results and Ecc/Con strength ratios, the one with the highest differentiating power among MAX, 50%MAX, and BREP was the difference between the Ecc/Con ratios at high and low velocities (P < .0006). Conclusions: Suboptimal knee extension effort can effectively be differentiated from optimal effort in healthy subjects using this protocol. (C) 1996 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation