PEAK VS AVERAGE TORQUE OF KNEE EXTENSOR MUSCLE PERFORMANCE IN ELDERLY PATIENTS WITH KNEE OSTEOARTHROSIS

Abstract

478 Peak torque (PT) represents maximal capacity at one transitory point on the torque curve, whereas average torque (AT) represents maximal voluntary capacity throughout a range of motion. Although PT and AT are closely related in young, healthy individuals, this relationship may differ in individuals with knee pathology. Comparison of PT vs AT as the criterion measure for eccentric and concentric isokinetic testing has not been reported for elderly persons with knee osteoarthrosis (OA). We tested 106 subjects with OA of one or both knees (36 male, 70 female, 60-81 yo, X69 yrs). Physician diagnosis of OA was based on clinical and radiographic criteria. All patients were ambulatory, with or without aids. Isokinetic testing (acceleration-controlled, gravity-corrected) was conducted at 30 °/s; eccentric and concentric efforts were tested separately, through a range of 80 °-10 °. PT was greater than AT for both eccentric (117 vs 99 Nm) and concentric (88 vs 75 Nm) actions (p<0.01). Eccentric PT and AT were significantly higher than concentric PT and AT (p<0.01). Pearson correlation coefficients between PT and AT for eccentric (r=.95) and concentric (r=.98) were significant (p<0.01). PT/AT torque ratios did not differ between eccentric ([horizontal bar over]X=1.20±.11) and concentric ([horizontal bar over]X=1.18±.09) actions (p >0.05). Our findings from elderly patients with knee OA agree with previous reports from healthy young subjects:(1) a significant relationship between PT and AT for both eccentric and concentric knee extensor actions; (2) significant difference in magnitude between AT and PT measurements (3) similar PT/AT ratios for eccentric and concentric conditions at slow test velocity. The data suggest that, in this group, PT may be an adequate criterion measure of knee extensor capacity to generate torque throughout the motion during eccentric or concentric action, but that, as with young healthy persons, AT and PT cannot be used interchangeably.