Eccentric and Concentric Resistance Exercise Comparison for Knee Osteoarthritis

Abstract

Introduction: This study aimed to compare the efficacy of eccentrically focused resistance exercise (ECC RT) to concentrically focused resistance exercise (CNC RT) on knee osteoarthritis (OA) symptoms and strength.

Methods: Ninety participants consented. Participants were randomized to CNC RT, ECC RT, or a wait-list, no-exercise control group. Four months of supervised exercise training was completed using traditional weight machines (CNC RT) or modified-matched machines that overloaded the eccentric action (ECC RT). Main outcomes included one-repetition maximal strength (knee extension, leg flexion, and leg press), weekly rate of strength gain, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) total score and subscores.

Results: Fifty-four participants (60-85 yr, 61% women) completed the study. Both CNC RT and ECC RT groups showed 16%-28% improvement relative to the wait-list, no-exercise control group (P = 0.003-0.005) for all leg strength measures. The rate of weekly strength gain was greater for CNC RT than for ECC RT for leg press and knee flexion (by 2.9%-4.8%; both, P < 0.05) but not knee extension (0.7%; P = 0.38). There were no significant differences in WOMAC total and subscores across groups over time. Leg press strength change was the greatest contributor to change in WOMAC total scores (R = 0.223). The change in knee flexion strength from baseline to month 4 was a significant predictor of the change in WOMAC pain subscore (F ratio = 4.84, df = 45, P = 0.032). Both modes of strength training were well tolerated.

Conclusions: Both resistance training types effectively increased leg strength. Knee flexion and knee extension muscle strength can modify function and pain symptoms irrespective of muscle contraction type. Which mode to pick could be determined by preference, goals, tolerance to the contraction type, and equipment availability.

Figure 1.

Study flow diagram. CNC RT= concentrically focused resistance exercise group, ECC RT = eccentrically focused resistance exercise group, wait-list control condition (CON).

Figure 2.

Change (pre- to post-intervention) in WOMAC scores for CNC RT group (dashed line), ECC RT group (dotted line) and CON group (solid grey line). Error bars represent 95% confidence intervals. A) WOMAC total scores, B) Pain sub-scores, C) Stiffness sub-scores, and D) Physical Function sub-scores.

Figure 3.

Change (pre- to post-intervention) in leg strength for concentric group (dashed line), eccentric group (dotted line) and control group (solid grey line). Error bars represent 95% confidence intervals.

Figure 4.

Mean percent (%) weekly improvement in leg strength for CNC RT group (white bars) and ECC RT group (black bars). Error bars represent 95% confidence intervals. There were statistically significant group differences for leg press and knee flexion weekly improvements.