The elliptical trainer was developed as an exercise machine to maximize the workouts while at the same time reducing joint impact forces. There have been no studies examining the loads on the knee joint during exercise on the elliptical trainer.
PURPOSE: To evaluate the knee joint reaction forces and moments during exercise at three different incline settings on the elliptical trainer exercise machine (Precor EFX).
METHODS: Twenty-six healthy individuals with no history of lower extremity injury and with previous experience exercising on an elliptical trainer volunteered for this study (age: 22.19 ±.85 y, 169.9 ±9.8 cm, 74.0 ± 19.3kg). Motion was captured with two cameras as subjects performed exercise (120 steps/min) at three workload conditions (13, 25, and 40 degree incline). The pedals of the elliptical were fitted with three orthogonal load cells. Video (60Hz) and force data (600Hz) were synchronized and used to perform an inverse dynamics analysis.
RESULTS: Statistical analyses (repeated measures ANOVA) revealed no significant differences in the mean peak anterior shear force at 13-, 25- and 40-degrees (149 N, 156 N, and 181 N, respectively) nor in the mean peak posterior shear force acting at the knee (110 N, 113 N, and 116 N, respectively). Mean peak compressive force increased significantly (p=.003) with increased ramp inclination. Compressive force values were 796 N, 833 N, and 864 Nat 13-, 25-, and 40-degrees, respectively. Knee joint moments also significantly changed with increased ramp inclination. The mean peak extension moment increased with 8 Nm at 13-degrees, 17 Nm at 25-degrees, and 38 Nm at 40-degrees (p=.000). The mean peak flexion moment values decreased across the ramp settings with 174 Nm at 13-degrees, 94 Nm at 25-degrees, and 47 Nm at 40-degrees (p=.000).
CONCLUSIONS: Exercising on an elliptical exercise machine does not generate large forces or moments at the knee joint although compressive forces and moments increase at higher incline workloads. Knee joint loads and moments while exercising on the elliptical were comparable to those previously collected for other exercises including running, walking, stair ascent and descent, and cycling. Pedal load cells provided by Precor, Inc.