THE INFLUENCE OF SEAT POSITION ON LOWER EXTREMITY MECHANICS DURING RECUMBENT STEPPING

Abstract

Recumbent stepping ergometers are effective for improving cardiovascular and muscular fitness, which are often goals of rehabilitation. Stationary cycling ergometers have traditionally filled this role. Seat position is normally an important variable that clinicians must consider relative to joint kinetics during cycling especially for individuals with lower extremity limitations. However, few data are available concerning recumbent steppers, seat position, and lower extremity mechanics. PURPOSE To evaluate the magnitude of hip and knee moments, knee reaction forces, and knee flexion angle during recumbent stepping. METHODS Twelve healthy males with no history of lower extremity injury participated (mean ±SD, age: 21.2 ±2.0 y; height: 1.77 ±0.05 m; mass: 76.3 ±11.5 kg). Subjects were videotaped with a pair of 60Hz cameras as they performed moderate (RPE=3, cadence=80 steps/min) exercise on a recumbent stepper. Four seat positions were used resulting in minimum knee flexion angles of 0° (full extension), 15°, 30°, and 45°. The right pedal of the stepper was fitted with a load cell to measure the forces and moments creates by the foot against the pedal. Video and force data were synchronized and combined with anthropometric data from each subject's right leg to perform an inverse dynamics analysis of the lower extremity. Peak flexion/extension moments for the hip and knee were extracted, as well as, anterior/posterior knee forces, proximal/distal knee forces, and maximum knee flexion angles. RESULTS Maximum knee flexion angle increased from the 0° initial seat position to the 45° initial seat position (p = .019). Hip and knee kinetics were not different across seat positions (p > .05). CONCLUSION Our results indicate that seat position does not influence lower extremity mechanics during recumbent stepping for healthy individuals exercising at moderate workloads. Contrary to rehabilitation performed on a stationary cycle, initial seat position on a recumbent stepper may not be an issue for clinicians when joint kinetics are the primary concern. Supported by NuStep, Inc. (UPN 01061905).