Osteoarthritis (OA) is a degenerative disease of cartilage and bone tissue and the most common form of arthritis, accounting for US$ 10.5 billion in hospital charges in 2006. Obesity (OB) has been linked to increased risk of developing knee OA due to increased knee joint loads and varus-valgus misalignment. Walking is recommended as a weight-loss activity but it may increase risk of knee OA as OB gait increases knee loads. Cycling has been proposed as an alternative weight-loss measure, however, lack of studies comparing normal weight (NW) and OB subjects in cycling and gait hinder identification of exercises that may best prevent knee OA incidence. The objective of this work is to determine if cycling is a better weight-loss exercise than gait in OB subjects as it relates to knee OA risk reduction due to decreased knee loads. A stationary bicycle was modified to measure forces and moments at the pedals in three dimensions. A pilot experiment was performed to calculate resultant knee loads during gait and cycling for NW (n = 4) and OB (n = 4) subjects. Statistical analyses were performed to compare knee loads and knee angles, and to determine statistical significance of results (p < 0.05). Cycling knee loads were lower than gait knee loads for all subjects (p < 0.033). OB axial knee loads were higher than NW axial knee loads in gait (p = 0.004) due to the weight-bearing nature of gait. No differences were observed in cycling knee loads between NW and OB subjects, suggesting cycling returns OB knee loads and biomechanics to normal levels. The lack of significant results in cycling could be due to the small sample size used or because rider weight is supported by the seat. Limitations to this study include small sample size, soft tissue artifact, and experimental errors in marker placement. Future studies should correct these limitations and find knee joint contact force rather than knee resultant loads using v EMG-driven experiments. In conclusion, cycling loads were lower than gait loads for NW and OB subjects suggesting cycling is a better weight-loss exercise than gait in the context of reducing knee OA risk.

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