Effects of recumbent and upright bicycle exercises on knee joint cartilage and lower extremity muscles

Bicycle is an increasingly popular means of transportation, entertainment, and exercise. It is also very popular for use in recreation and various rehabilitation areas. However, there is limited research on the effects of cycling exercises on knee joint cartilage. Using two different bicycles, this study aimed to investigate the effects of exercise on healthy knee joint cartilage and lower extremity muscle thickness. This is a non-randomized prospective study. Age- and gender-matched participants were enrolled in two groups: 17 participants for recumbent bike (9 men and 8 women, aged 18-35 years) and 17 participants for upright bike (8 men and 9 women, aged 18-35 years). Using ultrasound, distal femoral cartilage thickness and regional muscle thickness of the lower limb were evaluated before and after six-week cycling exercises (20 min, 3 days/week, 60 RPM (±5) at a work rate of 60 watts). No statistically significant difference was observed between/within the groups in terms of changes in medial, intercondylar and lateral distal femoral condyle cartilage thicknesses (all p > 0.05). Posterior thigh muscle thicknesses decreased significantly in the upright bicycle group (both p < 0.05). Recumbent and upright cycling exercises seem to exert similar/no effects on knee joint cartilage and regional muscle thickness (except posterior thigh) after six weeks.