To investigate the effects of daily mild supine exercise on physical performance capacity identified as maximal oxygen uptake rate (VO2max) after 20 days bedrest, 3 male students performed a supine pedaling at 40% intensity of VO2max for one hour every day, while 6 male and 5 female students were control. Before and after the bedrest, muscle mass and strength of exercising leg and cardiovascular responses during -40mmHg lower body negative pressure (LBNP) and moderate upright cycling exercise were measured. Despite the exercise programme VO2max was similarly decreased to the control subjects after bed-rest. The delta VO2max was correlated to delta % left ventricular fractional shortening during LBNP, and also % delta VO2max to % delta stroke volume of the moderate exercise (both p<0.05). The exercise programme should be too weak to maintain cardiovascular functions and thus to present the decrease in VO2max against prolonged bedrest as well as weightlessness stress.