An experiment was conducted varying bicycle crank length as a ratio of cyclist's crotch height over a range from 0.17 to 0.23. A light and a heavy load were used with ten young male subjects. Heart rate, oxygen consumption and perceived exertion measures were taken during bicycle ergometer pedaling sessions. All measures showed the superiority of a crank length of about 0.20 of crotch height (0.10 of standing height). A change of crank length of three percentage points of crotch height increases energy expenditure by one kcal/minute. The standard crank is too long for 60% of adult males and almost 100% of females. Varied crank lengths or adjustable cranks should be made available.
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