Influence of crank length and crank-axle height on standing arm-crank (grinding) power

To determine the optimal crank length and crank-axle height for maximum power production during standing arm-cranking (‘grinding’). Nine elite professional America’s Cup grinders (age: 36 ± 2 y; body mass: 104 ± 1 kg; body fat 13 ± 2%) performed eight maximal 6 s sprints on an adjustable standing arm-crank ergometer fitted with an SRM powercrank. The protocol included crank lengths of 162, 199, 236 and 273 mm and crank-axle heights of 850, 950, 1050 and 1150 mm. Peak power, ground reaction forces (GRF) and joint angles were determined and compared for different crank lengths and crank-axle heights with repeated-measures ANOVA. Results: Peak power was significantly different between crank lengths (P=0.006), with 162 mm lower than all others (P<0.03). Optimal crank length was 12.3% of arm-span, or 241 ± 9 mm for this cohort of athletes. Peak power was significantly less for the crank-axle height of 850 mm compared to 1150 mm (P=0.01). The optimal crank-axle height for peak power was between 50 and 60% of stature (950-1150 mm in this study). Hip flexion was greater at the lowest crank-axle height (850 mm) than at 1050 and 1150 mm (P<0.01), and the resultant GRF was also reduced compared to all other heights, indicating greater weight bearing by the upper body. Changes in crank length and crank-axle height influence performance during maximal standing arm-crank ergometry. These results, suggest that standard leg-cycle crank lengths are inappropriate for maximal arm-cranking performance. In addition, a crank-axle height of <50% of stature, which is typically used in America’s Cup sailing, may attenuate performance.