Influence of Crank Length and Crank-Axle Height on Standing Arm-Crank (Grinding) Power

OBJECTIVE: To determine the optimal crank length and crank-axle height for maximum power production during standing arm cranking ("grinding"). METHODS: Nine elite professional America's Cup grinders (age = 36 +/- 2 yr, 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 power crank. 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, 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 with 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 ground reaction force was also reduced compared with all other heights, indicating greater weight bearing by the upper body. CONCLUSIONS: 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.