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 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. 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.Keywords: Hand Cycle; Grinding; Upper body; America's Cup; Sailing INTRODUCTIONArm-cranking, in particular standing arm-cranking has become increasingly popular as a means of assessing upper-limb performance (2, 6, 17). However, the optimal configurations for power production during arm-cranking have not been determined. In cycling, the manipulation of joint angles, through changes in the structure of bicycle components, has been shown to influence performance (5, 10, 21). For example, changes in seat height and cycle crank lengths directly affect hip and knee joint angles, the range of motion and angular velocity of the joints, and thus cycling performance (21). The optimal crank length for maximum power production has been reported to be 20% of leg length (10) and the optimal seat height appears to be 109% of inseam length (ischium to ground when standing) (5). It seems highly likely therefore that changes to the configuration of arm-crank ergometry, specifically crank length and crank-axle height, could also affect performance. Given the angle-torque and torque-velocity relationships of human muscle function, there is a clear rationale for how interventions that effect upper extremity joint range of motion and angular velocities may influence arm cranking performance.Big-boat yacht racing is one of the only able bodied sports where arm-cranking is the primary ph...
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