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Grinding is integral to tacking and gybing manoeuvres in America’s Cup sailing. Grinding is a standing position cyclic upper body task requiring manual arm cranking of winches, which control movement of the mast and sails. Limited information exists on biomechanical factors involved in grinding performance. This thesis determined technique and muscular performance characteristics of sailors related to grinding performance, and effects of a training intervention on grinding performance. Reliability of grinding ergometer performance testing was evaluated across direction, load and heel conditions. In all conditions relative performance between individuals was consistent (r = 0.84-0.99) and the grinding performance test differentiated well between individuals. External work had lower overall variation (1.6-3.9%) than peak power (1.3-5.4%), especially when grinding against greater loads. Grinding performance was less consistent in heeled conditions (4.6-6.9%) than on the flat, but grinding direction did not affect reliability. Performance changes over 4% could be interpreted with confidence. Peak torque occurred at 95° (77 N m) and 35° (69 N m) for forward and backward grinding respectively (0° = grinding crank vertically up). Torque of >50 N m was maintained through 72% of the cycle during forward grinding but only 47% for backward grinding. Differences were attributed to a greater spread of active muscles throughout the cycle for forward grinding, and contrasting movements contributing most to torque – upper body push for forward grinding and pull for backward grinding. Variant characteristics of the two grinding directions provide some explanation for the significant advantage (+8.0%, p |
