Effect of chainring ovality on joint power during cycling at different workloads and cadences

Non-circular chainrings theoretically enhance cycling performance by increasing effective chainring diameter and varying crank velocity, but research has failed to consistently reproduce the benefits in cycling trials. The aim of this study was (1) to investigate the effect of different chainring shapes on sagittal knee joint moment and sagittal lower limb joint powers and (2) to investigate whether alterations are affected by cadence and workload. Fourteen elite cyclists cycled in six conditions (70, 90 and 110 rpm, each at 180 and 300 W), for 2 min each, using three chainrings of different ovalities (1.0–1.215). Kinematic data and pedal forces were collected. For most conditions, only the chainring with the highest ovality (1.215) was characterised by smaller sagittal knee joint moments, smaller relative sagittal knee joint power contribution and larger relative sagittal hip joint power contribution, which suggests a change from maximising efficiency to maximising power production. Effect sizes increased with higher cadences, but not with higher workload. This study has application for athletes, clinicians and sports equipment industry as a non-circular chainring can change joint-specific power generation and decrease knee joint moment, but certain ovality seems to be necessary to provoke this effect.     

Does local dynamic stability of kayak paddling technique affect the sports performance? A pilot study

During competition, kayak athletes must optimally adapt to environmental factors (e.g. wind, waves) to achieve peak performance. However, the ability to adapt to such perturbations has never been assessed in kayak paddling. Therefore, the aim of the current study was to evaluate the local dynamic stability in sports technique of youth sprint kayak athletes. In a cross-sectional study, 14 healthy male athletes were recruited from an elite youth sprint kayak squad. During an incremental kayak ergometer test, mean power, heart rates and local dynamic technique stability of hands, arms, trunk and paddle were registered and the association with the athletes 2000?m free-water times were estimated using mixed models. The 2000?m free-water performance significantly predicted the paddles (p?=?.037) local dynamic stability whereas no association was found for the trunk or the upper extremity kinematics. In conclusion, kayak athletes with high-performance capability over 2000?m paddling depict high local dynamic technique stability. This emphasizes the importance of a stable technique for advanced kayak skills, especially regarding paddling movements.