BACKGROUND Originally, the cranks of a handcycle were mounted with a 180° phase shift (asynchronous). However, as handcycling became more popular, the crank mode switched to a parallel mounting (synchronous) over the years. Differences between both modes have been investigated, however, not into great detail for propulsion technique or practice effects. Our aim is to compare both crank modes from a biomechanical and physiological perspective, hence considering force and power production as a cause of physiological outcome measures. This is done within a practice protocol, as it is expected that motor learning takes place in the early stages of handcycling in novices. METHODS Twelve able-bodied male novices volunteered to take part. The experiment consisted of a pre-test, three practice sessions and a post-test, which was subsequently repeated for both crank modes in a counterbalanced manner. In each session the participants handcycled for 3 × 4 minutes on a leveled motorized treadmill at 1.94 m/s. Inbetween sessions were 2 days of rest. 3D forces, handlebar and crank angle were measured on the left hand side. Kinematic markers were placed on the handcycle to monitor the movement on the treadmill. Lastly, breath-by-breath spirometry combined with heart-rate were continuously measured. The effects of crank mode and practice-based learning were analyzed using a two way repeated measures ANOVA, with synchronous vs asynchronous and pre-test vs post-test as within-subject factors. RESULTS In the pre-test, asynchronous handcycling was less efficient than synchronous handcycling in terms of physiological strain, force production and timing. At the post-test, the metabolic costs were comparable for both modes. The force production was, also after practice, more efficient in the synchronous mode. External power production, crank rotation velocity and the distance travelled back and forwards on the treadmill suggest that asynchronous handcycling is more constant throughout the cycle. CONCLUSIONS As the metabolic costs were reduced in the asynchronous mode, we would advise to include a practice period, when comparing both modes in scientific experiments. For handcycle users, we would currently advise a synchronous set-up for daily use, as the force production is more effective in the synchronous mode, even after practice.

中文翻译：

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身体健全的男性在基于实践的学习过程中同步和异步低强度骑行之间的生物力学和生理差异。

背景技术最初，手动自行车的曲柄安装有180°相移（异步）。然而，随着手动自行车变得越来越流行，曲柄模式多年来切换为平行安装（同步）。然而，这两种模式之间的差异已经被研究过，但并没有对推进技术或实践效果进行详细研究。我们的目标是从生物力学和生理学角度比较两种曲柄模式，因此将力和功率产生视为生理结果测量的原因。这是在练习方案中完成的，因为预计运动学习发生在新手手动骑行的早期阶段。方法 12 名身体健全的男性新手自愿参加。该实验包括一次预测试、三轮练习和一次后测试，随后以平衡的方式对两种曲柄模式重复进行该测试。在每次训练中，参与者在水平机动跑步机上以 1.94 m/s 的速度徒手骑行 3 × 4 分钟。会议期间有 2 天休息时间。3D 力、车把和曲柄角度是在左侧测量的。运动标记被放置在手动自行车上以监测跑步机上的运动。最后，连续测量每次呼吸肺活量测定和心率。使用双向重复测量方差分析来分析曲柄模式和基于实践的学习的效果，其中同步与异步以及测试前与测试后作为受试者内因素。结果在预测试中，异步手动循环在生理应变、力量产生和计时方面的效率低于同步手动循环。在事后测试中，两种模式的代谢成本相当。经过实践，同步模式下的力产生效率更高。外部发电量、曲柄转速以及跑步机上前后移动的距离表明，异步手动骑行在整个周期中更加稳定。结论 由于异步模式下的代谢成本降低，我们建议在科学实验中比较两种模式时包括一个练习期。对于手动自行车用户，我们目前建议日常使用同步设置，因为即使在练习之后，在同步模式下发力也更有效。