Cycling cleat positioning affects Achilles tendon strain, but at what cost?

Cyclists face a high risk of developing Achilles and/or patellar tendinopathy (de Bernardo et al. 2012), which are painful overuse injuries with lengthy recovery times. While tendinopathies likely occur from both biological and mechanical factors, they may be characterized using mechanical fatigue principles (Edwards, 2018). Peak Achilles (AT) and patellar (PT) tendon strains represent pertinent metrics to examine overuse injury risk, as both are highly correlated with fatigue life (i.e. the number of repetitive loading cycles to tissue failure). Cycling cleat fore/aft positioning is an extrinsic intervention to potentially alter peak AT/PT strains, yet its effect remains unknown. From a performance standpoint, cycling cleat position may also affect the energetic cost of cycling as altered tendon strains may influence muscle contraction dynamics (Lichtwark & Wilson, 2007). We hypothesized that posterior cleat positioning would reduce peak AT and PT tendon strains by shortening the moment arms of these tendons and that posterior cleat positioning would increase the energetic cost of cycling, due to suboptimal muscle contraction dynamics.