A Short Maximal Effort Induces Greater Low-Frequency Fatigue than Prolonged Cycling in Highly-Trained Road Cyclists

This study aimed to investigate the sensitivity of low-frequency fatigue (LFF) in high-level road cyclists following two distinct cycling efforts: a 30-minute maximal effort (30'TT) and a 4-minute maximal effort (4'TT). Twenty-one participants were included in this study (age: 22.8 ± 4.8 years; height: 169.9 ± 3.5 cm; body mass: 68.5 ± 8.5 kg), and LFF, perceived fatigue and muscle soreness were monitored at baseline, 30 minutes and 24 hours post-fatigue protocol. Linear mixed model analysis was employed to assess the changes caused by protocol, time, and limb dominance, and a repeated-measures correlation was used to assess the association between LFF and perceived fatigue or muscle soreness. Significant fatigue was induced by both protocols (p < 0.001), with LFF scores returning to baseline after 24 hours. Notably, following the fatigue protocols, a significantly lower LFF score was observed after the 4'TT compared to the 30'TT (d = 0.39, p = 0.032). Furthermore, a large and significant association between LFF scores and perceived fatigue (rm_corr = -0.5, p < 0.001) was identified, as well as a weak and significant association between LFF and perceived muscle soreness (rm_corr = -0.28, p < 0.001). Taken together, these findings seem to support LFF as a sensitive, field-based tool for monitoring acute peripheral fatigue following cycling efforts.