The effect of prior knowledge of test endpoint on the expression of non-local muscle fatigue

Abstract

To clarify if prior knowledge of test endpoint has an effect on the expression of nonlocal muscle fatigue (NLMF), fifteen male participants (22.4 ± 3.8 years) completed four conditions: 1) KN-fatigue (known endpoint after fatigue), 2) UNK-fatigue (unknown endpoint after fatigue), 3) KN-control (known endpoint without fatigue), 4) UNK-control (unknown endpoint without fatigue). For fatigue conditions, a maximal intensity, unilateral knee extension protocol was completed (two sets of 100s maximal voluntary contractions (MVIC), 60s rest between); control conditions involved rest (260s). The duration of a post-intervention strength-endurance test (contralateral leg extension, ≥30 seconds) was known (KN conditions) or unknown (UNK conditions) by the participant. UNK-fatigue demonstrated the largest anticipatory decreases from pre-MVIC to the start of the strength-endurance test (-18.9% MVIC force, and -25.6% VM RMS EMG). During the strength-endurance test, the UNK-fatigue and KN-control conditions displayed clinically meaningful differences in force (UNK-fatigue 12%↓ over first 30s), which were largest at epoch 6 (UNK-fatigue 21.6%↓ from 25-30s).