Increased Fatigue Response to Augmented Deceptive Feedback during Cycling Time Trial.

PURPOSE: This study aimed to investigate the effect of different magnitudes of deception on performance and exercise-induced fatigue during cycling time trial.

METHODS: After three familiarization visits, three women and eight men performed three 5-km cycling time trials while following a simulated dynamic avatar reproducing either 100% (5K100%), 102% (5K102%), or 105% (5K105%) of the subject's previous fastest trial. Quadriceps muscle activation was quantified with surface electromyography. Fatigue was quantified by preexercise to postexercise (10 s through 15 min recovery) changes in quadriceps maximal voluntary contraction (MVC) force, potentiated twitch force evoked by electrical femoral nerve stimulation (QTSingle) and voluntary activation (VA, twitch interpolation technique).

RESULTS: Greater quadriceps muscle activation in 5K102% versus 5K100% (12% ± 11%) was found in parallel with a 5% ± 2% and 2% ± 1% improvement in power output and completion time, respectively (P < 0.01). Exercise-induced reduction in MVC force and VA were 14% ± 19% and 28% ± 31% greater at exercise termination (at 10 s), whereas QTSingle recovery (from 10 s to 15 min) was 5% ± 5% less in 5K102% versus 5K100% (P < 0.01). No difference in performance or fatigue indices measured at exercise termination was found between 5K100% and 5K105%.

CONCLUSIONS: Muscle activation and performance improvements during a deceptive cycling time trial were achieved only with a 2% magnitude of deception and were associated with a further impairment in MVC force, QTSingle recovery and VA compared to control. Performance improvement during cycling time trial with augmented deceptive feedback therefore resulted in exacerbated exercise-induced peripheral and central fatigue.