Carbohydrate Mouth Rinsing Does Not Prevent the Decline in Maximal Strength Following Fatiguing Exercise

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Abstract

Carbohydrate (CHO) rinsing has been shown to attenuate the decline of maximal voluntary contractions (MVC) following fatiguing exercise—perhaps via a central mechanism. This study sought to determine the effect of a CHO rinse on MVC, voluntary activation, and contractile properties following fatiguing exercise. Thirteen adults participated in a double-blind, cross-over study. MVC of the dominant knee extensors was assessed and voluntary activation (%VA) was determined using twitch-interpolation. Participants then held 50% of MVC until volitional fatigue followed by a 20s rinse with a solution of 8% maltodextrin (CHO) or placebo (PLA). MVC and %VA were reassessed immediately and 5-minutes following exercise. MVC did not differ between the CHO and PLA conditions initially (230±90 vs. 232±90 Nm; p=0.69). MVC declined following exercise (p≤0.01), but no differences were found between the CHO and PLA conditions (p≥0.59). %VA did not differ between conditions (91.9±2.9% vs. 91.5±3.8%; p≥0.11) nor did it change following exercise(p=0.57). Twitch torque (TT), rate of torque development, and rate of torque relaxation were reduced following exercise (p<0.05), but were unaffected by CHO rinsing (p>0.05). Unlike a previous study, a CHO rinse did not preserve MVC following fatiguing exercise. This was likely due to a lack of central fatigue induced by the exercise protocol (as %VA was unaffected) as the CHO rinse is thought to work via a central mechanism.

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