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