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

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Black, CD, Schubert, DJ, Szczyglowski, MK, and Wren, JD. Carbohydrate mouth rinsing does not prevent the decline in maximal strength after fatiguing exercise. J Strength Cond Res 32(9): 2466–2473, 2018—Carbohydrate (CHO) rinsing has been shown to attenuate the decline of maximal voluntary contractions (MVCs) after fatiguing exercise—perhaps through a central mechanism. This study sought to determine the effect of a CHO rinse on MVC, voluntary activation, and contractile properties after fatiguing exercise. Thirteen adults participated in a double-blind, cross-over study. Maximal voluntary contraction 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 20-second rinse with a solution of 8% maltodextrin (CHO) or placebo (PLA). Maximal voluntary contraction and %VA were reassessed immediately and 5 minutes after exercise. Maximal voluntary contraction did not differ between the CHO and PLA conditions initially (230 ± 90 vs. 232 ± 90 N·m; p = 0.69). Maximal voluntary contraction declined after 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 after exercise (p = 0.57). Twitch torque, rate of torque development, and rate of torque relaxation were reduced after exercise (p ≤ 0.05) but were unaffected by CHO rinsing (p > 0.05). Unlike a previous study, a CHO rinse did not preserve MVC after 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 through a central mechanism.

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