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Janet R. Wojcik, Janet Walberg-Rankin, Lucille L. Smith, and F.C. Gwazdauskas

This study examined effects of carbohydrate (CHO), milk-based carbohydrate-protein (CHO-PRO), or placebo (P) beverages on glycogen resynthesis, muscle damage, inflammation, and muscle function following eccentric resistance exercise. Untrained males performed a cycling exercise to reduce muscle glycogen 12 hours prior to performance of 100 eccentric quadriceps contractions at 120% of 1-RM (day 1) and drank CHO (n = 8), CHO-PRO (n = 9; 5 kcal/kg), or P (n = 9) immediately and 2 hours post-exercise. At 3 hours post-eccentric exercise, serum insulin was four times higher for CHO-PRO and CHO than P (p < .05). Serum creatine kinase (CK) increased for all groups in the 6 hours post-eccentric exercise (p < .01), with the increase tending to be lowest for CHO-PRO (p < .08) during this period. Glycogen was low post-exercise (33 ± 3.7 mmol/kg ww), increased 225% at 24 hours, and tripled by 72 hours, with no group differences. The eccentric exercise increased muscle protein breakdown as indicated by urinary 3-methylhistidine and increased IL-6 with no effect of beverage. Quadriceps isokinetic peak torque was depressed similarly for all groups by 24% 24 hours post-exercise and remained 21 % lower at 72 hours (p < .01). In summary, there were no influences of any post-exercise beverage on muscle glycogen replacement, inflammation, or muscle function.

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Harry E. Routledge, Jill J. Leckey, Matt J. Lee, Andrew Garnham, Stuart Graham, Darren Burgess, Louise M. Burke, Robert M. Erskine, Graeme L. Close, and James P. Morton

Invasive team sports such as soccer, 1 , 2 rugby league, 2 and Australian Football (AF) 2 , 3 are characterized by high-intensity (>19.8 km/h) intermittent activity profiles. Given the duration of activity (ie, 80–120 min) and high-intensity intermittent profiles, muscle glycogen is considered

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Devin G. McCarthy and Lawrence L. Spriet

of CHO oxidized at high intensity coming from muscle glycogen. 1 , 2 Although muscle glycogen provides an important energy source for skeletal muscle, stores are limited, and whole-muscle depletion is associated with exercise fatigue. 3 Skeletal muscle glycogen is a complex structure that is stored

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Laís Monteiro Rodrigues Loureiro, Caio Eduardo Gonçalves Reis, and Teresa Helena Macedo da Costa

& Clarke, 2016 ) exercises. After cessation of endurance exercise, muscle glycogen is typically restored to preexercise concentrations within 24 hr when sufficient amounts of high-glycemic-index carbohydrates (CHOs) (≥1.0 g/kg) are immediately ingested ( Burke et al., 2016 ). However, for athletes involved

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Samuel G. Impey, Kelly M. Hammond, Robert Naughton, Carl Langan-Evans, Sam O. Shepherd, Adam P. Sharples, Jessica Cegielski, Kenneth Smith, Stewart Jeromson, David L. Hamilton, Graeme L. Close, and James P. Morton

adopted an experimental design whereby male cyclists completed a nonexhaustive training session in which glycogen remained within an absolute concentration (i.e., pre- and postexercise concentrations of <350 and >100 mmol/kg·dry weight (dw), respectively) considered representative of train-low conditions

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Campbell Menzies, Michael Wood, Joel Thomas, Aaron Hengist, Jean-Philippe Walhin, Robbie Jones, Kostas Tsintzas, Javier T. Gonzalez, and James A. Betts

Energy metabolism during moderate- to high-intensity exercise is predominantly supported by carbohydrate oxidation ( Hawley & Leckey, 2015 ). Consequently, finite endogenous stores (i.e., glycogen) are progressively depleted and are implicated in the initiation of fatigue ( Bergström et al., 1967

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Sally P. Waterworth, Connor C. Spencer, Aaron L. Porter, and James P. Morton

In addition to its well-documented role as an energy source, it is now recognized that the glycogen granule exerts regulatory roles in modulating skeletal muscle cell signaling and transcriptional responses to acute exercise sessions ( Bartlett et al., 2015 ; Hearris et al., 2018 ). Accordingly

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Robert A. Robergs

During the initial hours of recovery from prolonged exhaustive lower body exercise, muscle glycogen synthesis occurs at rates approximating 1-2 mmol·kg−1 wet wt·hr1 if no carbohydrate is consumed. When carbohydrate is consumed during the recovery, the maximal rate of glycogen synthesis approximates 7-10 mmol·kg−1 wet wt·hr1. The rate of postexercise glycogen synthesis is lower if the magnitude of glycogen degradation is small, if less than 0.7 gm glucose·kg−1 body wt·hr1 is ingested, when the recovery is active, and when the carbohydrate feeding is delayed. The rate of postexercise glycogen synthesis is not reduced during the initial hours (< 4) after eccentric exercise. For studies evaluating muscle glycogen synthesis in excess of 12 hours of recovery, average rates of glycogen synthesis are balow 4 mmo1·kg−1 wet wt·hr1. Glycogen synthesis is known to be impaired for time periods in excess of 24 hours following exercise causing eccentric muscle damage. Following intense exercise resulting in high concentrations of muscle lactate, muscle glycogen synthesis occurs at between 15-25 mmol·kg−1 wet wt·hr1. These synthesis rates occur without ingested carbohydrate during the recovery period and are maintained when a low intensity active recovery is performed.

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David R. Lamb, Ann C. Snyder, and Thomas S. Baur

This study compared two high carbohydrate (CHO) diets in 14 male runners for effects on muscle glycogen deposition, endurance, and sensations of gastrointestinal discomfort. Muscle glycogen was measured in the vastus lateralis at rest and run time to exhaustion at 75 % VO2max was measured following 3-1/2 days on a 50% CHO diet. After 14 days the subjects consumed a 20% CHO diet and continued training to reduce glycogen. During the next 3-1/2 days, subjects ran less and consumed a 90% CHO diet emphasizing pasta and rice (Pasta, n=7) or lesser amounts of pasta and rice supplemented by a maltodextrin beverage (Supplement, n=7). Glycogen was again measured, followed by a second run to exhaustion. Compared to the 50% CHO diet, Pasta increased muscle glycogen by 27.1 ± 12.2 mmoles/kg muscle (M±SE; p < 0.05) and run time by 15.7±5.9 min; Supplement increased glycogen by 43.2 ± 13.5 mmoles/kg (p < 0.05) and run time by 29.0 ± 7.4 min (p < 0.05). Total glycogen concentrations and run times were not significantly different for Pasta versus Supplement. Subjects reported less gastrointestinal discomfort and greater overall preference for Supplement than for Pasta. Thus, glycogen loading can be accomplished at least as effectively and more comfortably by substituting a maltodextrin drink for some of the pasta and rice in a glycogen loading diet.

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Andy J. King, Joshua T. Rowe, and Louise M. Burke

CHO availability benefit from an exogenous CHO supply ( Stellingwerff & Cox, 2014 ), with mechanisms including fuel provision once muscle glycogen is depleted ( Coyle et al., 1986 ), spared liver ( Gonzalez et al., 2015 ; Wallis et al., 2006 ) and muscle ( King et al., 2018 ; Tsintzas et al., 1995