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Alexander J. Koch, Jeffrey A. Potteiger, Marcia A. Chan, Stephen H. Benedict and Bruce B. Frey

The effect of carbohydrate supplementation (CHO) on the lymphocyte response to acute resistance exercise was examined in 10 resistance-trained males. Subjects completed a randomized double-blind protocol with sessions separated by 14 days. The exercise session consisted of a high intensity, short rest interval squat workout. Subjects consumed 1.0 g · kg body mass−1 CHO or an equal volume of placebo (PLC) 10 min prior to and 10 min following exercise. Blood was collected at rest (REST), immediately post exercise (POST), and at 1.5 hours and 4.0 hours of recovery, and analyzed for plasma glucose, serum cortisol, leukocyte subsets, and phytohemagglutinin (PHA)-stimulated lymphocyte proliferation. A significant Treatment × Time effect was observed for lymphocyte proliferation between CHO and PLC, but post hoc analyses revealed no between-treatment differences at any post-exercise time point. Lymphocyte proliferation was significantly depressed below REST at POST (−39.2% for PLC, −25.7% for CHO). Significant fluctuations in leukocyte subset trafficking were observed for both treatments at POST, 1.5 hours, and 4.0 hours. Plasma glucose was significantly increased POST in CHO compared to PLC. Cortisol was significantly increased from REST to POST in both treatments. These data support a minimal effect of carbohydrate ingestion on the lymphocyte response to high-intensity resistance exercise.

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Marcia A. Chan, Alexander J. Koch, Stephen H. Benedict and Jeffrey A. Potteiger

The effect of carbohydrate supplementation (CHO) on interleukin 2 (IL-2) and interleukin 5 (IL-5) secretion following acute resistance exercise was examined in 9 resistance-trained males. Subjects completed a randomized, double-blind protocol with exercise separated by 14 days. The exercise consisted of a high intensity, short rest interval squat workout. Subjects consumed 1.0 g · kg body mass-1 CHO or an equal volume of placebo (PLC) 10 min prior to and 10 min following exercise. Blood was collected at rest (REST), immediately post exercise (POST), and at 1.5 h of recovery (1.5 h POST). Isolated peripheral blood mononuclear cells were stimulated with PHA and assayed for IL-2 and IL-5 secretion. IL-2 secretion was significantly decreased at POST for both the PLC and CHO groups. However, the degree of decrease was less in the CHO group (16%) than in the PLC group (48%), and this difference was statistically significant. These responses were transient, and the values returned to normal by 1.5 h POST. A mild and transient but significant decrease in IL-5 secretion by the PLC group was observed at POST (26%) compared to REST. No significant decrease was observed in IL-5 secretion for CHO from REST to POST (12%). These data support a possible effect of carbohydrate supplementation on IL-2 and IL-5 secretion following high-intensity resistance exercise.

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Michael C. Riddell, Oded Bar-Or, Beatriz V. Ayub, Randolph E. Calvert and George J.F. Heigenhauser

There are currently no guidelines regarding the carbohydrate (CHO) dosage required to prevent exercise-induced hypoglycemia in children with insulin-dependent diabetes mellitus (IDDM). To prevent hypoglycemia by matching glucose ingestion with total-CHO utilization, 20 adolescents with IDDM attended 2 trials: control (CT; drinking water) and glucose (GT; drinking 6-8% glucose). Participants performed 60 min of moderate-intensity cycling 100 min after insulin injection and breakfast. CT's total-CHO utilization during exercise was determined using indirect calorimetry. In GT, participants ingested glucose in the amount equal to total CHO utilization in the CT. A total of 9 participants had BG <4.0 mmol/L in CT compared to 3 in GT (p < .05). In conclusion, glucose ingestion equal to total-CHO utilization attenuates the drop in blood glucose and reduces the likelihood of hypoglycemia during exercise in adolescents with IDDM.

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Stephanie K. Gaskell and Ricardo J.S. Costa

exercise-associated GIS, especially in recreationally competitive endurance athletes prone to GIS, but without IBS ( Lis et al., 2016a , 2018 ). FODMAPs are a collection of short-chain rapidly fermentable carbohydrates including fructose, lactose, polyols such as sorbitol and mannitol, galacto

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Edward A. Gray, Thomas A. Green, James A. Betts and Javier T. Gonzalez

Carbohydrate is the dominant energy source during moderate- to high-intensity exercise ( Romijn et al., 1993 ). Human carbohydrate stores are finite, with skeletal muscle and liver storing ∼500 g ( Jensen et al., 2011 ) and ∼100 g of glycogen ( Taylor et al., 1996 ), respectively. During moderate

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Christopher C. Webster, Jeroen Swart, Timothy D. Noakes and James A. Smith

Low-carbohydrate high-fat (LCHF) diets have gained in popularity among some ultraendurance athletes because they increase rates of fat oxidation during exercise and “spare” muscle glycogen. 1 However, prevailing opinion holds that carbohydrate restriction would compromise exercise performance at

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Jonathan P. Little, Philip D. Chilibeck, Dawn Ciona, Albert Vandenberg and Gordon A. Zello

The glycemic index (GI) of a pre exercise meal may affect substrate utilization and performance during continuous exercise.

Purpose:

To examine the effects of low- and high-GI foods on metabolism and performance during high-intensity, intermittent exercise.

Methods:

Seven male athletes participated in three experimental trials (low-GI, high-GI, and fasted control) separated by ~7 days. Foods were consumed 3 h before (~1.3 g·kg−1 carbohydrate) and halfway through (~0.2 g·kg−1 carbohydrate) 90 min of intermittent treadmill running designed to simulate the activity pattern of soccer. Expired gas was collected during exercise to estimate substrate oxidation. Performance was assessed by the distance covered on fve 1-min sprints during the last 15 min of exercise.

Results:

Respiratory exchange ratio was higher and fat oxidation lower during exercise in the high-GI condition compared with fasting (P < .05). The mean difference in total distance covered on the repeated sprint test between low GI and fasting (247 m; 90% confidence limits ±352 m) represented an 81% (likely, probable) chance that the low-GI condition improved performance over fasting. The mean difference between high GI and fasted control (223 m; ±385 m) represented a 76% (likely, probable) chance of improved performance. There were no differences between low and high GI.

Conclusions:

When compared with fasting, both low- and high-GI foods consumed 3 h before and halfway through prolonged, high-intensity intermittent exercise improved repeated sprint performance. High-GI foods impaired fat oxidation during exercise but the GI did not appear to influence high-intensity, intermittent exercise performance.

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Ching-Lin Wu and Clyde Williams

This study investigated the effects of ingesting a low (LGI) or high (HGI) glyce-mic index carbohydrate (CHO) meal 3 h prior to exercise on endurance running capacity. Eight male recreational runners undertook two trials (LGI or HGI) which were randomized and separated by 7 d. After an overnight fast (12 h) the subjects ingested either a LGI or HGI meal 3 h prior to running at 70% VO2max until exhaustion. The meals contained 2 g/kg body mass CHO and were isocaloric and iso-macronutrient with calculated GI values 77 and 37 for the HGI and LGI respectively. The run times for the LGI and HGI trials were 108.8 ± 4.1 min and 101.4 ± 5.2 min respectively (P = 0.038). Fat oxidation rates were higher during exercise after the LGI meal than after the HGI meal (P < 0.05). In summary, ingestion of a LGI meal 3 h before exercise resulted in a greater endurance capacity than after the ingestion of a HGI meal.

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Joanne G. Mirtschin, Sara F. Forbes, Louise E. Cato, Ida A. Heikura, Nicki Strobel, Rebecca Hall and Louise M. Burke

nutrition practices and food choices of three different sports nutrition philosophies (high carbohydrate [CHO] availability [HCHO], periodized CHO availability [PCHO], and the ketogenic low-CHO, high-fat [LCHF] diet), noting that these seem to be misunderstood across the scientific literature, social media

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Diana E. Thomas, John R. Brotherhood and Janette Brand Miller

It was hypothesized that slowly digested carbohydrates, that is, low glycemic index (GI) foods, eaten before prolonged strenuous exercise would increase the blood glucose concentration toward the end of exercise. Six trained cyclists pedaled on a cycle ergometer at 65-70% VO2max 60 min after ingestion of each of four test meals: a low-GI and a high-GI powdered food and a low-GI and a high-GI breakfast cereal, all providing 1 g of available carbohydrate per kilogram of body mass. Plasma glucose levels after more that 90 min of exercise were found to correlate inversely with the observed GI of the foods (p < .01). Free fatty acid levels during the last hour of exercise also correlated inversely with the GI (p < .05). The findings suggest that the slow digestion of carbohydrate in the preevent food favors higher concentrations of fuels in the blood toward the end of exercise.