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Postexercise muscle glycogen synthesis with glucose, galactose, and combined galactose-glucose ingestion.
Podlogar, T, Shad, BJ, Seabright, AP, Odell, OJ, Lord, SO, Civil, R, Salgueiro, RB, Shepherd, EL, Lalor, PF, Elhassan, YS, et al
American journal of physiology. Endocrinology and metabolism. 2023;(6):E672-E681
Abstract
Ingested galactose can enhance postexercise liver glycogen repletion when combined with glucose but effects on muscle glycogen synthesis are unknown. In this double-blind randomized study participants [7 men and 2 women; V̇o2max: 51.1 (8.7) mL·kg-1·min-1] completed three trials of exhaustive cycling exercise followed by a 4-h recovery period, during which carbohydrates were ingested at the rate of 1.2 g·kg-1·h-1 comprising glucose (GLU), galactose (GAL) or galactose + glucose (GAL + GLU; 1:2 ratio). The increase in vastus lateralis skeletal-muscle glycogen concentration during recovery was higher with GLU relative to GAL + GLU [contrast: +50 mmol·(kg DM)-1; 95%CL 10, 89; P = 0.021] and GAL [+46 mmol·(kg DM)-1; 95%CL 8, 84; P = 0.024] with no difference between GAL + GLU and GAL [-3 mmol·(kg DM)-1; 95%CL -44, 37; P = 0.843]. Plasma glucose concentration in GLU was not significantly different vs. GAL + GLU (+ 0.41 mmol·L-1; 95%CL 0.13, 0.94) but was significantly lower than GAL (-0.75 mmol·L-1; 95%CL -1.34, -0.17) and also lower in GAL vs. GAL + GLU (-1.16 mmol·-1; 95%CL -1.80, -0.53). Plasma insulin was higher in GLU + GAL and GLU compared with GAL but not different between GLU + GAL and GLU. Plasma galactose concentration was higher in GAL compared with GLU (3.35 mmol·L-1; 95%CL 3.07, 3.63) and GAL + GLU (3.22 mmol·L-1; 95%CL 3.54, 2.90) with no difference between GLU + GAL (0.13 mmol·L-1; 95%CL -0.11, 0.37) and GLU. Compared with galactose or a galactose + glucose blend, glucose feeding was more effective in postexercise muscle glycogen synthesis. Comparable muscle glycogen synthesis was observed with galactose-glucose coingestion and exclusive galactose-only ingestion.NEW & NOTEWORTHY Postexercise galactose-glucose coingestion or exclusive galactose-only ingestion resulted in a lower rate of skeletal-muscle glycogen replenishment compared with exclusive glucose-only ingestion. Comparable muscle glycogen synthesis was observed with galactose-glucose coingestion and exclusive galactose-only ingestion.
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Desk based prompts to replace workplace sitting with stair climbing; a pilot study of acceptability, effects on behaviour and disease risk factors.
Mat Azmi, ISM, Wallis, GA, White, MJ, Puig-Ribera, A, Eves, FF
BMC public health. 2022;(1):1985
Abstract
BACKGROUND Prolonged sitting is associated with increased risk of obesity, type 2 diabetes and cardiovascular disease. Occupational sitting accounts for up to 50 h/week for employees. This pilot study assessed the acceptability of stair climbing as an interruption to sitting throughout working hours, and provided preliminary data of the effects on glucose and lipid profiles. METHODS A quasi-experimental design was conducted involving 16 sedentary office workers (five females and 11 males) for intervention (n = 8) and control groups (n = 8) with mean age of 36.38 (5.58). For the eight-week intervention, a continuous four-floor stair climb and descent was performed eight times/day spread evenly over the working day. A prompt to climb was presented on the participant's computer eight times/day. Participants in the experimental group recorded daily floors climbed and steps (measured using pedometers) in a weekly log sheet. Blood samples were collected pre and post intervention to test effects on fasting glucose and 2 h plasma glucose, triglycerides, and total (TC), LDL and HDL cholesterol. Experimental participants were interviewed at the end of the study. The Wilcoxon signed rank test was used to compare the median changes (pre-post) of the dependent variables. RESULTS On average, the experimental group climbed 121 floors/week when prompted. There were significant reductions in fasting blood glucose, TC and LDL, as well as the derived measures of 'bad' cholesterol and the TC/HDL ratio in the experimental group. Post-experimental interviews indicated that the interruption to sitting was well tolerated. CONCLUSION Prompted stair climbing activity had impacts on health outcomes and was found acceptable to employees at work. TRIAL REGISTRATION Ethics for this study was approved by Science, Technology, Engineering and Mathematics Ethical Review Committee, University of Birmingham with ethics reference number ERN_15_0491.
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New Horizons in Carbohydrate Research and Application for Endurance Athletes.
Podlogar, T, Wallis, GA
Sports medicine (Auckland, N.Z.). 2022;(Suppl 1):5-23
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Abstract
The importance of carbohydrate as a fuel source for exercise and athletic performance is well established. Equally well developed are dietary carbohydrate intake guidelines for endurance athletes seeking to optimize their performance. This narrative review provides a contemporary perspective on research into the role of, and application of, carbohydrate in the diet of endurance athletes. The review discusses how recommendations could become increasingly refined and what future research would further our understanding of how to optimize dietary carbohydrate intake to positively impact endurance performance. High carbohydrate availability for prolonged intense exercise and competition performance remains a priority. Recent advances have been made on the recommended type and quantity of carbohydrates to be ingested before, during and after intense exercise bouts. Whilst reducing carbohydrate availability around selected exercise bouts to augment metabolic adaptations to training is now widely recommended, a contemporary view of the so-called train-low approach based on the totality of the current evidence suggests limited utility for enhancing performance benefits from training. Nonetheless, such studies have focused importance on periodizing carbohydrate intake based on, among other factors, the goal and demand of training or competition. This calls for a much more personalized approach to carbohydrate recommendations that could be further supported through future research and technological innovation (e.g., continuous glucose monitoring). Despite more than a century of investigations into carbohydrate nutrition, exercise metabolism and endurance performance, there are numerous new important discoveries, both from an applied and mechanistic perspective, on the horizon.
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Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h-1 versus 90 g h-1 at different ratios.
Podlogar, T, Bokal, Š, Cirnski, S, Wallis, GA
European journal of applied physiology. 2022;(11):2393-2401
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PURPOSE This study aimed to investigate whether carbohydrate ingestion during 3 h long endurance exercise in highly trained cyclists at a rate of 120 g h-1 in 0.8:1 ratio between fructose and glucose-based carbohydrates would result in higher exogenous and lower endogenous carbohydrate oxidation rates as compared to ingestion of 90 g h-1 in 1:2 ratio, which is the currently recommended approach for exercise of this duration. METHODS Eleven male participants (V̇O2peak 62.6 ± 7 mL kg-1 min-1, gas exchange threshold (GET) 270 ± 17 W and Respiratory compensation point 328 ± 32 W) completed the study involving 4 experimental visits consisting of 3 h cycling commencing after an overnight fast at an intensity equivalent to 95% GET. During the trials they received carbohydrates at an average rate of 120 or 90 g h-1 in 0.8:1 or 1:2 fructose-maltodextrin ratio, respectively. Carbohydrates were naturally high or low in 13C stable isotopes enabling subsequent calculations of exogenous and endogenous carbohydrate oxidation rates. RESULTS Exogenous carbohydrate oxidation rates were higher in the 120 g h-1 condition (120-180 min: 1.51 ± 0.22 g min-1) as compared to the 90 g h-1 condition (1.29 ± 0.16 g min-1; p = 0.026). Endogenous carbohydrate oxidation rates did not differ between conditions (2.15 ± 0.30 and 2.20 ± 0.33 g min-1 for 120 and 90 g h-1 conditions, respectively; p = 0.786). CONCLUSIONS The results suggest that carbohydrate ingestion at 120 g h-1 in 0.8:1 fructose-maltodextrin ratio as compared with 90 g h-1 in 1:2 ratio offers higher exogenous carbohydrate oxidation rates but no additional sparing of endogenous carbohydrates. Further studies should investigate potential performance effects of such carbohydrate ingestion strategies.
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High rates of fat oxidation are maintained after the sleep low approach despite delayed carbohydrate feeding during exercise.
Podlogar, T, Free, B, Wallis, GA
European journal of sport science. 2021;(2):213-223
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Training with low carbohydrate availability enhances endurance training adaptations but training volume may be compromised. We explored whole-body metabolism and performance with delayed carbohydrate feeding during exercise undertaken following acute sleep-low training. We hypothesised this strategy would not suppress fat oxidation and would maintain exercise performance. The study involved three experimental trials and included 9 men and 1 woman (⩒O2peak = 58.8 ± 5.5 mL kg-1 min-1). Each trial started in the afternoon with an exhaustive cycling protocol. The following morning 1-h of steady-state cycling (SS) was followed by a time trial (TT). Carbohydrates (CHO) were not ingested in recovery from exhaustive exercise or during next day exercise in the Placebo trial (PLA); CHO were not ingested during recovery but were fed (15 g every ∼15-min) from 30-min into SS and continued during the TT in the delayed feeding trial (DELAY); CHO were provided during recovery (1.2 g/kg/h for 7 h) and next day exercise (as in DELAY) in a third condition (CHO). Exercise metabolism was assessed using indirect calorimetry and blood sampling. Fat oxidation rates during SS were similar in PLA (0.83 ± 0.17 g/min) and DELAY (0.78 ± 0.14 g/min) (p > 0.05) and higher than CHO (0.57 ± 0.27 g/min) (p < 0.05). There were no significant differences in TT performance (49.1 ± 10.7, 43.4 ± 7.6, 41.0 ± 7.9 min in PLA, DELAY and CHO, respectively; p > 0.05). Delayed carbohydrate feeding could be a strategy to maintain high-fat oxidation rates typically associated with exercise undertaken after the sleep-low approach to training but the acute performance effects remain inconclusive.
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Carb-conscious: the role of carbohydrate intake in recovery from exercise.
Gonzalez, JT, Wallis, GA
Current opinion in clinical nutrition and metabolic care. 2021;(4):364-371
Abstract
PURPOSE OF REVIEW The present review summarized evidence on the role of carbohydrates in recovery from exercise within the context of acute and chronic effects on metabolism and performance. RECENT FINDINGS Recent studies demonstrate that, in contrast to recovery of muscle glycogen stores, the recovery of liver glycogen stores can be accelerated by the co-ingestion of fructose with glucose-based carbohydrates. Three recent studies suggest this can extend time-to-exhaustion during endurance exercise tests. However, periodically restricting carbohydrate intakes during recovery from some training sessions to slow the recovery of liver and muscle glycogen stores may, over time, result in a modest increase in the ability to oxidize fat during exercise in a fasted state. Whether this periodized strategy translates into a performance advantage in the fed state remains to be clearly demonstrated. SUMMARY To maximize recovery of glycogen stores and the capacity to perform in subsequent endurance exercise, athletes should consider ingesting at least 1.2 g carbohydrate per kilogram body mass per hour - for the first few hours of recovery - as a mixture of fructose and glucose-based carbohydrates. However, if a goal is increased capacity for fat oxidation, athletes should consider restricting carbohydrate intakes during recovery from some key training sessions. VIDEO ABSTRACT http://links.lww.com/COCN/A15.
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The effect of calcium co-ingestion on exogenous glucose oxidation during endurance exercise in healthy men: A pilot study.
Narang, BJ, Wallis, GA, Gonzalez, JT
European journal of sport science. 2021;(8):1156-1164
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The benefits of high exogenous glucose availability for endurance exercise performance are well-established. Exogenous glucose oxidation rates are thought to be limited by intestinal glucose transport. Extracellular calcium in rodent intestine increases the translocation of the intestinal glucose transporter GLUT2 which, if translated to humans, could increase the capacity for exogenous glucose availability during exercise. Therefore, this pilot study aimed to explore the effect of calcium co-ingestion during endurance exercise on exogenous glucose oxidation in healthy men. Eight healthy men cycled for 2 h at 50% peak power output, ingesting either 1.2 g min-1 dextrose alone (GLU) or with the addition of 2000 mg calcium (GLU + CAL), in a randomised crossover design. Expired breath samples were collected to determine whole-body and exogenous glucose oxidation. Peak exogenous glucose oxidation during GLU was 0.83 ± 0.15 g min-1, and was not enhanced during GLU + CAL (0.88 ± 0.11 g min-1, p = 0.541). The relative contributions of exogenous carbohydrate (19 ± 3% vs. 20 ± 2%, p = 0.434), endogenous carbohydrate (65 ± 3% vs. 65 ± 3%, p = 0.822) and fat (16 ± 3% vs. 15 ± 3%, p = 0.677) to total substrate utilisation did not differ between trials. These results suggest the addition of calcium to glucose ingestion, at saturating glucose ingestion rates, does not appear to alter exogenous glucose oxidation during endurance exercise in healthy men.
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Pectin-Alginate Does Not Further Enhance Exogenous Carbohydrate Oxidation in Running.
Barber, JFP, Thomas, J, Narang, B, Hengist, A, Betts, JA, Wallis, GA, Gonzalez, JT
Medicine and science in sports and exercise. 2020;(6):1376-1384
Abstract
PURPOSE Maximizing carbohydrate availability is important for many endurance events. Combining pectin and sodium alginate with ingested maltodextrin-fructose (MAL + FRU + PEC + ALG) has been suggested to enhance carbohydrate delivery via hydrogel formation, but the influence on exogenous carbohydrate oxidation remains unknown. The primary aim of this study was to assess the effects of MAL + FRU + PEC + ALG on exogenous carbohydrate oxidation during exercise compared with a maltodextrin-fructose mixture (MAL + FRU). MAL + FRU has been well established to increase exogenous carbohydrate oxidation during cycling compared with glucose-based carbohydrates (MAL + GLU). However, much evidence focuses on cycling, and direct evidence in running is lacking. Therefore, a secondary aim was to compare exogenous carbohydrate oxidation rates with MAL + FRU versus MAL + GLU during running. METHODS Nine trained runners completed two trials (MAL + FRU and MAL + FRU + PEC + ALG) in a double-blind, randomized crossover design. A subset (n = 7) also completed a MAL + GLU trial to address the secondary aim, and a water trial to establish background expired CO2 enrichment. Participants ran at 60% V˙O2peak for 120 min while ingesting either water only or carbohydrate solutions at a rate of 1.5 g carbohydrate per minute. RESULTS At the end of 120 min of exercise, exogenous carbohydrate oxidation rates were 0.9 (SD 0.5) g·min with MAL + GLU ingestion. MAL + FRU ingestion increased exogenous carbohydrate oxidation rates to 1.1 (SD 0.3) g·min (P = 0.038), with no further increase with MAL + FRU + PEC + ALG ingestion (1.1 (SD 0.3) g·min; P = 1.0). No time-treatment interaction effects were observed for plasma glucose, lactate, insulin, or nonesterified fatty acids, or for ratings of perceived exertion or gastrointestinal symptoms (all, P > 0.05). CONCLUSION To maximize exogenous carbohydrate oxidation during moderate-intensity running, athletes may benefit from consuming glucose(polymer)-fructose mixtures over glucose-based carbohydrates alone, but the addition of pectin and sodium alginate offers no further benefit.
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Lipid Metabolism Links Nutrient-Exercise Timing to Insulin Sensitivity in Men Classified as Overweight or Obese.
Edinburgh, RM, Bradley, HE, Abdullah, NF, Robinson, SL, Chrzanowski-Smith, OJ, Walhin, JP, Joanisse, S, Manolopoulos, KN, Philp, A, Hengist, A, et al
The Journal of clinical endocrinology and metabolism. 2020;105(3)
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Following exercise, various metabolic changes occur which may be of benefit in fighting diseases such as type 2 diabetes and obesity. However, the degree of change may vary depending on whether the exercise has been performed pre or post meal consumption. This 6-week randomised crossover trial of 30 overweight or obese men aimed to determine the effect of exercising before or after breakfast on the use of fats and sugars by the body. The results showed that exercise before breakfast increased fat and sugar use in the body and also resulted in the alteration of eight genes associated with metabolism. Exercise before carbohydrate consumption also increased lipid use and improved insulin sensitivity, however body composition was similar regardless of when exercise was performed. It was concluded that exercising in the fasted state can optimise the body’s response without having to change intensity or effort. This study could be used by health care professionals to advise patients with obesity or overweight that exercising whilst in the fasted state could optimise their outcomes without having to increase exercise intensity or frequency.
Abstract
CONTEXT Pre-exercise nutrient availability alters acute metabolic responses to exercise, which could modulate training responsiveness. OBJECTIVE To assess acute and chronic effects of exercise performed before versus after nutrient ingestion on whole-body and intramuscular lipid utilization and postprandial glucose metabolism. DESIGN (1) Acute, randomized, crossover design (Acute Study); (2) 6-week, randomized, controlled design (Training Study). SETTING General community. PARTICIPANTS Men with overweight/obesity (mean ± standard deviation, body mass index: 30.2 ± 3.5 kg⋅m-2 for Acute Study, 30.9 ± 4.5 kg⋅m-2 for Training Study). INTERVENTIONS Moderate-intensity cycling performed before versus after mixed-macronutrient breakfast (Acute Study) or carbohydrate (Training Study) ingestion. RESULTS Acute Study-exercise before versus after breakfast consumption increased net intramuscular lipid utilization in type I (net change: -3.44 ± 2.63% versus 1.44 ± 4.18% area lipid staining, P < 0.01) and type II fibers (-1.89 ± 2.48% versus 1.83 ± 1.92% area lipid staining, P < 0.05). Training Study-postprandial glycemia was not differentially affected by 6 weeks of exercise training performed before versus after carbohydrate intake (P > 0.05). However, postprandial insulinemia was reduced with exercise training performed before but not after carbohydrate ingestion (P = 0.03). This resulted in increased oral glucose insulin sensitivity (25 ± 38 vs -21 ± 32 mL⋅min-1⋅m-2; P = 0.01), associated with increased lipid utilization during exercise (r = 0.50, P = 0.02). Regular exercise before nutrient provision also augmented remodeling of skeletal muscle phospholipids and protein content of the glucose transport protein GLUT4 (P < 0.05). CONCLUSIONS Experiments investigating exercise training and metabolic health should consider nutrient-exercise timing, and exercise performed before versus after nutrient intake (ie, in the fasted state) may exert beneficial effects on lipid utilization and reduce postprandial insulinemia.
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Impact of Post-Exercise Fructose-Maltodextrin Ingestion on Subsequent Endurance Performance.
Podlogar, T, Wallis, GA
Frontiers in nutrition. 2020;:82
Abstract
Background: Current sports nutrition guidelines recommend athletes ingest carbohydrates at 1.0-1.2 g·kg-1·h-1 to optimize repletion of muscle glycogen during short-term recovery from endurance exercise. However, they do not provide specific advice on monosaccharides (e.g., fructose or glucose) other than to ingest carbohydrates of moderate to high glycaemic index. Recent evidence suggests that combined ingestion of fructose and glucose in recovery leads to enhanced liver glycogen synthesis and that this translates into improvement of subsequent endurance capacity. Purpose: The purpose of the present study was to investigate whether consuming a combination of fructose and glucose as opposed to glucose alone during short-term recovery (i.e., 4 h) from exhaustive exercise would also improve subsequent pre-loaded cycle time trial (TT) performance. Methods: Eight participants (seven men, one woman; V∙ O2peak: 56.8 ± 5.0 mLO2·min-1·kg-1; Wmax: 352 ± 41 W) participated in this randomized double-blind study. Each experimental session involved a glycogen reducing exercise bout in the morning, a 4-h recovery period and 1-h of steady state (SS) exercise at 50% Wmax followed by a ~40-min simulated TT. During recovery carbohydrates were ingested at a rate of 1.2 g·kg-1·h-1 in the form of fructose and maltodextrin (FRU + MD) or dextrose and maltodextrin (GLU + MD) (both in 1:1.5 ratio). Substrate oxidation rates, including ingested carbohydrate oxidation, were determined during the steady state (SS). Blood samples were collected during recovery, during the SS exercise and at the end of the TT for determination of glucose and lactate concentrations. Results: There were no differences in TT performance [37.41 ± 3.45 (GLU + MD); 37.96 ± 5.20 min (FRU + MD), p = 0.547]. During the first 45-min of SS oxidation of ingested carbohydrates was greater in FRU + MD (1.86 ± 0.41 g-1·min-1 and 1.51 ± 0.37 g-1·min-1 for FRU + MD and GLU + MD, respectively; time x condition interaction p = 0.003) and there was a trend toward higher overall carbohydrate oxidation rates in FRU + MD (2.50 ± 0.36 g-1·min-1 and 2.31 ± 0.37 g-1·min-1 for FRU + MD and GLU + MD, respectively; p = 0.08). However, at 60-min of SS, differences in substrate oxidation disappeared. Conclusion: Ingestion of combined fructose and glucose compared to glucose only during recovery from an exhaustive exercise bout increased the ingested carbohydrate oxidation rate during subsequent exercise. Under the conditions studied, subsequent TT performance was not improved with fructose-glucose.