Carbohydrate Oxidation in Elite Wheelchair Racers During Marathon Simulation

The timing of morning endurance competition may limit proper pre-race fueling and resulting performance. A nighttime, pre-sleep nutritional strategy could be an alternative method to target the metabolic and hydrating needs of the early morning athlete without compromising sleep or gastrointestinal comfort during exercise. Therefore, the purpose of this investigation was to examine the acute effects of pre-sleep chocolate milk (CM) ingestion on next-morning running performance, metabolism, and hydration status. Twelve competitive female runners and triathletes (age, 30 ± 7 years; peak oxygen consumption, 53 ± 4 mL·kg−1·min−1) randomly ingested either pre-sleep CM or non-nutritive placebo (PL) ∼30 min before sleep and 7–9 h before a morning exercise trial. Resting metabolic rate (RMR) was assessed prior to exercise. The exercise trial included a warm-up, three 5-min incremental workloads at 55%, 65%, and 75% peak oxygen consumption, and a 10-km treadmill time trial (TT). Physiological responses were assessed prior, during (incremental and TT), and postexercise. Paired t tests and magnitude-based inferences were used to determine treatment differences. TT performances were not different (“most likely trivial” improvement with CM) between conditions (PL: 52.8 ± 8.4 min vs CM: 52.8 ± 8.0 min). RMR was “likely” increased (4.8%) and total carbohydrate oxidation (g·min−1) during exercise was “possibly” or likely increased (18.8%, 10.1%, 9.1% for stage 1–3, respectively) with CM versus PL. There were no consistent changes to hydration indices. In conclusion, pre-sleep CM may alter next-morning resting and exercise metabolism to favor carbohydrate oxidation, but effects did not translate to 10-km running performance improvements.

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The relationship between human skeletal muscle pyruvate dehydrogenase phosphatase activity and muscle aerobic capacity

Journal of Applied Physiology ◽

10.1152/japplphysiol.00672.2010 ◽

2011 ◽

Vol 111 (2) ◽

pp. 427-434 ◽

Cited By ~ 8

Author(s):

Lorenzo K. Love ◽

Paul J. LeBlanc ◽

J. Greig Inglis ◽

Nicolette S. Bradley ◽

Jon Choptiany ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Content ◽

Endurance Training ◽

Aerobic Capacity ◽

Pyruvate Dehydrogenase ◽

Human Skeletal Muscle ◽

Citrate Synthase ◽

Tricarboxylic Acid Cycle ◽

Carbohydrate Oxidation ◽

Pyruvate Dehydrogenase Phosphatase

Pyruvate dehydrogenase (PDH) is a mitochondrial enzyme responsible for regulating the conversion of pyruvate to acetyl-CoA for use in the tricarboxylic acid cycle. PDH is regulated through phosphorylation and inactivation by PDH kinase (PDK) and dephosphorylation and activation by PDH phosphatase (PDP). The effect of endurance training on PDK in humans has been investigated; however, to date no study has examined the effect of endurance training on PDP in humans. Therefore, the purpose of this study was to examine differences in PDP activity and PDP1 protein content in human skeletal muscle across a range of muscle aerobic capacities. This association is important as higher PDP activity and protein content will allow for increased activation of PDH, and carbohydrate oxidation. The main findings of this study were that 1) PDP activity ( r2 = 0.399, P = 0.001) and PDP1 protein expression ( r2 = 0.153, P = 0.039) were positively correlated with citrate synthase (CS) activity as a marker for muscle aerobic capacity; 2) E1α ( r2 = 0.310, P = 0.002) and PDK2 protein ( r2 = 0.229, P =0.012) are positively correlated with muscle CS activity; and 3) although it is the most abundant isoform, PDP1 protein content only explained ∼18% of the variance in PDP activity ( r2 = 0.184, P = 0.033). In addition, PDP1 in combination with E1α explained ∼38% of the variance in PDP activity ( r2 = 0.383, P = 0.005), suggesting that there may be alternative regulatory mechanisms of this enzyme other than protein content. These data suggest that with higher muscle aerobic capacity (CS activity) there is a greater capacity for carbohydrate oxidation (E1α), in concert with higher potential for PDH activation (PDP activity).

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Carbohydrate Oxidation Rates in Patients With Anorexia Nervosa

Journal of Parenteral and Enteral Nutrition ◽

10.1177/014860719401800317 ◽

1994 ◽

Vol 18 (3) ◽

pp. 281-282

Author(s):

Richard E. Goldstein

Keyword(s):

Anorexia Nervosa ◽

Carbohydrate Oxidation ◽

Oxidation Rates

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Oxidation of combined ingestion of glucose and fructose during exercise

Journal of Applied Physiology ◽

10.1152/japplphysiol.00974.2003 ◽

2004 ◽

Vol 96 (4) ◽

pp. 1277-1284 ◽

Cited By ~ 132

Author(s):

Roy L. P. G. Jentjens ◽

Luke Moseley ◽

Rosemary H. Waring ◽

Leslie K. Harding ◽

Asker E. Jeukendrup

Keyword(s):

Power Output ◽

Statistical Significance ◽

Random Order ◽

Carbohydrate Oxidation ◽

Maximum Power ◽

The Other ◽

Cycling Exercise ◽

Oxidation Rates ◽

Maximum Power Output ◽

Exercise Period

The purpose of the present study was to examine whether combined ingestion of a large amount of fructose and glucose during cycling exercise would lead to exogenous carbohydrate oxidation rates >1 g/min. Eight trained cyclists (maximal O2consumption: 62 ± 3 ml·kg-1·min-1) performed four exercise trials in random order. Each trial consisted of 120 min of cycling at 50% maximum power output (63 ± 2% maximal O2consumption), while subjects received a solution providing either 1.2 g/min of glucose (Med-Glu), 1.8 g/min of glucose (High-Glu), 0.6 g/min of fructose + 1.2 g/min of glucose (Fruc+Glu), or water. The ingested fructose was labeled with [U-13C]fructose, and the ingested glucose was labeled with [U-14C]glucose. Peak exogenous carbohydrate oxidation rates were ∼55% higher ( P < 0.001) in Fruc+Glu (1.26 ± 0.07 g/min) compared with Med-Glu and High-Glu (0.80 ± 0.04 and 0.83 ± 0.05 g/min, respectively). Furthermore, the average exogenous carbohydrate oxidation rates over the 60- to 120-min exercise period were higher ( P < 0.001) in Fruc+Glu compared with Med-Glu and High-Glu (1.16 ± 0.06, 0.75 ± 0.04, and 0.75 ± 0.04 g/min, respectively). There was a trend toward a lower endogenous carbohydrate oxidation in Fruc+Glu compared with the other two carbohydrate trials, but this failed to reach statistical significance ( P = 0.075). The present results demonstrate that, when fructose and glucose are ingested simultaneously at high rates during cycling exercise, exogenous carbohydrate oxidation rates can reach peak values of ∼1.3 g/min.

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Gastric emptying, absorption, and carbohydrate oxidation during prolonged exercise

Journal of Applied Physiology ◽

10.1152/jappl.1992.72.2.468 ◽

1992 ◽

Vol 72 (2) ◽

pp. 468-475 ◽

Cited By ~ 86

Author(s):

N. J. Rehrer ◽

A. J. Wagenmakers ◽

E. J. Beckers ◽

D. Halliday ◽

J. B. Leiper ◽

...

Keyword(s):

Gastric Emptying ◽

Crossover Study ◽

Water Absorption ◽

Water Uptake ◽

Prolonged Exercise ◽

Carbohydrate Oxidation ◽

O2 Consumption ◽

Digestive Function ◽

Jejunal Perfusion ◽

Over Time

This study was designed to examine aspects of digestive function that may limit assimilation of water and oxidation of orally ingested carbohydrate (CHO) during exercise. Eight males completed a crossover study in which each cycled on four occasions for 80 min at 70% maximal O2 consumption. Beverage was consumed at 0, 20, 40, and 60 min. Beverages were water, 4.5% glucose (4.5G), 17% glucose (17G), and 17% maltodextrin (17MD). CHO beverages contained 20 meq/l NaCl and were 13C enriched to measure exogenous CHO oxidation. Gastric (beverage) volume was measured at 80 min. Water uptake was estimated by including 2H2O in the beverage and measuring 2H accumulation in blood. Jejunal perfusion tests were conducted at rest with the same subjects and beverages. In 60 min, 1,294 +/- 31 (SE) ml were ingested; at 80 min, volumes emptied with H2O (1,257 +/- 32 ml) and 4.5G (1,223 +/- 32 ml) were greater than with 17G (781 +/- 56 ml) and 17MD (864 +/- 71 ml; P less than 0.05). Total CHO oxidized was similar with all beverages, but there was a greater increase in exogenous CHO oxidation over time with 17G and 17MD than with 4.5G; 54, 19, and 18% of the CHO ingested with 4.5G, 17G, and 17MD, respectively, was oxidized. This represents 57, 32, and 27%, respectively, of the CHO emptied from the stomach. 2H accumulation in the blood was more rapid with H2O and 4.5G than with 17G or 17MD. Net jejunal water absorption was greater from 4.5G than from water. Net water absorption was also observed from 17MD, whereas net secretion was observed with 17G.(ABSTRACT TRUNCATED AT 250 WORDS)

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