Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion

Abstract

The time of ingestion of a carbohydrate supplement on muscle glycogen storage postexercise was examined. Twelve male cyclists exercised continuously for 70 min on a cycle ergometer at 68% VO2max, interrupted by six 2-min intervals at 88% VO2max, on two separate occasions. A 25% carbohydrate solution (2 g/kg body wt) was ingested immediately postexercise (P-EX) or 2 h postexercise (2P-EX). Muscle biopsies were taken from the vastus lateralis at 0, 2, and 4 h postexercise. Blood samples were obtained from an antecubital vein before and during exercise and at specific times after exercise. Muscle glycogen immediately postexercise was not significantly different for the P-EX and 2P-EX treatments. During the first 2 h postexercise, the rate of muscle glycogen storage was 7.7 mumol.g wet wt-1.h-1 for the P-EX treatment, but only 2.5 mumol.g wet wt-1.h-1 for the 2P-EX treatment. During the second 2 h of recovery, the rate of glycogen storage slowed to 4.3 mumol.g wet wt-1.h-1 during treatment P-EX but increased to 4.1 mumol.g wet wt-1.h-1 during treatment 2P-EX. This rate, however, was still 45% slower (P less than 0.05) than that for the P-EX treatment during the first 2 h of recovery. This slower rate of glycogen storage occurred despite significantly elevated plasma glucose and insulin levels. The results suggest that delaying the ingestion of a carbohydrate supplement post-exercise will result in a reduced rate of muscle glycogen storage.

The athlete’s diet: nutritional goals and dietary strategies

“…Recovery of the muscle and liver glycogen stores after exercise is a rather slow process, and complete recovery may not be achieved until 24-48 h after the end of exercise (Piehl, 1974). The rate of glycogen resynthesis after exercise is determined largely by the amount of carbohydrate supplied by the diet (Ivy, 2000), and the amount of carbohydrate consumed is of far greater importance for this process than the type of carbohydrate. The training diet, therefore, should be high in carbohydrate, with perhaps ≥ 60 % of the total energy intake coming from carbohydrate.…”

“…This recovery is best achieved when carbohydrate is consumed as soon as possible after training, as the rate of glycogen synthesis is most rapid at this time. It is normally recommended that at least 1-2 g/kg body mass (a total of 50-100 g carbohydrate) should be consumed in the first hour, and a high carbohydrate intake continued thereafter (Ivy et al 1988;Coyle, 1991). There is clearly a maximum rate at which muscle glycogen resynthesis can occur, and there appears to be no benefit in increasing the carbohydrate intake to levels in excess of 100 g every 2 h. The type of carbohydrate is less crucial than the amount consumed, but there may be some benefit from ingesting high-glycaemic index foods at this time to ensure a rapid elevation of the blood glucose level.…”

Dietary macronutrient recommendations for optimal recovery post-exercise: Part I

“…42,43 The rapid phase only occurs when post-exercise muscle glycogen concentrations are below 30 -35 mmol/kg ww 43 and CHO is provided immediately post-exercise. 28 Hence, of the abovementioned dietary factors, CHO availability remains the key factor affecting both phases of postexercise glycogen synthesis and rate of recovery.…”

“…28,48,51 The mechanism behind an increased rate of glycogen synthesis with immediate post-exercise CHO ingestion might be related to an increased glycogen synthase activity (for review see Nielsen and Richter 37 ) and GLUT-4 availability immediately following exercise. 36 However, in the absence of CHO ingestion, these exercise-induced increases in glycogen synthase and GLUT-4 availability (and hence the potential for glucose transport) may decline rapidly.…”

Impact of Intensive High-Fat Ingestion in the Early Stage of Recovery from Exercise Training on Substrate Metabolism during Exercise in Humans

“…Since muscle glycogen stores were effi ciently replenished if CHO was ingested as soon as possible after ET (12), CHO ingestion has been considered to be the fi rst priority in the early stage of recovery from ET. On the other hand, experimentally, blood TG concentration reached a peak around 4 h after ingestion of a high-fat diet (13), and blood insulin concentration reached a peak within 1 h after ingestion of a CHO-containing diet and then returned to the baseline about 4 h later (12). Although the negative effect of insulin on muscle LPL activity cannot be completely excluded, ingestion of a CHO-containing diet supplemented with high fat in the early stage of recovery from ET would not only replenish body CHO stores but also effectively increase muscle TG stores by making use of the time lag between blood insulin and TG responses.…”