High-intensity exercise and muscle glycogen availability in humans

Acta Physiol Scand. 1999 Apr;165(4):337-45. doi: 10.1046/j.1365-201x.1999.00517.x.


This study investigated the effects of muscle glycogen availability on performance and selected physiological and metabolic responses during high-intensity intermittent exercise. Seven male subjects completed a regimen of exercise and dietary intake (48 h) to either lower and keep low (LOW-CHO) or lower and then increase (HIGH-CHO) muscle glycogen stores, on two separate occasions at least a week apart. On each occasion the subjects completed a short-term (<10 min) and prolonged (>30 min) intermittent exercise (IEX) protocol, 24 h apart, which consisted of 6-s bouts of high-intensity exercise performed at 30-s intervals on a cycle ergometer. Glycogen concentration (mean +/- SEM) in m. vastus lateralis before both IEx(short) and IEx(long) was significantly lower following LOW-CHO [180 (14), 181 (17) mmol kg (dw)(-1)] compared with HIGH-CHO [397 (35), 540 (25) mmol kg (dw)(-1)]. In both IEx(short) and IEx(long), significantly less work was performed following LOW-CHO compared with HIGH-CHO. In IEx(long), the number of exercise bouts that could be completed at a pre-determined target exercise intensity increased by 265% from 111 (14) following LOW-CHO to 294 (29) following HIGH-CHO (P < 0.05). At the point of fatigue in IEx(long), glycogen concentration was significantly lower with the LOW-CHO compared with HIGH-CHO [58 (25) vs. 181 (46) mmol kg (dw)(-1), respectively]. The plasma concentrations of adrenaline and nor-adrenaline (in IEx(short) and IEx(long)), and FFAand glycerol (in IEx(long)), increased several-fold above resting values with both experimental conditions. Oxygen uptake during the exercise periods in IEx(long), approached 70% of Vo2max. These results suggest that muscle glycogen availability can affect performance during both short-term and more prolonged high-intensity intermittent exercise and that with repeated exercise periods as short as 6 s, there can be a relatively high aerobic contribution.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bicycling
  • Dietary Carbohydrates / administration & dosage
  • Epinephrine / blood
  • Exercise / physiology*
  • Exercise Test
  • Fatty Acids, Nonesterified / blood
  • Glycerol / blood
  • Glycogen / metabolism*
  • Humans
  • Hypoxanthine / blood
  • Lactic Acid / blood
  • Male
  • Muscle, Skeletal / metabolism*
  • Norepinephrine / blood
  • Oxygen Consumption / physiology


  • Dietary Carbohydrates
  • Fatty Acids, Nonesterified
  • Hypoxanthine
  • Lactic Acid
  • Glycogen
  • Glycerol
  • Norepinephrine
  • Epinephrine