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High‐intensity exercise and muscle glycogen availability in humans
- Source :
- Acta Physiologica Scandinavica. 165:337-345
- Publication Year :
- 1999
- Publisher :
- Wiley, 1999.
-
Abstract
- 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 (P0.05). 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.
- Subjects :
- Adult
Glycerol
Male
medicine.medical_specialty
Epinephrine
Physiology
Physical exercise
Fatty Acids, Nonesterified
Norepinephrine
chemistry.chemical_compound
Oxygen Consumption
Internal medicine
Dietary Carbohydrates
medicine
Humans
Lactic Acid
Muscle, Skeletal
Exercise
Hypoxanthine
Glycogen
High intensity
Dietary intake
Carbohydrate
Oxygen uptake
Bicycling
Endocrinology
chemistry
Plasma concentration
Exercise Test
Exercise intensity
Subjects
Details
- ISSN :
- 1365201X and 00016772
- Volume :
- 165
- Database :
- OpenAIRE
- Journal :
- Acta Physiologica Scandinavica
- Accession number :
- edsair.doi.dedup.....0beabb37926e8b7d67b1d57a320b4a38
- Full Text :
- https://doi.org/10.1046/j.1365-201x.1999.00517.x