The effect of a high carbohydrate diet on running performance during a 30-km treadmill time trial
- 640 Downloads
The purpose of the present study was to examine the influence of a high carbohydrate diet on running performances during a 30-km treadmill time trial. Eighteen runners (12 men and 6 women) took part in this study and completed a 30-km time trial on a level treadmill without modifying their food intake (trial 1). The runners were then randomly assigned to a control or a carbohydrate (CHO) group. The CHO group supplemented their normal diets with additional carbohydrate in the form of confectionery products during the 7 days before trial 2; the control group matched the increased energy intake of the CHO group by consuming additional fat and protein. The mean (SEM) carbohydrate intake of both groups was 334 (22) g before trial 1, after which the CHO group consumed 566 (29) g · day−1 for the first 3 days and 452 (26) g · day−1 for the remaining 4 days of recovery. Although there was no overall difference between the performance times for the two groups during trial 2, the CHO group ran faster during the last 5 km of trial 2 than during trial−1 [3.64 (0.24) m · s−1 vs 3.44 (0.26) m · s−1P < 0.05] . Furthermore, the 6 men in the CHO group ran the 30 km faster after carbohydrate loading [131.0 (5.4) min vs 127.4 (4.9) min;P < 0.05], whereas there was no such improvement in times of the men in the control group. Blood glucose concentrations of both groups decreased below pre-exercise values during trial−1 (P < 0.001), but only the control group had a decrease in blood glucose concentrations during trial 2 (P < 0.001). There were no differences between the concentrations of plasma catecholamines of the control group during the two trials. However, the adrenaline concentrations of the CHO group were lower (P < 0.05) during trial 2 than during trial 1, even though they ran faster during trial 2. These results confirm that dietary carbohydrate loading improves endurance performance during prolonged running and that confectionery can be used as an effective means of supplementing the normal carbohydrate intake in preparation for endurance races.
Key wordsDiet Endurance Carbohydrate metabolism Catecholamines Running
Unable to display preview. Download preview PDF.
- Bergstrom JB, Hermansen L, Hultman E, Saltin B (1967) Diet, muscle glycogen and physical performance. Acta Physiol Scand 71:140–150Google Scholar
- Brewer J, Williams C, Patton A (1988) The influence of high carbohydrate diets on endurance running performance. Eur J Appl Physiol 57:698–706Google Scholar
- Brooks S, Burrin J, Cheetham ME, Hall GM, Yeo T, Williams C (1988) The responses of the catecholamines and B-endorphin to maximal exercise in man. Eur J Appl Physiol 57:230–234Google Scholar
- Cohen L, Holliday M (1982) Statistics for Social Sciences. Harper and Row, LondonGoogle Scholar
- Hultman E (1967) Studies on muscle metabolism of glycogen and active phosphate in man with special reference to diet. Scand J Clin Lab Invest [Suppl] 94:19Google Scholar
- Paul AA, Southgate DAT (1978) The composition of foods. HMSO, LondonGoogle Scholar
- Roberts KM, Noble EG, Hayden DB, Taylor AW (1987) Simple and complex carbohydrate-rich diets and muscle glycogen content of marathon runners. Eur J Appl Physiol 57:70–74Google Scholar
- Savard G, Kiens B, Saltin B (1987) Central cardiovascular factors as limits to endurance; with a note on the distinction between maximal oxygen uptake and endurance fitness. In: Macleod D, Maughan R, Nimmo M, Reilly T, Williams C (eds) Exercise, benefits, limits and adaptations. Spon, London, pp 162–177Google Scholar
- Williams C, Nute MG, Broadbank L, Vinall S (1990) Influence of fluid intake on endurance running performance: a comparison between water, glucose and fructose solutions. Eur J Appl Physiol 60:112–119Google Scholar