Influence of Carbohydrate-electrolyte Drinks on Muscle Metabolism and Endurance Running Performance in Man
Year: 1993
Type: dissertation
Abstract: Prolonged running is an activity associated with a wide range of sports and\nimprovement in' running endurance is therefore important for those\ninvolved, The aims of the first and second studies were to investigate the\neffect of carbohydrate ingestion on endurance running capacity and\nperformance,\nIn the first study (Chapter 4), seven experienced endurance runners ingested\neither water (W), a 6.9% carbohydrate (CHO) solution (B) or a 5.5% CHO\nsolution (A) during 3 randomly assigned 42.2-km treadmill runs, 4 weeks\napart. Running times for W, B and A trials were 193.9 ± 5.0 min, 192.4 ± 3.3\nmin and 190.0 ± 3.9 min, respectively. Performance time for the A trial was\nfaster (p < 0.05) compared with that of the W trial. In the second study (Chapter 5), eleven recreational runners completed 3\nrandomly assigned treadmill runs at 70% V02 max to exhaustion, one week\napart. On the first and second occasions a 5.5% (A) and 6.9% (C) CHO\nsolutions were ingested for the first hour of exercise, water was then ingested\nuntil exhaustion. On the third occasion water (W) was ingested throughout\nthe run. Performance times for the W, A and C trials were 109.6 ± 9.6 min,\n, 124.5 ± 8.4 min and 121.4 ± 9.4 min, respectively. Running time to\nexhaustion for the A trial was significantly longer (p < 0.05) compared with\nthe W trial. The results of these studies suggested that the ergogenic effect of\nthe 5.5% CHO solution was not associated with the prevention of a declining\nblood glucose concentration and CHO oxidation rate. In the third study (Chapter 6), the possibility that sparing of muscle glycogen\ncould be the mechanism by which CHO ingestion exerts its ergogenic effect\nwas investigated. Seven subjects consumed either a 5.5% carbohydrate\nsolution (CHO) or water (W) during two 60-min treadmill runs at 70% V02\nmax a week apart. Biopsy samples from the vastus lateralis muscle were\nobtained at rest and 60 min for glycogen determination. A28% reduction in\nglycogen utilization was observed as a result of CHO ingestion when\ncompared with W ingestion 008.7 ± 16.3 mmol.kg dry muscle (dm)-l vs\n150.9 ± 19.9 mmol.kgdm-1 respectively, p < 0.01). In order to investigate the\nsite of glycogen sparing, individual fibres were dissected and analysed for\nglycogen. The ingestion of the CHO solution resulted in sparing of glycogen\nin Type I (slow twitch) fibres only (38.1 % degradation of glycogen as opposed\nto 66.2% during the W trial, p = 0.01).\nThis glycogen sparing in Type I fibres would only explain the delay in the\nonset of fatigue observed in the first two studies if glycogen depletion in\nthese fibres was associated with fa tigue during prolonged running. In the\nfourth study (Chapter 7), eight subjects consumed either a 5.5% carbohydrate\nsolution (CHO) or placebo (PL) during two treadmill runs at 75% V02 max to\nexhaustion performed one week apart. Biopsy samples from the vastus lateralis muscle were obtained at rest and exhaustion in the PL trial and at\nrest, the point coinciding with PL exhaustion and exhaustion in the CHO\ntrial. Running times to exhaustion in the PL and CHO trials were 104.3 ± 8.6\nmin and 132.4 ± 12.3 min (p < 0.01). Higher glycogen concentration was\nobserved at the point coinciding with PL exhaustion in the CHO trial when\ncompared with the value measured at the point of exhaustion in the PL trial\n025.6 ± 22.3 mmol.kg dm-1 vs 59.8 ± 7.9 mmol.kg dm -1 p < 0.05,\nrespectively). This sparing of muscle glycogen was almost totally restricted to\nType I fibres (87.1 ± 18 mmol.kg dm-1 in the CHO trial vs 31.6 ± 10.3 mmol.kg\ndm-1 in the PL trial, p < 0.01, respectively). In both the CHO and PL trials,\nfatigue coincided with glycogen depletion in Type I fibres (28.1 ± 7.1 mmol.kg\ndm-1 and 31.6 ± 10.3 mmol.kg dm-1, respectively).\nIt was suggested, that the spared glycogen became available during the latter\nstages of the run and, therefore, could account for the improved endurance\ncapacity and performance observed in studies I, 2 and 4 when the 5.5% CHO\nsolution was ingested.
DOI: 10.12681/eadd/4687
Author: Ορέστης - Κωνσταντίνος Τσίντζας
Language: English
Subfield: Nutrition and Dietetics
Field: Nursing
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W59515082