Off seasonal and pre-seasonal assessment of circulating energy sources during prolonged running at the anaerobic threshold in competitive triathletes

• Published in: British journal of sports medicine 2004-08, Vol.38 (4), p.402-407
• Main Authors: Knoepfli, B, Riddell, M C, Ganzoni, E, Burki, A, Villiger, B, von Duvillard, S P
• Format: Article
• Language: English
• Subjects: ACT; Adult; aerobic capacity; aerobic capacity test; aerobic power test; anaerobic threshold; Anaerobic Threshold - physiology; Analysis of Variance; APT; Athletes; Carbohydrates; Comparative studies; Energy; Energy Metabolism - physiology; Energy resources; Exercise; fat metabolism; Fatty acids; Fatty Acids, Nonesterified - metabolism; Female; FFA; free fatty acid; Glucose; Heart Rate - physiology; Human performance; Humans; Insulin; lactate threshold; Male; maximal oxygen consumption; Metabolism; Musculoskeletal system; Original; Oxidation; Oxygen Consumption - physiology; Physical Education and Training - methods; Physical Endurance - physiology; Physical fitness; prolonged exercise; Running; Running - physiology; Seasons; Sports medicine; Studies; Switzerland; Triathlon; triglyceride; Triglycerides - metabolism; V˙o2max
• ISSN: 0306-3674; 1473-0480
• DOI: 10.1136/bjsm.2002.003442

Objectives: To compare changes in circulating energy sources during prolonged exercise in off season (OS) and pre-season (PS) training of triathletes. Methods: Nine athletes of the Swiss national triathlon team (three female, mean (SD) age 28.7 (4.9) years, height 169.8 (6.0) cm, weight 57.0 (6.2) kg, V˙o2max 66.5 (5.3) ml/min/kg; six male, mean (SD) age 24.0 (4.1) years, height 181.4 (6.9) cm, weight 73.5 (6.0) kg, V˙o2max 75.9 (4.9) ml/min/kg) were tested twice (2.5 months apart) during a 25 km aerobic capacity test run at the end of the OS and just before the season. The average training load during the OS was 9.9 h/week, and this increased to 14.4 h/week in the PS. With heart rates as reference, exercise intensity during the aerobic capacity test was 97.0 (4.9)% of the anaerobic threshold and 91.2 (4.5)% of V˙o2max. Blood samples were collected before, during, and after the aerobic capacity test. Samples were collected every 5 km during three minute rest intervals. Results: Blood was analysed for triglyceride (TG), free fatty acids, cholesterol, high density lipoprotein cholesterol, glucose, insulin, lactate, and changes in plasma volume. A two factor (season by distance) repeated measures analysis of variance revealed an increase in capacity for prolonged exercise in the PS by a decrease in running intensity during the aerobic capacity test (% of speed at 2.0 mmol/l lactate threshold, p  =  0.008), an increase in running speed at the anaerobic threshold (p  =  0.003) and at 4.0 and 2.0 mmol/l (p