Metabolic Demand And Substrate Utilization Of On-water Rowing - Implications For Training And Nutrition

While elite rowers spent about 11 h/week with specific on-water endurance training, data about metabolic demand (MD) and substrate utilization (SU) are scarce, yet needed for precise planning, evaluation, and optimization of training. PURPOSE: We aimed to describe the MD and SU of on-water rowing at three low-intensity zones based on maximal heart rate (HRmax), namely zone 1, 2.1, and 2.2 (60-72, 72-79, 79-82% HRmax). METHODS: Eight male (body mass (BM) 82.6 ± 6.5 kg, maximal oxygen consumption (⩒O2max) 75.3 ± 4.0 ml/min/kg) and seven female (BM 74.6 ± 8.4 kg, ⩒O2max 63.5 ± 2.5 ml/min/kg) elite rowers completed one ergometer ramp test to determine ⩒O2max and HRmax, and two on-water trials in the single-scull, separated by 24 h. Each trial consisted of six 15-minute stages, with two stages in each zone. MD with %⩒O2max, energy expenditure (EE) and SU for carbohydrates (CHO) were determined via indirect calorimetry. Blood lactate concentration (BL) was measured after each stage. Mean with standard deviation was calculated based on the ⩒O2 steady-state phase of each stage. RESULTS: In zone 1, 2.1 and 2.2, males exercised at a %⩒O2max of 57.5 ± 5.1, 67.0 ± 3.1, 72.8 ± 2.9%; a BL of 1.1 ± 0.2, 1.1 ± 0.3, 1.4 ± 0.2 mmol/l; a EE of 16.9 ± 1.5, 19.5 ± 1.2, 21.7 ± 0.9 kcal/min; and at CHO utilization of 1.9 ± 0.7, 3.1 ± 0.9, 3.7 ± 0.8 g/min, respectively. In females, amounting to a %⩒O2max of 57.9 ± 4.7, 65.1 ± 5.3, 70.5 ± 5.6%;a BL of 1.1 ± 0.3, 1.0 ± 0.2, 1.2 ± 0.2 mmol/l; a EE of 13.6 ± 2.2, 14.7 ± 2.4, 16.0 ± 2.3 kcal/min; and a CHO of 1.6 ± 0.3, 2.4 ± 0.4, 2,7 ± 0,4 g/min, respectively. All values differed significantly between zones (p < 0.05). There were no sex-specific differences (p > 0.05) except for BL and SU (p < 0.05). CONCLUSION: MD and SU differed sig. between the three endurance training zones in on-water single-scull rowing. High agreement with intensity zone models by Seiler et al. (2010) and Bourden (2013) were observed. The SU data indicate a high CHO turnover and potential glycogen depletion during prolonged sessions. The small zone differences in BK of 0.1-0.3 mmol/l are within the measurement inaccuracy, indicating that BL is not suitable for a dedicated assessment of internal load during low endurance training in elite rowers. The precise description of MD and SU allows for individualized implications, e.g. potential training effects and required CHO intake.