Author(s): SZMODIS, M., PÁL, L., GYÖRE, I., Institution: HUNGARIAN UNIVERSITY OF SPORTS SCIENCE, Country: HUNGARY, Abstract-ID: 895

INTRODUCTION:
With increasing intensity, the energy supply shifts from fatty acids to carbohydrates. During a spiroergometric test, the RER (Respiratory Exchange Ratio) values can be used to infer substrate utilization. RER is the VCO2/VO2 ratio measured during gas exchange tests. During the oxidation of fats, the RER value is 0.7, in the case of carbohydrates is 1.0. The maximum oxidation rate of fatty acids (FATmax) is between 40-60% of VO2max.
The aim of our study is to clarify the substrate utilization under increasing load in recreational and elite athletes, as well as to determine the individual maximum fat oxidation (MFO) and thus the amount of metabolizable lipids.

METHODS:
In our study, 13 sports university students (23.2±1.9 years; 181.9±4.2 cm; 78.4±6.5 kg - recreational athletes) and 7 elite road cyclists (17.0±0.7 years; 175.6 ±8.0 cm; 61.5±9.6 kg) participated. The test consisted of a multi-stage, spiroergometric (Jaeger CPX Vyntus) and cycle ergometer (Monark Ergomedic 839E) load. The initial intensity started from 0 Watts and the load was increased by 35 Watts every 3 minutes. We calculated the current energy and substrate consumption, the MFO value and the VO2MFO/VO2RER=1 ratio from the 30-second averages of the gas exchange values. In addition to basic statistics, the groups were compared with a two-sample t-test and U-test, the significance level was p<0.05.
RESULTS:
Resting parameters did not differ between the two groups. Compared with literature data, the MFO values of our study subjects and several athletes, mainly ball players, were almost identical (0.59±0.18 vs 0.57±0.16 g/min).
In sports university students and in elite cyclists the maximum fatty acid oxidation was at 0.75±0.27 vs. 1.91±0.83 Watt/kg relative power with 17.8±3.4 vs 35.1±8.7 ml/kg/min oxygen uptake, respectively. The O2 uptake associated with the MFO value was 56.6±15.2% vs 64.6±10.7% compared to the value of VO2RER=1.
The MFO value of the competitive athletes was (0.68±0.16 g/min), which was related to a better restitution, while the MFO value of the recreational athletes was (0.52±0.14 g/min). Elite cyclists returned to RER=1 almost 2.5 minutes earlier than sports university students (326" vs. 542").

CONCLUSION:
The elite road cyclists achieved their higher performance on average with a higher oxygen uptake and higher consumption of fatty acids and carbohydrates. By determining the athletes individual MFO value, we can infer their aerobic fitness level, which is one of the key elements of both training planning and progress in sports.
(Randell et al., 2016; Maunder et al., 2018)