The ventilatory threshold (VT) was determined on a treadmill in highly trained male marathon, male and female long-distance, young male long-distance, adult male and female and young female middle-distance runners, modern pentathlonists, adult canoeists of both sexes, young male canoeists and football players, and on a bicycle ergometer in table tennis players, water slalom paddlers, young female canoeists rowers, and ice hockey players. Young female canoeists were also examined on the paddling ergometer and rowers on the rowing ergometer. VT expressed in %VO2 max was higher the longer the duration of racing performance (in marathoners 86.7%). %VO2 max at the VT level depends on the type of load and is higher the better the organism is adapted to a load. In young female canoeists and rowers examined on the bicycle ergometer, we found the VT level at 74.2% and 74.6% of %VO2 max, respectively. In the case of specific loading, we recorded 84.8% and 85.0% of %VO2 max, respectively, in the same athletes. In the case of nonspecific loading highly trained individuals may have low VT values close to the level characteristic for normal subjects. In relatively equally trained young and adult athletes we did not find significant differences in %VO2 max at the VT level (for long-distance runners, 85.2% and 85.3%, respectively, in female middle-distance runners, 82.8% and 82.7%, respectively, and in canoeists 81.3% and 78.9% of %VO2 max, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
1. In 3 groups of men, differing as to the amount and intensity of physical training loads, increasing in the order "sedentary": "sporting": "athletic", enzyme activities were estimated in biopsy samples of m. quadriceps femoris (vastus lateralis). The enzymes were: Hexokinase (HK), NAD: glycerol-3-phosphate dehydrogenase (GPDH), triosephosphate dehydrogenase (TPDH), lactate dehydrogenase (LDH), citrate synthase (CS), NAD: malate dehydrogenase (MDH), and 3-hydroxyacyl-CoA dehydrogenase (HOADH). Indicators of laboratory performance and whole-body metabolic capacities (maximal oxygen consumption etc.) were estimated in the "sporting" and "athletic" groups. 2. In the 2 latter groups, distinguished by greater physical activity, the atypical enzyme activity pattern, remarkable by a low activity of LDH and high relative activities of GPDH and HK, as reported earlier in a sedentary group (Bass et al., 1975a), disappeared. The possibility of the atypical low LDH enzyme activity pattern as resulting from lack of bodily exertion is discussed. 3. The moderately trained "sporting" group distinguishes itself from the "sedentary" one mainly by a higher activity of LDH and by lower activities of GPDH and MDH. In the intensively trained "athletic" group, enzymes connected to aerobic oxidation (MDH, CS, HOADH) and GPDH also show higher activities than in the "sporting" group. The difference between the two more active groups is further borne out by a higher maximum oxygen uptake and carbon dioxide release of the well-trained "athletic" group. This difference of enzyme activity pattern may not be confined to the quadriceps femoris muscle.
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