Adaptation in Sports Training by Viru Atko

Author:Viru, Atko [Неизв.]
Language: eng
Format: epub
Publisher: Taylor & Francis (CAM)

Chapter 6

SPECIFICITY OF TRAINING EFFECTS ON AEROBIC WORKING CAPACITY AND THE CARDIOVASCULAR SYSTEM

TRAINING EFFECTS ON ANAEROBIC THRESHOLD AND MAXIMAL OXYGEN UPTAKE

ANAEROBIC THRESHOLD

Training effects on the mitochondria enable the use of oxidative phosphorylation for ATP resynthesis during performance of more and more intensive exercises. The so-called anaerobic threshold is very likely a qualitative measure of the highest exercise intensity performed on the basis of oxidative phosphorylation without an extended use of anaerobic energy mechanisms. To put it more precisely, the anaerobic threshold expresses the highest exercise intensity during performance in which the pyruvate formation rate still does not exceed the maximal rate of oxidative phosphorylation. Accordingly, the formed lactate can be oxidized or used for gluconeogenesis by nonworking muscles, heart, and liver. Up to this qualitative point an equilibrium exists between lactate formation and elimination.1,2

Since the maximal oxygen uptake is obtained in exercise level, causing a pronounced lactate accumulation, exercise intensity at VO2max does not indicate maximal performance on the basis of aerobic resynthesis of ATP. Actually, it was found that there is no close coupling between the whole body VO2max and the oxidative capacity of a local muscle group in elite road cyclists during a session.3 There is a close relationship of these variables over the first 3 to 4 weeks of training. Thereafter, the increase in VO2max levels off, but the activity of mitochondrial enzymes continues to rise.4 The VO2max of athletes may be twice that of untrained persons, whereas their activity of mitochondrial enzymes of the muscle is three- to fourfold higher than that of sedentary individuals.5 When training was discontinued, the activity of oxidative enzymes dropped to the initial level within 2 to 4 weeks. However, VO2max remained high for 6 weeks.4

The anaerobic threshold is a variable rather accurately predicting athletic endurance performance, particularly in running races of 10 to 42 km.6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23 In male and female marathon runners, elevated relationships were found between the running velocities determined at 2.5, 3, and 4 mmol·l-1 of blood lactate and marathon running velocity. Running at marathon velocity did not cause a change in pH; the blood lactate rose up to 2.2 to 3.5 mmol·h1.24 Anaerobic threshold correlates closely to performance in race-walkers. The factor of submaximal economy, which partly determines the velocity at anaerobic threshold, is related to performance ability in race-walking25 more than in running.26 In 21 endurance-trained runners longitudinal changes in the anaerobic threshold and distance-running performance were in consistently high correlation over a 9-month training period.26

The anaerobic threshold appears at an exercise intensity of 75 to 90% VO2max. At 75 to 80% VO2max the ATP turnover rate is high enough to elevate ADP, AMP, Pi, and H° concentrations stimulating glycolysis. Therefore, at 75% VO2max, lactate begins to accumulate in muscles (most of all in type II fibers) and blood.27 A study of 25 members of the U.S. Olympic rowing team showed that a mean anaerobic threshold of 83% VO2max attests to the high aerobic capacity of oarsmen. Power output data indicated that 72% of total power is generated at the anaerobic threshold.

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