Surgery – Diagnostic testing
Patent
1997-06-23
1998-09-22
Lateef, Marvin M.
Surgery
Diagnostic testing
600520, A61B 50205
Patent
active
058107223
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and a device for determining threshold values for energy metabolism, in which method a testee is subjected to a gradually increasing stress in order to obtain the threshold values for his energy metabolism.
2. Description of the Prior Art
When a runner starts running, the lactic acid content of his blood first tends to drop below the original level. This is due to a faster circulation and the fact that the lactic acid elimination processing improves with muscle work. After this, if the speed of running is steadily increased, the lactic acid content begins to rise linearly with respect to the stress. The work rate at which the lactic acid content reaches its original value, and the corresponding levels of vital functions, such as pulse rate and oxygen consumption, are called an aerobic threshold.
At work rates that are lower than the aerobic threshold, energy is produced aerobically, i.e. fats and carbohydrates are burned by means of oxygen. At work rates exceeding the aerobic threshold, energy is in turn produced to a greater and greater extent anaerobically, i.e. without oxygen, so that more and more lactic acid is correspondingly formed in the tissues. Simultaneously, the proportion of fat consumption in the production of energy decreases rapidly and carbohydrates become the primary source of energy.
Increasing the level of performance further finally results in a situation in which the system of the athlete can no longer process the amount of lactic acid that develops in the energy production. The disturbance of the balance is detected as a sharply rising lactic acid content of blood and as a simultaneous clear increase in ventilation. This critical level of performance that is significant for training is called an anaerobic threshold.
In physiology, an aerobic threshold is thus defined as the stress level at which the lactic acid content in the blood of an athlete or a fitness enthusiast exceeds the level of rest, or at which the ventilation increases faster than previously with respect to the increasing stress. Pulse rate measurement can be utilized in estimating the work rate of an athlete or a fitness enthusiast, since the pulse rate and the work rate are linearly dependent on each other.
An anaerobic threshold, on the other hand, denotes the stress level at which the lactic acid content of blood starts rising rapidly and the ventilation begins to increase clearly faster than the stress or the oxygen consumption.
Determining the aerobic and the anaerobic threshold is primarily used in the training of endurance athletes in order to determine a suitable training efficiency and to monitor the effects of the training. Similarly, for example the optimum training efficiency of a dieter can be determined by means of the thresholds. The aerobic and anaerobic threshold are nowadays determined in special test laboratories by means of a so-called maximum stress test. The test is started with a small stress. The stress is increased step by step every 2 to 3 minutes without any pauses up to the maximum level of performance. During the last 30 seconds of each stress, a blood sample is taken from the testee in order to determine the lactic acid level, or alternatively, the ventilation is measured. The threshold values determined by means of lactic acid and ventilation are usually very close to each other. The results are strongly influenced by the manner of stressing, the rate at which the stress is increased, and the stress levels used, wherefore different physical stress situations, such as a treadmill and an ergometer, provide different threshold values.
Ventilation, i.e. the respiratory volume per minute (VE), is obtained by multiplying the respiratory volume per time (TV) by the respiratory frequency (fr).
Formula (1) shows that ventilation can be increased both by increasing the respiratory volume per time and by increasing the respiratory frequency. They both change when the stress on the system increases. The respirato
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Treese et al., "Ventilation and Heart Rate Response During Exercise In Normals: Relevance For Rate Variable Pacing", PACE, vol. 16, pp. 1693-1700 (Aug. 1993).
Lateef Marvin M.
Mantis Mercader Eleni
Polar Electro OY
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