From diving practice we know that breath-holding time (BHT) can be increased by training. This examination was set up to illuminate whether BHT underwater can be trained decisively in a short period of time. The authors investigated whether physiologic or psychological aspects are the main constituents of the above-mentioned BHT phenomenon. BHT and the "onset point" of involuntary respiratory movements of 64 subjects were registered after deep inspiration and immersion in ca. 1 m. Two different tests were set up: (I) 2 breath-holds per day on 5 consecutive days, (II) 5 repeated breath-holds with pauses of 3 min in between. BHT of the first test was shorter underwater than in similar experiments in air; the increase of BHT underwater was distinctly higher (series II: 160%). Thirty percent of the subjects inequivocally showed respiratory movements (group 1), 31% did not reach the "onset point" (group 3). In group 1 BHT was considerably higher than in group 3. In group 1 the mean time span without respiratory movements rose by 14% in series I and by 233% in series II, whereas the time span with respiratory movements rose by 105% and 119%. These results confirm and quantify the good trainability of BHT underwater. Two processes cause this increase: the increase in time span without respiratory movements probably by unconscious hyperventilation and the increase in time span with respiratory movements through psychological adaptation by suffering the need to breathe.
The assessment of an individual's degree of acclimatization to altitude is difficult. This is particularly applicable to military operations that have to be performed at altitude. This study describes a new and simple test that allows for the determination of an individual's risk for high-altitude illness at higher altitudes. The prediction is based on the lowest oxygen saturation (SaO2) found during an uphill run at high altitude (11,060 ft [3,371 m]), combined with the time needed to complete the run. The test results were compared against the severity of high-altitude symptomatology on the summit of Mont Blanc (15,762 ft [4,808 m]). The main outcome was the significant correlation between time as well as SaO2 and the severity of high-altitude symptomatology on the summit of Mont Blanc. The newly developed performance test allows, at a "safe" altitude, the prediction of an individual's risk of developing high altitude illness if they continue to ascend. It allows the determination of the best acclimatized subjects within a group, for example, before a military mission at greater altitude.
The perceived exertion rating (RPE) scale of Borg was used to investigate the relationship between perceived exertion and pedalling rate. Normal subjects and patients with chronic obstructive lung disease (Cold) were studied in repeated test series. Work load, applied in a random order, varied from 2.5 to 10 mkp/s (patients) and 5 to 20 mkp/s (normals). Pedalling rate varied from 2.5 to 10 mkp/s (patients) and 5 to 20 mkp/s (normals). Pedalling rate varied from 40 to 60, 80, 100 rpm. At constant work load, RPE decreases during increasing pedalling rate. With respect to validity, RPE, showing a closer relationship to work load than to heart rate, seems to reflect perception of physical stress rather than perception of physiological strain. In addition, the results raise the question of standardization of pedalling rate in bicycle ergometry.
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