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한국 해녀의 최대산소섭취능에 관한 연구

Maximal Aerobic Power of Korean Women Divers

소아과 1970년 13권 7호 p.1 ~ 10
김병길,
소속 상세정보
김병길 (  ) - 연세대학교 의과대학 소아과학교실

Abstract


In the course of studying various physiological functions of Korean women divers (ama), it has been observed earlier that physical fitness as evaluated by a modified Harvard step-test score was considerably suoerior in ama as compared to non-diving women(control) living in the same community. Moreover, the resting blood pressure, as well as the resulting heart rate, tended to be lower in ama than in control subjects. These observations suggest that the exercise load to which ama are subjected daily for years is big enough to make them athletes. According to an earlier analysis, the daily energy expenditure of ama is greater by 1,000 kcal a day as compared to the control. Although a greater fraction of this extra energy expenditure by ama is undoubtedly attributable to the extra heat lost to the aquatic surroundings, there is no doubt that a certain fraction is used to support their physical exercise in water.
In the present investigation, an attempt was made to determine the aerobic work capacity of ama for a comparison with non-drivers and established Korean athletes.
The experiments were carried out in our field laboratory on Yong-Do Island in Pusan. Each subject was invited to the laboratory for measurements in the summer(July 1967) and in the winter(January 1968). Thirty each of ama and control subjects were randomly selected from the same community and their average physical charaterisitics are tabulated in the table 1. On the average, the subjects in both groups were about 40 years old and 153 cm in height and 50-55 kg in weight. Although we attepted to use all of summer subjects in winter studies, there were inevitable drop-outs of some subjects on account of pregnancy or illness and hence we had to replace them with those similar in age and physical charateristics. The majority of subjects have been employed in some of our earlier studies and were not apprehensive to our laboratory procedures.
The aerobic work capacity was determined by measuring the maximal oxygen intake(MOI). Although the MOI could be best measured by a treadmill method, it is noteasy to use it in field studies such as the present investigation. Hence a continuous step-up method as described by Kasch et al. was slightly modified and was employed for the measurement of MOI in this investigation. Each subject rested in sitting position for approximately 30 minutes following which the restingⅤ(_o2) and heart rate were determined. A warming-up exercise consisting of stepping on and off a beach of 25 cm in height at a rate of 35 per minute was then performed for a period of 3 minutes. Toward the end of this warming-up period, the heart rate reached a level of 140 to 150 per minute. After 5 minutes resting following the warming-up exercise, a continuous step-up exercise was given until exhaustion. The starting rate of exercise was 30 steps per minute in ama and 24 in the control. From these starting rates, the stepping rate was increased every minute in increments of 3 to 4 per minute to maximal. Throughout the stepping exercise, the heart rate was continuously monitored by means of a telemetry. As the stepping rate approached a maximal level as indicated by the higher heart rate, i.e. above 160 per minute, serial bags of expired gas were collected during the last 20 seconds of exercise at each stepping rate.
Average heart rates,Ⅴ´(_E) and Ⅴ´(_O2) at rest, at the end of warming-up period and during various rates of stepping exercise are shown in the table 2. At rest the heart rates of ama were significantly lower than those of the control in both seasons (P<0.01), whereas the vales of Ⅴ´(_E) and Ⅴ´(_O2) were not significantly different netween the two groups. At the end of warming-up period, the heart rates were appoximately doubled in both groups.
During the stepping exercise, the heart rate increased almost linearly in proportion to the stepping rate. However, as the stepping rate approached a maximal level, changes in the heart rate leveled off somewhat, approaching 170 to 180 per minute. Similar findings were obtained with Ⅴ´(_E) and Ⅴ´(_O2). The maximal stepping rate was approximately 48 steps per minute in the control while it was 54 to 57 in ama.
Various measurements obtained at the maximal rate of exercise are summerized in the table 3. The average maximal stepping rate was significantly greater in ama as compared to the control. The maximal Ⅴ´(_E) was approximately 70 L per minute in both groups without showing any difference. The values of MOI were in the order of 2.3 L per minute (45ml/min/kg) in the ama in both seasons, which were approximately 20% greater than those of the control. Even when the values of Ⅴ(_o2) per kg of lean body mass were computed, the level significantly greater in qmq than in the control. Moreover, the Ⅴ(_o2) per heart beat(oxygen pulse) was also significantly greater in ama than in the control.
In the Fig. Ⅴ´(_E) and the heart rate are plotted as a function of Ⅴ´(_O2). It can be seen that both Ⅴ´(_E) and the heart rate a given Ⅴ´(_O2) are clearly lower in ama as compared to the control.
In general, the individual values of MOI are known to be inversely preportional to the age of subject. Similar findings were obtained in our subjects. However, the aerobic work capacity of ama is well maintained throughout their life as compared to the control. In earlier studies, it was noted that daily work load of ama was considerably less in winter than in summer. However, the magnitude of MOI was not different between the two seasons. In other works, the aerobic work capacity does not seem to change by such a difference in the magnitude of daily physical activity as seen in ama between summer and winter.
Comparing the present findings with data obtained in other Korean female, the MOI of 40 year-old ama is similar to that of 20 year-old non-athletes, but is slightly lower than that of 20 year-old women champion athletes.

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