All issues > Volume 13(7); 1970

Original Article

J Korean Pediatr Soc. 1970;13(7):385-394. Published online July 31, 1970.

Maximal Aerobic Power of Korean Women Divers

Pyung Kil Kim¹

¹Department of Pediatrics Yonsei University College of Medicine Seoul, Korea

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 superior in ama as compared to non-diving women (control) living in the same community. Moreover, the resting blood pressure, as well as the resting 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-divers 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 1957) and in the winter (January 1968). Thirty each of ama and control subjects were randomly selected from the same community and their average physical characteristics 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 attempted 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 characteristics. 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 not easy 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 resting V02, VE and heart rate were determined. A warming-up exercise consisting of stepping on and off a bench 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 maxima!. 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 begs of expired gas were collected during the last 20 seconds of exercise at each Stepping rate. Average heart rates, VE and V02 at rest, at the end of warming-up period and during various rates of stepping exercise are shown in the table 2. At fest the heart rates of ama were significantly lower than those of the control in both seasons (P<0. 01), whereas the values of VE and V02 were not significantly different between the two groups. At the end of warming-up period, the heart rates were appoximately doubled ill both gtbups. During the stepping exercise, the heart rate iiicresised diilost 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 VE and Vo2 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 summarized in the table 3. The average maximal stepping rate was significantly greater in ama as compared to the control. The maximal VE 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 (45 ml/min/kg) in the ama in both seasons, which were approximately 20% greater than those of the control. Even when the values of V02 per kg of lean body mass were computed, the level of MOI was significantly greater in ama than in the control Moreover, the V02 per heart beat (oxygen pulse) was also significantly greater in ama than in the control. In the Fig. 4, VE and the heart rate are plotted as a function of V02. It can be seen that both VE and the heart rate for a given V02 are clearly lower in ama as compared to the control. In general, the individual values of MOI are known to be inversely proportional to the age of subject. Similar findings were obtained in our subjects. However the aerobic work capacity of ama is well maintained throughout their Efe as compared to the control. In earlier studies, it was noted that the 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 words, 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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