There have been very few reports on the relationship between stroke volume and heart rate in the physically loaded children. Continuous records had been made onthe changes in SV and HR during the graded exercise in 16 eleven--year--old pupils(as subjects) of a youngster's sports school and 27 matched ordinary pupils (ascontrols) by the electrical impedance method. The results are as follows: (1) Thevalues of SV and HR in the subjects and controls present significant difference whenHR is 110--140 beats/min during exercise and 90--130 beats/min during recovery;(2) CO increases with the increasing HR when HR is 110--190 beats/min; (3) Thepeak SV appears in between HR 100--120 beats/min. Therefore, we consider that itis advanta geous to the development of function of the children's hearts by combi-ning the moderate continuous exercise with less load in longer time and submaximalload with short interval.

To study the effect of physical fitness exercise prescription on the cardiac function of collegians, three different exercise prescriptions on the collegians extra-curriculum exercises to develop their strength, cardiac function and overall physical fitness separately and one control were applied. The results show that after 8 weeks training, the rest HR of all exercise groups decreased while SV(stroke volumn), SI (stroke index), CO (cardiac output)and CI (cardiac index) increased significantly. Furthermore, the results also show that VPE (ventricular pumping effectiveness) and VPEI (ventricular pumping effectiveness index) of exercise groups increased while MSP(mean systolic pressure), MDP(mean diastolic pressure) and MAP (mean arterial pressure) decreased at variant degree. From the study it is not difficult to see that doing exercise prescription can develop the collegians' cardiac-function significantly. Comparing these three exercise prescriptions show that doing endurance exercise prescription can get the best effect on developing the cardiac-function, but doing the comprehensive-developing exercise prescription can get more comprehensive effect on cardiac and vascular function. Another result from comparing the control group shows that the females are easier to get the physiological function descent than the males if they do not do exercises actively. In conclusion, it is worth to extend physical fitness exercise prescription in collegians' extra-curriculum exercise because of the simple condition, scientific method and significant effect.

BACKGROUND: High-altitude training before competition aims to obtain maximum hypoxia physiological adaptability of athletes through hypoxia environmental irritation at high altitude. Physiological adaptability to high al titude is the substantial foundation for function improvement of athletes,reflecting adjustment of body to environmental changes.OBJECTIVE: In views of self-regulation, practical training and compressed spectral array (CSA) electroencephalogram (EEG), and by observing adaptive change rule of brain before (before competition) and after high-altitude training of swimming athletes, the influence of high-altitude training was analyzed systematically on self-organizing state of athletes before competition so as to probe into the impacts of high-altitude training from brain level.DESIGN: Randomized investigation.SETTING: Guangdong Scientific Institute of Physical Exercise and Physical Exercise College of South China Normal University.PARTICIPANTS: Nine swimming athletes were selected from Guangdong Swimming Team from March to April 2001.METHODS: Time-order observation was applied in the experiment, in which, the results 1 week (3rd March) before high-altitude training, during (22nd March) and on the 5th day (5th April) after the training, the results in competition on the 13th day (12th April) after high-altitude training and corresponding blood lactic acid were tested and SCA EEG was done successively one day before high-altitude training (10th March), on the 1st day after the training (30th March) and on the 11th day after training, that was two days before National Competition (10th April) to observe self- adaptive regulation of brain to sports training load.MAIN OUTCOME MEASURES: ① Training index and lactic acid change before and during high-altitude training and before competition. ②Comparison of results before high-altitude training and in competition. ③Changes in indexes of cerebral evaluation before, during and after high-altitude training and before competition.RESULTS: ① Training results were changeable in high-altitude training.In national competition after high-altitude training, the scores of 6 cases of 10 person-times were reduced. Changes in blood lactic acid after high-altitude training were in conformity with training results. ② After high-altitude training, the average frequency of brain information distribution in athletes was shifted towards high frequency. Before the competition, negative entropy was lessened and information entropy was dispersed and the score in competition was declined.CONCLUSION: ① Cerebral order parameters of athletes constitute multicentralization, form the dispersion of technique control information and result in re-adjustment of brain function at matrix coordinating level, suggesting declining capacity to athletics. ② Effects of high-altitude training and maintaining of its functions are based on coincidence and continuity of arrangement of rise-fall training intensity of individual state and on the recovery and maintaining of the intensity at flatlands.