To get basic data on exercise prescription in the growing stages, it was attempted to investigate the growth of white albino rats (JCL : SD strain) under the various swimming loads. Following results were obtained. A. The effects of exercise prescription to small cage raising: 1) Non-swimming small cage (7.5×15×20cm) group was resulted -17.5% accumulated food intake, -14.3% average body weight and -6.8% average tail length to the non-swimming normal cage (15×30×20cm) group. 2) In 16 min and 96 min actual swimming time/week, small cage groups were little or no diminished on the difference of the body weight and tail length to each corresponded normal cage groups. B. The amount of swimming time and the peak value of growth: 1) In 48 min actual swimming/week, peak values were observed on the femur length, gastrocnemius and femur weight. 2) In 96 min actual swimming/week, peak values were taken on the tail length, body, heart and adrenal weight. 3) In 384 min actual swimming/week, no peak value was observed, and significant decreases were indicated on the femur length, gastrocnemius and femur weight to the non-swimming. C. The growing difference between intermittent and continuous swimming: 1) In 16 min and 96 min actual swimming/week, continuous (repetitions 16 min swimming and 2 min rest) groups were obviously higher than in intermittent (repetitions 2 min swimming and 2 min rest) groups on the food intake, tail and femur length, heart, adrenal, liver, kidney, gastrocnemius and femur weight, cross section area and marrow cavity area of femur, except the body and spleen weight. 2) In 384 min actual swimming/week, however, continuous group was indicated such remarkable decrease on almost all tissues and organs that the body, spleen and gastrocnemius weight were showed lower than the non-swimming group. D. The tendency of growing process about training frequency and actual swimming time: 1) It was found that the larger grow in training frequency (1 day, 3 days and 6 days/week) and actual swimming time (60 min and 120 min/week), the more increase in the food intake, heart weight, adrenal weight, breaking bending load, proportion of muscle fiber and average area/fiber in cross section of gastrocnemius. 2) But, on 3 days training frequency in 60 min actual swimming and 1 day training frequency in 120 min actual swimming, the tail and femur length, and gastrocnemius and femur weight were the largest growth among these three training frequency. 3) The bending strength of femur on 3 days training frequency was indicated the strongest one in both of 60 min and 120 min actual swimming groups.
An experiment was carried with 15 males (60.2 years old on the average) and 12 females (43.3 years old on the average) who had made it a rule to run regularly for exercise in daily life. The females were before the climacteric stage. Its purpose was to study the serum cholesterol fraction in relation to food intake and distance, duration, and speed of running for exercise. The following results were obtained. 1) The composite variable of serum lipid synthesis tended to be affected more distinctly by the group with food intake as indicator than by the group with locomotion as indicator. It seemed to be influenced primarily by the amount of food intake to a remarkable extent, and secondarily by the group with locomotion as indicator. In this group an increase in consumption of energy with the practice of running exercises participated in bringing about such influence. 2) It was suggested that great care should be taken for food intake in performing running exercises as a habit, taking energy consumed by running into consideration.
Variation of the length of skeletal muscle fibers and sarcomere lengths were investigated in extensor digitorum longus (EDL) and soleus (SOL) muscles in mice (ICR) during postnatal growth in the range from 2 to 12 weeks after the birth. EDL and SOL were fixed in 2.5% gultaraldehyde contained Lock's solution at right angle position of articulatio genus and talocruralis. Single muscle fibers were dissected and lengths of fibers were measured under the dissecting microscope. For measuring sarcomere lengthes, laser diffraction technique was used. Following results were obtained; (1) the length of muscles and muscle fibers increased rapidly up to 8 and 5 weeks in EDL and SOL respectively; (2) relative muscle and fiber lengths at 12 weeks against 2 weeks were 1.72 and 1.30 in EDL, 1.60 and 1.32 in SOL; (3) sarcomere lengths at both ends of the fiber showed no significant change during growth; (4) on the other hand, sarcomere lengths at mid point showed maximum values at 8 and 5 weeks in EDL and SOL respectively. These observations suggest that the sarcomere are stretched especially at mid point when lengths of muscle fibers increase rapidly. It would be possible to consider that this changes of the sarcomere length during postnatal growth affect the contractile properties of muscles.