A study was conducted to analyze the height growth velocity curve based upon the maturity rate. Ninety-eight longitudinal data points for height (for subjects aged 6 to 17 years) were obtained retrospectively from health examination records in 1983. Growth distance and growth velocity curves of each individual were described by the wavelet interpolation method, and PHV age was determined with the described graph using computer simulation. We classified the growth velocity curve by the maturity rate approximated according to the PHV age. As a result, it was shown that the after-growth spurt in early maturity and somewhat early maturity type appeared more than in the average and somewhat late maturity types, and that conversely, the mid-growth spurt in the late maturity and somewhat late maturity types appeared more than in the early maturity and somewhat early maturity types. Specifically, it was demonstrated that two mid-growth spurts appeared in the late maturity and somewhat late maturity types.
The purpose of this study is to find a key to clarifying the mechanism of lactic acid production during exercise. Five healthy men performed the grip and wrist flexion exercises at different occasions. Exercise intensities were increased by 5% MVC (maximum voluntary contraction force) per minute from 10% MVC. Intracellular pH, oxygenated hemoglobin/myoglobin (Oxy-Hb/Mb), inorganic phosphate (Pi), and phosphocreatin (PCr) in forearm flexor muscles were measured by 31P-MRS and NIRS. The lowest Oxy-Hb/Mb concentrations during the grip and wrist flexion exercises were 40.7± 8.86% (average±SE) and 15.4 ± 2.26%, respectively. These results suggest that oxygen remain sufficient in the muscles at least during the grip exercise. Intracellular pH dropped as exercise intensity rose above 25% MVC for the grip and above 10% MVC for the wrist flexion exercise. These results support the idea that oxygen deficiency is not the only cause for lactic acid production during exercise. On the other hand, intracellular pH fell with either negative or positive relations to Pi/PCr ratio, Pi, and PCr in each exercise. These results support the suggestion that the main causes of lactic acid production during exercise are the changes in ADP, Pi, and PCr.