This article reports a study in which the equation for total body water (TBW) estimated from deuterium(²H₂0)-dilution method and bioelectrical impedance measurement (BIM) is described. Subjects were 60 healthy males aged 30±l8.3yr (18-74) and 31 healthy females aged 37±17.5yr (19-70). Total body water determined by the analysis of the dilution of orally ingested deuterium oxide (1g²H₂0, 99.75 atom % excess/kg body weight) in urine. Bioelectrical impedance was measured for each subjects in a supine position using an electrical impedance analyzer (500/lA, 50kHz, T-1988K, Toyo Physical Inc.) with a four electrodes (Y-250, Nihon Kohden). The mean values of total body water and the impedance in males and females subjects were 34.l±4.27l and 25.7±2.42l, 567±28.5Ω and 562±32.5Ω, respectively. Height squared divided by resistance (Ht²/R) correlated well with TBW as measured by ²H₂ O, r=0.530 (p<0.001) in males and r=0.782 (p<0.001) in females. The best-fitting regression equation to predlct TBW comprised Ht²/R(X₁) and body w-eight(X₂) (R =0.915, SEE= 1.70 l in males and R =0.834, SEE=1.28 l in females). Equation were provided with BIM instrument for the predrctlon of TBW for males TBW l=0.1983X₁-0.4004X₂ 0.7938 and for females TBW, l =0.3536X₁+0.1269X₂+3.3417. These results suggest that bioelectrical impedance measurement is a useful measure of total body water in Japanese subjects.

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The IVlechanism of Electromyographic Silent Periods a Ballistic Voluntary Planter Flexion Preceding Masashi SHIBATA and Toshio MORITANI Labolatory of Applied Physiology, College of Liberal Arts and Sciences, Kyoto University The present study was designed to investigate the neurophysiological mechanism of electromyographic silent periods(SP) preceding a ballistic voluntary movement. Ten male subjects were asked to respond to the flashing light by performing a plantar flexion as strongly and quickly as possible. The myoelectric signals from agonist (m. gastrocnemius, caput laterale : LG, m. soleus : SOL) and antagonist (m. tibialis anterior : TA) were simultaneously recorded together with the isometric contraction force signal. The excitability of the alpha motoneuron pools by means of the H reflex analysis was also determined at various phases of the movement. The results obtained are as follows : 1 ) In five out of 10 subjcts, the electromyographic silent period was consistently observed (SP Group), while the rest of the subjects did not show such changes (NSP Group). 2 ) The maximum rate of tension raise (dF/dt) in SP Group (32.3±24.9 N/ms) was significantly (p<.05) greater than NSP Group (15.I±12.0 N/ms). 3 ) In SP Group, the averaged H-wave mean amplitude decreased about 40ms prior to the appearence of SP. From these results, it can be concluded that SP in this study was attributable to the supraspinal influences so as to allow a speciflc motor program to be executed for selective recruitment of phasic (high threshold) motor units.

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A comparative study was conducted between two independent methods to estimate body fat in 13 college male distance-runners (20.2±1.1 yrs) and 11 male college students (19.6±0.7 yrs) as control group. The methods dealt with different body component parameters. Body fat was estimated (1) in terms of total body water based on the analysis of dilution of orally ingested deuterium oxide (D₂0) in urine, and (2) in terms of body density based on underwater weighing. The results were as follows : 1) The skinfold thickness at 14 sites in distance-runners were thinner than those in control group. The mean values for subcutaneous fat in distance-runners were 4.310.7kg (7.2±1.1%), which were lower than those (8.3±2.7kg & 13.3±3.4%) in control group signlfi-cantly. Oh the other hand, the mean values for internal fat in distance-runners were 8.7±l.4kg (14.4±1.6%), Which were larger than those (6.5±3.Ikg & 10.2±4.3%) in control group. 2) The mean values for percent body fat in control group were 16.1±l.6% by skinfolds method, 20.2±5.1% by body density method and 23.5±4.6% by total body water method. The estimated values of percent body fat by the methods of body density and total body water were approximately the same. 3) The mean values for percent body fat in distance-runners were 11.9±I.4% by skinfolds method, 11.8±I.7% by body density method and 21.5±I.9% by total body water method. The estimated values of percent body fat in distance-runners were lower than those in control group. The estimated value of percent body fat by total body water method was as much as 10% higher than those by the methods of skinfolds and body density. The results of this study suggest that total body water method tends to overestimate, and that body density method tends to underestimate the value of percent body fat in dis tance-runners.

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To determine the effects of exercise training on the anthropometric and physiologic characteristics, twenty-eight mildly obese women were studied prior to and following a 14-week exercise training program. The present data demonstrated that regular aeroblc training at an intensity corresponding to lactate threshold (LT) Ied to significant Improvements in VO₂max (12%) and VO₂LT (16%) and significant reductions in systolic (5%) and diastolic blood pressure (9%). Weight (5%) and percent body fat (11%) decreased significantly, while LBM remained essentially unchanged. Although the change in HDLC and HDLC/TC did not reach statistical significance, the TC (8%) and LDLC (7%) decreased significantly. These alterations in cardiorespiratory, anthropometric, and metabolic characteristics clearly demonstrate that training intensity relative to LT may be appropriate for obese individuals to improve the aerobic capacity, Iipid-lipoprotein metabolism, and anthropometric profile.

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It has been reported that respiratory frequency (F) serve to determine anaerobic threshold (AT). The purpose of this study was to investigate whether the method detecting AT by using F is influenced by the subject's condition such as the existence of sport experiences. Ten healthy adults volunteered to perform progressive cycle ergometer exercise with workloads increased by 30-W (female : 20-W) every 2 min at 60 rpm. Vo₂ at AT were determined by four differnt methods, which detect the point of 1)nonlinear increase in V_E, V_CO2, and increase in V_E/Vo₂ Without increasing in V_E/V_CO2 (AT-v), 2) nonlinear increase in F (visual estimation : AT-_V_F), 3) inflection in F by multisegment linear regression (AT-_C_F), 4) inflection with omitting above RC point as with 3) (AT-_CF2)' The mean Vo₂ at AT-_V_F (40.8±9.2ml/kg/min) and AT-_C_F (42.7±9.9ml/kg/min) was significantly higher compared with AT-_V (28.2±l0.4ml/kg/min) and not RC (42.3±10.0ml/kg/min). It would be possible that AT-_V_F and AT-_C_F indicated RC, but not AT. There were no significant differences between AT-_CF2 (28.2±l0. 9ml/kg/min) and AT-_V, and a highly positive correlation (r=0.79, p<0.05) was observed between them. It was recognized that F reached a plateau at AT in four of the subjects. The error between AT-_V and AT-_CF2 was observed individual variations and the error between them within 5% was observed in only one subject. These results suggest that F is inadequate as an indicator of the AT, because F may be influenced by entrainment of breathing and pedalling frequency.

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