The present study was conducted to investigate the effect of acid-base disturbance on blood lactate concentration (bLA) and OBLA (Onset of Blood Lactate Accumulation) during an incremental bicycle test.
Nine healthy male subjects underwent the incremental test at 60 min after the oral administration of NH₄Cl (acidotic-treatment ; Acid), NaHCO₃ (alkalotic-treatment ; Alk) and NaCI (control ; Cont) at 1.87 mM⋅kg^-1body weight. Exercise was started at a load of 80W, which was subsequently increased by 10W every minute until exhaustion. During exercise, O²intake (VO²), ventilatory volume (VE) and heart rate (HR) were monitored continuously. Venous blood samples were obtained before administration and every 2 min during exercise.
No change could be detected in resting VO₂, VE and HR following oral administration of NH₄Cl, NaHCO₃and/or NaCl. At 60 min after oral administration venous blood pH (_vpH) and bicarbonate ion concentration (_v [HCO₃^-] ) were significantly lower in Acid (7.265±0.033; p <0.001, 23.6±1.8 mM⋅1^-1; p<0.01) ; and significantly higher in Alk (7.370±0.045 ; p<0.01, 29.7±1.6 mM⋅1^-1; p<0.01) compared to Cont (7.318±0.041, 26.6±2.1 mM⋅1^-1) . Changes in VO₂, VE and HR during exercise were essentially the same in all cases. No differences were observed in exercise time. During exercise, vpH and_v [HCO₃^-] gradually decreased, but remained significantly lower in Acid and higher in Alk compared to Cont. Blood lactate concentration (bLA) increased during exercise. Peak values were observed at exhaustion, but it was lower in Acid (8.03±1.18mM⋅1^-1) and higher in Alk (10.73±1.48) compared to Cont (9.49±1.79) in all subjects. The Onset of Blood Lactate Accumulation (OBLA) was determined for each subject. OBLA was significantly higher in Acid (71.9±9.1%VO₂max) than Cont (62.5±9.9%VO₂max) and Alk (62.2±8.0%VO₂max) .
Changes in acid-base balance were found to cause differences in bLA responses to the same exercise load and possibly change OBLA. Care must be taken when using OBLA or LT as an index of aerobic capacity in some patients with acid-bace disorders; hemodialitic, obese or diabetic patient.

We examined the relationship between serum magnesium (sMg) change and urinary Mg (uMg) excretion, lipid metabolism and hormonal responses induced by prolonged physical exercise. Six recreational runners voluntary participated in the study, and their sMg, uMg, serum lipid and circulatory levels of plasma hormones (ACTH, cortisol, ADH, aldosterone) were determined during a 1-week recovery period after a full-marathon race. Immediately after the race, fall of sMg was significant, but recovered to the pre-race level in the next day. Urinary Mg excretion decreased significantly after the race and the tubular reabsorption rate (%TRMg) was elevated for one week. The negative correlation between sMg and %TRMg suggested that a decreased level of sMg enhanced tubular reabsorption of Mg. On the other hand, no correlation was observed between the plasma hormone levels and %TRMg, thus hormonal responses induced by prolonged exercise had less effect on the tubular reabsorption of Mg. Therefore, fall of sMg after the full marathon race may not be a reflection of Mg depletion, but seems to be the result of a Mg shift to other regions (muscle, erythrocytes and adipose cells) from the serum. Increased level of serum FFA after the race suggested enhanced lipolysis, which might be a cause of sMg reduction.

A cross-sectional study was carried out to investigate the effect of physical exercise in daily lives of healthy women on the aging process in terms of maximal aerobic capacity (VO₂max), body fat tissue mass (FTM), lean tissue mass (LTM), bone mineral density (BMD), serum triglyceride (TG), total cholesterol (TC), HDL-C and LDL-C concentrations, and systolic (SBP) and diastolic blood pressure (DBP) . These parameters are considered as risk factors of cerebrovascular disease and/or osteoporosis, which are the main causes of becoming bedridden and demented in middle-aged and older women. One hundred sixty-five healthy female volunteers aged 20 to 76 years participated in the study, 82 of whom were postmenopausal with a mean age at menopause of 49.7±3.1 years. Eighty-two of the subjects had been exercising regularly by jogging, swimming, aerobic dancing, or playing tennis more than twice a week for 2 years (Ex group), whereas 83 individuals had not been engaging in regular exercise (Cont group) . Serum lipid concentrations, SBP and DBP measurements at rest and treadmill VO₂max and HRmax measurements were determined in the morning after an overnight fast. Whole-body BMD (TBMD), head, lumbar, arm and leg BMD, FTM and LTM were measured by dual-energy X-ray absorptiometry one to two hours after a light lunch. The mean and SD of each measurement were calculated for five-year age groups between 40 and 60 years and one group each under 40 and over 60 years.
The results were as follows:
1, VO₂max (r=-0.590) and HRmax (r=-0.632) decreased significantly with age. The VO₂max of the Ex group was significantly higher than that of the Cont group in all each age groups. However, no differences in the aging process in terms of HRmax were found between the two groups.
2, Resting SBP (r=-0.391) and DBP (r=0.315) increased significantly with age. However, no hypertensive individuals (160/95 mmHg-) were found among the 165 subjects.
3. Only serum TC (r=0.346) and LDL-C (r=0.339) among the blood constituents measured changed with age. No changes in serum HDL-C were detected with age. Lower TC (189.2±23.3 mg/dl) and higher HDL-C (72.2±10.9 mg/dl) were observed in eleven runners (49.7±7.7 years) among the subjects who participated frequently in official races than in subjects of the same ages in the Cont group. The highest serum HDL-C (75.8±15.8 mg/dl) and HDLC/TC ratios (0.362) were noticed among the subjects (n=26) who both regularly exercised and consumed alcoholic beverages.
4. A tendency for FTM to increase and LTM to decrease with age were observed in both groups, and a lower %FTM (percentage of FTM to body weight) and higher %LTM were evident in the Ex group. Differences in %FTM and %LTM between the Ex and Cont groups at 40-45 years were significant.
5. Partial and whole BMDs decreased significantly with age (TBMD-Age ; r=- 0.527) . Significantly higher leg BMDs in both the 20-39-year and 40-45-year groups, and spine and TBMD in the 20-39 years in the Ex group, who were premenopausal women, were shown. No significant differences in BMDs between the two groups were observed in postmenopausal women, but the Ex group tended to have higher partial and whole BMDs. The postmenopausal official race runners (n=5.52.6-1.5years) also had higher TBMD and leg BMD values than subjects of the same ages in the Cont group.
6. Investigation of correlations between VO₂max, LTM, FTM, BMDs and serum lipid concentrations, yielded a significantly higher correlation (r=0.669) between LTM (kg) and absolute VO₂max (1/mm) . Although VO₂max per LTM (VO₂max/LTM) decreased with age (r=-0.595), VO₂max/LTM in the Ex group was significantly higher than in the Cont group in each age group. The VO₂max per body weight (ml/kg/min) was negatively correlated with %FTM (r=-0.442) and positively correlated with

The effect of ingestion of a chilled carbohydrate and electrolyte solution on metabolic and hormonal responses and water-electrolyte balance was studied after two 5-km runs in hot outdoor conditions (Temp, 30.6-30.9°C ; humidity, 61.3-62.4%) . Eight healthy females (mean age 21.8 years) participated in : 1) a control experiment (Copt) with no fluid intake, 2) an experiment with 500 ml of tap water (WI), and 3) an experiment with 500 ml of sports beverage (SB) containing carbohydrate and electrolytes each of which were given after the 1st 5-km run, followed by a second 5-km run with an equivalent to 68.7-72.3% of VO₂max. In the Cont, decreases in %ΔPV and blood glucose (BS) and increases in serum osmolality (Sosm), free fatty acid (sFFA) and plasma hormone concentrations related to regulation of the water-electrolyte balance in the body persisted after the 2 nd run. The intake of the sports beverage prevented hypoglycemia and ketoacidosis, as shown by an increase in sFFA and positive results for qualitative analysis of ketone body in the urine, and quick recovery of plasma volume following an endurance run under a hot environment. This study suggests that fluid replacement with a sports beverage containing carbohydrate and electrolytes was superior to plain water or no fluid ingestion in terms of metabolic and hormonal responses and the recovery of plasma volume and elevated rectal temperature following an endurance run under hot conditions.