ABSTRACT
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 VO<SUB>2</SUB>max. 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.
ABSTRACT
Eight young girls as an experimental group (E group) and another eight as a control group (C group), (all aged 4-5 years), participated in the present study to observe the effects of training from May 1992 through November 1993. E group performed a 915m endurance run on an agricultural road every day except Sundays for an 18 month training period. No special training was given to C group. In May 1992 (T 1), November 1992 (T 2), May 1993 (T 3), and November 1993 (T 4), both groups underwent treadmill tests in order to check aerobic variables such as heart rate (HR) and oxygen uptake (VO<SUB>2</SUB>) during the course of the training period.<BR>Times required for the run became shorter from summer to fall and from winter to spring (shortening phase), whereas they became prolonged from spring to summer and from fall to winter (prolongation phase) . Therefore, there was a definite seasonality of performance endurance. The rates of shortening in the required times observed from summer to fall were considerably higher than from winter to spring, and this was reflected in the significant improvement of maximal running speed on the treadmill (Vmax) and maximal oxygen uptake in terms of body weight (VO<SUB>2</SUB>max⋅ TBW<SUP>-1</SUP>) from T 1 to T 2 as well as from T 3 to T 4. Thus, significant differences were found between the groups at T 2 and T 4. HR levels during the endurance run were close to 95% HRmax regardless of the phase. Accordingly, the prolongation phases, during which circulatory parameters and ventilatory capacity were least improved, could be regarded as a preparatory period for the following shortening period, during which work load intensities furthermore increased the arteriovenous oxygen differences. Thus, when planning research on the effects of training on aerobic work capacity in the field, special attention should be paid to the season and the training period, and the timing of the examination for training effects, or otherwise, misleading conclusions could be drawn.
ABSTRACT
Twelve young boys as an experimental group and seven as a control group, aged 5-6 years, participated in a study to clarify whether circulorespiratory trainability exists in young children. The subjects in the experimental group performed a 915 m endurance run on an agricultural road every day except Sundays for six months. During the run, heart rates (HR) equivalent to 3-4 mmol⋅<I>l</I><SUP>-1</SUP> of blood lactate concentration (LA) were maintained for at least 3-4 min⋅m<SUP>-1</SUP>. The control group was given no special training.<BR>Before and after the training period, both groups were subjected to increased stepwise running velocity on a flat treadmill till subjective exhaustion to determine circulorespiratory variables such as heart rate (HR), oxygen uptake (Vo<SUB>2</SUB>) and blood lactate concentration (LA) at all steps.<BR>From the above mentioned procedure, the following findings were obtained :<BR>1) After the 6-month endurance run training, Vo<SUB>2</SUB>max/TBW was significantly (p<0.05) increased from 47.5 to 50.4 m<I>l</I>⋅kg<SUP>-1</SUP>⋅min<SUP>-1</SUP> and also the peak LA was significantly (p<0.05) increased from 5.41 to 6.36 mmol⋅<I>l</I><SUP>-1</SUP>in the experimental group. On the other hand, no significant increases were observed in the control group.<BR>2) Running velocity in the final stages (Vmax) was significantly (p<0.001) improved from 190.0 to 205.0 m⋅min<SUP>-1</SUP>in the experimental group. Such effects were due partly to the improvement of circulorespiratory function and partly to improved efficiency of running motion. However, no significant differences were found in the control group.<BR>3) Submaximal V, HR, and Vo<SUB>2</SUB>/TBW equivalent to 3 and 4 mmol⋅<I>l</I><SUP>-1</SUP> and their values relative to the maximum values showed no significant differences before and after the training period in both groups. The improvement of maximal circulorespiratory variables observed in the experimental group suggests the existence of trainability even in young children.