1.RESPIRATORY AND CIRCULATORY ADJUSTMENTS DURING PROLONGED EXERCISE IN ENDURANCE RUNNERS.
KOHJI HIRAKOBA ; KATSUMI ASANO
Japanese Journal of Physical Fitness and Sports Medicine 1983;32(5):293-301
It was the purpose of this study to elucidate the difference between endurance runners and normal men in respiratory and circulatory adjustments during prolonged exercise, and to evaluate the relationship between the magnitude of the respiratory and circulatory“drift”and the endurance exercise capacity.
Ten male endurance runners (runner group), aged 19-23 years, and nine normal men (control group), aged 19-28 years, exercised on a bicycle ergometer for 60 min at a constant work load requiring 60% of Vo2max for each subject.
In the control group, VE increased approximately 20% from 10th to 60th min of prolonged exercise (P<0.05), with a corresponding decrease in PAco2 (P<0.05), whereas in the runner group VE and PAco2were remained constant throughout prolonged exercise. The above differences of VE and PAco2responses between the control and the runner group could not be accounted for by a rising body temperature and lactic acidosis, because it was found that the magnitude of the rise in rectal temperature (Tre) and the behavior in lactic acid (LA) were not different for the two groups. On the other hand, we failed to find the difference of the pattern in HR and SV responses to prolonged exercise in the runner group as compared with the control group. At each comparable time period during prolonged exercise, however, the percentage changes from the values at the 10th min in HR and SV were less in the runner group than in the control group. In addition, Vo2max (ml/kg/min) correlated significantly with the percentage changes in VE (r=-0.534, P<0.05), HR (r=-0.565, P<0.05), and SV (r=0.588, P<0.01) from 10th to 60th min of prolonged exercise.
The results of this study suggest that the endurance training may improve the magnitude of the respiratory and circulatory “drift”, which appears to become a limiting factor to endurance performance.
2.Relationship between CO2 excess due to lactic acid production during exercise and endurance performance.
KOHJI HIRAKOBA ; ATSUO MARUYAMA ; KOHJI MISAKA
Japanese Journal of Physical Fitness and Sports Medicine 1990;39(1):69-77
A study was conducted to assess the relationship between CO2 excess due to lactic acid production during exercise and endurance performance in order to clarify the availability of CO2 excess as an index of endurance capacity. Four healthy males (control group; CON) aged 21-24 years, and six male long-distance runners (LDR) aged 18-22 years, were subjected to incremental maximal testing on a cycle ergometer and 12-min exhaustive track running. The results obtained are summarized as follows.
1) Mean values (±SD) of CO2 excess (ml) were 3, 442±677 ml for LDR and 2, 667±437 ml for CON, respectively. On the other hand, the mean value of CO2 excess per unit body weight (CO2 excess/w) obtained in LDR (59.1±9.07 ml⋅kg-1) was significantly higher than that in CON (40.3±3.54 ml⋅kg-1) (p<0.01) .
2) The ratio of CO2 excess/w to ΔLA (the difference between blood lactate at 1 min after exercise and that at rest) showed a tendency to be higher in LDR (5.59±1.16 ml⋅kg-1⋅mmol-1) than in CON (4.46±0.69 ml⋅kg-1⋅mmol-1) . However, there was no significant difference between these two groups in the ratio of CO2 excess/w to ΔLA.
3) The CO2 excess/w (ml⋅kg-1) was significantly related to Vo2max (r=0.813, p<0.01) and Vo2AT (r=0.892, p<0.001), respectively. Moreover, CO2 excess/w was significantly correlated with ΔHCO3- (the difference between blood bicarbonate at l min after exercise and that at rest) (r=0.649, p<0.05) .
4) The CO2 excess (ml) and CO2 excess/w (ml⋅kg-1) were significantly correlated with 12-min exhaustive running performance (r=0.715, p<0.05, r=0.933, p<0.001), as was the ratio of CO2 excess/w to d LA (r=0.671, p<0.05) .
5) From these results, it was suggested that the CO2 excess/w and the ratio of CO2 excess/w to ΔLA could be important factors related to performance of endurance exercise (i. e., 3, 000-5, 000 m running) accompanied by blood lactate accumulation.
3.Characteristics of blood lactate disappearance due to relative recovery exercise in endurance-trained man.
ATSUO MARUYAMA ; KOHJI HIRAKOBA ; KOUJI MISAKA
Japanese Journal of Physical Fitness and Sports Medicine 1991;40(2):156-163
Blood lactate disappearance in endurance-trained men (ET) and untrained men (UT) was investigated by application of recovery exercise with high relative intensity. Blood lactate was measured in five male long-distance runners as ET and in seven male relatively active students as UT, using a cycle ergometer (60 rpm) . Two kinds of recovery exercise were performed at intensities of 70% and 40% Vo2max for 20 min followed by main exercise at 90% Vo2max for 3 min. The rate of blood lactate removal was calculated by linear regression of time (min) against blood lactate (mmol·l-1) at 5, 10, 15 and 20 min during recovery exercise. Values of blood lactate at 10, 15 and 20 min during recovery exercise at 70% Vo2max were significantly more reduced in ET than in UT (P<0.05, P<0.01) . There was, however, no significant difference between ET and UT during recovery exercise at 40% Vo2max. The rate A of blood lactate removal during 70% recovery exercise was significantly greater in ET (0.2730±0.0920mmol·l-1.min-1) than in UT (0.0520±0.1010mmol·l-1·min-1) (P<0.01), but there was no significant difference in the rate between ET and UT during 40% recovery exercise. The rate B of blood lactate removal during 70% recovery exercise was significantly higher in ET (0.3770±0.08000 mmol·l-1· min-1) than in UT (0.1163±0.14416 mmol·l-1·min-1) (P<0.01), but there was no significant difference in the rate between ET and UT during 40% recovery exercise.
In conclusion, the present data indicate that endurance-trained men possess more pronounced capability for blood lactate removal during recovery exercise at high relative intensity.
4.Kinetics of VCO2 during increnental exercise.
TOKUO YANO ; KATSUMI ASANO ; TAKEO NOMURA ; AKIRA MATSUZAKA ; KOHJI HIRAKOBA
Japanese Journal of Physical Fitness and Sports Medicine 1984;33(4):201-210
The purpose of this study was to investigate the kinetics of Vco2during incremental exercise. The subjects were 7 males, age 21-28 years, exercised at two steady state work loads (540 kpm/min, 810 kpm/min) and incremental work load which was increased stepwise by every 1 min from 180 kpm/min to exhaustion. The Vo2and Vco2during steady state exercise (4 to 5 min) were determined by the Douglas bag method and arterialized blood samples were taken for lactate (LA) analysis and blood gas analysis. The Vo2, Vco2, and blood lactate were also determined throughout the incremental exercise. At exhaustion, mixed venous Pco2 (PVco2) was determined by the CO2rebreathing method.
1) The Vco2values at rest and during steady state exercise were linearly related to the Vo2values. When the regression line was compared with Vco2during the incremental exercise on the same Vo2, the Vco2during the incremental exercise below the anaerobic threshold showed lower values.
2) The total sum of the difference in Vco2between steady state and incremental exercise was defined as CO2store. The calculated CO2store and CO2store per body weight were significantly related to PVco2at exhaustion in incremental exercise, respectively (r=0.954, r=0.954) .
3) At work load below the anaerobic threshold, Vco2was linearly related to Vo2. If the Vco2above the anaerobic threshold is estimated from Vo2using the regression line obtained at work load below the anaerobic threshold, the estimated Vco2will be lower than the measured Vco2. The total sum of the difference in the Vco2was defined as CO2excess. The CO2excess and the CO2excess per body weight were significantly related to ΔLAmax (the difference between LA at 3rd min after exhastion and LA at exercise below the anaerobic threshold), respectively (r=0.870, r=0.930) .
4) HCO3-calculated from blood gases (pH and Pco2) was significantly related to LA (r=-0.902) . The increase of 1 mM/1 in LA was corresponding to the decrease of 0.843 mEq/l in HCO3-.
5) From these results, it appeared that the expired Vco2during the incremental exercise consisted of the stored Vco2, the exceeded Vco2, and the produced Vco2 (Vco2metabolically produced from Vo2) .