ABSTRACT
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% Vo<SUB>2</SUB>max for 20 min followed by main exercise at 90% Vo<SUB>2</SUB>max for 3 min. The rate of blood lactate removal was calculated by linear regression of time (min) against blood lactate (mmol·<I>l</I><SUP>-1</SUP>) 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% Vo<SUB>2</SUB>max 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% Vo<SUB>2</SUB>max. The rate A of blood lactate removal during 70% recovery exercise was significantly greater in ET (0.2730±0.0920mmol·<I>l</I><SUP>-1</SUP>.min<SUP>-1</SUP>) than in UT (0.0520±0.1010mmol·<I>l</I><SUP>-1</SUP>·min<SUP>-1</SUP>) (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·<I>l</I><SUP>-1</SUP>· min<SUP>-1</SUP>) than in UT (0.1163±0.14416 mmol·<I>l</I><SUP>-1</SUP>·min<SUP>-1</SUP>) (P<0.01), but there was no significant difference in the rate between ET and UT during 40% recovery exercise.<BR>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.
ABSTRACT
A study was conducted to assess the relationship between CO<SUB>2</SUB> excess due to lactic acid production during exercise and endurance performance in order to clarify the availability of CO<SUB>2</SUB> 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.<BR>1) Mean values (±SD) of CO<SUB>2</SUB> excess (m<I>l</I>) were 3, 442±677 m<I>l</I> for LDR and 2, 667±437 m<I>l</I> for CON, respectively. On the other hand, the mean value of CO<SUB>2</SUB> excess per unit body weight (CO<SUB>2</SUB> excess/w) obtained in LDR (59.1±9.07 m<I>l</I>⋅kg<SUP>-1</SUP>) was significantly higher than that in CON (40.3±3.54 m<I>l</I>⋅kg<SUP>-1</SUP>) (p<0.01) .<BR>2) The ratio of CO<SUP>2</SUP> 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 m<I>l</I>⋅kg<SUP>-1</SUP>⋅mmol<SUP>-1</SUP>) than in CON (4.46±0.69 m<I>l</I>⋅kg<SUP>-1</SUP>⋅mmol<SUP>-1</SUP>) . However, there was no significant difference between these two groups in the ratio of CO<SUP>2</SUP> excess/w to ΔLA.<BR>3) The CO<SUP>2</SUP> excess/w (m<I>l</I>⋅kg<SUP>-1</SUP>) was significantly related to Vo<SUB>2</SUB>max (r=0.813, p<0.01) and Vo<SUB>2</SUB>AT (r=0.892, p<0.001), respectively. Moreover, CO<SUB>2</SUB> excess/w was significantly correlated with ΔHCO<SUB>3</SUB>- (the difference between blood bicarbonate at l min after exercise and that at rest) (r=0.649, p<0.05) .<BR>4) The CO<SUB>2</SUB> excess (m<I>l</I>) and CO<SUB>2</SUB> excess/w (m<I>l</I>⋅kg<SUP>-1</SUP>) 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 CO<SUB>2</SUB> excess/w to d LA (r=0.671, p<0.05) .<BR>5) From these results, it was suggested that the CO<SUB>2</SUB> excess/w and the ratio of CO<SUB>2</SUB> 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.
ABSTRACT
The purpose of this study was to investigate the kinetics of Vco<SUB>2</SUB>during 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 Vo<SUB>2</SUB>and Vco<SUB>2</SUB>during 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 Vo<SUB>2</SUB>, Vco<SUB>2</SUB>, and blood lactate were also determined throughout the incremental exercise. At exhaustion, mixed venous Pco<SUB>2</SUB> (PVco<SUB>2</SUB>) was determined by the CO<SUB>2</SUB>rebreathing method.<BR>1) The Vco<SUB>2</SUB>values at rest and during steady state exercise were linearly related to the Vo<SUB>2</SUB>values. When the regression line was compared with Vco<SUB>2</SUB>during the incremental exercise on the same Vo<SUB>2</SUB>, the Vco<SUB>2</SUB>during the incremental exercise below the anaerobic threshold showed lower values.<BR>2) The total sum of the difference in Vco<SUB>2</SUB>between steady state and incremental exercise was defined as CO<SUB>2</SUB>store. The calculated CO<SUB>2</SUB>store and CO<SUB>2</SUB>store per body weight were significantly related to PVco<SUB>2</SUB>at exhaustion in incremental exercise, respectively (r=0.954, r=0.954) .<BR>3) At work load below the anaerobic threshold, Vco<SUB>2</SUB>was linearly related to Vo<SUB>2</SUB>. If the Vco<SUB>2</SUB>above the anaerobic threshold is estimated from Vo<SUB>2</SUB>using the regression line obtained at work load below the anaerobic threshold, the estimated Vco<SUB>2</SUB>will be lower than the measured Vco<SUB>2</SUB>. The total sum of the difference in the Vco<SUB>2</SUB>was defined as CO<SUB>2</SUB>excess. The CO<SUB>2</SUB>excess and the CO<SUB>2</SUB>excess 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) .<BR>4) HCO<SUB>3</SUB><SUP>-</SUP>calculated from blood gases (pH and Pco<SUB>2</SUB>) 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 HCO<SUB>3</SUB><SUP>-</SUP>.<BR>5) From these results, it appeared that the expired Vco<SUB>2</SUB>during the incremental exercise consisted of the stored Vco<SUB>2</SUB>, the exceeded Vco<SUB>2</SUB>, and the produced Vco<SUB>2</SUB> (Vco<SUB>2</SUB>metabolically produced from Vo<SUB>2</SUB>) .
ABSTRACT
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.<BR>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 Vo<SUB>2</SUB>max for each subject.<BR>In the control group, VE increased approximately 20% from 10th to 60th min of prolonged exercise (P<0.05), with a corresponding decrease in PAco<SUB>2</SUB> (P<0.05), whereas in the runner group VE and PAco<SUB>2</SUB>were remained constant throughout prolonged exercise. The above differences of VE and PAco<SUB>2</SUB>responses 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, Vo<SUB>2</SUB>max (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.<BR>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.