Influence of moderate cold exposure on blood lactate during incremental exercise

Summary This study examined the effect of exposure of the whole body to moderate cold on blood lactate produced during incremental exercise. Nine subjects were tested in a climatic chamber, the room temperature being controlled either at 30°C or at 10°C. The protocol consisted of exercise increasing in intensity in 35 W increments every 3 min until exhaustion. Oxygen consumption (VO₂) was measured during the last minute of each exercise intensity. Blood samples were collected at rest and at exhaustion for the measurement of blood glucose, free fatty acid (FFA), noradrenaline (NA) and adrenaline (A) concentrations and, during the last 15 s of each exercise intensity, for the determination of blood lactate concentration [la^–]_b. TheVO₂ was identical under both environments. At 10°C, as compared to 30°C, the lactate anaerobic threshold (Th_{an, la} ^–) occurred at an exercise intensity 15 W higher and [Th_{an, la} ^–]_b was lower for submaximal intensities above the Th_{an, la} ^– Regardless of ambient temperature, glycaemia, A and NA concentrations were higher at exhaustion while FFA was unchanged. At exhaustion the NA concentration was greater at 10°C [15.60 (SEM 3.15) nmol·l^–1] than at 30°C [8.64 (SEM 2.37) nmol·l^–1]. We concluded that exposure to moderate cold influences the blood lactate produced during incremental exercise. These results suggested that vasoconstriction was partly responsible for the lower [la^–]_b observed for submaximal high intensities during severe cold exposure.     

Blood lactate during constant-load exercise at aerobic and anaerobic thresholds

Summary Venous blood lactate concentrations [la_b] were measured every 30 s in five athletes performing prolonged exercise at three constant intensities: the aerobic threshold (Th_aer), the anaerobic threshold (Th_an) and at a work rate (IWR) intermediate between (Th_aer and Th_an. Measurements of oxygen consumption and heart rate (HR) were made every min. Most of the subjects maintained constant intensity exercise for 45 min at Th_aer and IWR, but at Th_an none could exercise for more than 30 min. Relationships between variations in [la_b] and concomitant changes in or HR were not statistically significant. Depending on the exercise intensity (Th_aer, IWR, or Th_an) several different patterns of change in [la_b] have been identified. Subjects did not necessarily show the same pattern at comparable exercise intensities. Averaging [la_b] as a function of relative exercise intensity masked spatial and temporal characteristics of individual curves so that a common pattern could not be discerned at any of the three exercise levels studied. The differences among the subjects are better described on individual [la_b] curves when sampling has been made at time intervals sufficiently small to resolve individual characteristics.     

Effect of acute sodium bicarbonate ingestion on excess C02 output during incremental exercise

Summary The effect of bicarbonate ingestion on total excess volume of CO₂ Output (CO₂ excess), due to bicaronate buffering of lactic acid in exercise, was studied in eight healthy male volunteers during incremental exercise on a cycle ergometer performed after ingestion (0.3 g · kg^–1 body mass) of CaCO₃ (control) and NaHCO₃ (alkalosis). The resting arterialized venous blood pH (P<0.05) and bicarbonate concentration ([HCO₃ ^–]_b;P<0.01) were significantly higher in acute metabolic alkalosis [AMA; pH, 7.44 (SD 0.03); [HCO₃ ^–]_b; 29.4 (SD 1.5) mmol·1^-1] than in the control [pH, 7.39 (SD 0.03); [HCO₃ ^–]_b, 25.5 (SD 1.0) mmol·1^–1]. The blood lactate concentrations ([la^–]_b) during exercise below the anaerobic threshold (AT) were not affected by AMA, while significantly higher [la^–]_b at exhaustion [12.29 (SD 1.87) vs 9.57 (SD 2.14) mmol·1^–1,P < 0.05] and at 3 min after exercise [14.41 (SD 1.75) vs 12.26 (SD 1.40) mmol · l^–1,P < 0.05] were found in AMA compared with the control. The CO₂ excess increased significantly from the control [3177 (SD 506) ml] to AMA [3897 (SD 381) ml;P < 0.05]. The CO₂ excess per body mass was found to be significantly correlated with both the increase of [la^–]_b from rest to 3 min after exercise ( [la^–]_b;r=0.926,P < 0.001) and with the decrease of [HCO₃ ^–]_b from rest to 3 min after exercise ( [HCO₃ ^–]_b;_r=0.872,P<0.001), indicating that CO₂ excess per body mass increased linearly with both [la^– _b and [HCO₃ ^–]_b. As a consequence, CO₂ excess per body mass per unit increase of [la^–]_b (CO₂ excess·mass^–1· [la^–]_b) was similar for the two conditions. The present results would suggest that the relationship between CO₂ excess and blood lactate accumulation was unaffected by acute metabolic alkalosis, because the relative contribution of bicarbonate buffering of lactic acid was the same as in the control.     

Effect of previous supramaximal work on lacticaemia during supra-anaerobic threshold exercise

Summary Twelve male and female subjects (eight trained, four untrained) exercised for 30 min on a treadmill at an intensity of maximal O₂ consumption (% O_2max) 90.0%, SD 4.7 greater than the anaerobic threshold of 4 mmol ·1^–1 (Th_an =83.6% O_2max, SD 8.9). Time-dependent changes in blood lactate concentration ([la_b]) during exercise occurred in two phases: the oxygen uptake ( O₂) transient phase (from 0 to 4 min) and the O₂ steady-state phase (4–30 min). During the transient phase, [la_b] increased markedly (l.30 mmol · l ^–1 · min ^–1, SD 0.13). During the steady-state phase, [la_b] increased slightly (0.02 mmol · 1^–1 · min^–1, SD 0.06) and when individual values were considered, it was seen that there were no time-dependent increases in [la_b] in half of the subjects. Following hyperlacticaemia (8.8 mmol -l^–1, SD 2.0) induced by a previous 2 min of supramaximal exercise (120% O_2max), [la_b] decreased during the O₂ transient (–0.118 mmol · 1^–1 · min^–1, SD 0.209) and steady-state (–0.088 mmol · 1^–1 · min ^–1, SD 0.103) phases of 30 min exercise (91.4% O_2max, SD 4.8). In conclusion, it was not possible from the Th_an to determine the maximal [la_b] steady state for each subject. In addition, lactate accumulated during previous supramaximal exercise was eliminated during the O₂ transient phase of exercise performed at an intensity above the Th_an. This effect is probably largely explained by the reduction in oxygen deficit during the transient phase. Under these conditions, the time-course of changes in [la_b] during the O₂ steady state was also affected.     

Threshold increases in plasma growth hormone in relation to plasma catecholamine and blood lactate concentrations during progressive exercise in endurance-trained athletes

Plasma human growth hormone ([HGH]), adrenaline ([A]), noradrenaline ([NA]) and blood lactate ([La^–]_b) concentrations were measured during progressive, multistage exercise on a cycle ergometer in 12 endurance-trained athletes [aged 32.0 (SEM 2.0) years]. Exercise intensities (3 min each) were increased by 50 W until the subjects felt exhausted. Venous blood samples were taken after each intensity. The [HGH] and catecholamine concentrations increased negligibly during exercise of low to moderate intensities revealing an abrupt rise at the load corresponding to the lactate threshold ([La^–]-T). Close correlations (P < 0.001) were found between [La^–]_b and plasma [HGH] (r = 0.64), [A] (r = 0.71) and [NA] (r = 0.81). The mean threshold exercise intensities for [HGH], [A] and [NA], detected by log-log transformation, [154 (SEM 19) W, 162 (SEM 15) W and 160 (SEM 17) W, respectively] were not significantly different from the [La^–]-T [161 (SEM 12) W]. The results indicated that the threshold rise in plasma [HGH] followed the patterns of plasma catecholamine and blood lactate accumulation during progressive exercise in the endurancetrained athletes.     

Relationship between plasma ammonia and blood lactate concentrations after maximal treadmill exercise in circumpubertal girls and boys

Summary The purpose of the study was to define a relationship between plasma ammonia [NH₃]_p1 and blood lactate concentrations [1a^–]_b after exercise in children and to find out whether the [NH₃]_p1, determined during laboratory treadmill tests, may be useful as a predictor of the children's sprint running ability. A group of 20 girls and 14 boys trained in athletics or swimming and 8 untrained boys, aged 13.2 to 13.7 years, participated in the study. Their [NH₃]_p1 and [1a^–]_b were measured before and after incremental maximal treadmill exercise. In addition, the subjects' running performance was tested in 30-, 60- and 600- or 1000-m runs under field conditions. The [NH₃]_p1 during the treadmill runs increased by 20.1 (SD 17.3), 24 (SD 16.7) and 10 (SD 4.3) mol·1^–1 in the girls, the trained boys and the untrained boys, respectively. The postexercise [NH₃]_p1 correlated positively with [1a^–]_b (r=0.565 in the girls and 0.812 in the boys) and treadmill speed attained during the test (r=0.489 in the girls and 0.490 in the boys). Significant correlations were also found between [NH₃]_p1 obtained during the treadmill test and the times of 30- and 60-m runs (r= –0.676 and –0.648, respectively) in the boys but not in the girls. A comparison of the present data with those reported previously in adults showed that increases in [NH₃]_p1 during maximal exercise in children would seem to be lower than in adult subjects both in absolute values and in relation to [1a^–]_b. The present data would also suggest that [NH₃]_p1 reflects involvement of anaerobic processes during maximal treadmill exercise in circumpubertal children but it has a small practical value for predictiton of their sprint running ability.     

Relationships between postcompetition blood lactate concentration and average running velocity over 100-m and 200-m races

The relationships between anaerobic glycolysis and average velocity () sustained during sprint running were studied in 12 national level male sprinters. A blood sample was obtained within 3 min of the completion of semi-finals and finals in the 100-m and 200-m Cameroon national championships and blood lactate concentration ([la^–]_b) was measured. The 35-m times were video-recorded. The 100-m and 200-m [la^–]_b were 8.5 (SD 0.8) and 10.3 (SD 0.8) mmol·l^–1, respectively. These were not correlated with the performances. Over 200 m [la^–]_b was correlated with the sustained over the last 165 m (r=0.65,P<0.05). In the 9 athletes who participated in both the 100-m and 200-m races, the difference between the [la^–]_b measured at the end of the two races was negatively correlated to the difference in v sustained over the two races (r=0.76,P>0.02). Energy expenditure during sprint running was estimated from the [la^–]_b values. This estimate was mainly based on the assumption that a 1 mmol·l^–1 increase in [la^–]_b corresponds to the energy produced by the utilization of 3.30 ml O₂·kg^–1. The energy cost of running was estimated at 0.275 (SD 0.02) ml O₂·kg^–1·m^–1 over 200-m and 0.433 (SD 0.03) ml O₂·kg^–1·m^–1 over 100-m races. These results would suggest that at the velocities studied anaerobic glycolysis contributes to at least 55% of the energy expenditure related to sprint running. However, the influence of both mechanical factors and the contribution of other energy processes obscure the relationship between [la^–]_b and performance.     

Lactate uptake by forearm skeletal muscles during repeated periods of short-term intense leg exercise in humans

We investigated the role of the forearm skeletal muscles in the removal of lactate during repeated periods of short-term intensive leg exercise, i.e. a force-velocity (FV) test known to induce a marked accumulation of lactate in the blood. The leg FV test was performed by seven untrained male subjects. Arterial and venous blood samples for determination of arterial ([la^–]_a) and venous ([la^–]_v) plasma lactate concentrations were concomitantly taken at rest before the test, during the FV test at the end of each period of intensive exercise just before the 5-min between-sprint recovery period, and after the completion of the test at 2, 4, 6, 8, 10, 15, and 20 min of the final recovery. The arteriovenous difference in concentration for plasma lactate ([la^–]_a–v) was determined for each blood sample. During the test, [la^–]_a and [la^–]_v increased significantly (P < 0.001;P < 0.001) with significantly higher values for [la^–]_a (P < 0.001). At the onset of the test, [la^–]_a–v became positive and increased up to a braking force of 6 kg, correlating significantly with [la^–]_a (r = 0.61,P < 0.001) with power (r = 0.58,P < 0.001) during the test. At the end of the test, [la^–]_a, [la^–]_v and [la^–]_a–v decreased (P < 0.001;P < 0.001;P < 0.001 respectively) but were still higher than the basal values after 20-min of passive recovery. In conclusion, forearm skeletal muscles would seem to have been involved in the removal of lactate from the blood during the leg FV test, with an increase in lactate uptake proportional to the increase in plasma lactate concentration and power.     

Effects of aerobic exercise conditioning at intensities corresponding to lactate threshold in the elderly

Summary In this study we attempted to determine the effects of exercise training at the intensity corresponding to lactate threshold (Th_la ^–) on various health-related variables in sedentary but apparently healthy elderly subjects. Six men and five women volunteers [mean age 68.9 (SD 3.4) years] performed supervised endurance-type training on stationary cycle ergometers for 30 min and recreational activities for 30 min, 3 days a week for 12 weeks. Four men and four women served as the control group [68.8 (SD 4.4) years]. As a result of the training programme, statistically significant increases in maximal oxygen consumption (10%), oxygen consumption at Th_la ^–(18%), distance covered in 12-min walk, side step, and leg extensor power were found in the training group, while no changes occurred in the control group. The changes in serum cholesterol and triglyceride concentrations from the pre- to post-training period were statistically significant. High-density lipoprotein cholesterol remained unchanged, and low-density lipoprotein cholesterol tended to decrease following the training programme. These data would indicate that exercise training at the intensity corresponding to Th_la ^–may have favourable effects on overall physical fitness and some serum lipid variables in older individuals.     

Heart rate deflection related to lactate performance curve and plasma catecholamine response during incremental cycle ergometer exercise

The correlation between the behaviour of the heart rate/work performance (f _c W) curve and blood lactate ([la]_b) and plasma adrenaline/noradrenaline concentrations ([A]/[NA]) during incremental cycle ergometer exercise was investigated. A group of 21 male sports students was divided into two groups: group I, with a clear deflection of thef _c W curve; group II, without or with an inverse deflection of thef _c W curve. The aerobic threshold (Th_aer) and the lactate turn point (LTP) were defined. Between Th_aer and maximal work performance (f _c W _max) the behaviour of thef _c W curve as well as the behaviour of [la^–]_b and [A]. [NA] were described mathematically. Thef _c, systolic blood pressure (BP_S),W, [la^–]_b, [A] and [NA] at rest, Th_aer, LTP,f _c W _max, after 3 and 6 min of recovery (Re₃/Re₆) were calculated. A significant difference between the two groups could only be detected forf _c at LTP, Re₃ and Re₆ (P < 0.05). No significant, correlation could be found between individualf _c W-behaviour and individual time course of [la^–]_b, [A] and [NA]. However, a significant correlation was visible between [la^–/W-behaviour and individual catecholamine response. These results and the fact that the different flattening at the top of thef _c W curve was related to diminished stress-dependent myocardial function led us to the conclusion that it is possible that sympathetic drive is not directly involved in mechanisms of regulation between load dependentf _c and myocardial function. In addition, individualf _c W behaviour was independent of BP_S andW _max, or individual conditions of energy supply.     

Maximal heart rates and plasma lactate concentrations observed in middle-aged men and women during a maximal cycle ergometer test

Summary The purpose of this study was to investigate criteria for maximal effort in middle-aged men and women undertaking a maximal exercise test until they were exhausted if no measurements of oxygen uptake are made. A large group of 2164 men and 975 women, all active in sports and aged between 40 and 65 years, volunteered for a medical examination including a progressive exercise test to exhaustion on a cycle ergometer. In the 3rd min of recovery a venous blood sample was taken to determine the plasma lactate concentration ([la^–]_{p, 3min}). Lactate concentration and maximal heart rate (f _{c, max}) were lower in the women than in the men (P<0.001). Multiple regression analyses were performed to assess the contribution of sex to [la^–]_{p, 3 min}, independent of age and f _c max, It was found that [la^–]_{p,3 min} was about 2.5 mmol·l^–1 lower in women than in men of the same age and f _{c, max}. In our population 88% of the men and 85% of the women met a combination of the following f _{c, max} and [la^–]_{p, 3min} criteria: f _{c, max} equal to or greater than 220 minus age beats·min^–1 and/or [la^–]_{p, 3min} equal to or greater than 8 mmol·l^–1 in the men and f _{c, max} equal to or greater than 220 minus age beats·min^–1 and/or [la^–]_{p, 3min} equal to or greater than 5.5 mmol·1^–1 in the women.     

The ventilatory threshold gives maximal lactate steady state

Summary The purpose of this study was to examine whether the ventilatory threshold (Th _v) would give the maximal lactate steady state ([1a]_{ss, max}), which was defined as the highest work rate (W) attained by a subject without a progressive increase in blood lactate concentration [1a]_b at constant intensity exercise. Firstly, 8 healthy men repeated ramp-work tests (20 W·min^–1) on an electrically braked cycle ergometer on different days. During the tests, alveolar gas exchange was measured breath-by-breath, and theW atTh _v (W _{Th v}) was determined. The results of two-way ANOVA showed that the coefficient of variation of a singleW _{Th v} determination was 2.6%. Secondly, 13 men performed 30-min exercise atW _{Th v} (Th _v trial) and at 4.9% aboveW _{Th v} (Th _v + trial), which corresponded to the 95% confidence interval of the single determination. The [1a]_b was measured at 15 and 30 min from the onset of exercise. The [1a]_b at 15 min (3.15 mmol·1^–1, SEM 0.14) and at 30 min (2.95 mmol·1^–1, SEM 0.18) were not significantly different inTh _v trial. However, the [1a]_b ofTh _v+ trial significantly increased (P<0.05) from 15 min (3.62 mmol·1^–1, SEM 0.36) to 30 min (3.91 mmol·1^–1, SEM 0.40). These results indicate thatTh _v gives the [1a]_ss,max, at which one can perform sustained exercise without continuous [1a]_b accumulation.     

Alterations of regular and mature monocytes are distinct,and dependent of intensity and duration of exercise

Circulating monocytes comprise functionally distinct regular (CD14^bright+) and mature (CD141^low+) cells. Cell surface receptors were determined by three colour flow cytometry in 8 healthy control subjects. Compared to regular monocytes, mature monocytes had lower levels of the high affinity Fcy receptor 1 (CD64), complement receptor 3 (CDllb), CD45RO and higher levels for HLA-DR, LFA-1 (CD11a/CD18), interleukin-2 receptor (CD25), CD45RA and the Fc receptor 3 (CD16). Both regular and mature monocytes were measured before and up to three hours after four different types of exercise (Ex) in endurance trained athletes (n=9-16). Immediately after anaerobic exercise of I min with a maximal lactate concentration (la_max) of I2.3 (SD I.4) mmol · l^–1 and exhaustive exercise of 24 (SD 8) min with a maximal lactate concentration (la_max) of 7.4 (SD 2.6) mmol· l^–1 mature monocytes increased more than regular monocytes. Exhaustive endurance exercise of 87 (SD 21) min [la_max 3.7 (SD I.0)] led to a similar increase of regular and mature monocytes. 15–33 min after a 100km run regular monocytes increased significantly, whereas mature monocytes decreased. Up to three hours after the end of all exercises mature monocytes fell below pre-exercise values. In conclusion, duration and intensity of exercise alter distinct maturation stages of monocytes differently. It is probable that the avidity of adhesion molecules like LFA-1 to their endothelial ligands is increased to enable the firm attachment to the endothelium.     

The comparison of peak oxygen uptake between swim-bench exercise and arm stroke

To compare maximal cardio-respiratory stress between swim-bench exercise (SB) and arm stroke (AS), peak oxygen uptake (VO_{2 peak}) was measured in six trained swimmers. The SB was performed at stroke frequency of 50 · min^–1. Oxygen uptake (VO₂) was measured during exercise at 3-min constant exercise intensities in SB and at 4-min constant water flow rates in AS. We measured a steady-state VO₂ within 3 or 4 min after the beginning of each exercise. The exercise intensity or the water flow rate was increased by 14.7 W or by 0.05 m · s^–1, respectively, until a levelling-off of VO₂ was observed. The VO₂ was measured by the Douglas bag method. Heart rate (HR) and blood lactate concentration ([1a^–]_b) were determined at the exercise intensity and the water flow rate at which VO_{2 peak} was obtained. At submaximal levels, VO₂ increased in proportion to exercise intensity for SB and to the water flow rate for AS. A levelling-off of VO₂ was observed in all subjects for both kinds of exercise. The VO₂ during SB [2.13 (SD 0.25)1 · min^–1] was significantly lower than that during AS [2.72 (SD 0.39)1 · min^–1] and corresponded to 78.9 (SD 7.0)% of AS VO_{2 peak}. Maximal HR during SB was also significantly lower than that during AS. No significant differences between SB and AS were found for either pulmonary ventilation or [1a^–]_b. The peak exercise duration in SB [2.4 (SD 0.5) min] was significantly shorter than that in As [3.6 (SD 0.5) min]. These results would suggest that even though both kinds of exercise use the muscles of the upper body, active muscle groups involved during SB are different and/or smaller, and maximal stress on the cardio-respiratory system is lower when compared to AS.     

A method for determining the maximal steady state of blood lactate concentration from two levels of submaximal exercise

The aim of this study was to estimate the characteristic exercise intensity _CL which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake _max 62 (SD 7) ml · min^–1 · kg^–1] exercisOed for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of _max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of _max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O₂ uptake were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between , lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities _CL which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration ([1a^–]_b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of _CL [68 (SD 9), 71 (SD 7), 73 (SD 6),71 (SD 11) % of _max (ANOVA test,P<0.05). Four subjects ran for 60 min at their _CL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the [la^–]_b at 5 min and at 20 min ( ([la^–]_b)) was computed. The [la^–]_b remained constant during exercise and ranged from 2.2 to 6.7 mmol · l^–1 [mean value equal to 3.9 (SD 1) mmol · l^–1]. These data suggest that the _CL protocol did not overestimate the exercise intensity corresponding to the maximal fractional utilization of _max at MLSS. For half of the subjects the _CL was very close to the higher stage (82% of _max where an accumulation of lactate in the blood with time was observed. It can be hypothesized that _CL was very close to the real MLSS considering the level of accuracy of [la^–]_b measurement. This study showed that exercise at only two intensities, performed at 65% and 80% of _max and separated by 40 min of complete rest, can be used to determine the intensity yielding a steady state of [la^–1]_b near the real MLSS workload value.     

Neuromuscular characteristics and fatigue in endurance and sprint athletes during a new anaerobic power test

The purpose of this study was to investigate neuromuscular and energy performance characteristics of anaerobic power and capacity and the development of fatigue. Ten endurance and ten sprint athletes performed a new maximal anaerobic running power test (MARP), which consisted ofn x 20-s runs on a treadmill with 100-s recovery between the runs. Blood lactate concentration [la^–]_b was measured after each run to determine submaximal and maximal indices of anaerobic power (P _3mmol·1 ^–1,P_5mmol·1 ^–1,P_10mmol·1 ^–1andP _max) which was expressed as the oxygen demand of the runs according to the American College of Sports Medicine equation: the oxygen uptake (ml·kg^–1·min^–1)=0.2·velocity (m·min^–1) +0.9·slope of treadmill (frac)·velocity (m·min^–1)+3.5. The height of rise of the centre of gravity of the counter movement jumps before (CMJ_rest) and during (CMJ) the MARP test, as well as the time of force production (t _F) and electromyographic (EMG) activity of the leg muscles of CMJ performed after each run were used to describe the neuromuscular performance characteristics. The maximal oxygen uptake ( _max), anaerobic and aerobic thresholds were determined in the _max test, which consisted ofn x 3-min runs on the treadmill. In the MARP-testP _max did not differ significantly between the endurance [116 (SD 6) ml·kg^–1·min^–1] and sprint [120 (SD 4) ml·kg^–1·min^–1] groups, even though CMJ_rest and peak [la^–]_b were significantly higher and _max was significantly lower in the sprint group than in the endurance group and CMJ_rest height correlated withP _max (r=0.50,P<0.05). The endurance athletes had significantly higher mean values ofP _3mmol·1 ^–1andP _5mmol·1 ^–1[89 (SD 7) vs 76 (SD 8) ml·kg^–1·min^–,P<0.001 and 101 (SD 5) vs 90 (SD 8) ml·kg^–1·min^–1,P<0.01. Significant positive correlations were observed between theP _3mmol·l ^–1and _max, anaerobic and aerobic thresholds. In the sprint group CMJ and the averaged integrated iEMG decreased andt _F increased significantly during the MARP test, while no significant changes occurred in the endurance group. The present findings would suggest thatP _max reflected in the main the lactacid power and capacity and to a smaller extent alactacid power and capacity. The duration of the MARP test and the large number of CMJ may have induced considerable energy and neuromuscular fatigue in the sprint athletes preventing them from producing their highest alactacidP _max at the end of the MARP test. Due to lower submaximal [la^–]_b (anaerobic sprinting economy) the endurance athletes were able to reach almost the sameP _max as the sprint athletes.     

Does the threshold of transcutaneous partial pressure of carbon dioxide represent the respiratory compensation point or anaerobic threshold?

On reaching the respiratory compensation point (RCP) during rapidly increasing incremental exercise, the ratio of minute ventilation (V_E) to CO₂ output (VCO₂) rises, which coincides with changes of arterial partial pressure of carbon dioxide (P _aCO₂). Since P _aCO₂ changes can be monitored by transcutaneous partial pressure of carbon dioxide (PCO_2,tc) RCP may be estimated by PCO_2,tc measurement. Few available studies, however, have dealt with comparisons between PCO_2,tc threshold (T _AT) and lactic, ventilatory or gas exchange threshold (V _AT), and the results have been conflicting. This study was designed to examine whether this threshold represents RCP rather than V _AT. A group of 11 male athletes performed incremental excercise (25 W · min^–1) on a cycle ergometer. The PCO_2,tc at (44°C) was continuously measured. Gas exchange was computed breath-by-breath, and hyperaemized capillary blood for lactate concentration ([la^–]_b) and P _aCO₂ measurements was sampled each 2 min. The T _AT was determined at the deflection point of PCO_2,tc curve where PCO_2,tc began to decrease continuously. The V _AT and RCP were evaluated with VCO₂ compared with oxygen uptake (VO₂) and V_E compared with the VCO₂ method, respectively. The PCO_2,tc correlated with P _aCO₂ and end-tidal PCO₂. At T _AT, power output [P, 294 (SD 40) W], VO₂ [4.18 (SD 0.57)l · min^–1] and [la^–] [4.40 (SD 0.64) mmol · l^–1] were significantly higher than those at V _AT[P 242 (SD 26) W, VO₂ 3.56 (SD 0.53) l · min^–1 and [la^–]_b 3.52 (SD 0.75), mmol · l^–1 respectively], but close to those at RCP [P 289 (SD 37) W; VO₂ 3.97 (SD 0.43) l · min^– and [la^–]_b 4.19 (SD 0.62) mmol · l^–1, respectively]. Accordingly, linear correlation and regression analyses showed that P, VO₂ and [la^–]_b at T _AT were closer to those at RCP than at V _AT. In conclusion, the T _AT reflected the RCP rather than V _AT during rapidly increasing incremental exercise.     

Dynamics of anaerobic and aerobic energy supplies during sustained high intensity exercise on cycle ergometer

Eight male subjects were examined for the transition from anaerobic to aerobic energy supplies during supramaximal pedalling for 120s on a cycle ergometer. The O₂ debt and O₂ deficit were measured for anaerobic supply, while O₂ intake during exercise was measured for aerobic supply. The lactic acid system was also observed through postexercise peak blood lactate concentration [la^–]_b,peak. Since a continuous observation of O₂ debt and [la^–]_b,peak during a single period of pedalling is not possible, pedalling of seven varying durations (5,15,30,45,60,90 and 120 s) were repeated. Mechanical power output reached its peak immediately after the beginning of exercise, then rapidly declined, becoming gradual after 60 s. The O₂ debt and O₂ deficit were highest immediately after the beginning of exercise, then rapidly decreased to nil in 60 s. The 0₂ intake was small at the beginning, then rapidly increased to attain a steady state in 30 s at 80%–90% of the maximal 02 intake of the subject. Energy supply from the lactic acid system indicated by the increment in [la^–]_b,peak reached its highest value during the period between 5 and 15 s, then rapidly decreased to nil in 60 s. The results would suggest that anaerobic supply was the principal contributor during the initial stage of exercise, but that aerobic supply gradually took over. In 60 s anaerobic supply ceased, and aerobic supply became the principal contributor. The cessation of anaerobic energy supply took place much sooner than the 2 min that is conventionally suggested.     

Saliva electrolytes as a useful tool for anaerobic threshold determination

The purpose of the present study was to determine the anaerobic threshold by analysis of changes in saliva composition during an incremental exercise test on a cycle ergometer. Thirteen healthy males underwent a submaximal test with an initial load of 50 W and load increases of 50 W per 3 min, until capillary blood lactate exceeded 4 mmol · l^–1. A maximal test for maximum O₂ uptake (VO_2max) determination (initial load of 100 W and load increases of 50 W per 2 min) was also performed. Saliva and blood samples were obtained only in the submaximal test. Saliva threshold (Th_sa) was defined as the point at which the first increase in either Cl^– or Na⁺ occurred. Catecholamine threshold (Th_ca) was defined as the point at which a nonlinear increase occurred in either adrenaline or noradrenaline. The lactate (Th_la) and ventilatory (Th_ve) thresholds were determined according to published criteria. No significant differences were found between Th_sa values and the other methods of threshold determination. A high correlation was found between Th_sa and Th_la (r = 0.82, P < 0.01), and Th_sa and Th_ca (r = 0.75, P < 0.05). These results support the validity of Th_sa as a new method for noninvasive determination of the anaerobic threshold.     

Changes in acid-base status of marathon runners during an incremental field test

Summary Four top-class runners who regularly performed marathon and long-distance races participated in this study. They performed a graded field test on an artificial running track within a few weeks of a competitive marathon. The test consisted of five separate bouts of running. Each period lasted 6 min with an intervening 2-min rest bout during which arterialized capillary blood samples were taken. Blood was analysed for pH, partial pressure of oxygen and carbon dioxide (P0₂ and PCO₂) and lactate concentration ([la^–]_b). The values of base excess (BE) and bicarbonate concentration ([HCO₃ ^–]) were calculated. The exercise intensity during the test was regulated by the runners themselves. The subjects were asked to perform the first bout of running at a constant heart rate f _c which was 50 beats · min^–1 below their own maximal f _c. Every subsequent bout, each of which lasted 6 min, was performed with an increment of 10 beats · min^–1 as the target f _c. Thus the last, the fifth run, was planned to be performed with fc amounting to 10 beats · min^–1 less than their maximal f _c. The results from these runners showed that the blood pH changed very little in the bouts performed at a running speed below 100% of mean marathon velocity ( _m). However, once _mwas exceeded, there were marked changes in acid-base status. In the bouts performed at a velocity above the _mthere was a marked increase in [la^–]_b and a significant decrease in pH, [HCO₃ ^–], BE and PCO₂. The average marathon velocity ( _m) was 18.46 (SD 0.32) km·h^–1. The [la^–]_b at a mean running velocity of 97.1 (SD 0.8) % of _mwas 2.33 (SD 1.33) mmol ·l^–1 which, compared with a value at rest of 1.50 (SD 0.60) mmol·l^–1, was not significantly higher. However, when running velocity exceeded the vm by only 3.6 (SD 1.9) %, the [la^–]b increased to 6.94 (SD 2.48) mmol·l-1 (P<0.05 vs rest). We concluded from our study that the highest running velocity at which the blood pH still remained constant in relation to the value at rest and the speed of the run at which [la^–]_b began to increase significantly above the value at rest is a sensitive indicator of capacity for marathon running.