Capillary Blood Lactate Concentration Research Articles

Physiological response to professional road cycling: climbers vs. time trialists.

The purpose of this study was to identify possible physiological differences between professional cyclists who show best performance in hill climbing ("climbers") and those who excel in time trials ("time trialists"). To this end, professional, top-level climbers (C; n=8; age 26 +/- 1yr; height 176.0 +/- 2.0cm; body mass 63.6 +/- 2.2 kg) and time trialists (TT; n=6; 27 +/- 1yr; height 181.6 +/- 1.7 cm; body mass 72.3 +/- 2.3 kg) were required to perform two laboratory exercise tests on a cycle ergometer: a) a maximal exercise test (ramp protocol) and b) a constant load test of 20-min duration at approximately 80% of VO2max. Capillary blood lactate concentration and several gas exchange variables were measured during the maximal tests while determinations made during the submaximal tests also included: pH and bicarbonate concentration [HCO3-] in venous blood, and electromyographic (EMG) recordings from the vastus lateralis muscle to estimate root mean square voltage (rms-EMG) and mean power frequency (MPF). Both the maximal lactate concentration in capillary blood and VO2max were greater (p<0.05) in C than in TT (6.6 +/- 0.9 mM vs. 5.0 +/- 0.4 mM, respectively, and 78.4 +/- 3.2 ml x kg(-1) x min(-1) vs. 70.5 +/- 2.4 ml x kg(-1) x min(-1), respectively). Higher mean venous blood pH and [HCO3-] (p<0.05), rms-EMG (p<0.01) and MPF (p<0.05 at 10 and 15min of exercise and p < 0.01 at 5 and 20 min) were recorded in C throughout the submaximal tests. Our findings suggest that in top-level professional cyclists, climbing performance is mainly related to physiological factors (VO2max normalized for body mass, anaerobicl buffer capacity, motor unit recruitment) whereas time trialists tend to achieve greater absolute power outputs. It would also seem that other "technical" requirements of the sport (i. e. pedaling efficiency probably related to biomechanical factors etc.) may be associated with successful time trial performance.

Importance of increased physical activity in ambulatory cardiovascular prevention

Current trends in public health provided potential arguments to, first, intensify the recommendations of a physically active lifestyle in the primary prevention of atherosclerosis and, second, to prescribe a supervised outpatient exercise training program for secondary prevention of cardiovascular diseases. Regular physical exercise may positively influence cardiovascular risk factors (overweight, hypertension, hyperlipoproteinaemia, insulin resistance, hemostatic markers). Physical conditioning modifies the body composition in favor of an increased skeletal muscle mass, changes the eating habits, and other life style characteristics. The dietary modifications characterized by a low-fat, more vegetarian food supports the weight control and the adjustment of the other metabolic risk factors. All these changes are suitable to reduce the manifestation of atherosclerosis and to minimize the risk of an acute thromboembolic arterial occlusion. Physical conditioning on one's own initiative in primary prevention or an exercise training program supervised by health professionals in secondary prevention of atherosclerosis should predominantly include a low intensive aerobic endurance exercise training. Lactate concentration in capillary blood can be measured to objectify and regulate exercise intensity. The additional energy turnover should amount to a minimum of 1,000 kcal and a maximum of 3,500 kcal weekly. This energy expenditure could be realized either with an increased physical activity level in daily routine (e.g., stair climbing, go for a walk, gardening) or by a regular leisure-time physical exercise. A turnover of 300 kcal per session should be prescribed. In long-term clinical trials investigating the benefit of primary and secondary cardiovascular prevention a reduction of the cardiovascular mortality of about 20-30% has been demonstrated.

The reliability of lactate measurements during exercise.

The purpose of this study was to establish the reliability of lactate threshold (LT) measurement across days. Twelve endurance-trained males aged 21-44 years participated in the study. Blood lactate concentration in capillary whole blood was measured at rest and at completion of 5 minute stages on a treadmill at 60%, 65%, 71%, 77%, 83% and 89% of VO2max during 3 separate days of testing. Velocity at LT (LT(VEL)), oxygen consumption at LT (LT(VO2)), and heart rate at LT (LT(HR)) are determined using each of the following criteria: fixed lactate concentrations of 2.0 mmol, 2.5 mmol, and 4.0 mmol, the breakpoint of the lactate-intensity curve, 1 mmol above rest, and 1 mmol above exercise baseline. A one factor repeated measures ANOVA model was used to calculate intraclass reliability coefficients across the 3 testing sessions. Confidence intervals (95%) were calculated around the point estimates of reliability for each LT criterion. Intraclass correlation coefficients ranged from 0.98 to 0.99 LT(VEL) (SEM 0.06 to 0.14 km x hr(-1)), from 0.91 to 0.96 for LT(VO2) (SEM 0.34 to 0.72 ml x kg(-1) x min(-1)), and from 0.75 to 0.96 for LTHR (SEM 0.7 to 1.9 beats x min(-1)). These results support the reliability of LT(VEL), LT(VO2), and LT(HR) measurement.

RELATION BETWEEN STEADY STATE LACTATE CONCENTRATION AND RESPIRATORY QUOTIENT DURING PROLONGED EXERCISE OF HIGH INTENSITY

1395 The purpose of the present study was to evaluate whether deviations of the respiratory quotient (RQ) measured by spirometry (RQs) exceeding 1,0 can be ascribed solely to changes in body CO2 content. 9 male middle and long distance runners (age 22.9 ± 3.9 years, LBM 61.3 ± 5.1 kg. 4 mmol-threshold 4.47 ± 0.31 m/s) underwent two exercise tests of a constant load (4.59 ± 0.19 m/s, 15 to 30 minutes duration) with and without a 3-minute preload of supramaximal intensity (5,48 ± 0.25 m/s) on a treadmill. VCO2, VO2 (by open spirometry), arterialized capillary blood lactate concentration, PaCO2 and pH were measured to correct RQs. We used the formula given by CLODE et al. 1969 and a self developed algorithm for calculating the metabolic RQ (RQm). Our findings show that under conditions of constant load near the maximal lactate steady state blood lactate concentration (SSCLa) is associated with values of RQs clearly exceeding 1,0. Even after using the correction formulas the RQm still remains elevated. Correction by the self developed algorithm (RQGM) diminishes the steady state RQ more effectively than by the formula of CLODE et al.(RQCC). TableTableOur self developed algorithm contains correction formulas for different influences, including ventilatory, acid-base-equilibrium and those dependent on further metabolic pathways. Neglecting the latter influence RQs still clearly exceeds 1,0 even during steady state conditions (no preload: 0.9843 ± 0.025, preload: 1.036 ± 0.047). It can be concluded that the deviation of the RQs during exercise of high intensity can not be assigned solely to changes of CO2 content. Further research is needed to elucidate the kind of metabolic pathways which influence the RQs to higher values.

EQUIFINALITY OF BLOOD LACTATE STEADY STATE DURING PROLONGED EXERCISE OF LOW AND HIGH INTENSITY

1557 It is known that during constant load steady state lactate concentration(CLass) can approach 2 to 10 mmol/l. The purpose of the present study was to investigate whether CLass is independent of a preload activity and preexisting blood lactate (PLaex) concentration. We investigated 11 male middle and long distance runners (age 24.3 ± 3.4 years, LBM 63.72 ± 5.4 kg, 4-mmol-threshold 4.38 ± 0.35 m/s) by two exercise tests of a constant load (20-30 minutes duration) near the aerobic threshold (3.64 ± 0.33 m/s) and near the maximal lactate steady state (4.47 ± 0.26 m/s) with and without a 3-minute preload of supramaximal intensity (5.38 ± 0.28 m/s) on a treadmill. Arterialized capillary blood lactate concentration(sample of ear lobe), VO2, VCO2 (by open spirometry), PaCO2 and pH were measured. TableTableOur results show the change of preexisting lactate concentration by accumulation or elimination to the equifinal blood lactate steady state concentration (CLass) in 15 to 25 minutes during exercise of low intensity(minimal CLass:1.08 mmol/l) and high intensity (maximal CLass:11.16 mmol/l). These data correspond to the theory of metabolic origin of anaerobic threshold by MADER et al. 1986. We suggest following conclusion: Even at higher intensity a time and preload independent CLass exists under true oxidative steady state conditions caused by a balance between gross lactate formation and lactate elimination.

Capillary blood lactate concentrations during intermittent all-out exercise

The average maximal peak torques of the knee extensor and knee flexor muscles were measured during one, two or three series of 20 maximal contractions at an angular velocity of pi rad s -1 . After the first series, a 10 min rest was allowed before the second series of contractions. In one case only was a third series of contractions performed. Various sequences of contractions of the dominant and contralateral limbs were tested. Capillary blood lactate concentration ([LA] cap ) was determined in the blood samples taken from an earlobe during each recovery. The difference between peak capillary blood lactate concentration and the concentration that would have occurred without any previous contraction (delta[LA] cap ) was taken as the index of metabolic comparison between the exercise bouts. The mechanical power output during the first series of contractions was similar to that in the second and third series, but the lactate elevation was significantly higher in the first series. The discrepancy between the constancy of the power output and the decrease in lactate elevation was even more evident if delta[LA] cap was calculated as the difference between peak capillary blood lactate concentration and the value measured immediately before the second or third series. The decrease in lactate elevation was not affected by the change of the contracting limb from the first to the second series. In conclusion, the capillary blood lactate concentration profile during intermittent maximal exercise cannot be considered a suitable technique for evaluating lactate production. Each series lasted about 20 s.

Effect of drafting on heart rate in cross-country skiing

The purpose of this study was to compare the heart rate responses during cross-country skiing as a leading skier, as well as in a drafting situation, 2 m behind the leader. Six male cross-country ski racers, paired for VO2max skied a 2-km course (two loops of 1 km) using the skating techniques at a fixed speed (5.6 m.s-1) on two different occasions, once as a leading skier, the other as a drafter. A recovery period of 30 min was allowed between the two trials. Heart rates (HR) were monitored every 5 s during all performances. Capillary blood lactate concentrations were taken before and at 5 min posttrial. Results revealed that HR were significantly lower (154 vs 163 beats.min-1) when skiing behind another skier as opposed to leading. Lactate concentrations were not significantly different between the two trials. Results also revealed that projected frontal areas appeared to influence the effects of drafting such that the HR differences between the leading and the drafting situations were larger for smaller skiers drafting behind larger skiers. These results showed that skiing behind another skier in a ski race would be very advantageous when the situation is encountered and that coaches should use the drafting situation in training so that athletes can practice this energy-saving strategy.

Physiological responses to different roller skiing techniques

This study compared the physiological responses during roller skiing with the V1 skate, kick double pole, and double pole techniques. Eight male nordic ski racers roller skied over a flat one-mile track at 14 and 18 km.h-1 using each of the three techniques under study. Heart rates and oxygen uptakes were measured during the last minute of each bout, ratings of perceived exertion were requested immediately after each bout, and capillary blood lactate concentrations were determined 3 min after each bout. The double pole technique was found to be significantly more economical (P less than 0.05) than the other techniques, as demonstrated by a 12% lower oxygen consumption. No differences were found between the V1 skate and the kick double pole techniques for any of the variables studied. The findings of similar physiological responses with the V1 skate and kick double pole techniques suggest that these techniques should induce similar cardiovascular adaptations when roller skiing at the same speed on flat terrain.

Recovery from short term intense exercise: its relation to capillary supply and blood lactate concentration.

Muscle force recovery from short term intense exercise was examined in 16 physically active men. They performed 50 consecutive maximal voluntary knee extensions. Following a 40-s rest period five additional maximal contractions were executed. The decrease in torque during the 50 contractions and the peak torque during the five contractions relative to initial torque were used as indices for fatigue and recovery, respectively. Venous blood samples were collected repeatedly up to 8 min post exercise for subsequent lactate analyses. Muscle biopsies were obtained from m. vastus lateralis and analysed for fiber type composition, fiber area, and capillary density. Peak torque decreased 67 (range 47-82%) as a result of the repeated contractions. Following recovery, peak torque averaged 70 (47-86%) of the initial value. Lactate concentration after the 50 contractions was 2.9 +/- 1.3 mmol X 1(-1) and the peak post exercise value averaged 8.7 +/- 2.1 mmol X 1(-1). Fatigue and recovery respectively were correlated with capillary density (r = -0.71 and 0.69) but not with fiber type distribution. A relationship was demonstrated between capillary density and post exercise/peak post exercise blood lactate concentration (r = 0.64). Based on the present findings it is suggested that lactate elimination from the exercising muscle is partly dependent upon the capillary supply and subsequently influences the rate of muscle force recovery.