The correlation of vectorcardiographic changes to blood lactate concentration during an exercise test

In this study, the correlations between blood lactate concentration (BLC), different vector electrocardiogram (VECG) parameters, ventilatory parameters and heart rate during exercise and recovery periods were investigated. The aim was to clarify the relationships between VECG parameters and different exercise intensity markers. Six (25–37 years old) nonathlete, healthy, male participants took part in the study. All participants performed two different bicycle ergospirometric protocols (P1 and P2) in order to attain different lactate levels with different heart rate profiles. A principal component regression (PCR) approach is introduced for preprocessing the VECG components. PCR was compared to Sawitzcy Golay and wavelet filtering methods using simulated data. The performance of the PCR approach was clearly better in low signal-to-noise ratio (SNR) situations, and thus, it enables reliable VECG estimates even during intensive exercise. As a result, strong positive mean individual correlations between BLC and T-wave kurtosis (P1: r = 0.86 and P2: r = 0.8, p < 0.05 in 12/12 measurements) and negative correlation between BLC and cos RT (P1: r = ?0.7, P2: r = ?0.62, p < 0.05 in 8/12 measurements) were observed. The results of this study indicate that VECG parameters (in addition to heart rate) can make a significant contribution to monitoring of exercise intensity and recovery.     

Oxygen uptake, heart rate and blood lactate concentration during a normal training session of an aerobic dance class

The aim of this research was to investigate the physiological responses and, in particular, the participation of lactic acid anaerobic metabolism in aerobic dance, which is claimed to be pure aerobic exercise. In contrast to previous studies, that have put subjects in very unfamiliar situations, the parameters were monitored in the familiar context of gymnasium, practice routine and habitual instructor. A group of 30 skilled fairly well-trained women performed their usual routine,␣a combination of the two styles: low (LI) and high impact (HI), and were continuously monitored for heart rate (HR) and every 8 min for blood lactate concentration ([La⁻]_b). Of the group, 15 were tested to determine their maximal aerobic power (V˙O_2max) using a cycleergometer. They were also monitored during the routine for oxygen uptake (V˙O₂) by a light telemetric apparatus. The oxygen pulses of the routine and of the corresponding exercise intensity in the incremental test were not statistically different. The mean values in the exercise session were: peak HR 92.8 (SD 7.8)% of the subject's maximal theoretical value, peak V˙O₂ 99.5 (SD 12.4)% of V˙O_2max, maximal [La⁻]_b 6.1 (SD 1.7) mmol · l^−l, and mean 4.8 (SD 1.3) mmol · l^−l. Repeated measures ANOVA found statistically significant differences between the increasing [La⁻]_b values (P < 0.001). In particular, the difference between the [La⁻]_b values at the end of the mainly LI phase and those of the LI-HI combination phase, and the difference between the samples during the combination LI-HI phase were both statistically significant (both P= 0.002 and P= 0.002). The similar oxygen pulses confirmed the validity of the present experiment design and the reliability of HR monitoring in this activity. The HR, V˙O₂ and, above all, the increase of [La⁻]_b to quite high values, showing a non steady state, demonstrated the high metabolic demand made by this activity that involved lactic acid metabolism at a much higher level than expected. Accepted: 23 September 1997     

Influence of cold exposure on blood lactate response during incremental exercise

This study examined the effect of acute exposure of the whole body to cold on blood lactate response during incremental exercise. Eight subjects were tested with a cycle ergometer in a climatic chamber, room temperature being controlled either at 24 degrees C (MT) or at -2 degrees C (CT). The protocol consisted of a step increment in exercise intensity of 30 W every 2 min until exhaustion. Oxygen consumption (VO2) was measured at rest and during the last minute of each exercise intensity. Blood samples were collected at rest and at exhaustion for estimations of plasma norepinephrine (NE), epinephrine (E), free fatty acid (FFA) and glucose concentrations, during the last 15 s of each exercise step and also during the 1st, 4th, 7th, and the 10th min following exercise for the determination of blood lactate (LA) concentration. The VO2 was higher during CT than during MT at rest and during nearly every exercise intensity. At CT, lactate anaerobic threshold (LAT), determined from a marked increase of LA above resting level, increased significantly by 49% expressed as absolute VO2, and 27% expressed as exercise intensity as compared with MT. The LA tended to be higher for light exercise intensities and lower for heavy exercise intensities during CT than during MT. The E and NE concentrations increased during exercise, regardless of ambient temperature. Furthermore, at rest and at exhaustion E concentrations did not differ between both conditions, while NE concentrations were greater during CT than during MT. Moreover, an increase off FFA was found only during CT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Caffeine increases maximal anaerobic power and blood lactate concentration

The aim of this study was to specify the effects of caffeine on maximal anaerobic power (Wmax). A group of 14 subjects ingested caffeine (250 mg) or placebo in random double-blind order. The Wmax was determined using a force-velocity exercise test. In addition, we measured blood lactate concentration for each load at the end of pedalling and after 5 min of recovery. We observed that caffeine increased Wmax [964 (SEM 65.77) W with caffeine vs 903.7 (SEM 52.62) W with placebo; P less than 0.02] and blood lactate concentration both at the end of pedalling [8.36 (SEM 0.95) mmol.l-1 with caffeine vs 7.17 (SEM 0.53) mmol.l-1 with placebo; P less than 0.01] and after 5 min of recovery [10.23 (SEM 0.97) mmol.l-1 with caffeine vs 8.35 (SEM 0.66) mmol.l-1 with placebo; P less than 0.04]. The quotient lactate concentration/power (mmol.l-1.W-1) also increased with caffeine at the end of pedalling [7.6.10(-3) (SEM 3.82.10(-5)) vs 6.85.10(-3) (SEM 3.01.10(-5)); P less than 0.01] and after 5 min of recovery [9.82.10(-3) (SEM 4.28.10(-5)) vs 8.84.10(-3) (SEM 3.58.10(-5)); P less than 0.02]. We concluded that caffeine increased both Wmax and blood lactate concentration.     

Blood lactate responses in incremental exercise as predictors of constant load performance

Seven trained male cyclists (VO2max = 4.42 +/- 0.23 l.min-1; weight 71.7 +/- 2.7 kg, mean +/- SE) completed two incremental cycling tests on the cycle ergometer for the estimation of the "individual anaerobic threshold" (IAT). The cyclists completed three more exercises in which the work rate incremented by the same protocol, but upon reaching selected work rates of approximately 40, 60 and 80% VO2max, the subjects cycled for 60 min or until exhaustion. In these constant load studies, blood lactate concentration was determined on arterialized venous ([La-]av) and deep venous blood ([La-]v) of the resting forearm. The av-v lactate gradient across the inactive forearm muscle was -0.08 mmol.l-1 at rest. After 3 min at each of the constant load work rates, the gradients were +0.05, +0.65* and +1.60* mmol.l-1 (*P less than 0.05). The gradients after 10 min at these same work rates were -0.09, +0.24 and +1.03* mmol.l-1. For the two highest work rates taken together, the lactate gradient was less at 10 min than 3 min constant load exercise (P less than 0.05). The [La-]av was consistently higher during prolonged exercise at both 60 and 80% VO2max than that observed at the same work rate during progressive exercise. At the highest work rate (at or above the IAT), time to exhaustion ranged from 3 to 36 min in the different subjects. These data showed that [La-] uptake across resting muscle continued to increase to work rates above the IAT. Further, the greater av-v lactate gradient at 3 min than 10 min constant load exercise supports the concept that inactive muscle might act as a passive sink for lactate in addition to a metabolic site.     

Influence of moderate cold exposure on blood lactate during incremental exercise.

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 degrees C or at 10 degrees 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. The VO2 was identical under both environments. At 10 degrees C, as compared to 30 degrees C, the lactate anaerobic threshold (Than,la-) occurred at an exercise intensity 15 W higher and [la-]b was lower for submaximal intensities above the Than,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 degrees C [15.60 (SEM 3.15) nmol.l-1] than at 30 degrees 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.     

Reliability of an incremental exercise test to evaluate acute blood lactate,heart rate and body temperature responses in Labrador retrievers

Thirteen healthy Labrador retrievers underwent a 5-stage incremental treadmill exercise test to assess its reliability. Blood lactate (BL), heart rate (HR), and body temperature (BT) were measured at rest, after each stage of exercise, and after a 20-min recovery. Reproducibility was assessed by repeating the test after 7 days. Two-way MANOVAs revealed significant differences between consecutive stages, and between values at rest and after recovery. There was also a significant reduction in physiological strain between the first and second trial (learning effect). Test reliability expressed as typical error (BL = 0.22 mmol/l, HR = 9.81 bpm, BT = 0.22°C), coefficient of variation (BL = 19.3%, HR = 7.9% and BT = 0.6%) and test–retest correlation (BL = 0.89, HR = 0.96, BT = 0.95) was good. Results support test reproducibility although the learning effect needs to be controlled when investigating the exercise-related problems commonly observed in this breed.     

Familial resemblance in maximal heart rate, blood lactate and aerobic power

There are considerable interindividual differences in maximal oxygen uptake per kilogram of body weight (VO2 max/kg), maximal heart rate (max HR) and maximal blood lactate (max blood La) measured during a progressive exercise test. The aim of the study was to quantify the familial relationships for these variables. Parents and children of 38 families of French-Canadian descent were submitted to a modified Balke treadmill test. VO2 max/kg and max HR were the highest values reached during the test for 1 min. Max blood La was obtained from a blood sample taken 2 min after the test. The effects of age and sex were significant for max blood La and VO2 max/kg in each generation. Scores were thus adjusted through multiple regression procedures (age + sex + age X sex + age2), yielding residuals which were submitted to further analysis. Intraclass correlations (ri) were significant in pairs of sibs for max blood La and max HR, i.e. 0.28 (p less than 0.01) and 0.43 (p less than 0.05), respectively. For VO2 max/kg, pairs of spouses and sibs were about similarly correlated (ri = 0.20 and 0.15; p less than 0.05). Data suggested that children were more related to their mother than to their father for VO2 max/kg, VO2 max/kg of fat-free weight, and particularly for max HR. It was concluded that familial resemblance and heritability estimates for maximal aerobic power, max HR and max blood La were quite low and generally nonsignificant. Correlations between biological sibs were, however, consistently significant for max HR and max blood La. The suggestion of a maternal effect in maximal aerobic power should be further investigated.     

The mathematical analysis of the heart rate and blood lactate curves during incremental exercise testing

This paper describes a new mathematical approach for the analysis of HR (heart rate) and BL (blood lactate) curves during incremental exercise testing using a HR/BL curve and its derivatives, taking into account the native shape of all curves, without any linear approximation. Using this approach the results indicate the appearance of three characteristic points (A, B and C) on the HR/BL curve. The point A on the HR/BL curve which is the value that corresponds to the load (12.73 ± 0.46 km h-1) at which BL starts to increase above the resting levels (0.9 ± 0.06 mM), and is analogous to Lactate Turn Point 1 (LTP1). The point C on the HR/BL curve which corresponds to a BL of approximately 4mM, and is analogous to LTP2. The point B on the HR/BL curve, which corresponds to the load (16.32 ± 0.49 km h-1) at which the moderate increase turns into a more pronounced increase in BL. This point has not been previously recognized in literature. We speculate this point represents attenuation of left ventricular ejection fraction (LVEF) increase, accompanied by the decrease in diastolic time duration during incremental exercise testing. Proposed mathematical approach allows precise determination of lactate turnpoints during incremental exercise testing.     

Reverse lactate threshold test accurately predicts maximal lactate steady state and 5 km performance in running

This study evaluated the accuracy of the reverse lactate threshold (RLT) and the onset of blood lactate accumulation (OBLA; 4 mmol·L^-1) to determine the running speed at the maximal lactate steady state (MLSS) and 5 km running performance in a field test approach. Study 1: 16 participants performed an RLT test, and 2 or more constant-speed tests, lasting 30 minutes each, to determine running speed at the MLSS. Study 2: 23 participants performed an RLT test and a 5000 m all-out run as an indicator of performance. The RLT test consisted of an initial lactate-priming segment, in which running speed was increased stepwise up to ~5% above the estimated MLSS, followed by a reverse segment in which speed was decreased by 0.1 m·s^-1 every 180 s. RLT was determined using the highest lactate equivalent ([La^-]/running speed) during the reverse segment. OBLA was determined during the priming segment and was set at a value of 4 mmol∙L¹. The mean difference in MLSS was +0.06 ± 0.05 m·s^-1 for RLT, and +0.13 ± 0.23 m·s^-1 for OBLA. OBLA showed a good concordance with the MLSS (ICC = 0.83), whereas RLT revealed excellent concordance with the MLSS with an ICC = 0.98. RLT showed a very high correlation with 5000 m speed (r = 0.97). The RLT exhibited exceptional agreement to MLSS and 5000 m running performance. Due to this high accuracy, especially concerning the small intraindividual differences, the RLT test may be superior to common threshold concepts. Further research is needed to evaluate its sensitivity during the training process.