Influence of exercise mode and maximal lactate-steady-state concentration on the validity of OBLA to predict maximal lactate-steady-state in active individuals

The aim of this study was to analyze the effects of exercise mode on the validity of onset of blood lactate accumulation (OBLA-3.5-mM fixed blood lactate concentration) to predict the work-rate at maximal lactate steady state (MLSSwork-rate). Eleven recreationally active mates (21.3 +/- 2.9 years, 72.8 +/- 6.7 kg, 1.78 +/- 0.1 m) performed randomly incremental tests to determine OBLA (stage duration of 3 min), and 2 to 4 constants work-rate exercise tests to directly determine maximal lactate steady state parameters on a cycle-ergometer and treadmill. For both exercise modes, the OBLA was significantly correlated to MLSSwork-rate, (cycling: r = 0.81 p = 0.002; running: r = 0.94, p < 0.001). OBLA (156.2 +/- 41.3 W) was lower than MLSSwork-rate (179.6 +/- 26.4 W) during cycling exercise (p = 0.007). However, for running exercise, there was no difference between OBLA (3.2 +/- 0.6 m s(-1)) and MLSSwork-rate (3.1 +/- 0.4 m s(-1)). The difference between OBLA and MLSSworkrate on the cycle-ergometer (r = 0.86; p < 0.001) and treadmill (r = 0.64; p = 0.048) was significantly related to the specific MLSS. We can conclude that the validity of OBLA on predicting MLSSwork-rate is dependent on exercise mode and that its disagreement is related to individual variations in MLSS. (C) 2007 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Aerobic fitness level typical of elite athletes is not associated with even faster VO2 kinetics during cycling exercise

The aim of this study was to address the question if the VO2 kinetics is further improved as the aerobic training status increases from trained to elite level athletes. Maximal oxygen uptake (VO(2)max), work-rate associated to VO(2)max (IVO(2)max) and VO2 kinetics of moderate (Mod) and maximal exercise (Max) were determined in fifty-five subjects. Then, they were assigned into three groups: low (LF), intermediate (IF) and high (HF) aerobic fitness level. In average, the VO(2)max of LF, IF and HF groups were, respectively, 36.0 +/- 3.1, 51.1 +/- 4.5 and 68.1 +/- 3.9 ml . kg . min(-1) (p <= 0.05 among each other). VO2 kinetics mean response time of both exercise intensities were significantly faster (p <= 0.05) in HF (Mod, 27.5 +/- 5.5 s; Max, 32.6 +/- 8.3 s) and IF (Mod, 25.0 +/- 3.1 s; Max, 42.6 +/- 10.4 s) when compared to LF (Mod, 35.7 +/- 7.9 s; Max: 57.8 +/- 17.8 s). We can conclude that VO2 kinetics is improved as the fitness level is increased from low to intermediate but not further improved as the aerobic fitness level increases from intermediate to high.

Relationship Between Speed and Time in Running

The purpose of this study was to evaluate the effect of using different mathematical models to describe the relationship between treadmill running speed and time to exhaustion. All models generated a value for an aerobic parameter (critical speed; S(critical)). 35 university students performed 5-7 constant-speed 0%-slope treadmill tests at speeds that elicited exhaustion in similar to 3 min to similar to 10 min. Speed and time data were fitted using 3 models: (1) a 2-parameter hyperbolic model; (2) a 3-parameter hyperbolic model; and (3) a hybrid 3-parameter hyperbolic + exponential model. The 2-parameter model generated values for S(critical) (mean (+/- SD): 186 +/- 33 m.min(-1)) and anaerobic distance capacity (ADC; 251 +/- 122 m) with a high level of statistical certainty (i.e., with small SEEs). The 3-parameter models generated parameter estimates that were unrealistic in magnitude and/or associated with large SEEs and little statistical certainty. Therefore, it was concluded that, for the range of exercise durations used in the present study, the 2-parameter model is preferred because it provides a parsimonious description of the relationship between velocity and time to fatigue, and it produces parameters of known physiological significance, with excellent confidence.

Anaerobic contribution during maximal anaerobic running test: correlation with maximal accumulated oxygen deficit

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Is maximal lactate steady state during intermittent cycling different for active compared with passive recovery?

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The relationship between onset of blood lactate accumulation, critical velocity, and maximal lactate steady state in soccer players

The objective of this study was to analyze the validity of the velocity corresponding to the onset of blood lactate accumulation (OBLA) and critical velocity (CV) to determine the maximal lactate steady state (MLSS) in soccer players. Twelve male soccer players (21.5 ± 1.0 years) performed an incremental treadmill test for the determination of OBLA. The velocity corresponding to OBLA (3.5 mM of blood lactate) was determined through linear interpolation. The subjects returned to the laboratory on 7 occasions for the determination of MLSS and CV. The MLSS was determined from 5 treadmill runs of up to 30-minute duration and defined as the highest velocity at which blood lactate did not increase by more than 1 mM between minutes 10 and 30 of the constant velocity runs. The CV was determined by 2 maximal running efforts of 1,500 and 3,000 m performed on a 400-m running track. The CV was calculated as the slope of the linear regression of distance run versus time. Analysis of variance revealed no significant differences between OBLA (13.6 ± 1.4 km·h-1) and MLSS (13.1 ± 1.2 km·h-1) and between OBLA and CV (14.4 ± 1.1 km·h-1). The CV was significantly higher than the MLSS. There was a significant correlation between MLSS and OBLA (r = 0.80), MLSS and CV (r = 0.90), and OBLA and CV (r = 0.80). We can conclude that the OBLA can be utilized in soccer players to estimate the MLSS. In this group of athletes, however, CV does not represent a sustainable steady-state exercise intensity. © 2005 National Strength & Conditioning Association.

Long-term creatine supplementation improves the aerobic capacity of horses

The aim of the present study was to investigate the effect of long-term oral supplementation of creatine on the physiological responses to aerobic training. Twelve purebred Arabian horses were submitted to aerobic training for 90 days, with and without creatine supplementation which consisted of the daily administration of 75g of creatine monohydrate mixed into the ration for 90 days of training. Physical conditioning was conducted on a high performance treadmill and training intensity was stipulated by calculating the V 4 (velocity at which blood lactate reaches 4mmol L -1) determined monthly for each animal. The individual intensity of physical force at 80% of aerobic threshold was established. An incremental exercise test was used to set the individual V4. After a warm up period of 4 min at 4m s -1), the speed was increased at 2min intervals to 6, 8 and 10m s -1). The blood samples were collected 15s before the end of each step to determine the concentration of lactate, packed cell volume, hemoglobin and red cell values. The results demonstrated a significant increase (P<0.05) in V4 in the groups that received creatine supplementation for 60 days or more when compared to the animals without creatine supplememntation. The other hematological variables were similar to all groups. The results showed that the prolonged creatine supplementation may have a beneficial al effect on the equine athletic performance.

Exercise training in the aerobic/anaerobic metabolic transition prevents glucose intolerance in alloxan-treated rats

Background: Ninety percent of cases of diabetes are of the slowly evolving non-insulin-dependent type, or Type 2 diabetes. Lack of exercise is regarded as one of the main causes of this disorder. In this study we analyzed the effects of physical exercise on glucose homeostasis in adult rats with type 2 diabetes induced by a neonatal injection of alloxan. Methods: Female Wistar rats aged 6 days were injected with either 250 mg/ kg of body weight of alloxan or citrate buffer 0.01 M (controls). After weaning, half of the animals in each group were subjected to physical training adjusted to meet the aerobic-anaerobic metabolic transition by swimming 1 h/day for 5 days a week with weight overloads. The necessary overload used was set and periodically readjusted for each rat through effort tests based on the maximal lactate steady state procedure. When aged 28, 60, 90, and 120 days, the rats underwent glucose tolerance tests (GTT) and their peripheral insulin sensitivity was evaluated using the HOMA index. Results: The area under the serum glucose curve obtained through GTT was always higher in alloxan-treated animals than in controls. A decrease in this area was observed in trained alloxan-treated rats at 90 and 120 days old compared with non-trained animals. At 90 days old the trained controls showed lower HOMA indices than the non-trained controls. Conclusion: Neonatal administration of alloxan induced a persistent glucose intolerance in all injected rats, which was successfully counteracted by physical training in the aerobic/anaerobic metabolic transition. © 2008 Mota et al; licensee BioMed Central Ltd.

Non-exhaustive test for aerobic capacity determination in running rats

A simple and applicable method for non-exhaustive aerobic evaluation in running rats is described. Wistar rats were submitted to running test at different velocities (10, 15, 20, 25 m/min) with 48 h recovery among them. At each velocity, the rats ran two bouts of 5 min with 2 min of rest between bouts. Blood samples were collected at the end of each bout for lactate determination. For each intensity, delta lactate was calculated and using deltas obtained by four tests, an individual linear interpolation was plotted. The y-intercept of linear interpolation was the null delta lactate equivalent to the critical velocity (CV). To verify the lactate stabilization at CV, the animals were submitted to 25 min of continuous exercise (15, 20, 25 m/min), with blood collection every 5 min. The estimated CV was 16.6±0.7 m/min, with significant linear regressions (R=0.90±0.03). The rats presented maximal lactate steady state (MLSS) at 3.9±0.4 mmol/L, at 20 m/min. The CV was less than MLSS but significantly correlated with this parameter (r=0.78). This non-exhaustive test seems to be valid for the aerobic evaluation of sedentary rats and this protocol underestimates the MLSS in 20%. This test seems to be the interesting method for the evaluation of rats submitted to acute exercise or physical training.

Maximal isokinetic peak torque and EMG activity determined by shorter ranges of motion

Purpose. Isokinetic tests are often applied to assess muscular strength and EMG activity, however the specific ranges of motion used in testing (fully flexed or extended positions) might be constrictive and/or be painful for patients with injuries or under-going rehabilitation. The aim of this study was to examine the effects of different ranges of motion (RoM) when determining maximal EMG during isokinetic knee flexion and extension with different types of contractions and velocities. Methods. Eighteen males had EMG activity recorded on the vastus lateralis, vastus medialis, semitendinosus and biceps femoris muscles during five maximal isokinetic concentric and eccentric contractions for the knee flexors and extensors at 60° • s -1 and 180° • s -1. The root mean square of EMG was calculated at three different ranges of motion: (1) a full range of motion (90°-20° [0° = full knee extension]); (2) a range of motion of 20° (between 60°-80° and 40°-60° for knee extension and flexion, respectively) and (3) at a 10° interval around the angle where peak torque is produced. EMG measurements were statistically analyzed (ANOVA) to test for the range of motion, contraction velocity and contraction speed effects. Coefficients of variation and Pearson's correlation coefficients were also calculated among the ranges of motion. Results. Predominantly similar (p > 0.05) and well-correlated EMG results (r > 0.7, p ≤ 0.001) were found among the ranges of motion. However, a lower coefficient of variation was found for the full range of motion, while the 10° interval around peak torque at 180° • s -1 had the highest coefficient, regardless of the type of contraction. Conclusions. Shorter ranges of motion at around the peak torque angle provides a reliable indicator when recording EMG activity during maximal isokinetic parameters. It may provide a safer alternative when testing patients with injuries or undergoing rehabilitation.

Aerobic and anaerobic performances in tethered swimming

The purpose of this study was to investigate whether the critical force (CritF) and anaerobic impulse capacity (AIC) - estimated by tethered swimming - reflect the aerobic and anaerobic performance of swimmers. 12 swimmers performed incremental test in tethered swimming to determine lactate anaerobic threshold (AnTLAC), maximal oxygen uptake (̇VO2MAX) and force associated with the ̇VO2MAX (i ̇VO2MAX). The swimmers performed 4 exhaustive (tlim) exercise bouts (100, 110, 120 and 130% i ̇VO2MAX) to compute the CritF and AIC (F vs. 1/tlim model); a 30-s all-out tethered swimming bout to determine their anaerobic fitness (ANF); 100, 200, and 400-m time-trials to determine the swimming performance. CritF (57.09±11.77 N) did not differ from AnTLAC (53.96±11.52 N, (P>0.05) but was significantly lower than i ̇VO2MAX (71.02±8.36 N). In addition, CritF presented significant correlation with AnTLAC (r=0.76; P<0.05) and i ̇VO2MAX (r=0.74; P<0.05). On the other hand, AIC (286.19±54.91 N.s) and ANF (116.10±13.66 N) were significantly correlated (r=0.81, p<0.05). In addition, CritF and AIC presented significant correlations with all time-trials. In summary, this study demonstrates that CritF and AIC can be used to evaluate AnTLAC and ANF and to predict 100, 200, and 400-m free swimming. © Georg Thieme Verlag KG Stuttgart . New York.

Insulin concentrations in cerebellum and body balance in diabetic male rats: Aerobic training effects

Brain insulin has had widespread metabolic, neurotrophic, and neuromodulatory functions and has been involved in the central regulation of food intake and body weight, learning and memory, neuronal development, and neuronal apoptosis. Purpose: The present study investigated the role of swimming training on cerebral metabolism on insulin concentrations in cerebellum and the body balance performance of diabetic rats. Methods: Forty Male Wistar rats were divided in four groups: sedentary control (SC), trained control (TC), sedentary diabetic (SD), and trained diabetic (TD). Diabetes was induced by alloxan (32 mg kg b.w.), single dose injection. The mean blood glucose of diabetic groups was 367 ± 40 mg/dl. Training program consisted in swimming 5 days/week, 1 h/day, 8 weeks, supporting a workload corresponding to 90% of maximal lactate steady state (MLSS). For the body balance testing rats were trained to traverse for 5 min daily for 5-7 days. All dependent variables were analyzed by one-way analysis of variance (ANOVA) and a significance level of p < 0.05 was used for all comparisons. Results: The body balance testing scores were different between groups. Insulin concentrations in cerebellum were not different between groups. Conclusion: It was concluded that in diabetic rats, aerobic training does not induce alterations on cerebellum insulin but induces important metabolic, hormonal and behavioral alterations which are associated with an improvement in glucose homeostasis, serum insulin concentrations and body balance. © 2013 Elsevier Inc.

Double effort test for evaluation of aerobic capacity of diet-induced obese rats

Introduction: The literature lacks studies about lactate actions and some limitations in studies involving healthy individuals or patients with some metabolic disorder. Objectives: This study aimed to evaluate the protocol of double effort test for obese-induced rats. Methods: Fourteen male Wistar rats were divided into two groups: Control (Con) and Obese (Obe). The control group was fed with standard chow and water ad libitum. The obese group was fed with standard chow, water ad libitum and hyperlipidic diet. Twelve weeks after the beginning of the hyperlipidic diet, insulin tolerance test, Maximal Lactate Steady State (MLSS) test and the double efforts test were performed. Results: The diet was effective to promote obesity. The obese group decreased insulin sensitivity in approximately 19% (Con = 2.156 ± 0.1187 AU vs Obe = 1.742 ± 0.1551 AU). The lactate concentration and velocity of anaerobic threshold at MLSS test were 3.780 ± 0.09 mmol/L e 18 m.min-1 in both groups. The velocity of anaerobic threshold estimated by double efforts test was 15.59±0.653 m.min-1 in Con group control animals and 16.42±0.672 m.min-1 in Obe group. The double effort test underestimated around 13% and 8.7% the aerobic capacity in control and obese groups respectively, however, presented significant correlation with MLSS (r = 0,88; P < 0,0075 controls / r = 0,92; P < 0,0031 obese). Conclusion: So, the double effort test can be an interesting alternative to evaluate the aerobic capacity for both healthy sedentary and obese animals.

Validation of the lactate minimum test as a specific aerobic evaluation protocol for table tennis players

The purpose of this study was to validate the lactate minimum test as a specific aerobic evaluation protocol for table tennis players. Using the frequency of 72 balls·min-1 for 90 sec, an exercise-induced metabolic acidosis was determined in 8 male table tennis players. The evaluation protocol began with a frequency of 40 balls·min-1 followed by an increase of 8 balls·min-1 every 3 min until exhaustion. The mean values that corresponded to the subjects' lactate minimum (Lacmin) were equal to 53.1 ± 1.5 balls·min-1 [adjusted for the time test (Lacmin_time)] and 51.6 ± 1.6 balls·min-1 [adjusted for the frequency of balls (Lacmin_Freq)], which resulted in a high correlation between the two forms of adjustment (r = 0.96 and (P = 0.01). The mean maximum lactate steady state (MLSS) was 52.6 ± 1.6 balls·min-1. Pearson's correlations between Lacmin_time vs. MLSS and Lacmin_freq vs. MLSS were statistically significant (P = 0.03 and r = 0.86, P = 0.03 and r = 0.85, respectively). These findings indicate that the Lacmin test predicts MLSS. Therefore, it is an excellent method to obtain the athletes' anaerobic threshold. Also, there is the advantage that it can be performed in 1 day in the game area. However, the Lacmin value does not depend on the Lacpeak value.

Estresse oxidativo em ratos exercitados em diferentes intensidades

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)