Effect of the chronological age and sexual maturation on the time to exhaustion at maximal aerobic speed

The purposes of this study were: a) to verify the effect of chronological age and sexual maturation on the time to exhaustion at VO(2)max (t(lim)) and; b) to examine the reproducibility of t(lim) in boys aged 10-15 years. Forty boys, divided into 4 groups, in accordance to the chronological age (G10-12 and G13-15) and sexual maturation (P1-P3 and P4-P5 levels for pubic hair), performed the following tests: 1) incremental test for determination of VO(2)max and; 2) all-out exercise bout performed at VO(2)max to determine the t(lim). There was no difference of t(lim) (sec) between G10-12 and G13-15 (181.5 +/- 96.3 vs. 199 105.5). While the two measures of t(lim) were moderately related (r = 0.78), t(lim) from the second test (226.6 +/- 96.1 s) was higher than that of the first (191.3 +/- 79.2 s). We can conclude that the t(lim) is not influenced by chronological age and sexual maturation. Besides, t(lim) presents a lower reproducibility in children and adolescents.

Effects of aerobic endurance training status and specificity on oxygen uptake kinetics during maximal exercise

The main purpose of this study was to analyze the effects of exercise mode, training status and specificity on the oxygen uptake ((V)over dot O-2) kinetics during maximal exercise performed in treadmill running and cycle ergometry. Seven runners (R), nine cyclists (C), nine triathletes (T) and eleven untrained subjects (U), performed the following tests on different days on a motorized treadmill and on a cycle ergometer: (1) incremental tests in order to determine the maximal oxygen uptake ((V)over dot O-2max) and the intensity associated with the achievement of (V)over dot O-2max (I(V)over dot O-2max); and (2) constant work-rate running and cycling exercises to exhaustion at I(V)over dot O-2max to determine the effective time constant of the (V)over dot O-2 response (tau(V)over dot O-2). Values for (V)over dotO(2max) obtained on the treadmill and cycle ergometer [R=68.8 (6.3) and 62.0 (5.0); C=60.5 (8.0) and 67.6 (7.6); T=64.5 (4.8) and 61.0 (4.1); U=43.5 (7.0) and 36.7 (5.6); respectively] were higher for the group with specific training in the modality. The U group showed the lowest values for VO2max, regardless of exercise mode. Differences in tau(V)over dot O-2 (seconds) were found only for the U group in relation to the trained groups [R=31.6 (10.5) and 40.9 (13.6); C=28.5 (5.8) and 32.7 (5.7); T=32.5 (5.6) and 40.7 (7.5); U=52.7 (8.5) and 62.2 (15.3); for the treadmill and cycle ergometer, respectively]; no effects of exercise mode were found in any of the groups. It is concluded that tauVO(2) during the exercise performed at I(V)over dot O-2max is dependent on the training status, but not dependent on the exercise mode and specificity of training. Moreover, the transfer of the training effects on tau(V)over dotO(2) between both exercise modes may be higher compared with (V)over dot O-2max.

Exercise mode affects the time to achieve VO2max without influencing maximal exercise time at the intensity associated with VO2max in triathletes

The objective of this study was to analyze, in triathletes, the possible influence of the exercise mode (running x cycling) on time to exhaustion (TTE) and oxygen uptake (VO2) response during exercise performed at the intensity associated with the achievement of maximal oxygen uptake (IVO2max). Eleven male triathletes (21.8 +/- 3.8 yr) performed the following tests on different days on a motorized treadmill and on a cycle ergometer: 1) incremental tests in order to determine VO2max and IVO2max and, 2) constant work rate tests to exhaustion at IVO2max to determine TTE and to describe VO2 response (time to achieve VO2max-TAVO(2max) and time maintained at VO2max-TMVO2max). No differences were found in VO2max, TTE and TMVO2max obtained on the treadmill tests (63.7 +/- 4.7 ml.kg(-1).min(-1); 324.6 +/- 109.1 s; 178.9 +/- 93.6 s) and cycle ergometer tests (61.4 +/- 4.5 ml.kg(-1).min(-1); 390.4 +/- 114.4 s; 213.5 +/- 102.4 s). However, TAVO(2max) was influenced by exercise mode (145.7 +/- 25.3 vs. 176.8 +/- 20.1 s; in treadmill and cycle ergometer, respectively; p = 0.006). It is concluded that exercise modality affects the TAVO(2max) without influencing TTE and TMVO2max during exercise at IVO2max in triathletes.

Maximal lactate steady state concentration independent of pedal cadence in active individuals

The maximal lactate steady state (MLSS) is defined as the highest blood lactate concentration that can be maintained over time without a continual blood lactate accumulation. The objective of the present study was to analyze the effects of pedal cadence (50 vs. 100 rev min(-1)) on MLSS and the exercise workload at MLSS (MLSSworkload) during cycling. Nine recreationally active males (20.9 +/- 2.9 years, 73.9 +/- 6.5 kg, 1.79 +/- 0.09 m) performed an incremental maximal load test (50 and 100 rev min(-1)) to determine anaerobic threshold (AT) and peak workload (PW), and between two and four constant submaximal load tests (50 and 100 rev min(-1)) on a mechanically braked cycle ergometer to determine MLSSworkload and MLSS. MLSSworkload was defined as the highest workload at which blood lactate concentration did not increase by more than 1 mM between minutes 10 and 30 of the constant workload. The maximal lactate steady state intensity (MLSSintensity) was defined as the ratio between MLSSworkload and PW. MLSSworkload (186.1 +/- 21.2 W vs. 148.2 +/- 15.5 W) and MLSSintensity (70.5 +/- 5.7% vs. 61.4 +/- 5.1%) were significantly higher during cycling at 50 rev min(-1) than at 100 rev min(-1), respectively. However, there was no significant difference in MLSS between 50 rev min(-1) (4.8 +/- 1.6 mM) and 100 rev min(-1) (4.7 +/- 0.8 mM). We conclude that MLSSworkload and MLSSintensity are dependent on pedal cadence (50 vs. 100 rev min(-1)) in recreationally active individuals. However, this study showed that MLSS is not influenced by the different pedal cadences analyzed.

MAXIMAL LACTATE STEADY-STATE INDEPENDENT of RECOVERY PERIOD DURING INTERMITTENT PROTOCOL

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

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.

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)

Maximal lactate steady state in rats submitted to swimming exercise

The higher concentration during exercise at which lactate entry in blood equals its removal is known as 'maximal lactate steady state' (MLSS) and is considered an important indicator of endurance exercise capacity. The aim of the present study was to determine MLSS in rats during swimming exercise. Adult male Wistar rats, which were adapted to water for 3 weeks, were used. After this, the animals were separated at random into groups and submitted once a week to swimming sessions of 20 min, supporting loads of 5, 6, 7, 8, 9 or 10% of body wt. for 6 consecutive weeks. Blood lactate was determined every 5 min to find the MLSS. Sedentary animals presented MLSS with overloads of 5 and 6% at 5.5 mmol/l blood lactate. There was a significant (P < 0.05) increase in blood lactate with the other loads. In another set of experiments, rats of the same strain, sex and age were submitted daily to 60 min of swimming with an 8% body wt. overload, 5 days/week, for 9 weeks. The rats were then submitted to a swimming session of 20 min with an 8% body wt. overload and blood lactate was determined before the beginning of the session and after 10 and 20 min of exercise. Sedentary rats submitted to the same acute exercise protocol were used as a control. Physical training did not alter the MLSS value (P < 0.05) but shifted it to a higher exercise intensity (8% body wt. overload). Taken together these results indicate that MLSS measured in rats in the conditions of the present study was reproducible and seemed to be independent of the physical condition of the animals. © 2001 Elsevier B.V. All rights reserved.

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.

Maximal lactate steady state in running rats

The higher concentration during exercise at which lactate entry in blood equals its removal is known as maximal lactate steady state (MLSS) and is considered an important indicator of endurance exercise capacity. The aim of the present study was to determine MLSS in running rats. Adult male Wistar sedentary rats, which were selected and adapted to treadmill running for three weeks, were used. After becoming familiarized with treadmill running, the rats were submitted to five exercise tests at 15, 20, 25, 30 and 35 m/min velocities. The velocity sequence was distributed at random. Each test consisted of continuous running for 25 min at one velocity or until the exhaustion. Blood lactate was determined at rest and each 5 min of exercise to find the MLSS. The running rats presented MLSS at the 20 m/min velocity, with blood lactate of 3.9±1.1 mmol/L. At the 15 m/min velocity, the blood lactate also stabilized, but at a lower concentration (3.2±1.1 mmol/L). There was a progressive increase in blood lactate concentration at higher velocities, and some animals reached exhaustion between the 10 th and 25 th minute of exercise. These results indicate that the protocol of MLSS can be used for determination of the maximal aerobic intensity in running rats.

Maximal clenching effort influence on the electromyographic activity of the trapezius muscle in healthy subjects

Alteration of the occlusion and the position of the jaw can affect the muscles of the neck, due to a relationship between the masticatory and cervical systems. Thus, the objective of this study was to verify whether the bite in maximal clenching effort, in centric occlusion, in individuals with clinically normal occlusion, and without a history of dysfunction in the masticatory system, influences the electromyographic activity of the upper trapezius muscle. A total of 19 normal individuals participated in the study, 14 of which were women (average age of 25.4 ± 4.14 years), and 5 were men (average age of 24.11 ± 3.28 years). The root mean square (RMS) amplitude and median frequency (MF) of the upper trapezium muscle with 40% and 60% of maximal voluntary contraction were analyzed under pre- and post-maximal clenching effort conditions in centric occlusion. The electromyographic signal was collected with a sampling frequency of 2. kHz and the value in RMS was obtained by a moving window of 200. ms. The paired Student's t-test was used to compare RMS amplitude and MF under pre- and post-maximal clenching effort conditions. The level of significance for each comparison was set to p<0.05. This study concluded that in individuals without a history of dysfunction of the masticatory system, maximum clenching effort in centric occlusion does not alter the electromyographic signal of the upper trapezius. © 2009 Elsevier Ltd.

A decomposition heuristic for the maximal covering location problem

This paper proposes a cluster partitioning technique to calculate improved upper bounds to the optimal solution of maximal covering location problems. Given a covering distance, a graph is built considering as vertices the potential facility locations, and with an edge connecting each pair of facilities that attend a same client. Coupling constraints, corresponding to some edges of this graph, are identified and relaxed in the Lagrangean way, resulting in disconnected subgraphs representing smaller subproblems that are computationally easier to solve by exact methods. The proposed technique is compared to the classical approach, using real data and instances from the available literature. © 2010 Edson Luiz França Senne et al.

Stroke phases responses around maximal lactate steady state in front crawl

The objective of this study was to analyze changes in stroke rate (SR), stroke length (SL) and stroke phases (entry and catch, pull, push and recovery) when swimming at (MLSS) and above (102.5% MLSS) the maximal lactate steady state. Twelve endurance swimmers (21±8 year, 1.77±0.10m and 71.6±7.7kg) performed in different days the following tests: (1) 200- and 400-m all-out tests, to determine critical speed (CS), and; (2) 2-4 30-min sub-maximal constant-speed tests, to determine the MLSS and 102.5% MLSS. There was significant difference among MLSS (1.22±0.05ms-1), 102.5% MLSS (1.25±0.04ms-1) and CS (1.30±0.08ms-1). SR and SL were maintained between the 10th and 30th minute of the test swum at MLSS and have modified significantly at 102.5% MLSS (SR - 30.9±3.4 and 32.2±3.5cyclesmin-1 and SL - 2.47±0.2 and 2.38±0.2mcycle-1, respectively). All stroke phases were maintained at 10th and 30th minute at MLSS. However, the relative duration of propulsive phase B (pull) increased significantly at 102.5% MLSS (21.7±3.4% and 22.9±3.9%, respectively). Therefore, the metabolic condition may influence the stroke parameters (SR and SL) and stroke strategy to maintain the speed during swim tests lasting 30min. © 2010 Sports Medicine Australia.