Constant Workload Tests Research Articles

Addition of tiotropium to formoterol improves inspiratory muscle strength after exercise in COPD

The addition of tiotropium bromide (TIO) to formoterol fumarate (FOR) improves exercise performance in patients with chronic obstructive pulmonary disease (COPD). In this study, we test the hypothesis that the addition of TIO to FOR may improve respiratory muscle performance and oxygen uptake kinetics after exercise in patients with COPD. Thirty eight patients with COPD were randomized to a 2 week treatment with FOR 12μg twice a day plus TIO 18μg once a day (FOR+TIO) or FOR 12μg twice a day plus placebo (FOR+PLA) once a day, using a double-blind crossover design. Inspiratory muscle. Strength was measured before, immediately after, as well as 2, 5, and 10min during recovery of exercise. Time to limit of tolerance on a constant work load exercise test and oxygen uptake kinetics during recovery were evaluated before and after intervention. Only FOR+TIO improved resting (63±10cm to 84±11 cmH(2)O) and post-exercise (49±7cm to 84±11 cmH(2)O) maximal inspiratory pressure. Time to limit of tolerance on the constant work load test was increased by FOR+PLA and by FOR+TIO, but the size of the increment was significantly larger with FOR+TIO (40.7±7.6% vs. 84.5±8.2%; p<0.05). Only FOR+TIO improved oxygen uptake kinetics during recovery (69±21 to 60±18s). The improvement in maximal inspiratory pressure (0.78, p<0.001) and in oxygen uptake kinetics (-0.91, p<0.001) correlated with the change in time to the limit of tolerance. The addition of TIO to FOR improves inspiratory muscle strength and oxygen uptake kinetics after exercise in COPD patients.

Maximal Lactate Steady-State Independent of Recovery Period During Intermittent Protocol

Barbosa, LF, de Souza, MR, Corrêa Caritá, RA, Caputo, F, Denadai, BS, and Greco, CC. Maximal lactate steady-state independent of recovery period during intermittent protocol. J Strength Cond Res 25(12): 3385-3390, 2011-The purpose of this study was to analyze the effect of the measurement time for blood lactate concentration ([La]) determination on [La] (maximal lactate steady state [MLSS]) and workload (MLSS during intermittent protocols [MLSSwi]) at maximal lactate steady state determined using intermittent protocols. Nineteen trained male cyclists were divided into 2 groups, for the determination of MLSSwi using passive (VO(2)max = 58.1 ± 3.5 ml·kg·min; N = 9) or active recovery (VO(2)max = 60.3 ± 9.0 ml·kg·min; N = 10). They performed the following tests, in different days, on a cycle ergometer: (a) Incremental test until exhaustion to determine (VO(2)max and (b) 30-minute intermittent constant-workload tests (7 × 4 and 1 × 2 minutes, with 2-minute recovery) to determine MLSSwi and MLSS. Each group performed the intermittent tests with passive or active recovery. The MLSSwi was defined as the highest workload at which [La] increased by no more than 1 mmol·L between minutes 10 and 30 (T1) or minutes 14 and 44 (T2) of the protocol. The MLSS (Passive-T1: 5.89 ± 1.41 vs. T2: 5.61 ± 1.78 mmol·L) and MLSSwi (Passive-T1: 294.5 ± 31.8 vs. T2: 294.7 ± 32.2 W; Active-T1: 304.6 ± 23.0 vs. T2: 300.5 ± 23.9 W) were similar for both criteria. However, MLSS was lower in T2 (4.91 ± 1.91 mmol·L) when compared with in T1 (5.62 ± 1.83 mmol·L) using active recovery. We can conclude that the MLSSwi (passive and active conditions) was unchanged whether recovery periods were considered (T1) or not (T2) for the interpretation of [La] kinetics. In contrast, MLSS was lowered when considering the active recovery periods (T2). Thus, shorter intermittent protocols (i.e., T1) to determine MLSSwi may optimize time of the aerobic capacity evaluation of well-trained cyclists.

Electromyographic Activity and Rate of Muscle Fatigue of the Quadriceps Femoris During Cycling Exercise in the Severe Domain

This study compared the activation pattern and the fatigue rate among the superficial muscles of the quadriceps femoris (QF) during severe cycling exercise. Peak oxygen consumption (VO(2)peak) and maximal accumulated oxygen Deficit (MAOD) were established by 10 well-trained male cyclists (27.5 ± 4.1 years, 71.0 ± 10.3 kg, 173.4 ± 6.6 cm, mean VO(2)peak 56.7 ± 4.4 ml·kg·min(-1), mean MAOD 5.7 ± 1.1 L). Muscle activity (electromyographic [EMG] signals) was obtained during the supramaximal constant workload test (MAOD) and expressed by root mean square (RMS) and median frequency (MF slope). The RMS of the QF, vastus lateralis (VL) and vastus medialis (VM) muscles were significantly higher than at the beginning after 75% of exercise duration, whereas for the rectus femoris (RF), this was observed after 50% of exercise duration (p ≤ 0.05). The slope of the MF was significantly higher in the RF, followed by the VL and VM (-3.13 ± 0.52 vs. -2.61 ± 0.62 vs. -1.81 ±0.56, respectively; p < 0.05). We conclude that RF may play an important role in limiting performance during severe cycling exercise.

Excessive skeletal muscle recruitment during strenuous exercise in McArdle patients

We compared the cardiorespiratory response and muscle recruitment [as determined by electromyography (EMG)] of 37 McArdle patients [19 males, 37.4±2.8years, body mass index (BMI): 25.1±4.7kgm(-2)] and 33 healthy controls (18 males, 36.4±10.0 years, BMI: 25.7±3.8kgm(-2)) during cycle-ergometer exercise (an incremental test to exhaustion and a 12-min submaximal constant workload test). We obtained cardiorespiratory [oxygen uptake and heart rate (HR)] and EMG data (rectus femoris and vastus lateralis muscles). During the incremental test, the patients exhibited the expected hyperkinetic cardiovascular response shown by a marked increase in the slope of the HR:Power relationship (p<0.001). Throughout the incremental test and at the point of fatigue, the patients produced significantly less power than the controls (peak power output: 67±21 vs. 214±56 watts respectively, p<0.001), yet they demonstrated significantly higher levels of muscle activity for a given absolute power. During the constant workload test, patients displayed higher levels of EMG activity than the controls during the second half of the test, despite a lower power production (34±13 vs. 94±29 watts respectively, p<0.001). In conclusion, since the McArdle patients required more motor unit recruitment for a given power output, our data suggest that the state of contractility of their muscles is reduced compared with healthy people. Excessive muscle recruitment for a given load could be one of the mechanisms explaining the exercise intolerance of these patients.

Predicting MAOD Using Only a Supramaximal Exhaustive Test

The objective of this study was to propose an alternative method (MAOD(ALT)) to estimate the maximal accumulated oxygen deficit (MAOD) using only one supramaximal exhaustive test. Nine participants performed the following tests: (a) a maximal incremental exercise test, (b) six submaximal constant workload tests, and (c) a supramaximal constant workload test. Traditional MAOD was determined by calculating the difference between predicted O(2) demand and accumulated O(2) uptake during the supramaximal test. MAOD(ALT) was established by summing the fast component of excess post-exercise oxygen consumption and the O(2) equivalent for energy provided by blood lactate accumulation, both of which were measured during the supramaximal test. There was no significant difference between MAOD (2.82+/-0.45 L) and MAOD(ALT) (2.77+/-0.37 L) (P=0.60). The correlation between MAOD and MAOD(ALT) was also high (r=0.78; P=0.014). These data indicate that the MAOD(ALT) can be used to estimate the MAOD.

Determinação visual do componente rápido do excesso do consumo de oxigênio após o exercício

O objetivo do presente estudo foi analisar a validade, a reprodutibilidade e a objetividade do método de inspeção visual durante a identificação da fase rápida do excesso do consumo de oxigênio após o exercício (EPOC RÁPIDO). Dez homens fisicamente ativos (idade de 23,0 ± 4,0 anos, estatura de 176,4 ± 6,8cm, massa corporal de 72,4 ± 8,2kg, V•O2max 3,0 ± 0,5L ? min-1) realizaram um teste incremental máximo e um teste de carga constante até a exaustão a 110% da carga máxima obtida no teste incremental. O consumo de oxigênio foi mensurado respiração a respiração durante dez minutos de recuperação passiva após o teste de carga constante. O EPOC RÁPIDO foi determinado matematicamente e visualmente por três avaliadores. O método visual foi aplicado duas vezes nos três avaliadores para verificar a sua reprodutibilidade. Não foram detectadas diferenças significativas entre os valores do EPOC RÁPIDO estabelecidos pelo método matemático (0,98 ± 0,45L) e pelo método visual identificado pelos três avaliadores (1,04 ± 0,45L, 1,02 ± 0,45L e1,02 ± 0,45L). Nenhuma diferença foi encontrada entre a primeira e a segunda identificação feita pelos avaliadores (avaliador 1: 1,04 ± 0,45L vs 1,04 ± 0,49L; avaliador 2: 1,02 ± 0,45L vs 1,01 ± 0,44L e avaliador 3: 1,02 ± 0,45L vs1,03 ± 0,47L). Além disso, o coeficiente de correlação intraclasse entre as duas identificações foi alto para todos os avaliadores (ICC entre 0,97 e0,99). Esses resultados sugerem que a inspeção visual é um método válido, objetivo e reprodutivo para a estimativa do EPOC RÁPIDO.

Prediction of time to exhaustion from blood lactate response during submaximal exercise in competitive cyclists

The aim of this investigation was to develop and validate a new method to predict time to exhaustion (pTE) from blood lactate variables measured during a submaximal non-exhaustive constant workload cycling test in professional cyclists. A multiple regression equation to estimate pTE from blood lactate variables measured within the first 10 min of a submaximal test and TE was determined in 40 competitive cyclists. Predicted TE reliability [individual coefficient of variation (CV)] was calculated in eight amateur cyclists who repeated the proposed test three times. Seasonal variations of pTE were monitored in 12 professional cyclists. Validity of pTE was determined by the known-group difference method in 49 professional cyclists. The prediction equation was: log(n)TE = 4.2067 - 0.8221(log(n) B) - 0.2519(log(n) C), where B is the lactate concentration at the 10th minute of the constant workload test and C is the lactate slope calculated between the 5th and 10th minute (adjusted r (2) =0.83, root mean square error in cross validation=23.1%). Predicted TE CV was 11.7%. The pTE obtained at the beginning of the season and the best and worst tests performed during the competitive season, resulted 162, 224 and 103% higher than the basic period test, respectively (P<0.05). Predicted TE was the only parameter discriminating elite from subelite professional cyclists. In conclusion, this study demonstrates that pTE is a valid and practical alternative to incremental tests and direct measures of endurance capacity requiring exhaustive efforts for the evaluation of competitive cyclists.

Efeito da cadência de pedalada sobre as respostas metabólica e cardiovascular durante o exercício incremental e de carga constante em indivíduos ativos

O objetivo central deste estudo foi analisar o efeito da cadência de pedalada (50 x 100rpm) sobre a freqüência cardíaca (FC) e a resposta de lactato sanguíneo durante o exercício incremental e de carga constante em indivíduos ativos. Nove indivíduos ativos do sexo masculino (20,9 ± 2,9 anos; 73,9 ± 6,5kg; 1,79 ± 0,9m) submeteram-se a dois testes incrementais e a 6-8 testes de carga constante para determinação da intensidade correspondente à máxima fase estável de lactato sanguíneo (MLSSintens) nas duas cadências. A potência máxima (Pmax) atingida no teste incremental e a MLSSintens foram significativamente menores a 100rpm (240,9 ± 12,6W; 148,1 ± 15,4W) quando comparada a 50rpm (263,9 ± 18,6W; 186,1 ± 21,2W), respectivamente. A FCmax não se alterou em função da cadência (50rpm = 191,1 ± 8,8bpm; 100rpm = 192,6 ± 9,9bpm). Independentemente da cadência, os percentuais da FCmax (70, 80, 90 e 100%) determinaram as mesmas concentrações de lactato durante o teste incremental. Entretanto, quando a intensidade foi expressa em percentuais da Pmax ou da potência absoluta, os valores de lactato e FC foram sempre maiores na cadência mais alta. A FC correspondente a MLSSintens foi semelhante para as duas cadências analisadas (50rpm = 162,5 ± 9,1bpm; 100rpm = 160,4 ± 9,2bpm). Com base nestes resultados, podemos concluir que, independente da cadência empregada (50 x 100rpm), a utilização da FC na individualização da intensidade de esforço indica respostas semelhantes do lactato sanguíneo, e que esta relação também se mantém no exercício de intensidade constante realizado na MLSSintens. Por outro lado, a utilização de percentuais da Pmax apresenta dependência da cadência utilizada, indicando diferentes respostas fisiológicas para um mesmo percentual.

BLOOD LACTATE CONCENTRATIONS DURING A CONSTANT LOAD AT AN INTENSITY CORRESPONDING TO THE AEROBICANAEROBIC THRESHOLD IN YOUNG ATHLETES

It is believed that the workload corresponding to a blood lactate concentration (BLC) of 4 mmol/l, determined through aerobic-anaerobic threshold, in adults may be maintained as long as 30min at a constant workload (steady-state BLC). However, there is a lack of studies that confirm if such a phenomenon occurs in young athletes. The purposes of this study were: (i) to investigate the existence of a steady-state of BLC during 30min of constant exercise (at an intensity corresponding to 4 mmol/l) in young athletes, and (ii) to assess possible intra-individual lactate differences during the test. Thirteen young athletes (age: 16.07 ± 1.38 yrs; weight: 61.0 ± 6.69 kg; height: 171.3 ± 5.6 cm) were evaluated both during an incremental and a constant workload test. The incremental step test was used for the determination of the workload corresponding to 4mmol/l of BLC (V4). After 3 days, the subjects performed a 30min constant load test at the previously determined V4. During both tests capillary blood was taken from the ear lobe and immediately analyzed using a enzymatic blood analyzer (YSI 1500L-Sport). During the constant test blood samples were taken at 5th, 10th, 15th, 20th, 25th and 30th min. Statistical analysis included a repeated measure Anova. The mean V4 value was 3.9 ± 0.28 m/s. Two of the thirteen subjects were not able to finish the 30 min test (final BLC was 9.82 and 7.25 mmol/l, respectively). According to Heck et al. (1985) criteria the remaining subjects completed the test with a mean steady-state BLC of 4.15 ± 1.11 mmol/l. The mean BLC in the different moments (5th, 10th, 15th, 20th, 25th and 30th) of the constnat test were, respectively: 4.21, 4.50, 4.67, 4.57, 4.87 and 4.25 mmol/l. There were no significant differences in the repeated observations (F(5,6) =1.035; p =0.474), pointing out that no evidence of intraindividual BLC differences during the 30 min test exists. Therefore, it is concluded that a blood lactate steady-state may be achieved at intensities corresponding to 4mmol/l in young athletes.

Ventilatory response to incremental and constant-workload exercise in the presence of a thoracic restriction.

In the presence of an externally applied thoracic restriction, conflicting ventilatory responses to exercise have been reported, which could be accounted for by differences in exercise protocol. Seven male subjects performed two incremental and two constant-workload ergometer tests either unrestricted or in the presence of an inelastic corset. Ventilatory variables and arterial estimates of PCO(2) were obtained breath by breath. Subjects hyperventilated in the presence of restriction during the constant-workload test (38.4 +/- 3.0 vs. 32.8 +/- 3.0 l/min for the average of the last 3 min of exercise, P < 0.05), whereas, at an equivalent workload during the incremental test, ventilation was similar to unrestricted values (unrestricted = 26.3 +/- 1.6 vs. restricted = 27.9 +/- 2.3 l/min, P = 0.36). We used a first-order linear model to describe the effects of change in workload on minute ventilation (24). When the time constants and minute ventilation values measured during unrestricted and restricted constant-workload exercise were used to predict the ventilatory response to the respective incremental exercise tests, no significant difference was observed. This suggests that hyperventilation is not seen in the restricted incremental test because the temporal dynamics of the ventilatory response are altered.

Determination of the maximum steady state of lactate (MLSS) in saliva: an alternative to blood lactate determination.

Based on previous research which shows parallelism between the saliva and blood lactate response during incremental exercise, we hypothesized that a "maximum salivary lactate steady state" (saliva-MLSS) might exist. Thus, the aim of the present investigation was to establish 1) which lower limit for the increase in salivary lactate concentration during a constant workload (i.e., from the 10th to the 20th min) test could be used to determine the saliva-MLSS and 2) if the exercise intensity corresponding to the saliva-MLSS is identical to that evoking the (blood) MLSS. Twelve male amateur athletes of mean ( +/- SD) age 24 +/- 5 year were selected for the study. Based on the results of a previous maximal cycle ergometer test for lactate threshold (LT) determination, each subject performed consecutive constant workload tests of 20-min duration on separate days for MLSS determination. Blood and saliva (25 microl) samples were collected at 0, 10, and 20 min during the tests for lactate determination. A Student's t-test for paired data demonstrated that a salivary lactate increase of 0.8 mM corresponded to the saliva-MLSS. At this value, indeed, no significant differences were observed between the mean V(.)O(2) and W values corresponding to the MLSS and the saliva-MLSS. In conclusion, the present findings indicate that 0.8 mM is the lower limit for the increase in saliva lactate concentration during a constant load test and thus is that which might be used as a reference to determine saliva-MLSS. Furthermore, saliva-MLSS might be used as an alternative to MLSS determination in blood samples.

Mechanism of increase in anaerobic threshold during recovery phase in patients with acute myocardial infarction.

The contribution of venous return to the increase in anaerobic threshold (AT) in patients with acute myocardial infarction (AMI) was investigated. Twenty-seven patients with uncomplicated AMI underwent supine and sitting cardiopulmonary exercise testing, and 10 out of these 27 patients performed constant-workload tests in which cardiac output before and after a phase II program was measured. Data from 8 patients were eliminated because of restenosis after direct percutaneous transluminal coronary angioplasty. The increase in AT was significantly greater in the sitting position than in the supine position, 15.0+/-9.9% and 6.3+/-6.0% respectively. Average O2 pulse at AT changed non-significantly from 8.6+/-1.5 to 8.7+/-1.2 ml min(-1) beat(-1) in the supine position, but it showed a significant increase from 8.1+/-1.3 to 9.2+/-1.3 ml min(-1) beat(-1) when measured in the sitting position. In the constant-workload studies, stroke index showed a significant increase during both supine and sitting exercise. Percent increase in the stroke index from rest to exercise did not differ significantly in the supine position, but did differ significantly in the sitting position. These results strongly suggest that increased venous return as well as improvement in cardiac pump function play a major role in the mechanism of AT increase in an upright position throughout the recovery phase in AMI patients.

Blood lactate threshold and type II fibre predominance in patients with exertional heatstroke.

OBJECTIVES: Severe damage to skeletal muscle is usually seen in patients with exertional heatstroke. Thirty seven young military recruits with exertional heatstroke in Taiwan from 1992 to 1995 were studied...

Microprocessor Exercise Physiology Systems vs a Nonautomated System: A Comparison of Data Output

Several microprocessor exercise physiology systems have been introduced recently. Comparison of the data output between these systems and more traditional nonautomated systems has not been reported extensively. Twelve normal adult men were exercised in random sequence on different days on a Sensormedics MMC Horizon system, the Medical Graphics Corporation System 2000, and a nonautomated system. heart rate, minute ventilation, tidal volume, respiratory frequency, oxygen consumption, and carbon dioxide production were compared at each level of work during a maximal incremental test and during a constant work load test. The overall data output between the three systems was comparable. However, minute ventilation was consistently higher on the Medical Graphics system, oxygen consumption was consistently lower on the Horizon system, and a technical error was discovered in the Medical Graphics system which resulted in a systematic overestimation of carbon dioxide production. Different methods of analyzing the data from the same test (60-s average, 15-s average, breath-by-breath, and 8-breath average) resulted in differences of up to 20 percent in the maximal values. This was greater than the differences between the three systems. Despite the comparability of the data output, important differences did exist which can be potentially significant when data output from one system are compared to predicted normal values obtained under different conditions.

Adaptation of human left ventricular volumes to the onset of supine exercise.

The purpose of this study was to measure the changes and rates of adaptation of left ventricular volumes at the onset of exercise. Eight asymptomatic subjects, in whom intramyocardial markers had been implanted 3-6 years previously during aortocoronary bypass surgery, exercised in the supine position at a constant workload of 73.6 W for 5 min. Six also exercised first at 16.4 W, and then against a workload which progressively increased by 8.2 W every 15 s. Cardiac volumes were measured by computer assisted analysis of the motion of the implanted markers. In the constant workload test, cardiac output increased rapidly from 5.7 +/- 1 min-1 to 10.3 +/- 1.9 1 min-1 by 2 min and then increased more slowly to 10.8 +/- 2.0 1 min-1 by 5 min. The cardiac output increase was mainly due to an increase in heart rate from 68 +/- 12 beats min-1 to 120 +/- 16 beats min-1 with minimal changes in stroke volume. The time constant for the early increase in cardiac output was 45s and for heart rate, 35s. With progressively increasing workloads, there was an almost linear increase of heart rate and cardiac output, but these increased at a slower rate than during the early phase of the constant load exercise test. rapid changes in cardiac output during supine exercise were produced by changes in heart rate; changes in stroke volume provided minor adjustments to cardiac output; the end-diastolic volume was almost constant.

Effects of Daily Physical Exercise on the Psychiatric State of Institutionalized Geriatric Mental Patients

Abstract Nine male geriatric mental patients exercised daily, Monday through Friday for a total of 12 weeks. Exercise was in the form of walking on a motor-driven treadmill at workloads which elicited 70% of the age adjusted, predicted maximal heart rate. Eight patients served as controls and received similar social stimulation as did the experimental patients. All patients were physiologically evaluated on treadmill and bicycle ergometer stress tests administered before and immediately following the 12 wk. training period. Psychiatric evaluation was in the form of a series of four psychological tests also administered pre- and posttraining. Results of the posttraining evaluation indicate a physiological training effect experienced by experimental patients as evidenced by significantly decreased heart rate and systolic blood pressure responses to treadmill and bicycle ergometer constant workload tests. Accompanying the physiological training effect was a significant change on two of the four psychological...