Standard Incremental Exercise Test Research Articles

Predicting maximal lactate steady state from lactate thresholds determined using methods based on an incremental exercise test in beagle dogs: A study using univariate and multivariate approaches

The reliability of four lactate threshold (LT) methods to estimate the maximal lactate steady state (MLSS), defined as the highest intensity that can be maintained without plasma lactate ([La−]) accumulation over time, was determined in Beagle dogs. Six male Beagle dogs performed a standardized incremental exercise test on a treadmill when plasma lactate ([La−]) measurements were performed. The LTs for predicting MLSS, were determined by visual inspection (LTV), using a bi-segmented linear regression model (LTBI), or using a polynomial function on the [La−]/velocity ratio (LTP) by considering the vertices of the curve and calculating the point that yields the maximal distance from a curve representing [La−] as a function of velocity to the line formed by the two endpoints of the curve (LTDMAX method). The agreement was assessed using Bland-Altman plots and ordinary least products (OLP) regression among the velocities corresponding to the LTs identified using different methods (VLTv, VLTBI, VLTP, and VLTDMAX) and the velocity corresponding to the MLSS (VMLSS). A principal component (PC) analysis approach was performed to detect the degree of co-relatedness among the variables. The mean ± SD [La−] at MLSS was 1.03 ± 0.24 mM. VMLSS had a lower mean bias with VLTv, followed by VLTBI. The VLTDMAX underestimated MLSS. VLTv and VLTBI had the lowest limits of agreement with the VMLSS. The VLTP and VLTDMAX showed relatively high limits of agreement with MLSS. VLTv, VLTBI, and VMLSS had more collinearity and were dominantly aligned with the second component (PC2). VLTv and VLTBI can be used as simple methods to objectively determine aerobic fitness in Beagle dogs.

Monitoring Performance in Show Jumping Horses: Validity of Non-specific and Discipline-specific Field Exercise Tests for a Practicable Assessment of Aerobic Performance

Show jumping is a highly specialized equestrian discipline that requires technical skill but also power and fitness. Monitoring the horses’ aerobic performance is therefore essential in order to verify whether the training has induced the desired cardiovascular and muscular adaptations. This study therefore aimed at evaluating the validity of non-specific and discipline-specific field exercise tests for objective evaluation of aerobic performance in show jumpers. For this purpose, data obtained from horses competing at Junior and Young Rider level during show jumping competitions as well as field exercise tests were retrospectively analyzed. The effect of the level of difficulty, the horses’ age, the penalty score and the horses’ previous level of performance on blood lactate concentrations after show jumping competitions (100 observations in 49 horses) was evaluated by linear mixed effects models (horse as random effect). Estimated marginal means significantly increased from 140 (4.1 mmol/L) to 150 cm (5.2 mmol/L) classes (P = 0.02). Furthermore, post-exercise lactate values significantly increased with the horses’ age (P = 0.001). Another group of 12 horses performed a standardized incremental field exercise test on a track (SETtrack), a standardized show jumping course (SETcourse) and a standardized grid exercise (SETgrid) each on three consecutive days. Indices of aerobic performance, derived from the SETtrack [velocity at a heart rate of 140 bpm (V140) and at a lactate concentration of 2 mmol/L (VLa2)] were highly correlated with heart rate (V140: r = −0.75, P = 0.005; VLa2: r =−0.66, P = 0.02) and lactate (V140: r = −0.73, P = 0.02; VLa2: r = −0.72, P = 0.02) in response to SETcourse as well as heart rate during SETgrid (V140: r = −0.73, P = 0.02; VLa2: r = −0.76, P = 0.01). Subjective rating of muscular fatigue was significantly correlated to the mean heart rate during SETcourse (r = −0.64, P = 0.05) and SETgrid (r = −0.74, P = 0.02) but not to the aerobic indices calculated from SETtrack. Besides non-specific incremental field tests, performance monitoring in show jumpers should therefore also include discipline-specific tests that more closely reflect the internal load induced by show jumping competitions.

Association of Innate and Acquired Aerobic Capacity With Resilience in Healthy Adults: Protocol for a Randomized Controlled Trial of an 8-Week Web-Based Physical Exercise Intervention.

BackgroundPhysical activity alleviates chronic stress. The latest research suggests a relationship between resilience and physical fitness. Beneficial adaptations of the hypothalamic-pituitary-adrenal axis, sympathetic nervous system, endocannabinoid system, and tryptophan pathway, which are induced by an active lifestyle, are considered to be conducive to resilience. However, detailed knowledge on the molecular link between the effects of acute and chronic physical exercise and improved resilience to stress in humans is missing. Moreover, the relationship between innate and acquired aerobic capacity and resilience is poorly understood.ObjectiveThe aim of this study is to implement a human exercise intervention trial addressing the following main hypotheses: a high innate aerobic capacity is associated with high resilience to stress, and web-based physical exercise training improves aerobic capacity of physically inactive adults, which is accompanied by improved resilience. In this setting, we will analyze the relationship between resilience parameters and innate and acquired aerobic capacity as well as circulating signaling molecules.MethodsA total of 70 healthy, physically inactive (<150 minutes/week of physical activity) adults (aged 18-45 years) will be randomly assigned to an intervention or control group. Participants in the intervention group will receive weekly training using progressive endurance and interval running adapted individually to their remotely supervised home training performance via web-based coach support. A standardized incremental treadmill exercise test will be performed before and after the intervention period of 8 weeks to determine the innate and acquired aerobic capacity (peak oxygen uptake). Before and after the intervention, psychological tests and questionnaires that characterize parameters implicated in resilience will be applied. Blood and saliva will be sampled for the analysis of cortisol, lactate, endocannabinoids, catecholamines, kynurenic acid, and further circulating signal transducers. Statistical analysis will provide comprehensive knowledge on the relationship between aerobic capacity and resilience, as well as the capacity of peripheral factors to mediate the promoting effects of exercise on resilience.ResultsThe study was registered in October 2019, and enrollment began in September 2019. Of the 161 participants who were initially screened via a telephone survey, 43 (26.7%) fulfilled the inclusion criteria and were included in the study. Among the 55% (17/31) of participants in the intervention group and 45% (14/31) of participants in the control group who completed the study, no serious adverse incidents were reported. Of 43 participants, 4 (9%) withdrew during the program (for individual reasons) and 8 (19%) have not yet participated in the program; moreover, further study recruitment was paused for an indeterminate amount of time because of the COVID-19 pandemic.ConclusionsOur study aims to further define the physiological characteristics of human resilience, and it may offer novel approaches for the prevention and therapy of mental disorders via an exercise prescription.International Registered Report Identifier (IRRID)DERR1-10.2196/29712

Estimation of anaerobic threshold by cardiac repolarization instability: a prospective validation study

BackgroundAssessing lactate (LT) or anaerobic thresholds (AT) in athletes is an important tool to control training intensities and to estimate individual performance levels. Previously we demonstrated that ECG-based assessment of cardiac repolarization instability during exercise testing allows non-invasive estimation of AT in recreational athletes. Here, we validate this method in professional and amateur team sports athletes.MethodsWe included 65 team sports athletes (32 professionals and 33 amateur athletes; 51 men, 14 women, mean age 22.3 ± 5.2 years) undergoing a standardized incremental cycle exercise test. During exercise testing a high-resolution ECG (1000 Hz) was recorded in Frank-leads configuration and beat-to-beat vector changes of cardiac repolarization (dT°) were assessed by previously established technologies. Repolarization-based AT (ATdT°) was estimated by its typical dT°-signal pattern. Additionally, LT was detected in accordance to methods established by Mader (LTMader) and Dickhuth (LTDickhuth).ResultsAll athletes performed exercise testing until exhaustion with a mean maximum workload of 262.3 ± 60.8 W (241.8 ± 64.4 W for amateur athletes and 283.4 ± 49.5 W for professional athletes). Athletes showed ATdT° at 187.6 ± 44.4 W, LTDickhuth at 181.1 ± 45.6 W and LTMader at 184.3 ± 52.4 W. ATdT° correlated highly significantly with LTDickhuth (r = 0.96, p < 0.001) and LTMader (r = 0.98, p < 0.001) in the entire cohort of athletes as well as in the subgroups of professional and amateur athletes (p < 0.001 for all).ConclusionsATdT°, defined by the maximal discordance between dT° and heart rate, can be assessed reliably and non-invasively via the use of a high-resolution ECG in professional and amateur athletes.

Increased body fat content in horses alters metabolic and physiological exercise response, decreases performance, and increases locomotion asymmetry.

ABSTRACTThis study examined the effect of altered body weight (BW) and body fat content on exercise performance and recovery. Nine horses were divided into two groups, and changes in BW and fat content were induced by feeding a high (HA) or restricted (RA) energy allowance for 36 days in a cross‐over design. In the last week of each treatment, BW and body condition score (BCS) were recorded, body fat percentage was estimated using ultrasound, and a standardized incremental treadmill exercise test (SET) and competition‐like field test were performed (scored by judges blinded to treatments). Blood samples were collected, and heart rate (HR), rectal temperature (RT), and respiratory rate (RR) were also recorded. Objective locomotion analyses were performed before and after the field test. Body weight, body fat percentage, and BCS were higher (5–8%) in HA than in RA horses (p < 0.05). In SET, HA horses showed higher HR, plasma lactate concentration, RR, and RT than RA horses (p < 0.05), and lower VLa4, hematocrit (Hct), plasma glucose, and plasma NEFA concentrations (p < 0.05). Hct was also lower in HA horses in the field test, while RA horses showed higher scores (p < 0.05). After both tests, resting plasma lactate concentrations were reached faster in RA than in HA horses (p < 0.05). Objective locomotion asymmetry was higher in HA than in RA (p < 0.05). These results clearly show that increased BW and body fat content in horses lower physiological fitness in terms of VLa4, plasma lactate removal, Hct levels, plasma glucose availability and reduce true performance evaluated by blinded judges.

Comparison of physiological demands in Warmblood show jumping horses over a standardized 1.10\u2009m jumping course versus a standardized exercise test on a track

BackgroundA greater understanding of exercise physiology and biochemistry is required for the sport horse disciplines, including show jumping. Conditioning of horses for show jumping is empirical because they are primarily trained on flat ground, however the equivalent workload between jumping and flat work is currently unknown. The objectives of the study were therefore to compare the physiological demands of Warmblood show jumpers over a standardized 1.10 m course vs a 600 m standardized incremental exercise test on flat ground, and to report reference field test values for competitive show jumping horses. In this prospective field study, 21 healthy, actively competing Warmblood show jumping horses were assessed to determine physiological variables after a standardized jumping course at 6.4 m/s (average speed) and track standardized incremental exercise test at 5 m/s, 8 m/s and 11 m/s. Heart rate, velocity, blood lactate, blood pH, pCO2, bicarbonate, PCV and TP concentrations were recorded. V200, V170 and VLa4 were calculated. Parametric statistics were performed on analysis of all 21 horses’ variables.ResultsContrary to exercise at 5 m/s and 11 m/s, cantering at 8 m/s did not induce any significant difference in blood lactate, mean heart rate or mean venous blood pH compared to after completion of the jumping course.ConclusionsJumping a 1.10 m course demands a statistically similar workload to cantering around a flat track at 8 m/s. This study will help to test fitness and design conditioning programs for Warmblood show jumping horses.

Hormonal Response to Incremental and Continuous Exercise in Cyclists with Left Ventricle Hypertrophy.

The aim of this study was to assess the effects of incremental and continuous exercise on the concentration of insulin-like growth factor-1 (IGF-1), growth hormone (GH), testosterone (T), and cortisol (C), as well as to investigate whether increased cardiac dimensions in cyclists were related to changes in these hormones and cardiac biomarkers. The study included 30 elite cyclists divided into two groups, i.e., athletes with left ventricle hypertrophy (a LVH group), and a control group (CG) without LVH. The study protocol included performance of a standard incremental exercise (IncEx) test to measure athletes’ maximum power (Pmax), maximum oxygen uptake (VO2max), and lactate threshold (LAT). The IncEx test results were then used to determine the intensity of the continuous exercise (ConEx) test which was performed after the 1-week washout period. Cyclists with LVH and without LVH did not differ in resting hormone concentrations and cardiac biomarkers levels. There was a significant effect of exercise on serum IGF-1 levels (p < 0.05) in the LVH group and a combined effect of the type of exercise and LVH on IGF-1 (p < 0.05). Cyclists with LVH demonstrated higher post exercise T levels recorded in response to exercise compared to the CG (p < 0.01). Significantly higher serum T levels were observed in response to ConEx compared to IncEx in the LVH group and the CG (p < 0.05 and p < 0.05, respectively). In the LVH group, a significant positive correlation between the post-exercise T/C ratio and left ventricular mass index was observed (r = 0.98, p < 0.01). There were no effects of heart hypertrophy on cardiac standard biomarkers. Incremental and continuous exercise caused a marked increase in steroid hormone concentrations and moderate strengthening of insulin growth factors effects. Regular incremental exercise seems to induce beneficial cardiac adaptations via significant increases in the concentration of anabolic factors compared to the same training mode yet with constant exercise intensity.

Lactate and glucose thresholds and heart rate deflection points for Beagles during intense exercise.

OBJECTIVE To determine whether the lactate threshold of dogs could be determined by a visual method and to assess the extent of agreement and bias among treadmill velocities for the lactate threshold as determined by visual (LTv) and polynomial (LTp) methods, glucose threshold as determined by visual (GTv) and polynomial (GTp) methods, and heart rate deflection point (HRdp) as a method for estimating the aerobic capacity of dogs. ANIMALS 18 healthy adult Beagles. PROCEDURES Each dog underwent a standardized incremental treadmill exercise test once. The test ended when the dog began to show signs of fatigue. Plasma lactate and glucose concentrations and heart rate (HR) were plotted against exercise intensity (treadmill velocity) for the duration of the test, and the LTv, GTv, and HRdp were determined visually. The LTp and GTp were determined by means of a second-order polynomial function. One-way ANOVA, Pearson correlation, Bland-Altman analyses, and ordinary least products regression were used to assess the extent of agreement and bias among the various threshold velocities. RESULTS Mean velocity did not differ significantly among the thresholds evaluated. There was a strong positive correlation between the LTv velocity and the velocity for GTv (r = 0.91), LTp (r = 0.96), GTp (r = 0.94), and HRdp (r = 0.95). CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that LTv could be determined for dogs undergoing intense exercise on a treadmill, and the treadmill velocity corresponding to the LTv was associated with the velocity for the other hallmarks of endurance. Thus, that method may be useful for prescription and evaluation of conditioning programs for dogs.

Dynamic Changes of Cardiac Repolarization Instability during Exercise Testing.

Physical exercise triggers efferent cardiac sympathetic activation. Here, we tracked the spatiotemporal properties of cardiac repolarization on a beat-to-beat basis throughout a standardized exercise test and hypothesized a detectable change at the point of the anaerobic threshold (AT). The study included 20 healthy adults (age 35.3 ± 6.7 yr) undergoing a standardized incremental exercise test on a cycle ergometer. During exercise testing, high-resolution (2000 Hz) ECG monitoring in Frank lead configuration was performed. Three-dimensional beat-to-beat repolarization instability (dT°) was assessed by a novel vector-based method according to a previously published technology. In parallel, the lactate threshold (LT) was detected according to Dickhuth and Mader. We could identify a characteristic pattern of dT° signal during exercise testing. With increasing physical activity, dT° increased concordantly to heart rate. At an average of 164 ± 38 W, dT° and heart rate abruptly showed a discordant behavior, characterized by a transient drop of dT°. The maximal discordance between dT° and heart rate was defined as ATdT° and highly significantly correlated with LTDickhuth (r = 0.841, P < 0.001) and LTMader (r = 0.819, P < 0.001), which were at 156 ± 39 and 172 ± 46 W, respectively. The characteristic of dT° could not be provoked by fast atrial pacing in the absence of exercise. Repolarization instability shows a characteristic pattern during standardized exercise in healthy individuals that allows for a noninvasive estimation of AT.

Offspring of Mothers with Diabetes have Reduced Muscle Oxidative Capacity Measured by Near Infrared Spectroscopy

Adult offspring of mothers with type 2 diabetes have been reported to have reduced skeletal muscle mitochondrial oxidative capacity (OXPHOS) using in vivo31P-Magnetic Resonance Spectroscopy (31P-MRS). Near Infrared Spectroscopy (NIRS) also has the capability of measuring skeletal muscle OXPHOS, and provides indices of skeletal OXPHOS comparable to 31P-MRS. Moreover, the cost of measuring skeletal muscle OXPHOS by NIRS is substantially less than by 31P-MRS. PURPOSE: To determine whether NIRS could detect OXPHOS differences in adult offspring of mothers with type 2 diabetes (n=8) compared to controls (n=9). METHODS: Using continuous-wave NIRS (Artinis, Oxymon) coupled with transient arterial occlusions (~ 300 mm Hg, 5 on/5 off x 9, 10 on/10 off x 11), we measured muscle oxygen consumption (mVO2) in the vastus lateralis following a 7 sec maximal isometric knee extension performed in the supine position. We express the mVO2 as a percent per second (%/s), relative to an ischemic calibration. We fit the recovery mVO2 following the isometric contraction to an exponential curve using custom routines written in MATLAB by Terence Ryan to calculate the time constant (Tc) for the recovery of mVO2, which is an index of mitochondrial OXPHOS. These routines also help correct for changes in blood volume that occur during the atrial occlusion. We also measured peak oxygen uptake (VO2peak) using a standardized incremental exercise test with indirect calorimetry on a cycle ergometer. RESULTS: Age (21±1 vs. 21±2 y, p>0.05), BMI (24±3 vs. 23±2 kg/m2, p>0.05), and VO peak (32±4 vs. 32±5 ml[BULLET OPERATOR]kg-1[BULLET OPERATOR]min-1, p>0.05) were similar between offspring and controls. In contrast, offspring had higher recovery Tc compared to controls (47±24 vs. 28±10 sec, p<0.05) suggestive of reduced OXPHOS. CONCLUSIONS: Our results support the use of NIRS to measure expected differences in skeletal muscle OXPHOS between offspring and controls. Of interest, we also found that the Tc measured in the offspring to have a greater degree of variability than controls suggesting the potential for prescribing therapeutic interventions early to possibly reduce incidence of type 2 diabetes. The present study was funded in part by the Robert and Patricia Hines Endowed Professorship in Kinesiology, LSU and a College of Human Sciences and Education Dean’s Circle Grant.

Brain and Cardiorespiratory Responses to Exercise in Hot and Thermoneutral Conditions.

The aim of this study was to test whether or not concurrent evaluations of brain (electroencephalography [EEG]) and cardiorespiratory responses to exercise are influenced by environmental conditions. 10 adult male participants performed a standardized incremental exercise test to exhaustion on a cycle ergometer in an environment controlled laboratory on 2 separate occasions, in a randomized order; one in a hot condition (34.5°C) and one in a thermoneutral condition (20°C). EEG, heart rate and expired air were collected throughout. EEG data were decontaminated for artefacts, log-transformed and expressed as aggregated alpha and beta power responses across electrodes reflecting the frontal cortex of the brain. Performance outcomes showed there was no difference in V˙O2 peak across hot (42.5 ml/kg/min) and neutral (42.8 ml/kg/min) conditions, although ventilatory threshold (VT) occurred at a lower threshold (68%) in hot compared to neutral condition (74%) (p<0.05). EEG alpha and beta wave responses both demonstrated significant increases from baseline to VT (p<0.01). EEG beta-band activity was significantly elevated in the heat compared to the neutral condition. In conclusion, elevated EEG beta-band activity in response to incremental exercise in the heat suggests that beta-band activation and cortical awareness increases as exercise becomes increasingly intense.

Comparison of Endothelial Function in Pre‐ and Post‐exercise States between Obese and Normal‐weight Children

Background and RationaleMicroangiopathy is a common comorbidity associated with adult obesity. We hypothesize that microvascular function may be altered following an age‐specific pattern in pediatric obesity, occurring well before any clinical sign of vascular impairment. As exercise provides a strong, relatively homogeneous vasodilatory stimulus, these early alterations in endothelial function may be more easily detected in the post‐exercise state. We therefore designed the present study with the objective to detect differences between obese (Ob) and normal‐weight (Nw) children in endothelial function, via Laser Doppler Flowmetry (LDF), both at rest and following a standard incremental exercise test to exhaustion.MethodsThirteen Ob children (13 ± 2 yrs, 97 ± 0.8 BMI%, 6F) and 11 Nw children (14 ± 2 yrs, 61 ± 14 BMI%, 6F) participated in the study. An optical probe connected with a Periflux 5000 Laser Doppler system (Perimed, Sweden) was placed on the base of the middle finger, and LDF measurements of skin perfusion were obtained before, during, and after a 1‐min occlusion induced at the wrist with a blood pressure cuff inflated at 200 mmHg. Subjects then performed a standard incremental cycling exercise test to exhaustion, using a commercial metabolic cart/cycle ergometer system (Carefusion, San Diego, USA). The incremental phase of the test was tailored to last ~ 10 min after 2 min of unloaded pedaling. LDF measurements were then repeated 8 min after exercise cessation. Baseline pre‐occlusive perfusion (Plat1), post‐occlusive hyperemic peak (pMax), and the time from release of occlusion to reach pMax (PkT) were obtained from perfusion tracings. Comparisons were made using two‐tailed, independent Student's t‐tests.ResultsPerfusion variables (in arbitrary perfusion Units) were greater in Ob throughout the study (Plat1, pre‐exercise 76 ± 13 vs. 43 ± 12 in Nw, p = 0.068; post‐exercise, 86 ± 13 vs. 41 ± 6 in Nw, p&lt;0.05; pMax, pre‐exercise, 165 ± 16 vs. 99 ± 21, p&lt;0.05, post‐exercise, 164 ± 16 vs. 117 ± 13, p&lt;0.05). The magnitude of the hyperemic peak relative to baseline, while quantitatively larger in Nw in the pre‐exercise state, only reached significance in the post‐exercise state (pMax/Plat1, post‐exercise, 3.0 ± 0.3 vs. 2.1 ± 0.2, p&lt;0.05). In general, therefore, a similar pattern of differences was present in all studies, but significance was more clearly delineated in the post exercise state. PkT was similar across weight groups, and unchanged by prior exercise.ConclusionsOverall, our cohort of Ob children displayed characteristic perfusion alterations relative to Nw children, possibly including a state of chronic baseline vascular dilation, and reduced responsiveness to additional vasodilatory stimuli, such as physical exercise. Our findings are consistent with the concept that obesity, even in its very early stages in pediatric populations, is associated with microvascular dysfunction.Support or Funding InformationNIH NICHD P01HD048721 &amp; UL1 TR000153

Perspective: Does Laboratory-Based Maximal Incremental Exercise Testing Elicit Maximum Physiological Responses in Highly-Trained Athletes with Cervical Spinal Cord Injury?

The physiological assessment of highly-trained athletes is a cornerstone of many scientific support programs. In the present article, we provide original data followed by our perspective on the topic of laboratory-based incremental exercise testing in elite athletes with cervical spinal cord injury. We retrospectively reviewed our data on Great Britain Wheelchair Rugby athletes collected during the last two Paralympic cycles. We extracted and compared peak cardiometabolic (heart rate and blood lactate) responses between a standard laboratory-based incremental exercise test on a treadmill and two different maximal field tests (4 min and 40 min maximal push). In the nine athletes studied, both field tests elicited higher peak responses than the laboratory-based test. The present data imply that laboratory-based incremental protocols preclude the attainment of true peak cardiometabolic responses. This may be due to the different locomotor patterns required to sustain wheelchair propulsion during treadmill exercise or that maximal incremental treadmill protocols only require individuals to exercise at or near maximal exhaustion for a relatively short period of time. We acknowledge that both field- and laboratory-based testing have respective merits and pitfalls and suggest that the choice of test be dictated by the question at hand: if true peak responses are required then field-based testing is warranted, whereas laboratory-based testing may be more appropriate for obtaining cardiometabolic responses across a range of standardized exercise intensities.

Three-Phase Time Course of Physiological Variables During Incremental Cycling In Young Male and Female Subjects

There is still some debate on the time course of selected physiological variables during incremental exercise that may be used for the determination of objective sub maximal markers of performance. PURPOSE: The aim of our study was to re-examine the lactate turn-point concept introduced schematically in 1980 compared to selected markers of exercise performance. METHODS: Fifty young, healthy male (25) and female (25) sport students served as subjects in this investigation. The first (LTP1) and the second (LTP2) lactate turn-point as well as first and second turn-points (TP) for heart rate (HR) and the ventilatory variables of pulmonary ventilation (VE), fractional expired oxygen (FEO2) and carbon dioxide (FECO2), tidal volume (VT), breathing frequency (fB), oxygen uptake (VO2), and carbon dioxide production (VCO2) were determined by means of computer aided linear regression break point analysis. RESULTS: All measured variables showed an observable three-phase behavior and two turn-points could be determined in most cases. LTP1 and LTP2 could be detected in all subjects. Most of the first and all of the second turn-points were significantly related in both female and male subjects, respectively. No significant difference could be found between all first turn-points with the exception of HRTP1 in male and female subjects, respectively. No significant difference could be found between all second turn-points for power output (P), heart rate (HR), blood lactate concentration (La) and oxygen uptake (VO2) in both male and female subjects. All variables except lactate (LA) and breathing frequency (fB) were significantly different between female and male subjects at comparable sub-maximal percentages of maximal power output. CONCLUSION: We suggest that the turn-point concept may be applied to almost all physiological variables obtained in a standard incremental cycle ergometer exercise test. The significant relationship of all second TPs suggests a general change in the whole body regulation at this defined submaximal exercise performance.

APLICAÇÃO DA ESPIROMETRIA DURANTE TESTE PADRÃO DE EXERCÍCIO PROGRESSIVO EM ESTEIRA PARA AVALIAÇÃO DA TROCA GASOSA RESPIRATÓRIA DE EQUINOS DA RAÇA ÁRABE

No presente estudo avaliou-se a troca gasosa respiratória pela mensuração do consumo de oxigênio (VO2),dióxido de carbono produzido (VCO2) e quociente respiratório (R), e determinou-se o consumo máximo deoxigênio (VO2max) de cavalos da raça Árabe durante o teste padrão de exercício progressivo em esteira dealta velocidade. Seis equinos adultos da raça Árabe, clinicamente hígidos foram submetidos ao teste emesteira com inclinação de 6%, o qual consistiu da velocidade inicial de 1,8 m/s por 5 minutos, a 4 m/s por 3minutos, a 6 m/s por 2 minutos e fases a 8 m/s, 9 m/s, 10 m/s e 11 m/s por 1 minuto cada, de modo que amanta da esteira foi parada quando os cavalos não conseguiram acompanhar a velocidade da mesma. Atroca gasosa foi monitorada por meio da máscara de análise de gases respiratórios para equinos, nosúltimos 10 segundos finais de cada mudança de velocidade e a 1, 2 e 3 minutos após o término doexercício. Durante o exercício há elevação do VO2 e VCO2 com relação linear conforme a intensidade deexercício. O VO2max dos cavalos da raça Árabe é de 114,9 mL/kg/min. O quociente respiratório eleva-separa valores maiores que 1,0 a partir da velocidade de 9,0 m/s, indicando o predomínio do metabolismoanaeróbico, e mantêm-se ainda elevado no período pós-exercício.

Exercise-induced hypoxemia and cardiac arrhythmia in cystic fibrosis

Background Physical activity has become part of the therapy of patients with cystic fibrosis (CF) despite possible risks. The objectives of this study were to identify predictors of hypoxemia and to search for cardiac arrhythmia during exercise. Methods The data of 75 patients (12 to 41 years old) with CF who underwent a standardized incremental exercise test on a cycle ergometer was analyzed. Oxygen saturation (SpO 2) and ECG were monitored. The results were related to spirometric and SpO 2 measurements at rest. Results During exercise, 17 patients suffered from significant desaturations (SpO 2 < 90%). SpO 2 at peak exercise was independently related to SpO 2 at rest and 1/FEV1 (multiple regression R 2 = 0.63). Five patients demonstrated ventricular arrhythmias during exercise. No unambiguous prediction of exercise-induced hypoxemia or cardiac arrhythmia was possible. Conclusion In order to detect all patients with exercise-induced hypoxemia and cardiac arrhythmia, an incremental exercise test to volitional fatigue must be performed.

Comparison of Physical Fitness in Type 1 Diabetic and Healthy Children Matched by Age, Gender, and BMI

Physical activity is important in the growth and development of children and long‐term prevention of cardiovascular disease (CVD). Children with chronic diseases, such as diabetes, with increased risk for CVD, may display altered exercise adaptations requiring individually tailored exercise regimens. While assessment of physical fitness is a crucial component in the design of exercise strategies, conflicting conclusions exist concerning fitness in type 1 diabetic (T1DM) children (with both normal and reduced levels reported), possibly due to difficulty in recruiting closely‐matched controls. Our study aimed to compare fitness in 40 T1DM (19 F, ages 11–15) children and 40 healthy controls rigorously selected as one‐on‐one matches for gender, age (0.13 years mean difference) and BMI (1.5 mean difference). Maximal aerobic capacity (VO2peak) was determined through a standard incremental exercise test on a cycle ergometer. VO2peak was comparable across groups (38 ± 1 vs. 37 ± 1 ml/min/kg, NS), even when subdivided by gender (T1DM vs. control: girls 34 ± 2 vs. 35 ± 2; boys 44 ± 2 vs. 40 ± 2 ml/min/kg). Physical fitness was similar between T1DM and rigorously‐matched healthy children, suggesting that T1DM does not intrinsically limit a child's ability to fully derive the physiological health benefits associated with exercise.Support: NIH grants M01‐RR00827–28; K‐23 RR018661–01; &amp; JDRF #11–2003–332

Is the elevated slope relating ventilation to carbon dioxide production in chronic heart failure a consequence of slow metabolic gas kinetics?

Patients with heart failure have slow metabolic gas exchange kinetics, which may contribute to the elevated slope of the relationship between ventilation and carbon dioxide production (Ve/Vco(2) slope). A tertiary referral centre for cardiology. Eleven patients with stable chronic heart failure and 11 age-matched controls. Each subject underwent maximal bicycle-based peak exercise testing with metabolic gas exchange analysis and three further repeated tests at 15%, 25% and 50% of the load achieved at peak exercise. The ventilation and carbon dioxide production from each of these steady-state tests was used to re-calculate the Ve/Vco(2) slope and compared with the Ve/Vco(2) slope derived from the maximal test. Peak oxygen consumption [mean (S.D.)] was lower in heart failure patients [18.2 (4.0) vs. 31.2 (6.3) ml/kg per min; P<0.001] than in controls. The Ve/Vco(2) slope was steeper in patients than controls [32.7 (8.3) vs. 27.1 (1.6); P<0.05]. There was no difference between the Ve/Vco(2) slope reconstructed from the three steady state tests and resting data and that gained from the maximal test [35.3 (7.8) vs. 25.9 (3.2); P=0.43]. The elevated slope of the relationship between ventilation and carbon dioxide production is not a consequence of the short stages of a standard incremental exercise test combined with delayed metabolic gas kinetics in heart failure patients.

Effects of aerosolized albuterol on physiologic responses to exercise in standardbreds.

To examine the effects of an aerosolized beta2-adrenoreceptor agonist, albuterol, on performance during a standardized incremental exercise test in clinically normal horses. 8 Standardbred pacing mares. Clinically normal horses, as judged by use of physical examination, hematologic findings, serum biochemical analysis, and airway endoscopy, were randomly assigned to 2 groups and were given 900 microg of albuterol via a metered-dose inhaler 30 minutes before beginning a standardized incremental exercise test in a crossover design with a 7-day minimum washout. Further examination included measurement of baseline lung mechanics, response to histamine bronchoprovocation, and bronchoalveolar lavage. No significant differences (albuterol vs placebo) were seen for any incremental exercise test variables (ie, maximum oxygen consumption, maximum carbon dioxide consumption, respiratory quotient, treadmill speed at heart rate of 200 beats/min, or number of steps completed during an incremental exercise protocol). Mast cell percentage was significantly (r = -0.84) associated with the concentration of aerosolized histamine that evoked a 100% increase in total respiratory system resistance. No other direct correlations between bronchoalveolar lavage fluid cell types and any indices of exercise capacity or airway reactivity were found. Although no horse had exercise intolerance, 4 horses had airway hyperreactivity with bronchoalveolar lavage fluid mastocytosis; these horses may have been subclinically affected with inflammatory airway disease. In our study, albuterol did not enhance performance in 8 clinically normal racing-fit Standardbreds.

Changes in blood lactate and pyruvate concentrations and the lactate-to-pyruvate ratio during the lactate minimum speed test

The aim of this study was to assess the responses of blood lactate and pyruvate during the lactate minimum speed test. Ten participants (5 males, 5 females; mean +/- s: age 27.1 +/- 6.7 years, VO 2max 52.0 +/- 7.9 ml kg -1 min -1 ) completed: (1) the lactate minimum speed test, which involved supramaximal sprint exercise to invoke a metabolic acidosis before the completion of an incremental treadmill test (this results in a ‘U-shaped’ blood lactate profile with the lactate minimum speed being defined as the minimum point on the curve); (2) a standard incremental exercise test without prior sprint exercise for determination of the lactate threshold; and (3) the sprint exercise followed by a passive recovery. The lactate minimum speed (12.0 +/- 1.4 km h -1 ) was significantly slower than running speed at the lactate threshold (12.4 +/- 1.7 km h -1 ) (P < 0.05), but there were no significant differences in VO 2 , heart rate or blood lactate concentration between the lactate minimum speed and running speed at the lactate threshold. During the standard incremental test, blood lactate and the lactate-topyruvate ratio increased above baseline values at the same time, with pyruvate increasing above baseline at a higher running speed. The rate of lactate, but not pyruvate, disappearance was increased during exercising recovery (early stages of the lactate minimum speed incremental test) compared with passive recovery. This caused the lactate-to-pyruvate ratio to fall during the early stages of the lactate minimum speed test, to reach a minimum point at a running speed that coincided with the lactate minimum speed and that was similar to the point at which the lactate-to-pyruvate ratio increased above baseline in the standard incremental test. Although these results suggest that the mechanism for blood lactate accumulation at the lactate minimum speed and the lactate threshold may be the same, disruption to normal submaximal exercise metabolism as a result of the preceding sprint exercise, including a three- to five-fold elevation of plasma pyruvate concentration, makes it difficult to interpret the blood lactate response to the lactate minimum speed test. Caution should be exercised in the use of this test for the assessment of endurance capacity.