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Physiologic responses to training
Abstract
Endurance training improves exercise tolerance principally by inducing structural and biochemical changes in the exercising muscles. These changes yield improved oxygen delivery to the site of muscle metabolism, which improves oxygen use and forestalls the onset of anaerobic metabolism. The physiologic stress of heavy exercise is thereby reduced. The molecular mechanisms that induce these changes are unclear, but the characteristics of an effective training program have been well described. Cessation of training leads to prompt regression of the accumulated benefits.
... el ATP es hidrolizado en ADP y fosfato inorgánico y se utiliza en las proteínas miofibrilares en el complejo actina-miosina a través de cuatro sistemas energéticos (15)(16)(17)(18). ...
... 3) Cuando se realiza un estiramiento se tiene sensación de tirantez. Se debe de realizar del siguiente modo: se mantiene la postura hasta que disminuye el dolor entonces es cuando se vuelve a estirar y se mantiene otros segundos (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). Si tenemos sensación de tirantez excesiva entonces no lo estamos haciendo bien. ...
The role of exercise in improving individual and social welfare is becoming increasingly important as the number of people with anxiety or depression. Aerobic exercise is associated with reductions in the latter. Their relationship to psychological well has a correlational rather than causal character. The effects of physical exercise tend to be more acute than chronic, and people say they feel better immediately after exercise, an effect that tends to remain for several hours. Have been suggested psychological, physiological and social explanations for the ways in which physical exercise improves psychological well-being. Since exercise is related to these positive changes, your practice should be encouraged, promoted and facilitated by the individuals and institutions responsible as a treatment and as a preventative thereof .
... A disparity in the time-course for adaptation in endurance performance indicators suggests that there may be differences in the way CT and IT protocols elicit adaptive change. Thex differcnces could be due to the intensity differences between protocols, aithough exercise intensity is one of the most controversial aspects of an exercise training program design (Casaburi, 1994). A review of literature by Wenger and Bell (1986) suggcsted that intensity is of key importance in stimulating adaptive change. ...
... ness indicators had noticeable benefits for these subjects. As a result of their training programs, they were able to exercise at higher maximal workloads. More importantly, increases in Tvi suggest that their 'anaerobic threshold' had also increased due to better oxygen delivery and a larger capacity for oxidative metabolism in the trained muscle (Casaburi. 1994). This training effect dlowed the subjects to perform physical activity at higher workloads for extended periods of time. without the fatigue and discomfon associated with build-up of anaerobic by-products. Activities such as climbing stairs, running to catch a bus. or walking the family dog will place less physiological stress on the b ...
... the patient education part of the programme was occasionally extended, which left little time for physical training. In addition, the CRR training intervention is far less streamlined than an RCt intervention; it involves less coaching, and CRR participants may be disadvantaged in terms of motivation, programme adherence and ability to follow programme guidelines and to tolerate exercise (28)(29)(30)(31). Poorly prescribed exercise regimes may cause patients to complete training sessions at suboptimal activity levels. ...
... Poorly prescribed exercise regimes may cause patients to complete training sessions at suboptimal activity levels. the intensity, duration and frequency of the training performed may therefore simply have been insufficient to achieve improvements (10,(28)(29)(30)(32)(33)(34)(35). Furthermore, the practical and physical conditions might not provide optimal conditions for training. ...
Objective:
The effect of rehabilitation for chronic obstructive pulmonary disease has been well-documented in randomized controlled trials. Evidence-based guidelines support rehabilitation programmes for chronic obstructive pulmonary disease, but knowledge of their outcome in clinical practice is limited. The aim of this study was to assess the outcome of a clinical routine rehabilitation programme for chronic obstructive pulmonary disease implemented by a Danish regional hospital.
Material and methods:
Changes in walk-distance (6-min walk-distance test; 6MWD), dyspnoea (Medical Research Council dyspnoea scale; MRC) and health-related quality of life (Short-Form 36; SF-36) were compared between and within completers and non-completers from baseline to the end of clinical routine rehabilitation, and at 6 and 12 months. The 8-week clinical routine rehabilitation comprised bi-weekly 90-min sessions of patient education and physical training.
Results:
The hospital treated 521 patients during the study period. Of these, 175 were invited to join the study, 148 participated at baseline, and 98 at the 12-month follow-up. Completers' 6MWD was sustained from baseline to the end of clinical routine rehabilitation, but had declined by 12 months. Dyspnoea and health-related quality of life did not change. Seventy-five percent of completers felt better or much better after rehabilitation.
Conclusion:
The failure of completers to achieve expected outcomes shows a need for a stronger implementation effort and continuous quality control. Successful implementation in clinical routine requires targeted recruitment and overall programme improvement in general, and a stronger focus on physical training and staff competences.
... Training sessions should range between 30 and 60 minutes [14,26]; however, benefit is achieved with higher intensity exercise for durations of at least 20 minutes [27]. Frequency should be at least twice weekly; still greater benefits are associated with more frequent exercise. ...
... Training benefit reaches its maximum in 3 to 4 weeks if training work is initiated at 50% VO 2 max [25,28,29]. Because patients and many normal subjects rarely start at these levels of training intensity, an 8-week program is advisable [27]. The mode of training depends on the goals, as only those muscles trained will benefit [14]. ...
The respiratory system rarely limits exercise in the normal subject. In patients with chronic pulmonary processes or in the elite athlete, however, the respiratory system may indeed be the limiting factor. Common respiratory disorders include chest pain syndromes, cough, exercise-induced asthma, and vocal cord dysfunction. Chronic lung diseases such as asthma, COPD, and interstitial lung disease impact exercise capacity and endurance. Exercise testing can be useful to distinguish acute and chronic pulmonary causes of dyspnea during exercise, as well as to differentiate between cardiac and pulmonary causes.
... 8,32,33 Aerobic training in humans causes cardiovascular adaptations, with greater oxygen delivery to contracting muscle and structural changes in skeletal muscle that promote aerobic metabolism. 5,16 According to this, some studies have confirmed the beneficial effects of aerobic training for increasing work and oxidative capacity in MM. 29,[32][33][34]36 Already developed exercise protocols for MM only include classic aerobic leg training on cycle or treadmill. However, most patients need and must do some form of lifting, carrying, or pushing activity in their daily routine. ...
... Patients were capable of achieving greater levels of effort, and the anaerobic threshold was delayed significantly as an expression of aerobic improvement. 5 Increases in VO 2 max (28.5%) were comparable to those recently reported in MM (20% increase) and measured with an equivalent procedure to ours. 36 Posttraining peak workload was somewhat superior to that obtained by Taivassalo and coworkers, 36 but, in contrast, improvement was not large enough to reach significance. ...
Patients with mitochondrial myopathies (MM) usually suffer from exercise intolerance due to their impaired oxidative capacity and physical deconditioning. We evaluated the effects of a 12-week supervised randomized rehabilitation program involving endurance training in patients with MM. Twenty MM patients were assigned to a training or control group. For three nonconsecutive days each week, patients combined cycle exercise at 70% of their peak work rate with three upper-body weight-lifting exercises performed at 50% of maximum capacity. Training increased maximal oxygen uptake (28.5%), work output (15.5%), and minute ventilation (40%), endurance performance (62%), walking distance in shuttle walking test (+95 m), and peripheral muscle strength (32%-62%), and improved Nottingham Health Profile scores (21.47%) and clinical symptoms. Control MM patients did not change from baseline. Results show that our exercise program is an adequate training strategy for patients with mitochondrial myopathy.
... We found that the reference values of VAT were determined by natural logarithms of height and weight. The VAT is an indicator of aerobic fitness, useful for exercise prescription, especially in cardiac rehabilitation programs to monitor the effect of physical training [7,35,36]. In adult studies, wide range of normal values for VAT from 35 to 80% of the predicted VO 2max have been reported [19]. ...
... We found that the reference values of VAT were determined by natural logarithms of height and weight. The VAT is an indicator of aerobic fitness, useful for exercise prescription, especially in cardiac rehabilitation programs to monitor the effect of physical training [7,35,36]. In adult studies, wide range of normal values for VAT from 35 to 80% of the predicted VO 2max have been reported [19]. ...
Background
The evaluation of health status by cardiopulmonary exercise test (CPET) has shown increasing interest in the paediatric population. Our group recently established reference Z-score values for paediatric cycle ergometer VO2max, applicable to normal and extreme weights, from a cohort of 1141 healthy children. There are currently no validated reference values for the other CPET parameters in the paediatric population. This study aimed to establish, from the same cohort, reference Z-score values for the main paediatric cycle ergometer CPET parameters, apart from VO2max.
Results
In this cross-sectional study, 909 healthy children aged 5–18 years old underwent a CPET. Linear, quadratic, and polynomial mathematical regression equations were applied to identify the best CPET parameters Z-scores, according to anthropometric parameters (sex, age, height, weight, and BMI). This study provided Z-scores for maximal CPET parameters (heart rate, respiratory exchange ratio, workload, and oxygen pulse), submaximal CPET parameters (ventilatory anaerobic threshold, VE/VCO2 slope, and oxygen uptake efficiency slope), and maximum ventilatory CPET parameters (tidal volume, respiratory rate, breathing reserve, and ventilatory equivalent for CO2 and O2).
Conclusions
This study defined paediatric reference Z-score values for the main cycle ergometer CPET parameters, in addition to the existing reference values for VO2max, applicable to children of normal and extreme weights. Providing Z-scores for CPET parameters in the paediatric population should be useful in the follow-up of children with various chronic diseases. Thus, new paediatric research fields are opening up, such as prognostic studies and clinical trials using cardiopulmonary fitness outcomes.
Trial registration NCT04876209—Registered 6 May 2021—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04876209.
... The VAT is an indicator of aerobic tness, useful for exercise prescription, especially in cardiac rehabilitation programs to monitor the effect of physical training. [7,36,37] In adult studies, wide range of normal values for VAT from 35-80% of the predicted VO 2max have been reported. [19] Furthermore, percent-predicted VAT values from 50-60% observed in adult sedentary subjects are commonly used to de ne physical deconditioning and patient eligibility for rehabilitation programs. ...
Background: The evaluation of health status by cardiopulmonary exercise test (CPET) has shown increasing interest in the paediatric population. Our group recently established reference Z-score values for paediatric cycloergometer VO2max, applicable to normal and extreme weights, from a cohort of 1141 healthy children. There are currently no validated reference values for the other CPET parameters in the paediatric population. This study aimed to establish, from the same cohort, reference Z-score values for the main paediatric cycloergometer CPET parameters, apart from VO2max.
Results: In this cross-sectional study, 909 healthy children aged 5 to 18 years old underwent a CPET. Linear, quadratic, and polynomial mathematical regression equations were applied to identify the best CPET parameters Z-scores, according to anthropometric parameters (sex, age, height, weight, and BMI). This study provided Z-scores for maximal CPET parameters (heart rate, respiratory exchange ratio, workload, and oxygen pulse), submaximal CPET parameters (ventilatory anaerobic threshold, VE/VCO2 slope, and oxygen uptake efficiency slope), and maximum ventilatory CPET parameters (tidal volume, respiratory rate, breathing reserve, and ventilatory equivalent for CO2 and O2).
Conclusions: This study defined paediatric reference Z-score values for the main cycloergometer CPET parameters, in addition to the existing reference values for VO2max, applicable to children of normal and extreme weights. Providing Z-scores for CPET parameters in the paediatric population should be useful in the follow-up of children with various chronic diseases. Thus, new paediatric research fields are opening up, such as prognostic studies and clinical trials using cardiopulmonary fitness outcomes.
Trial registration: NCT04876209 - Registered 6 May 2021 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04876209.
... Several researches show that participation in a physical activity can help solving some of these problems (Bauman, 2004;Daley et al., 2007;Penedo and Dahn, 2005;WHO, 2000)In principle, the human body is designed to be in movement. Muscles, tendons, ligaments and bones in human body work as a whole and are organized in such a way that they can do several movements (Casaburi, 1994 andWasserman et al, 1987). This functional team works in tandem with the centralized nervous system, the cardiovascular system, the breathing, digestion and the endocrinal system (Jette et al, 1999;Rodman et al, 2002;Wasserman et al, 1987). ...
This study focuses on the non-participation of adults in physical activity and the reasons that have been preventing them to participate. The study is carried out with 283 participants (116 men and 167 women) who live in Adana, Turkey. Their ages range from 18-66. The average age of the adult participants is 31.81 ±10.12. The demographical features, their conditions to be able to participate in physical activity and the conditions that restrain them from participation have been determined by the 35 question through a questionnaire prepared by the researcher. In analyzing the information the x² test has been used. According to the results of the analysis it is found out that 59.5% of the man and 53.7% of the woman who have participated in the study are involved in physical activities.. In the study it has been observed that participation in physical activity increases in direct proportion to better education and higher income. The marital status has also affected the participation. The participants have brought to the fore the most important reasons for not participating in physical activities as, not finding friends, that the places where physical activity is performed is crowded, not having enough time, not being supported by the family or not having enough information in their answers. As a result, participation in physical activity is made up by factors related to each other and at the same time independent of them.
... Se ha observado que en presencia de inactividad física el riesgo de enfermedad cardiovascular se duplica, la aparición de diabetes mellitus tipo 2 es mayor, la presencia de obesidad se incrementa, la posibilidad de aparición de la osteoporosis aumenta, se eleva el riesgo de padecer depresión y ansiedad, entre otras patologías 6,7,8 . ...
Coronary artery diseases (CAD) are main cause of morbidity and mortality in western world. Multiple risk factors are involved in CAD, among them, a sedentary life style or low physical activity level is a well-recognized modifiable risk factor. Numerous investigations had explained both, organism adaptations during the exercise and benefits in different system and metabolic routes of the body. Throughout the last decades, some questionnaires have been developed with the aim to measure physical degree practice and to indicate CAD risk level in a sedentary person. Many of these instruments are validated internationally showing to be easily applicable and perfectly accessible to scientist, which does not justify its low current exploit, because perhaps by ignorance of their existence. Physical activity constitutes an essential gear in bio-psycho-social human health; this one can become the base of lifestyle change aimed to CAD risk factors reduction and to optimize the quality of life.
... La liberación de energía permite que los bastones de las moléculas de miosina se desplacen; este hecho fue estudiado y descrito por Huxley. El consumo de ATP durante la contracción será proporcional a la actividad de las bandas de contracción (8,53). Para disponer de los compuestos de alta energia, que en cierto modo representan la moneda corriente para la transferencia de energía, el organism o lo regenera continuamente durante largos periodos de ejercicio, resintetizándolo desde el ADP y fósforo inorgánico y a través de cuatro sistemas energéticos (3,52,53). ...
AIDS remains one of the most serious health problems in this millennium. In fact, WHO estimated at 5 million cases of AIDS worldwide and about twelve million people are infected with HIV (HIV, viral etiological agent of AIDS).
In recent years, they have made considerable efforts in the prevention, diagnosis and treatment of the disease of AIDS, however a cure for this disease does not exist. This has facilitated complementary strategies appearing in AIDS therapeutics and interventions based training. This was done on the basis of scientific evidence indicated that physical training is not only appropriate but suitable for people infected with AIDS.
... La principal fuente de energía para la contracción del músculo es el ATF! Esta molécula de ATP a través de transformaciones energéticas se convierte en energía cinética. La energía se obtiene cuando el ATP es hidrolizado en ADP y fosfato inorgánico y se utiliza en las proteínas miofibrilares en el complejo actina-miosina a través de cuatro sistemas energéticos (4,8,47. 48). ...
The movement expressed in the form of exercise is acquiring increasingly important role in the lives of individuals, to have unequivocal evidence through multiple investigations, the beneficial effects on different organ systems, their help in preventing various day diseases, especially cardiovascular and metabolic type, and as an adjunct to pharmacological and non-pharmacological treatment of others .
The diabetes affects over 190 million people and it is estimated that by the year 2005 are 330 million people affected by this disease.
Knowing that exercise is a key element in the prevention of type 2 diabetes and a therapeutic step further to improving blood glucose levels for type 1 diabetes, it is necessary to review some basic knowledge about the adaptation of the organism to physical effort and know the different systems by which the body captures energy in terms of physical effort, in order to carry out this requirement.
... Esta molécula de ATP a través de transformaciones energéticas se convierte en energía cinética. La energía se obtiene cuando el ATP es hidrolizado en ADP y fosfato inorgánico y se utiliza en las proteínas miofibrilares en el complejo actina-miosina a través de cuatro sistemas energéticos (7,14,70,71). ...
Every day more research redound on the beneficial effects of exercise in different organ systems, being, therefore, a source of health and protective factor against disease of modernity, especially cardiovascular type and as an adjunct to pharmacological and non-pharmacological treatment of other . Health we seek is not only physical, but mental health, or the strength to face difficult situations, resist pressure and overcome difficulties. This can be achieved with a prescribed and appropriately planned well sport.
That is why the concept of exercise prescription has begun to prevail, especially in the medical field as a process by which a person, healthy or sick, he recommends a regime of individualized and appropriate physical activity to your needs unlike the classic prescribe or prescribe a drug, treatment or procedure concept.
In the case that concerns us is the physical exercise in hypertensive, has seen a 20 to 30% of hypertensive patients achieve good control of your blood pressure with a simple exercise program combined with a series of measures dietetic hygiene; this shows that exercise prominently in the primary prevention of hypertension especially in mild or borderline type instead.
... • Ofrecer más oxígeno al músculo que realiza el esfuerzo, actuando a su vez sobre la recogida de oxígeno de los alvéolos del aire inspirado y su posterior transporte por la sangre a los tejidos (11)(12)(13). ...
El paciente con cefaleas que se inicia a la práctica deportiva se le deben indicar unos consejos generales sobre la realización de mismo que seguramente le serán de gran utilidad y beneficio:
• Evitar factores de riesgo: cafeína, alcohol, evitar el aumento de temperatura corporal, deshidratación, hipoglucemia (no entrenar en ayunas), no llegar a la extenuación.
• En general, debe realizarse un calentamiento lento y suficientemente largo.
• Avanzar a lo largo de un entrenamiento poco a poco y a un ritmo lento .
• Vigilar la hidratación: hidratarse antes, durante y después del ejercicio.
• Evitar realizar actividades físicas en temperaturas extremas o en altitud elevada.
• Pueden administrarse antinflamatorios no esteroideos (AINEs) antes de realizar ejercicio, para evitar su aparición.
• Evitar realizar ejercicios extenuantes:
• En el caso de deportes aeróbicos: se debe instar al paciente a encontrar el momento (tiempo, intensidad) a partir del cual empiezan a aparecer los síntomas, buscando el punto del que no debe pasar para evitar desencadenar la cefalea o migraña.
• En caso de realizar ejercicios de fuerza y de levantamiento de peso, debe recomendarse un programa de entrenamiento limitado a la intensidad a partir de la cual aparecen los síntomas.
• En el caso de cefalea desencadenada por realizar deportes en altitud elevada (relacionada con el mal de altura), utilizar aspirina para prevenirla. En caso de no conseguirlo, deberá evitarse la realización actividades físicas en altitud elevada.. La acetazolamida (que es dopaje-positivo)) también puede ser de ayuda para este tipo de cefalea, así como el ibuprofeno o el sumatriptán .
... This is important to note sinceFigure 1 The association between (A) treadmill 85% age predicted maximum heart rate endpoint, (B) treadmill AT endpoint, and (C) Arc trainer AT endpoint submaximal tests with maximal oxygen uptake. anaerobic threshold is a helpful indicator for determining fitness level and for measuring the effect of exercise training (Casaburi 1994; Casaburi et al. 1991). Overall, the submaximal VO 2 endpoint at 85% age predicted maximum heart rate showed the highest correlation to actual measured VO 2max , as seen inFigure 1. ...
Maximal oxygen uptake (VO2max) has been used to assess risk for all-cause mortality and cardiovascular disease (CVD), and low VO2max has recently been associated with increased mortality from breast cancer. The purpose of this study was to determine the proportion of breast cancer survivors with 2 or more risk factors for CVD exhibiting a low VO2max and to determine whether sub-maximal endpoints which could be applied more readily to intervention research would correlate with the maximal treadmill test. We performed a single VO2max test on a treadmill with 30 breast cancer survivors age 30-60 (mean age 50.5 ± 5.6 years) who had 2 or more cardiac risk factors for CVD not related to treatment and who had received systemic therapy and or left chest radiation. Submaximal VO2 endpoints were assessed during the VO2max treadmill test and on an Arc trainer. Resting left ventricular ejection fraction (LVEF) was also assessed by echocardiogram (ECHO) or multi-gated acquisition scan (MUGA). A majority (23/30) of women had a VO2max below the 20th percentile based on their predicted normal values. The group mean resting LVEF was 60.5 ± 5.0%. Submaximal VO2 measures were strongly correlated with the maximal test including; 1) 85% age predicted maximum heart rate VO2 on treadmill, (r = .89; p < 0.001), 2) treadmill VO2 at anaerobic threshold (AT), (r = .83; p < 0.001), and 3) Arc VO2 at AT, (r = .80; p < 0.001). Breast cancer survivors with 2 or more CVD risk factors but normal LVEF had a low cardiorespiratory fitness level compared to normative values in the healthy population placing them at increased risk for breast cancer and cardiovascular mortality. Submaximal VO2 exercise testing endpoints showed a strong correlation with the VO2max test in breast cancer survivors and is a good candidate for testing interventions to improve cardiorespiratory fitness.
... Aerobic training, alone or in conjunction with strengthening exercises, induces structural changes and adaptations in cardiovascular and muscular systems. These adaptations mainly concern the improvement of oxygen delivery and uptake at exercising muscle level, with adaptations reflecting an increase of muscle capillaries and a conversion from fast fibre type (type II) to slow fibre type (type I), which indicates an increased oxidative capacity of the muscle [84, 85]. As result of these adaptations, the muscle metabolism will be modified promoting the use of the aerobic pathway instead of the glycolytic pathway [86, 87]. ...
Exercise intolerance is a key element in the pathophysiology and course of Chronic Obstructive Pulmonary Disease (COPD). As such, evaluating exercise tolerance has become an important part of the management of COPD. A wide variety of exercise-testing protocols is currently available, each protocol having its own strengths and weaknesses relative to their discriminative, methodological, and evaluative characteristics. This paper aims to review the responsiveness of several exercise-testing protocols used to evaluate the efficacy of pharmacological and nonpharmacological interventions to improve exercise tolerance in COPD. This will be done taking into account the minimally important difference, an important concept in the interpretation of the findings about responsiveness of exercise testing protocols. Among the currently available exercise-testing protocols (incremental, constant work rate, or self-paced), constant work rate exercise tests (cycle endurance test and endurance shuttle walking test) emerge as the most responsive ones for detecting and quantifying changes in exercise capacity after an intervention in COPD.
... Literature reports however some other parameters derived from CPT, like the anaerobic threshold (AT) [4] and the aerobic threshold (AerT) [5] expressed as a percentage of VO 2 max. While the AT determination is employed particularly in athletes to classify the fitness level and to follow the effects of physical training [6], on the contrary the AerT is not currently used in athletes population for the poor relationship with an high performance level, but it is use among the deconditioned patients where the 20% to 40% of their VO 2 max should be the initial intensity of exer- cise [7]. The last one has been recently considered in evaluating non-athletes subjects, even if regularly trained, where the physical exercise is prescribed as therapy to contrast the risks factors derived from an improper life style. ...
Purpose: The Anaerobic Threshold (AT) and VO2 max are currently used to evaluate the athlete’s performance while the Aerobic Threshold (AerT), (for blood lactate of 2 mmol/litre), has been recently used. The aim of this study it is to compare VO2 max, AT and AerT of different sports.
Methods: A group of 41 athletes (16 soccer, 10 basket and 15cyclists) and 10 healthy subjects were submitted to a Cardio Pulmonary Test (CPT). The AerT, AT (in three different methods: V-slope, Ventilatory Equivalents, Respiratory Exchange Ratio) and VO2max were evaluated. The statistical analysis was performed with T student test (P< 0.05 significant).
Results: The AT values, were in athletes statistically different vs controls. On the contrary the AerT values were higher only in the cyclist group.
Conclusions: The results confirm the consistency of the methods to calculate the AT. Only in cyclist the AerT measure seems to give an additional information in evaluating the cardiovascular performance. The VO2max and AT remain the main parameters in defining the athletes performance. Therefore we cannot exclude any further utility of the AerT in normal subject but regularly trained.
... Currently among the parameters usually evaluated during the cardiopulmonary exercise test, the main factor for the assessment of the heart performance, is considered the maximum oxygen uptake (VO 2max ) expressed in ml/kg/ min [1]. However, parallel to this one, the Anaerobic Threshold (AT) is often employed to adjust the fitness level and to follow the effects of physical training [2], directly associated with the athlete's performance. In athletes the AT, as well as VO 2max , are generally indistinctly used even if they do not exactly correspond to the same metabolic modifications [3]. ...
Purpose: The Anaerobic Threshold (AT) and VO2max are both indistinctly used to evaluate the athlete’s
cardiovascular performance however; they do not correspond to the same metabolic modifications. Despite this
aspect could partially depends on the different static and dynamic work-load of the sports practiced, it can also
derive from the training variety, where the “cyclic and acyclic” component can be diversely represented. The aim of
this study is to evaluate any possible difference of these parameters, among sports at different dynamic and static
component undergoing to a diverse kind of training with prevalent cyclic or acyclic preparation.
Methods: A group of 44 athletes from three different sports was submitted to a Cardio Pulmonary Test (CPT) and
to a 2D echocardiography exam calculating the AT and VO2max and the standard heart systo-diastolic parameters.
The statistical analysis was performed using Anova Test (P< 0.05 significant).
Results: Only in cyclists, at high dynamic component and cyclic training, both the parameters were statistically
highest (p<0.01). In soccer players, at the lowest static class and practicing an acyclic training, the values of AT and
VO2max were higher than the basketball. A negative relationship of CMI and CPT parameters has been found in them.
Conclusions: The results support the hypothesis that both AT and VO2max, resulted to be strongly related to the
dynamic component of the sport practiced while the AT value can partially depends on the kind of the cyclic or acyclic
training. This single parameter can therefore be employed particularly during the follow–up of the athletes training.
... Literature reports however some other parameters derived from CPT, like the anaerobic threshold (AT) [4] and the aerobic threshold (AerT) [5] expressed as a percentage of VO 2 max. While the AT determination is employed particularly in athletes to classify the fitness level and to follow the effects of physical training [6], on the contrary the AerT is not currently used in athletes population for the poor relationship with an high performance level, but it is use among the deconditioned patients where the 20% to 40% of their VO 2 max should be the initial intensity of exer- cise [7]. The last one has been recently considered in evaluating non-athletes subjects, even if regularly trained, where the physical exercise is prescribed as therapy to contrast the risks factors derived from an improper life style. ...
The Aerobic Threshold (AerT), is an aged cardiovascular parameter not commonly used to evaluate the heart’s performance
in athletes. It indirectly evaluated by ventilator parameters during Cardio Pulmonary Test (CPT). Considering
that” exercise as prescription therapy “for the diseases, includes training normally established around at the 40%
of the peak VO2, this parameter could be taken in care as initial level for the effort prescribed. The aim of the study was
to estimate the behavior of the AerT and also Anaerobic Threshold (AT), VO2max in sedentary people. A group of athletes
coming from different sports at the same and highest dynamic component were enrolled as control. A group of 41
athletes (16 soccer, 10 basket and 15 cyclists) and 9 healthy subjects were submitted to a CPT. The AerT, AT (assessed
by V-slope method) and VO2max were evaluated. The statistical analysis was performed with T student test (P < 0.05
significant). As expected in sedentary all the values were lower than athletes, however for Aer T value appears to be not
significantly inferior respect of this one, with the exclusion of the comparison with the cyclists. In sedentary the AerT
measure seems to give additional information in evaluating the cardiovascular performance. The VO2max and AT remain
the main parameters in defining the athletes performance. Therefore we cannot exclude any further utility of the
AerT in normal subject but regularly trained.
... It leads to more aerobic metabolism and therefore less lactic acid and less CO 2 production for a given level of exercise. [15][16][17] Dynamic hyperinflation present in COPD patients is also reduced because exercise conditioning leads to reduced demand on the system and hence lower respiratory rate for a given level of exercise. [17] Additional beneficial effect of rehabilitation is desensitization to dyspnea [ Figure 1]. ...
The burden of chronic obstructive pulmonary disease (COPD) has increased recently in developing countries. On the other hand, structured or non-structured rehabilitation services for COPD patients are not routinely available in these countries. We, therefore, planned this review to re-emphasize the emerging benefits of pulmonary rehabilitation in COPD population. Aim of this review is to stimulate pulmonary physicians in India and other resource-poor areas of the world so that they start using pulmonary rehabilitation or its components more often. The search included standard english literature PubMed citation of relevant original articles, review articles and practice guidelines. The articles and reviews were searched including standard MeSH terms - Rehabilitation (TIAB) and pulmonary disease, chronic obstructive/therapy (MAJOR) and guidelines (TIAB). Available 58 articles in English including 23 reviews from July 2001 to October 2010 were screened for evidence-based benefits regarding respiratory rehabilitation as a whole or its different components. The cross references and current citations relating to primary articles were also included for description. No attempt was done to make a systematic analysis because our purpose was not to derive evidence-based recommendations from database and because sufficient evidence is already available for benefits of selected components of pulmonary rehabilitation in COPD patients. Pulmonary rehabilitation has emerged as an important modality as an adjunct to other therapies in patients of COPD. Limited and more cost-effective protocols are to be developed and executed by healthcare providers, especially in developing countries like India.
... The fact that dyspnoea scores were lower in the second test in control subjects contrasted with the remarkable reproducibility of physiological variables. The duration of practice during each session, in particular above 60–80% of maximal f C (the critical training f C) and the number of sessions were certainly too small to induce any training effect in either group [30]. Given the lack of any observable change in breathing pattern, pulmonary gas exchange, or power output in controls, the decrease in dyspnoea scores may reveal the effect of prior experience on dyspnoea sensation, an effect which has presumably influenced dyspnoea scores in LFB subjects as well. ...
Exercise rehabilitation programmes are increasingly recommended in young asthmatics, but it is unclear whether or not training should incorporate instructions on breathing pattern. In this study, we examined the effects of voluntarily decreasing breathing frequency on their ventilatory equivalents for oxygen and carbon dioxide (minute ventilation (V'E)/oxygen consumption (V'O2) and V'E/CO2 production (V'CO2), respectively), noninvasively determined physiological dead space/tidal volume (VD/VT) and dyspnoea. Fifteen young asthmatic subjects were assigned to two groups: low frequency breathing (LFB) and controls. They first underwent an exercise test at a cardiac frequency of 150 beats x min(-1). They were trained at this level for nine sessions. LFB subjects were instructed to decrease respiratory frequency by 40% during exercise. Control subjects received no instructions. A second test was then performed in the same conditions. LFB subjects decreased V'E/V'O2, V'E/V'CO2 and VD/VT by 22, 19 and 12%, respectively. Arterial oxygen saturation (Sa,O2) fell to 89+/-4% and end-tidal carbon dioxide tension (PET,CO2) rose to 6.5+/-0.7 kPa (49+/-5 mmHg). In controls, these variables were identical in the two tests. Dyspnoea was lower in the second test in all subjects. In conclusion, breathing pattern may be profoundly altered during exercise without concomitant increase in dyspnoea. However, directing breathing patterns for exercise rehabilitation requires an individual assessment of the desired pattern in order to prevent hypercapnia or hypoxia.
... tification of arrhythmia, arterial desaturation, and the presence As LVRS continues to be actively investigated, an expanding and timing of lactic acidosis can be obtained by CPET. CPET database from several studies has yielded improvements An increasing number of studies have used CPET to docuin the quantification of many clinically relevant exercise performent improvement in exercise tolerance and V o 2 peak (153, 157), mance variables after LVRS, which may not be revealed in reduced ventilatory requirements (155, 158), and improved musstandard pulmonary function studies (81,(129)(130)(131)(132)(133)(134)(135). Significant cle oxidative capacity (159) resulting from exercise training in improvement in right ventricular performance, particularly dur-COPD. ...
Patients with impaired pulmonary function are at increased risk for the development of postoperative complications. Recently exercise testing and predicted postoperative (ppo) function have gained increasing importance in the evaluation of lung resection candidates. We prospectively evaluated an algorithm for the preoperative functional evaluation that was developed at our institution. This algorithm incorporated the cardiac history including an electrocardiogram (ECG), and the three parameters FEV1, diffusing capacity of the lungs for carbon monoxide (DLCO), and maximal oxygen uptake (VO2max), as well as their respective ppo values (FEV1-ppo, DLCO-ppo, and VO2max-ppo) calculated based on radionuclide perfusion scans. A consecutive group of 137 patients (mean age 62 yr; range 23 to 81; 102 males, 35 females) with clinically resectable lesions underwent assessment according to our algorithm. Five patients were deemed functionally inoperable, 132 passed the algorithm and underwent pulmonary resections with standard thoracotomy: 9 segmental or wedge resections, 85 lobectomies (inclusive 3 bilobectomies), and 38 pneumonectomies. All patients were extubated within 24 h. The mean stay in the ICU was 1.4 (+/- 1.8) d, and the mean hospital stay was 14.6 (+/- 5) d. Postoperative complications (within 30 d) occurred in 15 patients (11%), of whom two died (overall mortality rate 1.5%). In comparison to our previous series this meant a 50% reduction in complications whereas the percentage of inoperable patients remained unchanged (4% now, 5% before). We conclude that adherence to our algorithm resulted in a very low complication rate (morbidity and mortality), and excluded more rigorous patient selection as a bias for the improved results.
... [32][33][34] In contrast, endurance exercise training, an intervention that alters muscle structure and biochemistry, has been clearly shown to speed V o 2 kinetics following the onset of moderate exercise in both healthy subjects and COPD patients. 5, 35 We cannot with certainty explain the difference between our results and those of Palange et al 10 who found that supplemental oxygen substantially increased the speed of V o 2 kinetics. They employed a mixing-chamber system to evaluate kinetics and observed only a single exercise transition for each inhalation. ...
The slow oxygen uptake (VO(2)) kinetics observed in COPD patients is a manifestation of skeletal muscle dysfunction of multifactorial origin. We determined whether oxygen supplementation during exercise makes the dynamic VO(2) response faster and reduces transient lactate increase.
Ten patients with severe COPD (ie, mean [+/- SD] FEV(1), 31 +/- 10% predicted) and 7 healthy subjects of similar age performed four repetitions of the transition between rest and 10 min of moderate-intensity, constant-work rate exercise while breathing air or 40% oxygen in random order. Minute ventilation (VE), gas exchange, and heart rate (HR) were recorded breath-by-breath, and arterialized venous pH, PCO(2), and lactate levels were measured serially.
Compared to healthy subjects, the time constants (tau) for VO(2), HR, carbon dioxide output (VCO(2)), and VE kinetic responses were significantly slower in COPD patients than in healthy subjects (70 +/- 8 vs 44 +/- 3 s, 98 +/- 14 vs 44 +/- 8 s, 86 +/- 8 vs 61 +/- 4 s, and 81 +/- 7 vs 62 +/- 4 s, respectively; p < 0.05). Hyperoxia decreased end-exercise E in the COPD group but not the healthy group. Hyperoxia did not increase the speed of VO(2) kinetics but significantly slowed VCO(2) and E response dynamics in both groups. Only small increases in lactate occurred with exercise, and this increase did not correlate with the tau for VO(2).
In nonhypoxemic COPD patients performing moderate exercise, the lower ventilatory requirement induced by oxygen supplementation is not related to improved muscle function but likely stems from direct chemoreceptor inhibition.
Rehabilitation is a highly person-centered health strategy, with
interventions focusing on the function and capacities of an individual as well
as the goals and preferences of the user. Rehabilitation usually includes the
interventions provided by rehabilitation professionals such as
physiotherapists, occupational therapists, speech and language therapists,
orthotic and prosthetic technicians, psychologists and physical and
rehabilitation medicine doctors. The goal of chronic illnesses, health care is
to control symptoms and prevent disability rather than curing the disease.
Therefore, the objectives of chronic disease mediates incorporate overseeing
physical side effects, improving autonomy and expanding personal
satisfaction. Most of sickness management happens outside of formal health
care. Patients are responsible for using medication properly, changing
behavior to improve symptoms or slow disease progressions, interpreting
and reporting symptoms correctly, adjusting to new social and economic
circumstances, coping with emotional consequences, participating in
treatment decisions, and preventing transmission of contagious diseases.
Keywords: Community based rehabilitation, follow up care, infected
patients
In two freestanding volumes, Textbook of Neural Repair and Rehabilitation provides comprehensive coverage of the science and practice of neurological rehabilitation. Revised throughout, bringing the book fully up to date, this volume, Medical Neurorehabilitation, can stand alone as a clinical handbook for neurorehabilitation. It covers the practical applications of the basic science principles presented in Volume 1, provides authoritative guidelines on the management of disabling symptoms, and describes comprehensive rehabilitation approaches for the major categories of disabling neurological disorders. New chapters have been added covering genetics in neurorehabilitation, the rehabilitation team and the economics of neurological rehabilitation, and brain stimulation, along with numerous others. Emphasizing the integration of basic and clinical knowledge, this book and its companion are edited and written by leading international authorities. Together they are an essential resource for neuroscientists and provide a foundation of the work of clinical neurorehabilitation professionals.
There is little question that the most disabling symptom of chronic pulmonary disease is exercise intolerance. The patient often becomes homebound, isolated and depressed out of fear of experiencing the dyspnea that exertion brings. The sedentary lifestyle these patients adopt only serves to make the situation worse. The inactive muscles atrophy, which increases the energetic cost of activity and, in fact, may increase dyspnea on exertion.
This study was undertaken to assess whether maximal O2 uptake (VO2max) can be used as an index of measuring aerobic capacity under the condition of increased respiratory resistance. Seven male subjects performed two incremental exercise tests on a cycle ergometer on different days: one control (C) and one breathing through an 8 mm bore diameter respiratory resistance (R). Ventilatory and gas exchange responses were measured with a turbine volume transducer and mass spectrometry, and processed breath-by-breath. VO2max was measured and anaerobic threshold (AT) was estimated noninvasively using the V-slope method. Maximal exercise performance was reduced significantly (by paired t-test, P<0.05) in the resistance study (233±14 W) compared to the control (260±29 W). The plateau in VO2 is not a consistent feature of incremental exercise tests even in the control study at the subjects' maximum effort. VO2 at maximal exercise performance was also reduced significantly from 3.25±0.40 1/min (C) to 2.83±0.20 1/min (R). However, there were no significant differences between AT for both tests: 1.80±0.28 1/min (C) and 1.81±0.28 1/min (R). These results establish that AT actually reflects aerobic capacity. Therefore, AT should be determined systematically in addition to VO2max during maximal exercise tests to better evaluate physical fitness.
Solunumla alınan havadaki oksijenin kaslara su-nulmasından enerji üretimi amacıyla mitokondri-de kullanılmasına kadar geçen süreç, akciğerler, pulmoner dolaşım, kalp, periferik dolaşım, kas ve mitokondrinin birlikte ve kusursuz çalışması sonucunda gerçekleşir. Alınan havadaki oksijen ÖZET Solunumsal ve kardiyak fonksiyonları değerlendirmek için istirahatte yapılan ölçümlerin tek başına yeterli olmadığı anlaşılmıştır. Egzersiz kısıtlanmasının nedenleri araştırılırken, kardiyopulmoner egzersiz testleri (KPET) solunumsal ve kardiyovasküler sistemlerle birlikte kas-iskelet sistemi ve nörofizyolojik sistemlerin de değerlendirilebilmesine olanak sağlamaktadır. Bundan dolayı egzersiz kısıtlanmasının, egzersize bağlı oluşan semptomların, fonksiyonel kapasitenin ve yetersizliğin değerlendirilmesinde KPET'e olan ilgi artmaktadır. Anahtar Kelimeler: Kardiyopulmoner egzersiz testleri, egzersiz kısıtlanması.
A beneficial method
Heart failure combines with peripheral vascular and muscular abnormalities that can be effectively imrpoved by rehabilitation. The data in the literature appears to demonstrate the efficacy and excellent tolerance of such exercise.
Regarding functional results and improved quality of life
rehabilitation is as equally efficient as the medical treatment that it completes. It can currently be proposed to the majority of patients exhibiting left ventricular systolic dysfuntion and who are are only partially improved with medical treatment alone.
Modalities
the rehabilitation of heart failure must, optimally, be set-up in ambulatory settings, notably within the context of a health care network. Its modalities remain to be specified in on-going studies and its impact on prognosis has to be determined.
Pulse oximetry is used to determine the percentage saturation of oxygen in blood. Its main feature is that it is a noninvasive and relatively inexpensive. There are few studies relating physical activity and pulse oximetry with most abundant studies are clinical trials. The authors review the definition of pulse oximetry, the grounds upon which it is based. We review the application of pulse oximetry to maximum exercise testing, and the behavior of oxygen saturation in the blood for testing of maximum effort. In addition, different studies on the oxygen saturation values in blood during physical exercise and its correlation with other ventilatory variables. We analyze the consequences of the use of pulse oximetry in tests of maximal effort.
Exercise training is one of the most powerful interventions to provide symptomatic relief in patients with COPD. The purpose of this mini-review is to discuss how exercise training can improve limb muscle dysfunction in this disease. Various exercise training strategies will be outlined, along with their beneficial effects and potential limitations. Strategies to optimize the gains achievable with exercise training will be presented. Whether exercise training may exert deleterious effects in some patients will also be discussed.
Coronary artery diseases (CAD) are main cause of morbidity and mortality in western world. Multiple risk factors are involved in CAD, among them, a sedentary life style or low physical activity level is a well-recognized modifiable risk factor. Numerous investigations had explained both, organism adaptations during the exercise and benefits in different system and metabolic routes of the body.
Throughout the last decades, some questionnaires have been developed with the aim to measure physical degree practice and to indicate CAD risk level in a sedentary person. Many of these instruments are validated internationally showing to be easily applicable and perfectly accessible to scientist, which does not justify its low current exploit, because perhaps by ignorance of their existence. Physical activity constitutes an essential gear in bio-psycho-social human health; this one can become the base of lifestyle change aimed to CAD risk factors reduction and to optimize the quality of life.
This study objectively evaluates the effectiveness of a 6-week Preparatory Training Phase (PTP) programme prior to Basic Military Training (BMT) for less physically conditioned conscripts in the Singapore Armed Forces.
We compared exercise test results of a group of less fi t recruits who underwent a 16-week modified-BMT (mBMT) programme (consisting of a 6-week PTP and 10-week BMT phase) with their 'fitter' counterparts enlisted in the traditional 10-week direct-intake BMT (dBMT) programme in this prospective cohort study consisting of 36 subjects. The main outcome measures included cardiopulmonary responses parameters (VO(2)max and V(O2AT)) with clinical exercise testing and distance run timings.
Although starting off at a lower baseline in terms of physical fitness [VO(2)max 1.73 +/- 0.27 L/min (mBMT group) vs 1.97 +/- 0.43 L/min (dBMT), P = 0.032; V(O2AT) 1.02 +/- 0.19 vs 1.14 +/- 0.32 L/min respectively, P = 0.147], the mBMT group had greater improvement in cardiopulmonary indices and physical performance profiles than the dBMT cohort as determined by cardiopulmonary exercise testing [VO(2)max 2.34 +/- 0.24 (mBMT) vs 2.36 +/- 0.36 L/min (dBMT), P = 0.085; V(O2AT) 1.22 +/- 0.17 vs 1.21 +/- 0.24 L/min respectively, P = 0.303] and 2.4 kilometres timed-run [mBMT group 816.1 sec (pre-BMT) vs 611.1 sec (post-BMT), dBMT group 703.8 sec vs 577.7 sec, respectively; overall P value 0.613] at the end of the training period. Initial mean difference in fitness between mBMT and dBMT groups on enlistment was negated upon graduation from BMT.
Pre-enlistment fitness stratification with training modification in a progressive albeit longer BMT programme for less-conditioned conscripts appears efficacious when measured by resultant physical fitness.
We determined the effect on exercise tolerance and physiological exercise responses of rigorous rehabilitative exercise training in chronic obstructive pulmonary disease (COPD). Fifteen men and 10 women (mean age, 68 +/- 6 yr; FEV1, 0.93 +/- 0.27 L) participated in a rehabilitation program with an exercise component of three per week 45-min sessions of cycle ergometer training for 6 wk with exercise intensity kept near maximal targets. Before and after rehabilitation, patients performed an incremental test and a constant work rate (CWR) test at 80% of the peak work rate in the preprogram incremental test. Ventilation (V(E)) and gas exchange were measured breath by breath; arterialized venous blood was analyzed for blood gas determinations and lactate. Rehabilitation yielded an average increase in peak work rate in the incremental test of 36% (p < 0.001), and in the duration of the CWR test of 77% (p < 0.001). In the CWR test, the kinetics of O2 uptake, CO2 output, V(E), and heart rate were markedly slower than those of healthy subjects. After training, mean response time decrease averaged 17, 22, 34, and 29%, respectively (p < 0.02), evidence of a physiologic training effect. Further, for identical CWR tasks, V(E) was 10% lower (p < 0.02) after training, attributable to altered breathing pattern: tidal volume increased by 8% and respiratory rate decreased by 19%, yielding lower V(D) /V(T) (0.46 versus 0.53 p < 0.005). Rigorous exercise training for patients with severe COPD yields more efficient exercise breathing pattern and lower V(E); this is associated with improved exercise tolerance.
Systematic exercise training results in changes in skeletal muscle that increase oxidative capacity and vascular conductance, which lead to an increase in maximal A-VO2. Also, maximal cardiac output is increased, largely because of an increase in maximal stroke volume. Heart rate is decreased at rest and during submaximal exercise because of increased parasympathetic tone and the effect of increased stroke volume on reflex sympathetic tone. The increases in maximal A-VO2 and cardiac output result in increased maximal VO2, the hallmark of the dynamically trained individual. Predominant static exercise training results in fewer increases in maximal VO2 and more local muscle strength enhancements. The systematic application of cross-training can increase both cardiovascular and strength parameters, leading to enhanced athletic performance.
Chronic obstructive pulmonary disease (COPD) afflicts millions of people and is severely disabling. Exercise intolerance is usually the chief complaint. There are few effective therapies. Pulmonary rehabilitation seeks to return the patient to the highest possible level of function but cannot reverse the underlying pulmonary abnormalities. Several lines of evidence have recently pointed to abnormalities of the muscles of ambulation as a remediable source of exercise intolerance in COPD. Possible mechanisms of the muscle abnormalities include deconditioning, malnutrition, low levels of anabolic hormones and, perhaps, a specific myopathy. To date, most reports of attempts to reverse muscle dysfunction in COPD have focused on exercise training. However, abnormalities in the level of circulating anabolic hormones have recently been described, suggesting that anabolic hormone supplementation may be rational therapy for these patients. Accumulating evidence that anabolic steroids increase muscle mass and improve strength in older men is encouraging trials of anabolic steroids in men with COPD.
To investigate whether a 12-week pulmonary rehabilitation program that includes moderately intensive exercise training performed twice weekly can induce a training effect in patients with a wide variation of airflow limitation.
Sixty patients with COPD (38 men) with a mean +/- SD FEV(1) % predicted of 55.1 +/- 19.8 (range, 0.51 to 2.99). All patients performed identical incremental symptom-limited cycle ergometer testing before and after a 12-week study period. Measurements and results: After 12 weeks, the patients demonstrated a significant (p < 0.05) increase in the peak values for work rate (WR; 77 +/- 30 vs 91 +/- 36 W) and oxygen uptake (1.14 +/- 0.45 vs 1.20 +/- 0.52 L/min). Furthermore, at a given WR during incremental symptom-limited cycle ergometer testing, there were significant (p < 0.05) reductions in minute ventilation (42.4 +/- 16.1 vs 37.0 +/- 13. 6 L/min), carbon dioxide output (1.13 +/- 0.49 vs 1.03 +/- 0.42 L/min), ventilatory equivalent for oxygen (37.6 +/- 8.1 vs 36.0 +/- 6.3), and heart rate (135 +/- 15 vs 128 +/- 16 beats/min). None of the observed physiologic changes correlated with FEV(1) % predicted.
A pulmonary rehabilitation program performed twice weekly with moderate exercise workloads can lead to a physiologic training response irrespective of the degree of airflow limitation.
Little is known about work performance of women in hypobaric hypoxia. Moreover, whether native women of moderate altitude (2,000-2,100 m) differ from their lowland counterparts in their ability to adjust to hypobaric hypoxia is also not known. Hence, physiological alterations on work performance due to mountaineering training with altitude adaptation was evaluated in two groups of women and compared to the differences in the responses of the native women of moderate altitudes (Highlanders-HL) with those of the plains (Lowlanders-LL).
Pre-training tests were conducted at 2,100 m, then during sojourn to 4,350 m and re-tested again after return to 2,100 m. Physical work performance was assessed following standard step-test-exercise on a 30 cm stool with 24 cycles x min(-1) for 5 min. Heart rate, BP, ventilation, oxygen consumption and oxygen saturation were monitored at rest and during exercise followed by 5 min recovery in all three situations.
During initial assessment, HL showed higher cardiovascular efficiency with faster recovery of exercise heart rate. Both groups showed significant improvement in physical performance due to mountaineering training at high altitude (HA). The difference in performance between two groups narrowed down at 4,350 m and further reduced during re-test with maintenance of initial superiority of the HL.
a) Native women of moderate altitude (HL) are more fit compared with their plains counterparts (LL); b) All women achieved marked improvement in cardiovascular and respiratory efficiency as well as the step-test score due to intense mountaineering training at HA, and the rate of improvement in physical performance was higher in LL; c) Further, induction by trekking under progressive hypoxia coupled with rigorous mountaineering activity at HA merits in understanding better acclimatization and improved physical performance.
Clinical exercise testing is increasingly being utilized in clinical practice because of the valuable, often unique information that it provides in patient diagnosis and management. This is also due to a growing awareness that resting cardiopulmonary measurements provide an unreliable estimate of functional capacity. A continuum of exercise testing modalities for functional evaluation from "low tech" to "high tech" will be discussed. These include the six minute walk test, shuttle walk test, exercise induced bronchoconstriction test, cardiac stress test, and cardiopulmonary exercise testing. The main focus of this article will be cardiopulmonary exercise testing including indications, important measurements, salient methodological considerations, and interpretation.
Circulating IGF-I is correlated with fitness, but results of prospective exercise training studies have been inconsistent, showing both increases and decreases in IGF-I. We hypothesized that energy balance, often not accounted for, is a regulating variable such that training plus an energy intake deficit would cause a reduction in IGF-I, whereas training plus energy intake excess would lead to an increased IGF-I. To test this, 19 young, healthy men completed a 7-day strenuous exercise program in which they were randomly assigned to either a positive energy balance [overfed (OF), n = 10] or negative energy balance [underfed (UF), n = 9] group. IGF-I (free and total), insulin, and IGF-binding protein-1 were measured before, during, and 1 wk after the training. Weight decreased in the UF subjects and increased in the OF subjects. Free and total IGF-I decreased substantially in the UF group (P < 0.0005 for both), but, in the OF group, IGF-I remained unchanged. The UF group also demonstrated an increase in IGF-binding protein-1 (P < 0.027), whereas glucose levels decreased (P < 0.0005). In contrast, insulin was reduced in both the OF and UF exercise-training groups (P < 0.044). Finally, within 7 days of the cessation of the diet and training regimen, IGF-I and IGF-binding protein-1 in the UF group returned to preintervention levels. We conclude that energy balance during periods of exercise training influences circulating IGF-I and related growth mediators. Exercise-associated mechanisms may inhibit increases in IGF-I early in the course of a training protocol, even in overfed subjects.
A BENEFICIAL METHOD: Heart failure combines with peripheral vascular and muscular abnormalities that can be effectively improved by rehabilitation. The data in the literature appears to demonstrate the efficacy and excellent tolerance of such exercise. Regarding functional results and improved quality of life, rehabilitation is as equally efficient as the medical treatment that it completes. It can currently be proposed to the majority of patients exhibiting left ventricular systolic dysfunction and who are are only partially improved with medical treatment alone. MODALITIES: The rehabilitation of heart failure must, optimally, be set-up in ambulatory settings, notably within the context of a health care network. Its modalities remain to be specified in on-going studies and its impact on prognosis has to be determined.
The outcome of a 20 week expiratory muscle strength training program (EMST) is documented in a patient with early idiopathic Parkinson's disease. A pressure threshold device was utilized and training occurred in the home setting. The training was intensive with a physiologically challenging load specific to the expiratory muscles, adjusted weekly based on the participant's performance. Results indicated that strength, as indexed by the generation of maximum expiratory pressure (MEP), increased by 50% in the first 4 weeks of training, consistent with the average strength increase obtained in previous research. Strength increases continued beyond the traditional 4 weeks of training with a final improvement in MEP of 158% from baseline over the 20 weeks. When the EMST was discontinued for a period of 4 weeks, the participant's MEP decreased by 16% from the 20 week endpoint measurement. The strength training pattern of the expiratory muscles observed in this study was similar to the pattern previously reported for limb muscles.
The resting pulmonary and cardiac function testing cannot reliably predict exercise performance and functional capacity. Cardiopulmonary exercise testing (CPET) provides to assessment of the pulmonary, cardiovascular, hematopoietic, neuropsychological, and skeletal muscle systems. Thus, CPET has gained increasing popularity for the evaluation of undiagnosed exercise intolerance and exercise related symptoms, and to reveal functional capacity and impairment.
We tested the hypothesis that the lactate threshold (Tlac) during incremental exercise could be increased significantly during the first 3 wk of endurance training without any concomitant change in the ventilatory threshold (Tvent). Tvent is defined as O2 uptake (VO2) at which ventilatory equivalent for O2 [expired ventilation per VO2 (VE/VO2)] increased without a simultaneous increase in the ventilatory equivalent for CO2 (VE/VCO2). Weekly measurements of ventilatory gas exchange and blood lactate responses during incremental and steady-rate exercise were performed on six subjects (4 male; 2 female) who exercised 6 days/wk, 30 min/session at 70–80% of pretraining VO2max for 3 wk. Pretraining Tlac and Tvent were not significantly different. After 3 wk of training, significant increases (P less than 0.05) occurred for mean (+/- SE) VO2max (392 +/- 103 ml/min) and Tlac (482 +/- 135 ml/min). Tvent did not change during the 3 wk of training, despite significant (P less than 0.05) reductions in VE responses to both incremental and steady-rate exercise. Thus ventilatory adaptations to exercise during the first 3 wk of exercise training were not accompanied by a detectable alteration in the ventilatory “threshold” during a 1-min incremental exercise protocol. The mean absolute difference between pairs of Tlac and Tvent posttraining was 499 ml/min. Despite the significant training-induced dissociation between Tlac and Tvent a high correlation between the two parameters was obtained posttraining (r = 0.86, P less than 0.05). These results indicate a coincidental rather than causal relationship.(ABSTRACT TRUNCATED AT 250 WORDS)
The validity of the relative percent concept for equating training intensity was investigated using the point of metabolic acidosis (anaerobic threshold) as the criterion variable. Percent oxygen uptake, heart rate and metabolic acidosis were determined at 60, 70, and 80% of max heart rate on a bicycle ergometer test(N = 31). At 60 and 70% of max heart rate only one individual was definitely in metabolic acidosis. At 80% max heart rate 17 subjects were working at a level above the point of metabolic acidosis while 14 were working at or below this point. Thus, it was suggested that even if subjects are exercising at the same relative percent miximum HR, the metabolic stress using metabolic acidosis as the criterion is not constant across subjects. It was further shown that the regression of percent VO2 max on percent max HR was a spurious one resulting in poor prediction of individual VO2 values. The data presented suggest that the relative percent concept for equating exercise or subsequent training intensity needs careful re-evaluation.
Arterial pH, PCO2, standard bicarbonate, lactate, and ventilation were measured with a high sampling density during rest, exercise, and recovery in normal subjects performing upright cycle ergometer exercise. Three 6-min constant-work exercise tests (moderate, heavy, and very heavy) were performed by each subject. We found a small respiratory acidosis during the moderate-intensity exercise and an early respiratory acidosis followed by a metabolic acidosis for the heavy- and very-heavy-intensity exercise. During recovery, arterial pH rapidly returned to the preexercise value for the moderate-intensity work. However, arterial pH decreased further during the first 2 min of recovery for the heavy- and very-heavy-intensity work, before a slower return toward the resting values. We conclude that arterial acidosis is the consistent arterial pH reaction for moderate-, heavy-, and very-heavy-intensity cycle ergometer exercise in humans and that this acidosis is blunted but not eliminated by the ventilatory response. During recovery, the return to resting arterial pH and PCO2 and standard bicarbonate appears to be determined by the rate of lactate decline.
The present study sought to evaluate the inconsistencies previously observed regarding the predominance of continuous or interval training for improving fitness. The experimental design initially equated and subsequently maintained the same relative exercise intensity by both groups throughout the program. Twelve subjects were equally divided into continuous (CT, exercise at 50% maximal work) or interval (IT, 30 s work, 30 s rest at 100% maximal work) training groups that cycled 30 min day-1, 3 days.week-1, for 8 weeks. Following training, aerobic power (VO2max), exercising work rates, and peak power output were all higher (9-16%) after IT than after CT (5-7%). Vastus lateralis muscle citrate synthase activity increased 25% after CT but not after IT. A consistent increase in adenylate kinase activity (25%) was observed only after IT. During continuous cycling testing the CT group had reduced blood lactate (lab) levels and respiratory quotient at both the same absolute and relative (70% VO2max) work rates after training, while the IT group displayed similar changes only at the same absolute work rates. By contrast, both groups responded similarly during intermittent cycling testing with lower lab concentrations seen only at absolute work rates. These results show that, of the two types of training programs currently employed, IT produces higher increases in VO2max and in maximal exercise capacity. Nevertheless, CT is more effective at increasing muscle oxidative capacity and delaying the accumulation of lab during continuous exercise.
Rates of performing work that engender a sustained lactic acidosis evidence a slow component of pulmonary O2 uptake (VO2) kinetics. This slow component delays or obviates the attainment of a stable VO2 and elevates VO2 above that predicted from considerations of work rate. The mechanistic basis for this slow component is obscure. Competing hypotheses depend on its origin within either the exercising limbs or the rest of the body. To resolve this question, six healthy males performed light nonfatiguing [approximately 50% maximal O2 uptake (VO2max)] and severe fatiguing cycle ergometry, and simultaneous measurements were made of pulmonary VO2 and leg blood flow by thermodilution. Blood was sampled 1) from the femoral vein for O2 and CO2 pressures and O2 content, lactate, pH, epinephrine, norepinephrine, and potassium concentrations, and temperature and 2) from the radial artery for O2 and CO2 pressures, O2 content, lactate concentration, and pH. Two-leg VO2 was thus calculated as the product of 2 X blood flow and arteriovenous O2 difference. Blood pressure was measured in the radial artery and femoral vein. During light exercise, both pulmonary and leg VO2 remained stable from minute 3 to the end of exercise (26 min). In contrast, during severe exercise [295 +/- 10 (SE) W], pulmonary VO2 increased 19.8 +/- 2.4% (P less than 0.05) from minute 3 to fatigue (occurring on average at 20.8 min). Over the same period, leg VO2 increased by 24.2 +/- 5.2% (P less than 0.05). Increases of leg and pulmonary VO2 were highly correlated (r = 0.911), and augmented leg VO2 could account for 86% of the rise in pulmonary VO2.(ABSTRACT TRUNCATED AT 250 WORDS)
A linear system has the property that the kinetics of response do not depend on the stimulus amplitude. We sought to determine whether the responses of O2 uptake (VO2), CO2 output (VCO2), and ventilation (VE) in the transition between loadless pedaling and higher work rates are linear in this respect. Four healthy subjects performed a total of 158 cycle ergometer tests in which 10 min of exercise followed unloaded pedaling. Each subject performed three to nine tests at each of seven work rates, spaced evenly below the maximum the subject could sustain. VO2, VCO2, and VE were measured breath by breath, and studies at the same work rate were time aligned and averaged. Computerized nonlinear regression techniques were used to fit a single exponential and two more complex expressions to each response time course. End-exercise blood lactate was determined at each work rate. Both VE and VO2 kinetics were markedly slower at work rates associated with sustained blood lactate elevations. A tendency was also detected for VO2 (but not VE) kinetics to be slower as work rate increased for exercise intensities not associated with lactic acidosis (P less than 0.01). VO2 kinetics at high work rates were well characterized by the addition of a slower exponential component to the faster component, which was seen at lower work rates. In contrast, VCO2 kinetics did not slow at the higher exercise intensities; this may be the result of the coincident influence of several sources of CO2 related to lactic acidosis. These findings provide guidance for interpretation of ventilatory and gas exchange kinetics.
When moderate exercise begins, O2 uptake (VO2) reaches a steady state within 3 min. However, with heavy exercise, VO2 continues to rise beyond 3 min (VO2 drift). We sought to identify factors contributing to VO2 drift. Ten young subjects performed cycle ergometer tests of 15 min duration for each of four constant work rates, corresponding to 90% of the anaerobic threshold (AT) and 25, 50, and 75% of the difference between maximum VO2 (VO2 max) and AT for that subject. Time courses of VO2, minute ventilation (VE), and rectal temperature were recorded. Blood lactate, norepinephrine, and epinephrine were measured at the end of exercise. Eight weeks of cycle ergometer endurance training improved average VO2 max by 15%. Subjects then performed four tests identical to pretraining studies. For the above AT tests, training reduced VO2 drift substantially; reduction in each of the possible mediators we measured was also demonstrated. The training-induced decrease in VO2 drift was well correlated with decreases in end exercise lactate and less well correlated with the drift in VE seen at above AT work rates. The training-induced reduction in VO2 drift was not significantly correlated with attenuation of rectal temperature rise or decrease in end-exercise level of the catecholamines. Thus the slow rise in VO2 during heavy exercise seems linked to lactate, though a component dictated by the work of breathing cannot be ruled out.
The purpose of this study was to determine the effect of training on the rating of perceived exertion (RPE) at the ventilatory threshold. College students were assigned to either training (n = 17) or control (n = 10) groups. Trainers completed 18 interval training sessions (five X 5 min cycling at 90-100% VO2max) and 8 continuous training sessions (40 min running or cycling) in 6 weeks. Pre- and post-training, cardiorespiratory, metabolic, and perceptual variables were measured at the ventilatory threshold during graded exercise tests on a cycle ergometer. Ventilatory threshold was that point above which VE X VO2-1 increased abruptly relative to work rate. Post-training means of trained and control subjects were compared using analysis of covariance, with pre-training values as covariates. Following training, the adjusted means for the trained subjects were significantly greater (p less than 0.05) than for controls for VO2max (6%), and for work rate (20%), VO2 (23%), and %VO2max (13%) at the ventilatory threshold. However, adjusted means for RPE at the ventilatory threshold were not significantly different (2%). Both before and after training, exercise at the ventilatory threshold was perceived as 'somewhat hard' to 'hard' (RPE = 13-15) by both groups. The relationship between RPE and %VO2max was altered by training, with trained subjects having a lower RPE at a given %VO2max. It is concluded that RPE at the ventilatory threshold is not affected by training, despite that after training the ventilatory threshold occurs at a higher work rate and is associated with higher absolute and relative metabolic and cardiorespiratory demands.
The purpose of this study was to evaluate the effects of continuous and interval training on changes in lactate and ventilatory thresholds during incremental exercise. Seventeen males were assigned to one of three training groups: group 1:55 min continuous exercise at approximately 50% maximum O2 consumption (VO2max); group 2: 35 min continuous exercise at approximately 70% VO2max; and group 3: 10 X 2-min intervals at approximately 105% VO2max interspersed with rest intervals of 2 min. All of the subjects were tested and trained on a cycle ergometer 3 day/wk for 8 wk. Lactate threshold (LT) and ventilatory threshold (VT) (in addition to maximal exercise measures) were determined using a standard incremental exercise test before and after 4 and 8 wk of training. VO2max increased significantly in all groups with no statistically significant differences between the groups. Increases (+/- SE) in LT (ml O2 X min-1) for group 1 (569 +/- 158), group 2 (584 +/- 125), and group 3 (533 +/- 88) were significant (P less than 0.05) and of the same magnitude. VT also increased significantly (P less than 0.05) in each group. However, the increase in VT (ml O2 X min-1) for group 3 (699 +/- 85) was significantly greater (P less than 0.05) than the increases in VT for group 1 (224 +/- 52) and group 2 (404 +/- 85). For group 1, the posttraining increase in LT was significantly greater than the increase in VT (P less than 0.05). We conclude that both continuous and interval training were equally effective in augmenting LT, but interval training was more effective in elevating VT.(ABSTRACT TRUNCATED AT 250 WORDS)
Seven endurance exercise-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Maximal O2 uptake (VO2 max) declined 7% (P less than 0.05) during the first 21 days of inactivity and stabilized after 56 days at a level 16% (P less than 0.05) below the initial trained value. After 84 days of detraining the experimental subjects still had a higher VO2 max than did eight sedentary control subjects who had never trained (50.8 vs. 43.3 ml X kg-1 X min-1), due primarily to a larger arterial-mixed venous O2 (a-vO2) difference. Stroke volume (SV) during exercise was high initially and declined during the early detraining period to a level not different from control. Skeletal muscle capillarization did not decline with inactivity and remained 50% above (P less than 0.05) sedentary control. Citrate synthase and succinate dehydrogenase activities in muscle declined with a half-time of 12 days and stabilized at levels 50% above sedentary control (P less than 0.05). The initial decline in VO2 max was related to a reduced SV and the later decline to a reduced a-vO2 difference. Muscle capillarization and oxidative enzyme activity remained above sedentary levels and this may help explain why a-vO2 difference and VO2 max after 84 days of detraining were still higher than in untrained subjects.
Development of lactic acidosis is essential in performance of heavy work. H+, locally produced with lactate during inadequate O2 flow to tissues, raises capillary PO2 and facilitates O2 diffusion to mitochondria. This provides feedback control when there is imbalance between O2 requirement and supply.
The sections in this article are:
We postulated that the commonly observed constant linear relationship between
[(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} }
and work rate during cycle ergometry to exhaustion is fortuitous and not due to an unchanging cost of external work. Therefore we measured
[(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} }
continuously in 10 healthy men during such exercise while varying the rate of work incrementation and analyzed by linear regression techniques the relationship between
[(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} }
and work rate (
[(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} }
/
[(V)\dot]\textO\text2 \dot V_{{\text{O}}_{\text{2}} }
/ wr in ml min–1 W–1 to be 11.20.15, 10.20.16, and 8.80.15 for the 15, 30, and 60 Wmin–1 tests, respectively, expressed as mlJ–1 the values were 0.1870.0025, 0.1700.0027 and 0.1470.0025. The slopes of the lower halves of the 15 and 30 Wmin–1 tests were 9.90.2 mlmin–1W–1 similar to the values for aerobic work reported by others. However the upper halves of the 15, 30, and 60 Wmin–1 tests demonstrated significant differences: 12.40.36 vs 10.50.31 vs 8.70.23 mlmin–1W–1 respectively. We postulate that these systematic differences are due to two opposing influences: 1) the fraction of energy from anaerobic sources is larger in the brief 60 Wmin–1 tests and 2) the increased energy requirement per W of heavy work is evident especially in the long 15 Wmin–1 tests.
The effects of various regimes of bicycle ergometer exercise varying in intensity, duration and frequency of effort on directly measured maximum aerobic power ( max) have been studied on 28 healthy male subjects aged 18–38 years.
Analysis of the results showed that the two most important factors in training the max were intensity and duration; these parameters being interdependent. No subject who trained at or below 50% of max showed an improvement in his maximum aerobic power output. Even at the highest intensities and longest durations of effort the improvement in max was quite small (1–9 ml/kg/min). The responses to submaximal work mirrored in part these changes: and for a given work load remained constant whereas cardiac frequency (fH) decreased after training.
It would seem that in order to effect an improvement in max an individual must be prepared to work at or close to his maximum for prolonged periods of time; even then the improvement may be disappointingly small.
Insulinlike growth factors (IGFs), their binding proteins, and receptors are expressed by many different tissues, suggesting that they may act as parts of an autocrine paracrine system in addition to having a classic endocrine role. Since these growth factors are essential for the normal growth and development of the organism, their altered rate of production in a number of important disease states results in severe growth alterations. These include nutritional deprivation, growth hormone deficiency, diabetes, and malignancy.
This description of some of the present knowledge on skeletal muscle fibers, their metabolic potentials, and their interplay with the degree of physical activity has revealed that skeletal muscle of man has a very large capacity for adaptation. Moreover, this adaptability appears to be of utmost importance for the metabolic response as well as for performance. Although all this is true, it should not distract us from the fact that we are lacking the most important information. The questions that need to be answered are: What triggers the changes to take place? Which are the regulatory mechanisms?
Skeletal muscle adapts to endurance excerise, such as long distance running, with an increase in the capacity for aerobic metabolism. This is reflected in an increased capacity of whole homogenates and of the mitochondrial fraction of muscle to oxidize pyruvate and long chain fatty acids. Underlying this increase in the ability to obtain energy by respiration is an increase in the levels of a number of mitochondrial enzymes. These include the enzymes involved in fatty acid oxidation, the enzymes of the citric acid cycle, the components of the respiratory chain that link the oxidation of succinate and NADH to oxygen, and coupling factor 1. These increases in mitochondrial enzyme activity appear to be due to an increase in enzyme protein as evidenced by a doubling of the concentration of cytochrome c and a 60% increase in the protein content of the mitochondrial fraction skeletal muscle. Electronmicroscopic studies suggest that increases in both the size and number of mitochondria are responsible for the increase in mitochondrial protein. An alteration in mitochondrial composition also occurs, with some mitochondrial enzymes increasing 2-fold, others increasing only 35% to 60%, while others, including mitochondrial alpha-glycerophosphate dehydrogenase, creatine phosphokinase and adenylate kinase do not increase at all. As a result of these and other exercise induced biochemical adaptations skeletal muscle tends to become more like heart muscle in its enzyme pattern.
Komi, P. V., J. H. T. Viitasalo, M. Havu, A. Thorstensson, B. Sjödin and J. Karlsson. Skeletal muscle fibres and muscle enzyme activities in monozygous and dizygous twins of both sexes. Acta physiol. scand. 1977. 100. 385‐392.
Significance of the genetic component in determining the interindividual variation observed in skeletal muscle fibre composition and enzyme activities was investigated in 31 pairs of male and female monozygous (MZ) and dizygous (DZ) twins, whose ages ranged in all but one pair (11 years) from 15 to 24 years. Percent distribution of slow twitch muscle fibres and activities of Ca²⁺ and Ng²⁺ stimulated ATPases, creatine phosphokinase, myokinase, phosphorylase, lactate dehydrogenase (LDH) and distribution of its isozyme LDH‐1 were all analyzed in biopsy samples taken from the vastus lateralis muscle. The data disclosed that in contrast to DZ twins the MZ twins of both sexes had an essentially identical muscle fibre composition. Calculation of the heritability estimate for this parameter gave the values of 99.5% and 92.8%, respectively for males and females. In contrast to the fibre composition presence of a significant genetic component was not observed in any of the enzyme activities studied. It was concluded that there is a predominant genetic influence on the skeletal muscle fibre composition in man, and thus also on the potential capacity of the muscles to perform work.
To investigate the role of the carotid bodies in exercise hyperpnea and acid-base control, normal and carotid body-resected subjects (CBR) were studied during constant-load and incremental exercise. There was no significant difference in the first-breath ventilatory responses to exercise between the groups; some subjects in each reproducibly exhibited abrupt responses. The subsequent change in Ve toward steady state was slower in the CBR group. The steady-state ventilatory responses were the same in both groups at work rates below the anaerobic threshold (AT). However, above the AT, the hyperpnea was less marked in the CBR group. Ve and acid-base measurements revealed that the CBR group failed to hyperventilate in response to the metabolic acidosis of either constant-load or incremental exercise. We conclude that the carotid bodies 1) are not responsible for the initial exercise hyperpnea, 2) do affect the time course of Ve to its steady state, and 3) are responsible for the respiratory compensation for the metabolic acidosis of exercise.
Plasma glucagon and catecholamines increase during prolonged submaximal exercise, but the magnitude of the increase is less in endurance-trained individuals than in untrained subjects. We have studied the rapidity at which this adaptation occurs. Six initially untrained healthy subjects exercised vigorously (on bicycle ergometers and by running) 30-50 min/day, 6 days/wk, for 9 wk. Prior to the beginning of training and at 3-wk intervals thereafter, participants were subjected to 90-min bicycle ergometer test work loads that elicited 58 +/- 2% of the subjects' initial maximal oxygen consumption. The major proportion of the training-induced decrement in plasma glucagon and catecholamine responses to exercise was seen after 3 wk of training. We conclude that the hormonal component of the training adaptation occurs very early in the course of a vigorous endurance training program.
Following exercise onset, CO2 output (VCO2) and O2 uptake (VO2) increase exponentially, but with appreciably different time constants. To determine the sensitivity of the time courses of these variables to altered ventilatory kinetics, rhythmic exercise was induced abruptly in anesthetized dogs by bilateral stimulation of the peripheral ends of the cut sciatic and femoral nerves. This increased the metabolic rate by 83 +/- 25 (SD) %. The dogs were ventilated with a constant-volume pump, the frequency of which was changed exponentially from the start of the exercise up to the ventilation that returned arterial CO2 and O2 pressure (PCO2 and PO2) in the steady state to resting levels. The time constant (tau) of the increase in ventilation (VE) was varied among trials. VCO2, VO2, end-tidal PCO2 and PO2, and arterial PCO2 were measured breath by breath. tauVO2 was constant at approximately 18 s regardless of alterations in tauVE. In contrast, tauVCO2 was strongly dependent on tauVE, apparently due to the larger body stores for CO2; the transitions were isocapnic when tau VE was approximately 40 s. We conclude that ventilatory dynamics can markedly influence the dynamics of CO2 exchange during exercise, but has no appreciable effect on O2 uptake dynamics.
Nine previously sedentary middle-aged males underwent cycle endurance training 45 min/day for 9 wk with an average attendance of 4.1 days/wk. Seven males served as controls. Before and after the training period, the subjects performed three cycle ergometer tests. Work rate was incremented by 15 W/min, to the limit of the subjects' tolerance, in the first two tests; the third test consisted of contant-load cycling at an O2 uptake (VO2) just below the pretraining anaerobic threshold (AT). After training, the AT increased significantly by 44%, expressed as absolute VO2, and by 15%, expressed relative to VO2 max. Significant increases were also noted in VO2max (25%), maximal minute ventilation (19%), and maximal work rate (28%). The test-retest correlation coefficients for the AT (%VO2max) were 0.91, pre- and posttraining. Training did not alter steady-state VO2 during the submaximal exercise test whereas significant decreases occurred in CO2 output, VE, respiratory quotient, and VE/VO2. No changes occurred in the control subjects during this period. These results demonstrate that the AT is profoundly influenced by endurance training in previously sedentary middle-aged males.
Anaerobic and aerobic-anaerobic threshold (4 mmol/l lactate), as well as maximal capacity, were determined in seven cross country skiers of national level. All of them ran in a treadmill exercise for at least 30 min at constant heart rates as well as at constant running speed, both as previously determined for the aerobic-anaerobic threshold. During the exercise performed with a constant speed, lactate concentration initially rose to values of nearly 4 mmol/l and then remained essentially constant during the rest of the exercise. Heart rate displayed a slight but permanent increase and was on the average above 170 beats/min. A new arrangement of concepts for the anaerobic and aerobic-anaerobic threshold (as derived from energy metabolism) is suggested, that will make possible the determination of optimal work load intensities during endurance training by regulating heart rate.
The metabolic responses of 30 college-aged males were compared following high power (30-sec runs with 19 repetitions-Group HP) and low power (120-sec runs with 7 repetitions-Group LP) interval training programs (8-wk, 3 days/wk). Measurements included: maximal aerobic power (Vo2max, open circuit spirometry); maximal lactacid capacity (net-LAmax, blood LA accumulation following exhaustive exercise); net energy production (net Vo2 and netLA) following a 2-min run that was exhaustive before but not following training; and maximal muscular power (stair-climbing procedure). The results indicated: 1) significant but equal increases in Vo2 max in both groups; 2) no change in either group in netLAmax; 3) net Vo2 during the 2-min run was unchanged, however, netLA was significantly greater in Group LP; 4) no changes in either group in muscular power. It was concluded that low power and high power output interval training programs elicit similar changes in maximal aerobic and anaerobic metabolism, and that the physiological and or biochemical changes responsible for lowered lactic acid production during heavy, but submaximal exercise following training are produced to a greater extent by the low power program.
5 men underwent a 10-wk endurance training programme which resulted in an 18% increase in max VO2 from a mean of 3.1 l/min. Measurements were made at 2 submaximal O2 intakes of 1.2 and 2.0 l/min to examine the physiological interdependence of mechanisms changed by training. At both levels of VO2, reductions were observed following training in cardiac frequency (fc), CO2 output (VCO2), respiratory exchange ratio (R), ventilation (VE), alveolar-arterial PO2 difference (A-aPO2) and blood lactate (La); the changes were statistically significant at the higher VO2. No change was observed in cardiac output, blood free fatty acids (FFA) and blood glycerol (gly). A small increase was found in arterial PCO2 (PaCO2) and HCO3-. Changes in fc were not significantly related to changes in other variables. The reductions in La were related to falls in VCO2 and VE, and inversely related to increases in PaCO2. Only a portion of the fall in R could be ascribed to increased usage of fat as a fuel, the main factor being a fall in lactate production. Reductions in A-aPO2 were due to decreases in PAO2 and falls in R, with no change in venous admixture. Changes in FFA and gly were small and not related to changes in other variables. Training led to an increased usage of aerobic metabolic pathways. The resultant fall in lactic acid production led to a fall in VCO2 and maintained HCO3-. These changes accounted for a marked reduction in VE following training.
The dynamic relationships between ventilation and gas exchange variables during exercise were determined utilizing frequency analysis techniques. Five subjects exercised on a cycle ergometer for 30 min at work rates which fluctuated sinusoidally between 25 W and 80% of the anaerobic threshold at sinusoidal periods of 0.7, 1,2,4,6, and 10 min. VE, VCO2, VO2, and HR were computed and displayed breath-by-breath. From these and steady-state response data, digital computer routines extracted amplitude and phase relations between each variable and the perturbing work load. These response characteristics were well described by first-order linear dynamics with time constants for VE, VCO2, VO2, and HR averaging 1.4, 1.2, 0.8, and 0.8 min, respectively. The time constants of VE and VCO2 were strongly correlated among subjects (r = 0.97). Further, there was no evidence that neural afferents from the exercising limbs induced fast components in the ventilatory response to these forcings. These results are consistent with the hypothesis that exercise hyperpnea is linked to metabolism via carbon dioxide production.
1. Six subjects were trained using a one‐leg bicycle exercise for 2 months. The untrained leg served as control. After the training period, muscle oxidative capacity, determined as succinate dehydrogenase activity, was 27% higher in the trained (as opposed to the control) leg ( P < 0·05).
2. When the subjects in this situation performed a 1 h two‐legged submaximal bicycle exercise bout (150‐225 W), determinations of V O 2 of the single leg (leg blood flow × (A—V)O 2 difference) revealed that they appeared to choose to work harder with their trained than with their untrained leg, so as to make the relative loads for the two legs the same.
3. Determinations of O 2 and CO 2 on femoral arterial and venous blood demonstrated that the R.Q. was lower in the trained as compared to the untrained leg, 0·91 cf. 0·96 (10 min) and 0·91 cf. 0·94 (50 min) ( P < 0·05).
4. That metabolism of fat was more pronounced in the trained leg was further supported by the finding of a significant net uptake of free fatty acids in this leg only. Moreover, a lower release of lactate from the trained leg was demonstrated.
5. It is suggested that the shift towards a more pronounced metabolism of fat in the trained leg is a function of an increased muscle oxidative capacity.
The purpose of this investigation was to determine the comparative effects on middle-aged men of training by running, walking, and bicycling. Sedentary men (X age = 38 yrs), who volunteered to participate, were assigned randomly to one of the following training groups: I, running (n = 9); II, walking (n = 9); and III, bicycling (n = 8). All groups trained for 30 min, 3 times/week for 20 weeks at 85 to 90% of maximal heart rate. A control group of seven men of similar qualifications also were evaluated. Training heart rates averaged 90%, 87%, and 87% of maximum for groups I, II, and III, respectively. All experimental groups improved significantly in cardiovascular and body composition measures. The former was shown by significant increases in Vo2max, VEmax, and O2 pulse and a significant decrease in resting heart rate. Body composition results showed that the experimental groups had a significant reduction in body weight, skinfold fat, and abdominal girth measurements. The control group showed no significant changes for any of the variables. It was concluded that improvement in the experimental groups was independent of mode of training.
The VCO2-VO2 (alveolar CO2 output-alveolar O2 uptake) relationship (V-slope) during increasing work rate (ramp) cycle ergometer exercise has two approximately linear components: a lower component slope (S1) with a value of about 0.95 and a steeper, upper component (S2). We examined the effect of muscle glycogen depletion (protocol 1) and the rate of increase in work rate (ramp rate) without muscle glycogen depletion (protocol 2) on S1 and S2. In protocol 1, ten healthy men with a mean age of 31.4 years (S.D. 6.2) were studied on each of 3 days (days 1 and 3 were control days). They performed a ramp exercise test to maximum tolerance and steady-state tests at rest, during unloaded pedalling and at two constant work rates below their anaerobic threshold (AT). To deplete muscle glycogen before the test on day 2, the subjects performed 2 h of very heavy cycle exercise on the preceding day and fasted overnight. S1 was reduced on day 2 (0.79 compared with 0.95, P less than 0.001), as was the VCO2-VO2 slope derived from steady-state measurements (0.81 compared with 0.99, P less than 0.001), but AT and the slope difference (S2 - S1) were unchanged. In protocol 2, seven healthy men with a mean age of 20.6 years (S.D. 2.4) performed ramp tests at three different rates of increasing work rate (15, 30 and 60 W min-1), each ramp rate being performed twice in random sequence. The ramp rate did not affect S1 but S2 was steeper with the faster rates of work rate increase (1.27, 1.43 and 1.63, respectively, P less than 0.01). Our findings support the concept that the lower component of the V-slope plot (below AT) represents muscle substrate respiratory quotient (RQ) while the difference between S1 and S2 reflects 'excess CO2' derived from bicarbonate buffering of lactic acid.
Serum concentrations of insulin‐like growth factors 1 and 2 (IGF‐1 and IGF‐2), the low molecular weight form of IGF binding protein (IGFBP‐1), insulin, C‐peptide and GH were determined in six healthy subjects and four patients with GH deficiency during 30 min of moderate physical exercise on the cycle ergometer. The load corresponded to 60% of individual maximal oxygen uptake. IGF‐1 and IGF‐2 were determined by radioimmunoassays developed with antibodies isolated from immunized hens egg‐yolk after separation by automated acid gel filtration of serum samples prior to assay.
Significant increases in the serum concentrations (mean±SEM) of IGF‐1 (157±24 to 196 ± 29 μg l ‐1 , P <0.05) and IGF‐2 (451±37 to 678 ±85 μg 1 ‐1 , P < 0.01) were seen in the healthy subjects after 10 min of exercise. The mean percentage increase was 26 ± 5% for IGF‐1 and 50± 11% for IGF‐2. No relation to the GH release was found. In GH‐deficient patients the mean IGF‐2 concentration rose 48 ± 17% from basal 216 ± 63 μg 1 ‐1 to a peak concentration of 324 ±115 μg 1 ‐1 ( P <0.01) after 30 min, while the 38 ±20% rise of IGF‐1 from basal 36± 13 μg 1 ‐1 to a peak concentration of 55 ±27 μg 1 ‐1 was not significant. The serum IGFBP‐1 concentration did not change during exercise, while insulin and C‐peptide concentrations, as well as blood glucose, decreased in both healthy subjects and GH‐deficient patients.
In conclusion, exercise induced an increase in the serum concentrations of IGF‐1 and IGF‐2 independently of the GH response. It may be hypothesized that IGFs have a physiological role in the glucose transport into working muscles.
Factors contributing to maximal incremental and short-term exercise capacity were measured before and after 12 wk of high-intensity endurance training in 12 old (60-70 yr) and 10 young (20-30 yr) sedentary healthy males. Peak O2 uptake in incremental cycle ergometer exercise increased from 1.60 +/- 0.073 to 2.21 +/- 0.073 (SE) l/min (38% increase) in the old subjects and from 2.54 +/- 0.141 to 3.26 +/- 0.181 l/min (29%) in the young subjects. Peak cardiac output, estimated by extrapolation from a series of submaximal measurements by the CO2 rebreathing method, increased by 30% (from 12.7 to 16.5 l/min) in the old subjects, associated with a 6% increase (from 126 to 135 ml/l) in arteriovenous O2 difference; in the young subjects there were equal 14% increases in both variables (18.0 to 20.5 l/min and 140 to 159 ml/l, respectively). Submaximal mean arterial pressure and cardiac output were lower posttraining in the old subjects; total vascular conductance and cardiac stroke volume increased. Although peak power at the start of a short-term maximal isokinetic test did not change, total work accomplished in 30 s at a pedaling frequency of 110 revolutions/min increased in both groups, from 11.2 to 12.6 kJ and from 15.7 to 16.9 kJ in the old and young, respectively; fatigue during the 30-s test was less, and postexercise plasma lactate concentrations were lower. In older subjects, increases in aerobic power after high-intensity endurance training are at least as large as in younger subjects and are associated with increases in vascular conductance, maximal cardiac output, and stroke volume.
We have investigated the hypothesis that there is local regulation of insulin-like growth factor (IGF) gene expression during skeletal muscle growth. Compensatory hypertrophy was induced in the soleus, a predominantly slow-twitch muscle, and plantaris, a fast-twitch muscle, in 11- to 12-wk-old female Wistar rats by unilateral cutting of the distal gastrocnemius tendon. Animals were killed 2, 4, or 8 days later, and muscles of the nonoperated leg served as controls. Muscle weight increased throughout the experimental period, reaching 127% (soleus) or 122% (plantaris) of control values by day 8. In both growing muscles, IGF-I mRNA, quantitated by a solution-hybridization nuclease-protection assay, rose by nearly threefold on day 2 and remained elevated throughout the experimental period. IGF-II mRNA levels also increased over controls. A more dramatic response was seen in hypophysectomized rats, where IGF-I mRNA levels rose by 8- to 13-fold, IGF-II values by 3- to 7-fold, and muscle mass increased on day 8 to 149% (soleus) or 133% (plantaris) of the control contralateral limb. These results indicate that signals propagated during muscle hypertrophy enhance the expression of both IGF genes, that modulation of IGF-I mRNA levels can occur in the absence of growth hormone, and that locally produced IGF-I and IGF-II may play a role in skeletal muscle growth.
This study determined the effects of endurance or resistance exercise training on maximal O2 consumption (VO2max) and the cardiovascular responses to exercise of 70- to 79-yr-old men and women. Healthy untrained subjects were randomly assigned to a control group (n = 12) or to an endurance (n = 16) or resistance training group (n = 19). Training consisted of three sessions per week for 26 wk. Resistance training consisted of one set of 8-12 repetitions on 10 Nautilus machines. Endurance training consisted of 40 min at 50-70% VO2max and at 75-85% VO2max for the first and last 13 wk of training, respectively. The endurance training group increased its VO2max by 16% during the first 13 wk of training and by a total of 22% after 26 wk of training; this group also increased its maximal O2 pulse, systolic blood pressure, and ventilation, and decreased its heart rate and perceived exertion during submaximal exercise. The resistance training group did not elicit significant changes in VO2max or in other maximal or submaximal cardiovascular responses despite eliciting 9 and 18% increases in lower and upper body strength, respectively. Thus healthy men and women in their 70s can respond to prolonged endurance exercise training with adaptations similar to those of younger individuals. Resistance training in older individuals has no effect on cardiovascular responses to submaximal or maximal treadmill exercise.
Avian pectoralis muscle cells differentiated in vitro are mechanically stimulated by repetitive stretch-relaxation of the cell's substratum using a computerized mechanical cell stimulator device. Initiation of mechanical stimulation increases the efflux of creatine kinase from the cells during the first 8-10 h of activity, but the efflux rate returns to control levels after this time period. Decreased total cell protein content accompanies the temporary elevation of creatine kinase efflux. With continued mechanical stimulation for 48-72 h, total cell protein loss recovers and significantly increases in medium supplemented with serum and embryo extract. Myotube diameters increase and cell hyperplasia occurs in the stimulated cultures. In basal medium without supplements, mechanical activity prevents myotube atrophy but does not lead to cell growth. Mechanically induced growth is accompanied by significant increases in protein synthesis rates. The increases in protein synthesis and accumulation induced by mechanical stimulation are not inhibited by tetrodotoxin but are significantly reduced in basal medium without supplements. Mechanically stimulated cell growth is thus dependent on medium growth factors but independent of electrical activity.
Twelve subjects participated in an exercise program of cycling and running 40 min/day, 6 days/wk. After 10 wk, they continued to train with either a one-third or two-thirds reduction in work rates for an additional 15 wk. Frequency and duration for the additional training remained the same as during the 10 wk of training. The average increases in maximum O2 uptake (VO2 max) were between 11 and 20% when measured during cycling and treadmill running after 10 wk of training. VO2 max was not maintained at the 6-day/wk training levels with a one-third reduction in training intensity but was still higher than pretraining levels. With a two-thirds reduction in intensity, VO2 max declined to an even greater extent than with the one-third reduction. Short-term endurance (approximately 5 min) was maintained in the one-third reduced group but was markedly reduced in the two-thirds reduced group. Long-term endurance was decreased significantly from training by 21% in the one-third reduced group (184-145 min) and by 30% in the two-thirds reduced group (202-141 min). Calculated left ventricular mass, obtained from echocardiographic measurements, increased approximately 15% after training but returned to control levels after reduced training in both groups. These results demonstrate that training intensity is an essential requirement for maintaining the increased aerobic power and cardiac enlargement with reduced training.(ABSTRACT TRUNCATED AT 250 WORDS)
We determined the time course of adaptation in blood lactate concentration ([La]) during constant-load exercise in response to training. Thirteen healthy subjects (11 males, 2 females) exercised on a cycle ergometer for 30 min/day at a work rate calculated to elicit 70% of pre-training VO2max, 6 days/week for 3 weeks. VO2max and blood [La] during constant-load exercise (training work rate) were determined at the end of each week of training. Training increased VO2max 8.5% (from 48.2 +/- 1.5 ml.kg-1.min-1 pre-training to 52.3 +/- 1.4 ml.kg-1.min-1 post-training, P less than 0.01) and decreased constant-load blood [La] 53% (from 7.8 +/- 0.6 mM pre-training to 3.7 +/- 0.3 mM post-training, P less than 0.01). The training-induced reduction in exercise blood [La] was well fit to an exponential (5.5e (-t/2.2) + 2.3, r = 0.99) with a half-time of 10.7 days. However, this was not the case for the time course of VO2max adaptation. The absolute decrease in blood [La] was correlated with the initial blood [La] (r = 0.88, P less than 0.01), but changes in VO2max were not significantly correlated with initial blood [La] (r = -0.14) nor with changes in blood [La] (r = -0.02). We conclude that (1) blood [La] response to constant-load exercise decreases rapidly and exponentially with training, with a t1/2 of 10.7 days, (2) the magnitude of training adaptation is positively related to the initial blood [La], and (3) the time course and extent of the training-induced adaptations of blood [La] and VO2max appear to be independent of one another.
The purpose of this study was to evaluate the effects of 6 weeks of low-intensity continuous exercise training (CE; 40 min at 50% VO2peak, 3 days/week) and high-intensity interval exercise training (IE: 10 x 2 min at VO2peak, 3 days/week) on the parameters of the power-endurance time relationship for cycle ergometry. The hyperbolic relationship between power and endurance time was linearized by expressing the power against the inverse of time, as described by Whipp et al. (22). This model consists of two parameters: theta f, a fatigue threshold reflecting the capability for sustained aerobic power, and W', a constant postulated to reflect a finite energy store (i.e., those factors comprising the O2 deficit: Phosphagen stores, anaerobic glycogenolysis, myoglobin O2 stores). Prior to training, test-retest reliability coefficients (r2) for theta f and W' were 0.92 and 0.62, respectively (P less than 0.01). Training resulted in significant (P less than 0.01) increases in theta f for both CE [27 +/- 3 W (13.4%) increase] and IE [33 +/- 5 W (15.0%) increase], with no difference between groups. Increases in theta f were not dependent upon improvements in VO2peak. W' was not changed significantly in either group after training. However, a significant negative correlation between the training-induced changes in theta f and W' (R = 0.76; P less than 0.01) was obtained. The minimum intensity threshold for exercise training necessary to elicit increases in theta f has yet to be identified, but is at least as low as 50% of VO2peak.
Five normal men, aged 23 to 35 years, participated in two bouts of continuous aerobic cycling separated by five days. The first type of exercise (EI) was cycling at a pedalling frequency of 50 rev X min-1 with a load which produced a steady state O2 uptake of approximately 40% of the subjects' VO2max. The second type of exercise (EII) was cycling at a pedalling frequency of 90 rev X min-1 with a load such that an equal steady state VO2 was reached and maintained. Both EI and EII lasted 40 min. GH levels increased in EI and EII, reaching their maximum at 8 min of recovery (245 and 300% of resting values, respectively). No significant differences were observed between EI and EII in GH, lactate, glucagon, insulin, cortisol and glucose levels between the two exercises. While it has been reported earlier that GH levels were frequently related to lactate levels and/or decreased O2 availability (Sutton 1977; Raynaud et al. 1981; Kozlowski et al. 1983; VanHelder et al. 1984a, b), this study suggests that the opposite is also valid, that is, different types of exercise of equal VO2, duration and lactate production do not produce significantly different GH responses.
This review has grouped many studies on different populations with different protocols to show the interactive effects of intensity, frequency and duration of training as well as the effects of initial fitness levels and programme length on cardiorespiratory fitness as reflected by aerobic power (V̇O2max). Within each level of exercise duration, frequency, programme length or initial fitness level, the greatest improvements in aerobic power occur when the greatest challenge to aerobic power occurs i.e., when intensity is from 90 to 100% of V̇O2max. The pattern of improvement where different intensities are compared with different durations suggests that when exercise exceeds 35 minutes, a lower intensity of training results in the same effect as those achieved at higher intensities for shorter durations. Frequencies of as low as 2 per week can result in improvements in less fit subjects but when aerobic power exceeds 50 ml/kg/min, exercise frequency of at least 3 times per week is required. As the levels of initial fitness improve, the change in aerobic power decreases regardless of the intensity, frequency or duration of exercise.
Although these pooled data suggest that maximal gains in aerobic power are elicited with intensities between 90 to 100% V̇O2 max, 4 times per week with exercise durations of 35 to 45 minutes, it is important to note that lower intensities still produce effective changes and reduce the risks of injury in non-athletic groups.
Intracellular pH of in vitro diaphragm preparations was determined following low- (5 Hz, 1.5 min) and high- (75 Hz, 1 min) frequency stimulation, using glass microelectrodes of the liquid membrane type (pHm). Results were compared with values obtained by the standard homogenate technique (pHh). High- and low-frequency stimulation reduced peak tetanic tension to 21 +/- 1 (SE) and 71 +/- 2% of initial values, respectively. Peak tetanic tension returned to resting values after 10- to 15-min recovery from high- or low-frequency stimulation. Resting pHm was 7.063 +/- 0.011 (n = 72), and after fatiguing stimulation declined to values as low as 6.33. During recovery pHm significantly increased and by 10 min had returned to prefatigue values. No difference was observed in the recovery of pHm between the low- and high-frequency stimulation groups (analysis of variance test, ANOVA), and in both groups pHm recovery was highly correlated to the recovery of peak tetanic tension (r = 0.94, P less than 0.001). Resting pHh was 7.219 +/- 0.023 (n = 13), which was significantly higher than the pHm value. In contrast to pHm, intracellular pHh was significantly higher during recovery from 75- vs. 5-Hz stimulation (P less than 0.05). For both groups pHh increased significantly with time and by 10 min returned to prestimulation values. The ANOVA test demonstrated that pHh values were significantly higher than pHm values during recovery from fatigue. The results from this study support our hypothesis that fatigue from both high- and low-frequency stimulation is at least partially due to the deleterious effects of intracellular acidosis on excitation-contraction coupling.
Five normal men performed seven sets of seven squats at a load equal to 80% of their seven repetition maximum. Plasma growth hormone (GH) and lactate levels increased during and after the completion of the exercise. A significant (r = 0.93, P less than 0.001) linear correlation was found between GH changes and the corresponding oxygen Demand/Availability (D/A) ratio expressed by (equation; see text) (where f = [lactate at time x]/[lactate at time 0]). A retrospective examination of previously published data from our laboratory and others also demonstrated the existence of a significant correlation between changes in plasma GH levels and the D/A ratios over a wide variety of exercise; aerobic and anaerobic, continuous and intermittent, weight lifting and cycling, in both fit and unfit subjects under normoxic and hypoxic conditions. It is suggested that the balance between oxygen demand and availability may be an important regulator of GH secretion during exercise.
To investigate the mechanism by which ventilatory (VE) demand is modulated by endurance training, 10 normal subjects performed cycle ergometer exercise of 15 min duration at each of four constant work rates. These work rates represented 90% of the anaerobic threshold (AT) work rate and 25, 50, and 75% of the difference between maximum O2 consumption and AT work rates for that subject (as determined from previous incremental exercise tests). Subjects then underwent 8 wk of strenuous cycle ergometer exercise for 45 min/day. They then repeated the four constant work rate tests at work rates identical to those used before training. During tests before and after training, VE and gas exchange were measured breath by breath and rectal temperature (Tre) was measured continuously. A venous blood sample was drawn at the end of each test and assayed for lactate (La), epinephrine (EPI), and norepinephrine (NE). We found that the VE for below AT work was reduced minimally by training (averaging 3 l/min). For the above AT tests, however, training reduced VE markedly, by an average of 7, 23, and 37 l/min for progressively higher work rates. End-exercise La, NE, EPI, and Tre were all lower for identical work rates after training. Importantly, the magnitude of the reduction in VE was well correlated with the reduction in end-exercise La (r = 0.69) with an average decrease of 5.8 l/min of VE per milliequivalent per liter decrease in La. Correlations of VE with NE, EPI, and Tre were much less strong (r = 0.49, 0.43, and 0.15, respectively).
Logic suggests that training the ventilatory muscles of patients with chronic airflow obstruction might not be effective, since the accessory muscles of respiration are already overloaded and are well trained relative to other muscles. Alternatively, attempts to diminish the ventilatory requirement by reducing the rate of hydrogen ion accumulation through training of the major muscle groups used in the activities of daily living would seem more reasonable, because this type of training aims to relieve the stress on a sick organ system. On a practical level, however, we may have to tailor our approaches to pulmonary rehabilitation to the individual patient, according to the severity of disease and the goals of treatment. In patients who become limited above the anaerobic threshold, training the leg or arm muscles at a work rate set above the anaerobic threshold might reduce the powerful respiratory stimulus, hydrogen ion. In contrast, patients who are so limited that they cannot exercise at a work level that would result in systemic lactic acidosis may gain most from training the respiratory muscles. This approach would be expected to decrease the lactate production of the respiratory muscles, thereby reducing fatigue in these muscles and the associated sensation of dyspnea. Viewed from this perspective, exercise training directed at the peripheral skeletal muscles on the one hand, or the muscles of respiration on the other, may be complementary in improving the functional capacity of selected patients with chronic airflow obstruction.
Seven endurance-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Heart rate, ventilation, respiratory exchange ratio, and blood lactate concentration during submaximal exercise of the same absolute intensity increased (P less than 0.05) progressively during the first 56 days of detraining, after which a stabilization occurred. These changes paralleled a 40% decline (P less than 0.001) in mitochondrial enzyme activity levels and a 21% increase in total lactate dehydrogenase (LDH) activity (P less than 0.05) in trained skeletal muscle. After 84 days of detraining, the experimental subjects' muscle mitochondrial enzyme levels were still 50% above, and LDH activity was 22% below, sedentary control levels. The blood lactate threshold of the detrained subjects occurred at higher absolute and relative (i.e., 75 +/- 2% vs. 62 +/- 3% of maximal O2 uptake) exercise intensities in the subjects after 84 days of detraining than in untrained controls (P less than 0.05). Thus it appears that a portion of the adaptation to prolonged and intense endurance training that is responsible for the higher lactate threshold in the trained state persists for a long time (greater than 85 days) after training is stopped.