Dyspnoea,disability, and distance walked: comparison of estimates of exercise performance in respiratory disease.

Forty-four patients with airway obstruction and 18 with pulmonary infiltration were studied in an attempt to correlate exercise tolerance, as assessed by a simple walking test, with basic respiratory function values and differing subjective assessments of exercise performance. The distance walked in 12 minutes was significantly correlated with the response to a structured questionnaire and with the patients'' assessment of performance using an oxygen-cost diagram. The distance walked did not agree well with simple subjective estimates obtained in the clinical history. It was better correlated with forced vital capacity than with forced expiratory volume in one second in both groups of patients, and was well correlated with carbon monoxide transfer factor in those with pulmonary infiltration. The scatter of results, however, was such that exercise performance could not usefully be predicted from the respiratory function values or from subjective assessments. Simple exercise tests are an essential part of assessing disability and response to treatment in patients with respiratory impairment.     

Carbon monoxide and exercise tolerance in chronic bronchitis and emphysema.

The effects of carbon monoxide on exercise tolerance as assessed by the distance walked in 12 minutes were studied in 15 patients with severe chronic bronchitis and emphysema (mean forced expiratory volume in one second 0.56 1, mean forced vital capacity 1.54 1). Each subject walked breathing air and oxygen before and after exposure to sufficient carbon monoxide to raise their venous carboxyhaemoglobin concentration by 9%. There was a significant reduction in the walking distance when the patients breathed air after exposure to carbon monoxide (p less than 0.01), and the significant increase in walking distance seen after exercise when breathing oxygen at 2 1/minute via nasal cannulae was abolished if carbon monoxide has previously been administered. Thus concentrations of carboxyhaemoglobin frequently found in bronchitic patients who smoke may reduce their tolerance of everyday exercise, possibly by interfering with the transport of oxygen to exercising muscles.     

Influence of knee osteoarthritis on exercise capacity and quality of life in obese adults

Objective: The objective was to determine whether knee osteoarthritis (OA) reduces exercise ambulatory capacity and impairs quality of life (QOL) in obese individuals. Research Methods and Procedures: There were 56 subjects, with and without knee OA, who were obese. The subjects were evaluated with anthropometric measurements, a body composition assessment, maximal cardiopulmonary exercise test, 6‐minute walk test (6‐MWT), perceived exertion (RPE), self‐reported disability [Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)], and the Medical Outcomes Study Short Form 36 (SF‐36). Results: VO_2peak was significantly higher in the controls when compared with the patients (mean ± standard deviation, 1.584 ± 0.23 L/kg per min vs. 0.986 ± 0.20 L/kg per min; p < 0.001). Obese subjects without knee OA walked a significantly longer distance in the 6‐MWT than obese patients with knee OA (p < 0.001). We also observed significant negative correlation between Vo ₂max and RPE, WOMAC pain and physical limitation, and bodily pain and general health domains of short‐form 36. Discussion: Knee OA reduces exercise and ambulatory capacity and impairs QOL in obese individuals. RPE, WOMAC pain, and SF‐36 items might provide information about exercise capacity in the obese subjects with knee OA. Our study confirms that exercise capacity and QOL might be improved by energetic and intensive treatment of pain resulting from knee OA.     

Carnitine metabolism during exercise in patients with peripheral vascular disease

The distribution between carnitine and the acyl derivatives of carnitine reflects changes in the metabolic state of a variety of tissues. Patients with peripheral vascular disease (PVD) develop skeletal muscle ischemia with exertion. This impairment in oxidative metabolism during exercise may result in the generation of acylcarnitines. To test this hypothesis, 11 patients with PVD and 7 age-matched control subjects were evaluated with graded treadmill exercise. Subjects with PVD walked to maximal claudication pain at a peak O2 consumption (VO2) of 19.9 +/- 1.3 ml X kg-1 X min-1 (mean +/- SE). Control subjects were taken to a near-maximal work load at a VO2 of 31.3 +/- 1.0 ml X kg-1 X min-1. In patients with PVD, the plasma concentration of total acid-soluble, long-chain acylcarnitine and total carnitine was increased at peak exercise compared with resting values. Four minutes postexercise, the plasma short-chain acylcarnitine concentration was also increased. In control subjects taken to the higher work load, only the long-chain acylcarnitine concentration was increased at peak exercise. In patients with PVD, plasma short-chain acylcarnitine concentration at rest was negatively correlated with subsequent maximal walking time (r = -0.51, P less than 0.05). In conclusion, acylcarnitines increased in patients with PVD who walked to maximal claudication pain, whereas control subjects did not show equivalent changes even when taken to a higher work load. The relationship between short-chain acylcarnitine concentration at rest and subsequent exercise performance suggests that repeated episodes of ischemia may cause chronic accumulation of short-chain acylcarnitine in plasma in proportion to the severity of disease.(ABSTRACT TRUNCATED AT 250 WORDS)     

Portable oxygen and exercise tolerance in patients with chronic hypoxic cor pulmonale.

Breathing 30% oxygen during exercise alleviated arterial hypoxaemia and reduced minute ventilation in patients with severe chronic bronchitis. A similar level of oxygen (2 or 4 litres of oxygen/minute) from nasal prongs also increased their exercise tolerance, as assessed by the distance that they could walk on the level in 12 minutes. Nevertheless, a single-blind controlled study showed that the effort of carrying their portable supply of liquid oxygen, in the Union Carbide Oxygen Walker, abolished this gain in exercise tolerance. The improvement in walking distance was restored when oxygen on exercise was provided by wheeling the oxygen walker on a light-weight shopping trolley.     

Effect of alcohol on perceived exertion in relation to heart rate and blood lactate

The purpose of the study was to determine whether the perception of exertion is affected by alcohol during physical performance and whether altered self-rating of exertion is the result of an altered perception per se or of an altered physical capacity to perform work. Ten healthy men participated. Each subject was his own control and received an alcohol dose corresponding to 1 g.kg-1 body mass in 40% solution in the experimental session. The exercise test was performed on a cycle ergometer with an initial intensity of 50 W which was increased stepwise by 50 W at 4-min intervals up to near-maximal. The rating of perceived exertion (RPE) did not differ between alcohol and control sessions. Alcohol induced a significant increase in heart rate during exercise at 50 W (delta x = 8 beats.min-1) and at 100 W (delta x = 10 beats.min-1), while the change at higher intensities was insignificant. The systolic blood pressure and the blood lactate concentration were not significantly changed by alcohol. It is concluded that a moderate dose of alcohol does not alter RPE during physical exercise either per se or secondarily to an altered physical capacity to perform work.     

Analysis of longitudinal changes in dyspnea of patients with chronic obstructive pulmonary disease: an observational study

Background

Guidelines recommend that symptoms as well as lung function should be monitored for the management of patients with chronic obstructive pulmonary disease (COPD). However, limited data are available regarding the longitudinal change in dyspnea, and it remains unknown which of relevant measurements might be used for following dyspnea.

Methods

We previously consecutively recruited 137 male outpatients with moderate to very severe COPD, and followed them every 6 months for 5 years. We then reviewed and reanalyzed the data focusing on the relationships between the change in dyspnea and the changes in other clinical measurements of lung function, exercise tolerance tests and psychological status. Dyspnea with activities of daily living was assessed with the Oxygen Cost Diagram (OCD) and modified Medical Research Council dyspnea scale (mMRC), and two dimensions of disease-specific health status questionnaires of the Chronic Respiratory Disease Questionnaire (CRQ) and the St. George’s Respiratory Questionnaire (SGRQ) were also used. Dyspnea at the end of exercise tolerance tests was measured using the Borg scale.

Results

The mMRC, CRQ dyspnea and SGRQ activity significantly worsened over time (p < 0.001), but the OCD did not (p = 0.097). Multiple regression analyses revealed that the changes in the OCD, mMRC, CRQ dyspnea and SGRQ activity were significantly correlated to changes in forced expiratory volume in one second (FEV₁) (correlation of determination (r²) = 0.05-0.19), diffusing capacity for carbon monoxide (r² = 0.04-0.08) and psychological status evaluated by Hospital Anxiety and Depression Scale (r² = 0.14-0.17), although these correlations were weak. Peak Borg score decreased rather significantly, but was unrelated to changes in clinical measurements.

Conclusion

Dyspnea worsened over time in patients with COPD. However, as different dyspnea measurements showed different evaluative characteristics, it is important to follow dyspnea using appropriate measurements. Progressive dyspnea was related not only to progressive airflow limitation, but also to various factors such as worsening of diffusing capacity or psychological status. Changes in peak dyspnea at the end of exercise may evaluate different aspects from other dyspnea measurements.     

The 6-minute walk: a new measure of exercise capacity in patients with chronic heart failure

Cycle and treadmill exercise tests are unsuitable for elderly, frail and severely limited patients with heart failure and may not reflect capacity to undertake day-to-day activities. Walking tests have proved useful as measures of outcome for patients with chronic lung disease. To investigate the potential value of the 6-minute walk as an objective measure of exercise capacity in patients with chronic heart failure, the test was administered six times over 12 weeks to 18 patients with chronic heart failure and 25 with chronic lung disease. The subjects also underwent cycle ergometer testing, and their functional status was evaluated by means of conventional measures. The walking test proved highly acceptable to the patients, and stable, reproducible results were achieved after the first two walks. The results correlated with the conventional measures of functional status and exercise capacity. The authors conclude that the 6-minute walk is a useful measure of functional exercise capacity and a suitable measure of outcome for clinical trials in patients with chronic heart failure.     

Are "pink puffers" more breathless than "blue bloaters"?

Breathlessness, disability, and exercise tolerance were assessed in 26 patients with severe chronic airflow limitation (forced expiratory volume in one second (FEV1) less than or equal to 1 litre) divided into two groups--15 patients who were normocapnic (pressure of arterial carbon dioxide (Paco2) less than 5.5 kPa (less than 41.4 mm Hg)), and 11 patients who were hypercapnic (Paco2 greater than 6 kPa (greater than than 45.1 mm Hg)). The two groups were well matched for spirometric values (FEV1 0.59 1 and 0.62 1, respectively). All of the hypercapnic patients could improve blood gas tensions towards normal by hyperventilation. There were no significant differences in visual analogue scores of breathlessness during treadmill exercise, disability (oxygen-cost diagram, dyspnoea grade), or exercise tolerance (six-minute walk, maximal consumption of oxygen during bicycle ergometry, distance walked to exhaustion in progressive treadmill test). The findings show that the "fight" to maintain normal blood gas tensions in the face of severe airflow limitation does not have an appreciable cost in terms of disability.     

Healthy Exercise

Persons at any age can substantially improve their fitness for work and play through appropriate exercise training. Considerable evidence indicates that physical activity is valuable for weight control, modifying lipids and improving carbohydrate tolerance. Less rigorous scientific data are available for associated long-term blood pressure and psychological changes with habitual exercise. Strenuous physical activity most likely reduces the incidence of coronary heart disease and the detrimental impact of certain chronic diseases on health. Adverse effects may result from a training program, but the major concern is the susceptibility to cardiovascular events during and immediately after exertion. To achieve optimal benefits with minimal risk, exercise must be carefully prescribed within the context of overall health and training objectives. Taken altogether, a distinct rationale exists for regular vigorous exercise as an integral part of a personal health maintenance program.     

Effect of induced alkalosis on perception of exertion during intermittent exercise

The purpose of this study was to evaluate the effects of metabolic alkalosis on differentiated ratings of perceived exertion during intermittent high-intensity exercise. Six endurance-trained females participated as subjects in this investigation. Each subject underwent three separate experimental trials in which NaHCO3 was ingested in either a single (0.3 g NaHCO3/kg body wt) or periodic schedule (0.12 g NaHCO3/kg body wt initially, with 0.18 g/kg body wt distributed in equal doses before each 5-min exercise bout). Calcium carbonate served as a placebo control. An intermittent exercise protocol was used in which each subject rode a cycle ergometer at 90% maximum O2 consumption for 5 min. Within each acid-base condition, the exercise protocol was repeated three times with 10-min rest periods interspersed. Differentiated ratings of perceived exertion for the legs (RPE-L), chest (RPE-C), and overall body (RPE-O) were attenuated under alkalotic treatment relative to placebo control regardless of pattern of NaHCO3 administration. RPE-L, RPE-C, and RPE-O were negatively correlated to the bicarbonate concentration of venous blood. This investigation suggests that perception of effort during high-intensity intermittent exercise can be related to buffering capacity of the blood.     

The acute effect of a caffeine-containing energy drink on mood state, readiness to invest effort, and resistance exercise to failure

ABSTRACT: Duncan, MJ, Smith, M, Cook, K, and James, RS. The acute effect of a caffeine-containing energy drink on mood state, readiness to invest effort, and resistance exercise to failure. J Strength Cond Res 26(10): 2858-2865, 2012-The efficacy of caffeine ingestion in enhancing aerobic performance is well established. The evidence for caffeine's effects on resistance exercise is mixed and has not fully examined the associated psychological and psychophysiological changes. This study examined acute effects of ingesting a caffeine-containing energy drink on repetitions to failure, the rating of perceived exertion (RPE), and the readiness to invest physical effort (RTIPE) and mental effort during resistance exercise to failure. Thirteen resistance-trained men took part in this double-blind, randomized cross-over experimental study whereby they ingested a caffeinated (179 mg) energy drink or placebo solution 60 minutes before completing a bout of resistance exercise comprising bench press, deadlift, prone row, and back squat exercise to failure at an intensity of 60% 1-repetition maximum. Experimental conditions were separated by at least 48 hours. Participants completed significantly greater repetitions to failure, irrespective of exercise, in the energy drink condition (p = 0.015). Rating of perceived exertion was significantly higher in the placebo condition (p = 0.02) and was significantly higher during lower-body exercises compared with upper-body exercises irrespective of the substance ingested (p = 0.0001). Readiness to invest mental effort was greater with the energy drink condition (p = 0.04), irrespective of time. A significant time × substance interaction (p = 0.036) for RTIPE indicated that RTIPE increased for both placebo and energy drink conditions preingestion to pre-exercise, but the magnitude of increase was greater with the energy drink condition compared with placebo. This resulted in higher RTIPE postexercise for the energy drink condition. These results suggest that acute ingestion of a caffeine-containing energy drink can enhance resistance exercise performance to failure and positively enhance psychophysiological factors related to exertion in trained men.     

Effect of mild-to-moderate airflow limitation on exercise capacity

To determine the effect of mild-to-moderate airflow limitation on exercise tolerance and end-expiratory lung volume (EELV), we studied 9 control subjects with normal pulmonary function [forced expired volume in 1 s (FEV1) 105% pred; % of forced vital capacity expired in 1 s (FEV1/FVC%) 81] and 12 patients with mild-to-moderate airflow limitation (FEV1 72% pred; FEV1/FVC % 58) during progressive cycle ergometry. Maximal exercise capacity was reduced in patients [69% of pred maximal O2 uptake (VO2max)] compared with controls (104% pred VO2max, P less than 0.01); however, maximal expired minute ventilation-to-maximum voluntary ventilation ratio and maximal heart rate were not significantly different between controls and patients. Overall, there was a close relationship between VO2max and FEV1 (r2 = 0.62). Resting EELV was similar between controls and patients [53% of total lung capacity (TLC)], but at maximal exercise the controls decreased EELV to 45% of TLC (P less than 0.01), whereas the patients increased EELV to 58% of TLC (P less than 0.05). Overall, EELV was significantly correlated to both VO2max (r = -0.71, P less than 0.001) and FEV1 (r = -0.68, P less than 0.001). This relationship suggests a ventilatory influence on exercise capacity; however, the increased EELV and associated pleural pressures could influence cardiovascular function during exercise. We suggest that the increase in EELV should be considered a response reflective of the effect of airflow limitation on the ventilatory response to exercise.     

The effect of caffeine ingestion on mood state and bench press performance to failure

Research has suggested that caffeine enhances aerobic performance. The evidence for high-intensity, short-term exercise, particularly resistance exercise is mixed and has not fully examined the psychological changes that occur after this mode of exercise with caffeine ingestion. This study examined the effect of caffeine (5 mg · kg(-1)) vs. placebo on bench press exercise to failure and the mood state response pre to postexercise. Thirteen moderately trained men (22.7 ± 6.0 years) completed 2 laboratory visits, after determination of 1 repetition maximum (1RM) on the bench press, where they performed bench press repetitions to failure at a load of 60% 1RM. Mood state was assessed 60 minutes pre and immediately post-substance ingestion. Borg's rating of perceived exertion (RPE) and peak blood lactate (PBla) were assessed after each test, and peak heart rate (PHR) was determined using heart rate telemetry. Participants completed significantly more repetitions to failure (p = 0.031) and lifted significantly greater weight (p = 0.027) in the caffeine condition compared to the placebo condition. The PHR (p = 0.0001) and PBla (p = 0.002) were higher after caffeine ingestion. The RPE was not different across conditions (p = 0.082). Mood state scores for vigor were greater (p = 0.001) and fatigue scores lower (p = 0.04) in the presence of caffeine. Fatigue scores were greater postexercise (p = 0.001) compared to scores pre exercise across conditions. Caffeine ingestion enhances performance in short-term, resistance exercise to failure and may favorably change the mood state response to exercise compared to a placebo.     

Quantitative analysis of changes occurring in muscle vastus lateralis in patients with heart failure after low-intensity training

OBJECTIVE: To quantitate the changes occurring in muscle vastus lateralis after exercise training of low intensity adopted for the rehabilitation of patients with chronic heart failure. STUDY DESIGN: Nine consecutive males with a clinical diagnosis of idiopathic dilated and ischemic cardiomyopathy underwent an eight-week period of training. The intensity of the work was calculated as 40% of peak VO2. The program consisted of 30 minutes of cycling three times per week. A cardiopulmonary exercise test, hemodynamic measurements and echocardiographic studies were carried out. Needle biopsies were taken from muscle vastus lateralis before starting and after completing training. Quantitative analysis was carried out on sections stained with ATPase at pH 9.5 for measurement of the lesser diameter of type 1 and 2 fibers (by using an image analyzer) and on UEA 1-stained sections for capillary density and capillary/fiber ratio (by using a frame in the eyepiece of the microscope). The Wilcoxon test was applied to identify significant differences before and after training. Spearman's rank correlation coefficient was also calculated to highlight any correlation between the morphologic data and results of clinical tests. RESULTS: After completing the training program, all the patients experienced an improvement in exercise tolerance and a significant increase (P < .004) in the VO2 and VCO2 peak. Skeletal muscle showed a significant (P < .02) increase in the capillary/fiber ratio. The changes were not significantly correlated with any of the clinical findings. CONCLUSION: Low-intensity training can improve the functional capacity of patients with heart failure while producing only mild morphologic changes in their muscles.     

Plasma theophylline concentrations,six minute walking distances,and breathlessness in patients with chronic airflow obstruction.

Twenty patients with chronic bronchitis were given incremental dosages of a new slow release preparation of theophylline and observed for its effect on lung function and exercise tolerance. Measurements were made subjectively by using visual analogue scales and objectively using six minute walking distances and spirometry. The study was placebo controlled and had a double blind randomised design. In the dosages used (200, 400, 600, and 800 mg) theophylline produced no significant improvement in forced expiratory volume in one second or forced vital capacity, and there was no overall improvement in peak expiratory flow rate. Similarly, neither effort tolerance nor degree of breathlessness appeared to be influenced by the drug, even when unacceptably high dosages were used. By contrast, placebo yielded a 7% increase in the six minute walking distance. From these results it seems difficult to justify the routine, indiscriminate use of theophylline for chronic bronchitis.     

Internalized societal attitudes moderate the impact of weight stigma on avoidance of exercise

Experiences with weight stigma negatively impact both psychological outcomes (e.g., body dissatisfaction, depression) and behavioral outcomes (e.g., dieting, exercise). However, not everyone is equally affected by experiences with weight stigma. This study examined whether internalized societal attitudes about weight moderated the impact of weight stigma. Adult participants (n = 111) completed measures of experiences with weight stigma, as well as two indexes of internalized societal attitudes (the moderators): Internalized anti-fat attitudes and internalization of societal standards of attractiveness. Psychological outcomes included self-esteem, body dissatisfaction, drive for thinness, and bulimic symptoms; behavioral outcomes included avoidance of exercise and self-reported exercise behavior. Weight stigma was positively correlated with body dissatisfaction, drive for thinness, and bulimic symptoms, and was negatively correlated with state and trait self-esteem. Both indexes of internalized attitudes moderated the association between weight stigma and avoidance of exercise: Individuals high in anti-fat attitudes and high in internalization of societal standards of attractiveness were more motivated to avoid exercise if they also experienced a high degree of weight stigma; individuals low in anti-fat attitudes and low in internalization were relatively unaffected. Avoidance of exercise was negatively correlated with self-reported strenuous exercise. These findings suggest that weight stigma can negatively influence motivation to exercise, particularly among individuals who have internalized societal attitudes about weight. Reducing internalization might be a means of minimizing the negative impact of weight stigma and of facilitating healthy weight management efforts.     

A prospective study of seasonal variation in shift-work tolerance

Seasonal effects on shift-work tolerance were assessed using the Standardized Shiftwork Index and the 21-item Hamilton Depression Scale. Participants (N=88) mainly worked a two-day, two-night, four-off rotation with 12 h shifts changing at 06:00 and 18:00 h in Vancouver, Canada. At this latitude (approximately 49 degrees N), daylength varies seasonally from approximately 16 to approximately 8 h, and both daily commutes occur in the dark in mid-winter and in sunlight in mid-summer. Questionnaires were completed twice, near the summer and winter solstices (order counterbalanced). Outcome variables were mood, general psychological health, sleep quality, chronic fatigue, physical health, job satisfaction, and social and domestic disruption. Of these, general psychological health and mood were significantly worse in winter, while sleep was more disturbed in summer. In winter, 31% exceeded the cutoff for psychological distress, and >70% scored in the higher than normal range for depressive symptoms. In summer, the proportions dropped to 19% and 53%, respectively. Measures of physical health and psychosocial well-being showed no seasonal effects. Relationships among explanatory and outcome variables, assessed by linear regression and canonical correlations, were also stable across season. Neuroticism was the strongest predictor of tolerance to shift work. Age was predictive only of sleep disturbance in both summer and winter. These results indicate that time of year can affect important outcome measures in shift-work assessment and intervention studies. The high average scores on measures of psychological distress and depression in winter suggest that at northern latitudes, some shift schedules may increase the risk of seasonal-type depression.     

Association between recombinant human erythropoietin and quality of life and exercise capacity of patients receiving haemodialysis. Canadian Erythropoietin Study Group.

OBJECTIVE--To determine whether recombinant human erythropoietin improves the quality of life and exercise capacity of anaemic patients receiving haemodialysis. DESIGN--A double blind, randomised, placebo controlled study. SETTING--Eight Canadian university haemodialysis centres. PATIENTS--118 Patients receiving haemodialysis aged 18-75 with haemoglobin concentrations less than 90 g/l, no causes of anaemia other than erythropoietin deficiency, and no other serious diseases. INTERVENTIONS--Patients were randomised to three groups to receive placebo (n = 40), erythropoietin to achieve a haemoglobin concentration of 95-110 g/l (n = 40), or erythropoietin to achieve a haemoglobin concentration of 115-130 g/l (n = 38). Erythropoietin was given intravenously thrice weekly, initially at 100 units/kg/dose. The dose was subsequently adjusted to achieve the target haemoglobin concentration. All patients with a serum ferritin concentration less than 250 micrograms/l received oral or intravenous iron for one month before the study and as necessary throughout the trial. MAIN OUTCOME MEASURES--Scores obtained with kidney disease questionnaire, sickness impact profile, and time trade off technique; and results of six minute walk test and modified Naughton stress test. RESULTS--The mean (SD) haemoglobin concentration at six months was 74 (12) g/l in patients given placebo, 102 (10) g/l in those in the low erythropoietin group, and 117 (17) g/l in those in the high erythropoietin group. Compared with the placebo group, patients treated with erythropoietin had a significant improvement in their scores for fatigue, physical symptoms, relationships, and depression on the kidney disease questionnaire and in the global and physical scores on the sickness impact profile. The distance walked in the stress test increased in the group treated with erythropoietin, but there was no improvement in the six minute walk test, psychosocial scores on the sickness impact profile, or time trade off scores. There was no significant difference in the improvement in quality of life or exercise capacity between the two groups taking erythropoietin. Patients taking erythropoietin had a significantly increased diastolic blood pressure despite an increase in either the dose or number of antihypertensive drugs used. Eleven of 78 patients treated with erythropoietin had their sites of access clotted compared with only one of 40 patients given placebo. CONCLUSIONS--Patients receiving erythropoietin were appreciably less fatigued, complained of less severe physical symptoms, and had moderate improvements in exercise tolerance and depression compared with patients not receiving erythropoietin. At the doses used in this trial there was a higher incidence of hypertension and clotting of the vascular access in patients treated with erythropoietin.     

Gait analysis in chronic heart failure: The calf as a locus of impaired walking capacity

Reduced walking capacity, a hallmark of chronic heart failure (CHF), is strongly correlated with hospitalization and morbidity. The aim of this work was to perform a detailed biomechanical gait analysis to better identify mechanisms underlying reduced walking capacity in CHF. Inverse dynamic analyses were conducted in CHF patients and age- and exercise level-matched control subjects on an instrumented treadmill at self-selected treadmill walking speeds and at speeds representing +20% and –20% of the subjects’ preferred speed. Surprisingly, no difference in preferred speed was observed between groups, possibly explained by an optimization of the mechanical cost of transport in both groups (the mechanical cost to travel a given distance; J/kg/m). The majority of limb kinematics and kinetics were also similar between groups, with the exception of greater ankle dorsiflexion angles during stance in CHF. Nevertheless, over two times greater ankle plantarflexion work during stance and per distance traveled is required for a given triceps surae muscle volume in CHF patients. This, together with a greater reliance on the ankle compared to the hip to power walking in CHF patients, especially at faster speeds, may contribute to the earlier onset of fatigue in CHF patients. This observation also helps explain the high correlation between triceps surae muscle volume and exercise capacity that has previously been reported in CHF. Considering the key role played by the plantarflexors in powering walking and their association with exercise capacity, our findings strongly suggest that exercise-based rehabilitation in CHF should not omit the ankle muscle group.