Monitoring training progress during exercise training in cancer survivors: a submaximal exercise test as an alternative for a maximal exercise test?

OBJECTIVE: To examine the use of a submaximal exercise test in detecting change in fitness level after a physical training program, and to investigate the correlation of outcomes as measured submaximally or maximally. DESIGN: A prospective study in which exercise testing was performed before and after training intervention. SETTING: Academic and general hospital and rehabilitation center. PARTICIPANTS: Cancer survivors (N=147) (all cancer types, medical treatment completed > or =3 mo ago) attended a 12-week supervised exercise program. INTERVENTIONS: A 12-week training program including aerobic training, strength training, and group sport. MAIN OUTCOME MEASURES: Outcome measures were changes in peak oxygen uptake (Vo(2)peak) and peak power output (both determined during exhaustive exercise testing) and submaximal heart rate (determined during submaximal testing at a fixed workload). RESULTS: The Vo(2)peak and peak power output increased and the submaximal heart rate decreased significantly from baseline to postintervention (P<.001). Changes in submaximal heart rate were only weakly correlated with changes in Vo(2)peak and peak power output. Comparing the participants performing submaximal testing with a heart rate less than 140 beats per minute (bpm) versus the participants achieving a heart rate of 140 bpm or higher showed that changes in submaximal heart rate in the group cycling with moderate to high intensity (ie, heart rate > or =140 bpm) were clearly related to changes in VO(2)peak and peak power output. CONCLUSIONS: For the monitoring of training progress in daily clinical practice, changes in heart rate at a fixed submaximal workload that requires a heart rate greater than 140 bpm may serve as an alternative to an exhaustive exercise test.

Assessment of the effects of physical training in patients with chronic heart failure: the utility of effort-independent exercise variables.

Traditionally, the effects of physical training in patients with chronic heart failure (CHF) are evaluated by changes in peak oxygen uptake (peak VO(2)). The assessment of peak VO(2), however, is highly dependent on the patients' motivation. The aim of the present study was to evaluate the clinical utility of effort-independent exercise variables for detecting training effects in CHF patients. In a prospective controlled trial, patients with stable CHF were allocated to an intervention group (N = 30), performing a 12-week combined cycle interval and muscle resistance training program, or a control group (N = 18) that was matched for age, gender, body composition and left ventricular ejection fraction. The following effort-independent exercise variables were evaluated: the ventilatory anaerobic threshold (VAT), oxygen uptake efficiency slope (OUES), the V(E)/VCO(2) slope and the time constant of VO(2) kinetics during recovery from submaximal constant-load exercise (tau-rec). In addition to post-training increases in peak VO(2) and peak V(E), the intervention group showed significant within and between-group improvements in VAT, OUES and tau-rec. There were no significant differences between relative improvements of the effort-independent exercise variables in the intervention group. In contrast with VAT, which could not be determined in 9% of the patients, OUES and tau-rec were determined successfully in all patients. Therefore, we conclude that OUES and tau-rec are useful in clinical practice for the assessment of training effects in CHF patients, especially in cases of poor subject effort during symptom-limited exercise testing or when patients are unable to reach a maximal exercise level.

Are oxygen uptake kinetics in chronic heart failure limited by oxygen delivery or oxygen utilization?

BACKGROUND: The delay in O(2) uptake kinetics during and after submaximal physical activity (O(2) onset and recovery kinetics, respectively) correlates well with the functional capacity of patients with chronic heart failure (CHF). This study examined the physiological background of this delay in moderately impaired CHF patients by comparing kinetics of cardiac output (Q) and O(2) uptake (V(O(2))). METHODS: Fourteen stable CHF patients (New York Heart Association class II-III) and 8 healthy subjects, matched for age and body mass index, were included. All subjects performed a submaximal constant-load exercise test to assess O(2) uptake kinetics. Furthermore, in 10 CHF patients Q was measured by a radial artery pulse contour analysis method, which enabled the simultaneous modelling of exercise-related kinetics of Q and V(O(2)). RESULTS: Both O(2) onset and recovery kinetics were delayed in the patient group. There were no significant differences between the time constants of Q and V(O(2)) during exercise-onset (62+/-25 s versus 59+/-28 s, p=0.51) or recovery (61+/-25 s versus 57+/-20 s, p=0.38) in the patient group, indicating that O(2) delivery was not in excess of the metabolic demands in these patients. CONCLUSION: The delay in O(2) onset and recovery kinetics in moderately impaired CHF patients is suggested to be due to limitations in O(2) delivery. Therefore, strategies aimed at improving exercise performance of these patients should focus more on improvements of O(2) delivery than on O(2) utilization.

Skeletal muscle metabolic recovery following submaximal exercise in chronic heart failure is limited more by O(2) delivery than O(2) utilization.

CHF (chronic heart failure) is associated with a prolonged recovery of skeletal muscle energy stores following submaximal exercise, limiting the ability to perform repetitive daily activities.However, the pathophysiological background of this impairment is not well established. The aim of the present study was to investigate whether muscle metabolic recovery following submaximal exercise in patients with CHF is limited by O2 delivery or O2 utilization. A total of 13 stable CHF patients (New York Heart Association classes II-III) and eight healthy subjects, matched for age and BMI (body mass index), were included. All subjects performed repetitive submaximal dynamic single leg extensions in the supine position. Post-exercise PCr (phosphocreatine) resynthesis was assessed by 31P-MRS (magnetic resonance spectroscopy). NIRS (near-IR spectroscopy) was applied simultaneously, using the rate of decrease in HHb (deoxygenated haemoglobin) as an index of post-exercise muscle re-oxygenation. As expected, PCr recovery was slower in CHF patients than in control subjects (time constant, 47+/-10 compared with 35+/-12 s respectively; P=0.04). HHb recovery kinetics were also prolonged in CHF patients (mean response time, 74+/-41 compared with 44+/-17 s respectively; P=0.04). In the patient group, HHb recovery kinetics were slower than PCr recovery kinetics (P=0.02), whereas no difference existed in the control group(P=0.32). In conclusion, prolonged metabolic recovery in CHF patients is associated with an even slower muscle tissue re-oxygenation, indicating a lower O(2) delivery relative to metabolic demands. Therefore we postulate that the impaired ability to perform repetitive daily activities in these patients depends more on a reduced muscle blood flow than on limitations in O(2) utilization.

Predicting effects of exercise training in patients with heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

The purpose of this study was to investigate which patient characteristics may predict training effects on maximal and submaximal exercise performance in patients with heart failure. Together with commonly used clinical and performance-related variables, oxygen uptake kinetics during exercise recovery were included as possible predictors. Fifty patients with heart failure (New York Heart Association class II or III) performed a 12-week training program (cycle interval and resistance training). Training effects were expressed as changes in peak oxygen uptake (Vo(2)), Vo(2) at ventilatory threshold (VT), and the time constant of Vo(2) recovery after submaximal exercise (tau-rec). After training, peak Vo(2), Vo(2) at VT, and tau-rec improved significantly, with a wide variety in training responses. Changes in peak Vo(2) were related to changes in VT (r = 0.79, p <0.001), but both changes were not related to changes in tau-rec. Using multivariate regression analyses, post-training changes in peak Vo(2) could be predicted by recovery halftime of peak Vo(2) (T1/2), peak Vo(2) (percentage of predicted), and peak respiratory exchange ratio (R(2) = 36%). Post-training changes in VT could be predicted by T1/2 and VT (predicted) (R(2) = 29%), whereas changes in tau-rec could be predicted only by tau-rec at baseline (R(2) = 34%). In conclusion, oxygen recovery kinetics after maximal and submaximal exercise substantially add to the prediction of training effects in patients with heart failure, presumably because of their relations with, respectively, central and peripheral impairments of exercise capacity. However, the explained variance in training effects is not sufficient to make a definite distinction between training responders and nonresponders.

Improved physical fitness of cancer survivors: a randomised controlled trial comparing physical training with physical and cognitive-behavioural training.

We compared the effect of a group-based 12-week supervised exercise programme, i.e. aerobic and resistance exercise, and group sports, with that of the same programme combined with cognitive-behavioural training on physical fitness and activity of cancer survivors. One hundred and forty seven cancer survivors (all cancer types, medical treatment >or=3 months ago)were randomly assigned to physical training (PT, n=71) or PT plus cognitive-behavioural training (PT+CBT, n=76). Maximal aerobic capacity, muscle strength and physical activity were assessed at baseline and post-intervention. Analyses using multilevel linear mixed-effects models showed that cancer survivors' physical fitness increased significantly in PT and PT+CBT from baseline to post-intervention. Changes did not differ between PT and PT+CBT. Physical fitness of cancer survivors was improved following an intensive physical training programme. Adding a structured cognitive-behavioural intervention did not enhance the effect.

Reproducibility of onset and recovery oxygen uptake kinetics in moderately impaired patients with chronic heart failure.

Oxygen (O2) kinetics reflect the ability to adapt to or recover from exercise that is indicative of daily life. In patients with chronic heart failure (CHF), parameters of O2 kinetics have shown to be useful for clinical purposes like grading of functional impairment and assessment of prognosis. This study compared the goodness of fit and reproducibility of previously described methods to assess O2 kinetics in these patients. Nineteen CHF patients, New York Heart Association class II-III, performed two constant-load tests on a cycle ergometer at 50% of the maximum workload. Time constants of O2 onset- and recovery kinetics (tau) were calculated by mono-exponential modeling with four different sampling intervals (5 and 10 s, 5 and 8 breaths). The goodness of fit was expressed as the coefficient of determination (R2). Onset kinetics were also evaluated by the mean response time (MRT). Considering O2 onset kinetics, tau showed a significant inverse correlation with peak- VO2 (R = -0.88, using 10 s sampling intervals). The limits of agreement of both tau and MRT, however, were not clinically acceptable. O2 recovery kinetics yielded better reproducibility and goodness of fit. Using the most optimal sampling interval (5 breaths), a change of at least 13 s in tau is needed to exceed normal test-to-test variations. In conclusion, O2 recovery kinetics are more reproducible for clinical purposes than O2 onset kinetics in moderately impaired patients with CHF. It should be recognized that this observation cannot be assumed to be generalizable to more severely impaired CHF patients.

The effect of physical training on workload, upper leg muscle function and muscle areas in patients with chronic heart failure.

OBJECTIVE: To investigate the effect of physical training (PTr) on upper leg muscle area, muscle strength and muscle endurance expressed as upper leg muscle function (ULMF) in relation to exercise performance in CHF. DESIGN: Randomised to a training (TG) or control group (CG). SETTING: Outpatient cardiac rehabilitation centre of community hospital. PATIENTS: 77 CHF patients (59 men and 18 women), NYHA class II/III, age 59.8+/-9.3 years, LVEF 27+/-8%. Sixteen patients dropped out during the intervention period, 61 patients (M/F:46/15) completed the study. INTERVENTION: PTr (combined strength and endurance exercises) four times per week, twice supervised and twice at home, during 26 weeks. MAIN OUTCOME MEASURES: LVEF, body composition, daily physical activity, exercise performance, upper leg muscle area and isokinetic leg muscle variables. RESULTS: Workload and peak oxygen consumption decreased in the CG (-4.1% and -4%) but increased in the TG (+5% and +4%) following PTr (p<0.05, ANOVA repeated measures). Hamstrings area decreased in the CG and did not change in the TG (p<0.05, ANOVA repeated measures). ULMF improved in the TG, but remained unchanged in the CG (+13.0% and 0.0, respectively, p<0.05; ANOVA repeated measures). At baseline and after intervention nearly 60% of the variance in maximal workload was explained by ULMF and quadriceps muscle area (multiple regression analysis). CONCLUSIONS: In CHF patients, home-based training in conjunction with a supervised strength and endurance training program is safe, feasible and effective and does not require complex training equipment. Physical training prevented loss of hamstrings muscle mass and improved exercise performance by enhancing muscle strength and endurance.

Determinants of maximal exercise performance in chronic heart failure.

BACKGROUND: Chronic heart failure (CHF) is characterized by symptoms like fatigue, dyspnoea and limited exercise performance. It has been postulated that maximal exercise performance (Wmax) is predominantly limited by skeletal muscle function and less by heart function. AIM: To study the interrelation between most relevant muscle and anthropometrical variables and Wmax in CHF patients in order to develop a model that describes the impact of these variables for maximal exercise performance. DESIGN: In 77 patients with CHF Wmax was assessed by incremental cycle ergometry until exhaustion (20 Watt/3 min). Peak torque (strength) and total work (endurance) for the quadriceps and hamstrings were assessed by isokinetic dynamometry. Isometric strength was measured by hand dynamometry. Relevant muscle areas were calculated by computerized tomography scan. RESULTS: Significant correlations between Wmax and isokinetic muscle parameters (peak torque and total work) ranged from 0.41-0.65 (P<0.01). Other significant relationships (P<0.01) with Wmax were obtained for age (r=-0.22), gender (r=0.45), fat free mass (FFM) (r=0.51), quadriceps muscle area (r=0.73), hamstrings muscle area (r=0.50), upper leg muscle function (i.e., a combination of muscle strength and muscle endurance) (r=0.71) and isometric strength (r=0.63). Multiple regression analysis showed that upper leg muscle function and quadriceps muscle area could predict 57% of the variance in Wmax. CONCLUSION: Muscle strength and muscle endurance, combined with quadriceps muscle area are the main predictors of maximal exercise performance in patients with CHF.