Interval training as an alternative modality to continuous exercise in patients with COPD. Interval versus continuous high-intensity exercise in chronic obstructive pulmonary disease: a randomized trial. Interval training versus continuous training in patients with chronic obstructive pulmonary disease. Effects of interval-load versus constant-load training on the BODE index in COPD patients. Effects of home-based pulmonary rehabilitation in patients with chronic obstructive pulmonary disease: a randomized trial. Interval training compared with continuous training in patients with COPD. Skeletal muscle adaptations to interval training in patients with advanced COPD. Reductions in exercise lactic acidosis and ventilation as a result of exercise training in patients with obstructive lung disease. Supervised high intensity continuous and interval training vs. self-paced training in COPD.
Understanding of what constitutes a training load adequate to induce training effects in patients with chronic obstructive pulmonary disease (COPD) is still evolving. The present study investigated whether interval training (IT) is effective in terms of inducing measurable improvements in physiological response and compared its effects on exercise tolerance (ET) and quality of life to those of continuous training (CT). Thirty-six COPD patients, with a forced expiratory volume in one second of 45+/-4% of the predicted value (mean+/-SEM), were randomly assigned to CT (exercise at 50% of baseline peak work-rate) or IT (work for 30 s at 100% of peak work-rate alternating with 30-s rest intervals) groups that cycled 40 min x day(-1) and 2 days x week(-1) for 12 weeks. After training, both groups showed significantly improved ET (IT, 57+/-6 to 71+/-8 W; CT, 57+/-5 to 70+/-6 W) and total quality-of-life score of the Chronic Respiratory Disease Questionnaire (IT, 77+/-3 to 88+/-2; CT, 78+/-3 to 93+/-2). At identical levels of exercise, minute ventilation was significantly reduced (IT, 35.8+/-2.5 to 31.7+/-2.5 L x min(-1); CT, 36.4+/-2.7 to 32.5+/-2.7 L x min(-1)). The magnitude of improvement in these variables was not significantly different among groups. The present data expand on the principles of exercise prescription for chronic obstructive pulmonary disease patients by demonstrating that interval training elicits substantial training effects, which are similar in magnitude to those produced by continuous training at half the exercise intensity but double the exercise time. Guidelines recommend high-intensity continuous exercise to reduce peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease but acknowledge that interval exercise might be an equally effective alternative that is better tolerated by patients.
                To assess whether interval exercise is no less effective than high-intensity continuous exercise and whether it is tolerated better by patients with severe chronic obstructive pulmonary disease.
                Randomized, noninferiority trial.
                Publicly funded rehabilitation hospital in Switzerland.
                98 patients with severe chronic obstructive pulmonary disease, with or without recent exacerbations.
                12 to 15 supervised interval or high-intensity continuous exercise sessions (over 3 weeks) followed by exercise at home.
                Health-related quality of life determined by using the Chronic Respiratory Questionnaire (CRQ) (scores from 1 [most severe impairment] to 7 [no impairment]) after 5 weeks and number of unintended breaks during supervised exercise.
                Both groups experienced large improvements in health-related quality of life (increase of CRQ total scores of 1.00 [SD, 0.98] for the interval exercise group and 1.02 [SD, 1.05] for the continuous exercise group). Adjusted between-group differences between the interval exercise group and the continuous exercise group (-0.05 [95% CI, -0.42 to -0.32] for CRQ and 1.1 meters [CI, -25.4 to 27.6 meters] for 6-minute walking distance) were within the a priori defined boundaries of noninferiority (0.5 for CRQ and 45 meters for 6-minute walking distance). Twenty-one (47.9%) patients using interval exercise and 11 (24.0%) patients using continuous exercise were able to adhere to the protocol (difference, 23.9 percentage points [CI, 5.0 to 42.8 percentage points]; P = 0.014). The median number of unintended breaks lasting 1 minute or more was 2 (interquartile range, 0 to 16) for patients in the interval exercise group and 11 (interquartile range, 2 to 26) for patients in the continuous exercise group (P = 0.023).
                The study focused on initiation of exercise and not on outpatient or home-based maintenance of exercise.
                Clinicians and patients can choose either of the 2 exercise plans to initiate physical exercise. International Standard Randomized Controlled Trial number: SRCTN11611768. The purpose of this study was to compare the effects of interval training (IT) and continuous steady-pace training (CT) in patients with COPD.
                Patients (n = 21) (mean forced expiratory volume in 1 second ([FEV1] = 44.6% +/- 13.9%) were randomized to IT, and 20 patients (mean FEV1 = 41.7% +/- 12.6%) to CT. Outcome measures included 6-minute walk distance, maximal work capacity, endurance exercise time during constant workload exercise at 60% to 70% of maximal work capacity, and quality of life including fatigue and dyspnea. Participants exercised 3 times per week for 8 weeks, and total work was the same for both training regimens.
                Significant improvement in mean score was observed in each variable within each of the 2 groups: 6-minute walk distance (IT = 158 +/- 178 ft, CT = 106 +/- 165 ft); maximal work capacity (IT = 10.0 +/- 13.0 W, CT = 11.5 +/- 13.1 W); endurance exercise time (IT = 15.0 +/- 12.5 minutes, CT = 18.7 +/- 10.6 minutes); and quality of life domains, fatigue (IT = 3.1 +/- 3.0, CT = 2.8 +/- 4.7), and dyspnea (IT = 4.4 +/- 5.3, CT = 5.4 +/- 5.1). There was no significant difference in the extent of improvement between the 2 training regimens for any of the outcome variables.
                Compared with CT, IT was well tolerated and produced similar improvements in exercise performance and quality of life. The BODE index is frequently used to assess functional capacity in patients with COPD. The aim of this study was to investigate the effectiveness of interval-load training (ILT) to improve the BODE index in comparison to the commonly implemented constant-load training (CLT). Forty-two patients with COPD [FEV(1): (mean+/-SEM) 42+/-3% predicted] were randomly allocated to either ILT (n=21) or CLT (n=21). The training program consisted of cycling exercise 3 days/week for 10 weeks. Patients assigned to ILT exercised at a mean intensity of 126+/-4% of baseline peak work rate (Wpeak) with 30-s work periods alternated with 30-s rest periods for 45 min per day, whereas patients allocated to CLT exercised at a mean intensity of 76+/-5% of baseline Wpeak for 30 min per day. The BODE index and its components: body mass index, FEV(1), MMRC dyspnea score and the 6-min walk test (6-MWT) as well as cycling Wpeak were assessed before and after both exercise training regimes. Both ILT and CLT significantly (p<0.001) decreased the BODE index (from 4.8+/-0.5 to 4.0+/-0.5 units and from 4.4+/-0.5 to 3.8+/-0.5 units, respectively). In addition, both ILT and CLT significantly decreased the MMRC dyspnea score by 0.4+/-0.1 units and increased the 6-MWT (by 52+/-16 and 44+/-12 m, respectively) as well as cycling Wpeak (by 14+/-2 and 10+/-2W, respectively). The magnitude of these changes was not significantly different between ILT and CLT. Consequently, ILT is equally effective to CLT in terms of improving the BODE index in patients with COPD and as such it may constitute an alternative rehabilitative modality in COPD. Home-based rehabilitation is a promising approach to improve access to pulmonary rehabilitation.
                To assess whether self-monitored, home-based rehabilitation is as effective as outpatient, hospital-based rehabilitation in patients with chronic obstructive pulmonary disease (COPD).
                Randomized, multicenter, noninferiority trial.
                10 academic and community medical centers in Canada.
                252 patients with moderate to severe COPD.
                After a 4-week education program, patients took part in home-based rehabilitation or outpatient, hospital-based rehabilitation for 8 weeks. They were followed for 40 weeks to complete the 1-year study.
                The primary outcome was the change in Chronic Respiratory Questionnaire dyspnea subscale score at 1 year. The primary analysis took a modified intention-to-treat approach by using all patients who provided data at the specified follow-up time, regardless of their level of adherence. The analysis used regression modeling that adjusted for the effects of center, sex, and baseline level. All differences were computed as home intervention minus outpatient intervention.
                Both interventions produced similar improvements in the Chronic Respiratory Questionnaire dyspnea subscale at 1 year: improvement in dyspnea of 0.62 (95% CI, 0.43 to 0.80) units in the home intervention (n = 107) and 0.46 (CI, 0.28 to 0.64) units in the outpatient intervention (n = 109). The difference between the 2 treatments at 1 year was small and clinically unimportant. The 95% CI of the difference did not exceed the prespecified noninferiority margin of 0.5: difference in dyspnea score of 0.16 (CI, -0.08 to 0.40). Most adverse events were related to COPD exacerbations. No serious adverse event was considered to be related to the study intervention.
                The contribution of the educational program to the improvement in health status and exercise tolerance cannot be ascertained.
                Home rehabilitation is a useful, equivalent alternative to outpatient rehabilitation in patients with COPD. The aim of this study was to compare the effects of interval training (3-min intervals) with continuous training on peak exercise capacity (W peak), physiological response, functional capacity, dyspnoea, mental health and health-related quality of life (HRQoL) in patients with moderate or severe COPD. Sixty patients exercised twice weekly for 16 weeks after randomisation to interval- or continuous training. Target intensity was 80% of baseline W peak in the interval group (I-group) and 65% in the continuous group (C-group). Patients were tested by spirometry, ergometer cycle test, cardiopulmonary test and a 12 min walk test. Dyspnoea was measured by the dyspnoea scale from Chronic Obstructive Disease Questionnaire (CRDQ), mental health by Hospital Anxiety and Depression scale (HAD) and HRQoL by the Medical Outcomes Survey Short Form 36 (SF-36). After training, W peak, peak oxygen uptake (VO(2) peak) and exhaled carbon dioxide (VCO(2) peak) increased significantly in both groups, no significant differences between the groups. Minute ventilation (V(E) peak) increased only in the C-group. At identical work rates (isotime) VO(2), VCO(2) and V(E) were significantly more decreased in the I-group than in the C-group (p<0.05). Functional capacity, dyspnoea, mental health, and HRQoL improved significantly in both groups, no difference between the groups. Interval training and continuous training were equally potent in improving peak exercise capacity, functional exercise capacity, dyspnoea, mental health and HRQoL in patients with moderate or severe COPD. At isotime, the physiological response to training differed between the groups, in favour of the interval training. To investigate the response to interval exercise (IE) training by looking at changes in morphologic and biochemical characteristics of the vastus lateralis muscle, and to compare these changes to those incurred after constant-load exercise (CLE) training.
                Randomized, controlled, parallel, two-group study (IE vs CLE training).
                Multidisciplinary, outpatient, hospital-based, pulmonary rehabilitation program.
                Nineteen patients with stable advanced COPD (mean +/- SEM FEV1, 40 +/- 4% predicted).
                Patients (n = 10) assigned to IE training exercised at a mean intensity of 124 +/- 15% of baseline peak exercise capacity (peak work rate [Wpeak]) with 30-s work periods interspersed with 30-s rest periods for 45 min/d. Patients (n = 9) allocated to CLE training exercised at a mean intensity of 75 +/- 5% Wpeak for 30 min/d. Patients exercised 3 d/wk for 10 weeks.
                Needle biopsies of the right vastus lateralis muscle were performed before and after rehabilitation. After IE training, the cross-sectional areas of type I and IIa fibers were significantly increased (type I before, 3,972 +/- 455 microm2; after, 4,934 +/- 467 microm2 [p = 0.004]; type IIa before, 3,695 +/- 372 microm2; after, 4,486 +/- 346 microm2 [p = 0.008]), whereas the capillary-to-fiber ratio was significantly enlarged (from 1.13 +/- 0.08 to 1.24 +/- 0.07 [p = 0.013]). Citrate synthase activity increased (from 14.3 +/- 1.4 to 20.5 +/- 4.2 micromol/min/g), albeit not significantly (p = 0.097). There was also a significant improvement in Wpeak (by 19 +/- 5%; p = 0.04) and in lactate threshold (by 17 +/- 5%; p = 0.02). The magnitude of changes in all the above variables was not significantly different compared to that incurred after CLE training. During training sessions, however, ratings of dyspnea and leg discomfort, expressed as fraction of values achieved at baseline Wpeak, were significantly lower (p < 0.05) for IE training (73 +/- 9% and 60 +/- 8%, respectively) compared to CLE training (83 +/- 10% and 87 +/- 13%, respectively).
                High-intensity IE training is equally effective to moderately intense CLE training in inducing peripheral muscle adaptations; however, IE is associated with fewer training symptoms. Though exercise training is part of most pulmonary rehabilitation programs, whether there is a physiologic basis for increased exercise tolerance is unclear. We sought to determine whether patients with chronic obstructive pulmonary disease (COPD) are capable of obtaining a physiologic training effect, as manifested by a reduction in blood lactate and ventilation (VE) at a given level of exercise. We also sought to determine whether training work rate determines the size of the training effect. Nineteen participants with COPD of predominantly moderate severity in an inpatient rehabilitation program performed two cycle ergometer exercise tests at a low and a high work rate for 15 min or to tolerance and also an incremental exercise test to tolerance. Arterial blood was sampled for blood gas and lactate analyses. Identical tests were performed before and after 5-day-per-week cycle ergometer training for 8 wk either for 45 min/day at a high work rate (average, 71 W) or for a proportionally longer time at a low work rate (average, 30 W). Average FEV1 was 56 +/- 12% predicted and did not change with training. Peak exercise lactate (average, 6.5 mEq/L) was not correlated with FEV1. For the high work rate training group, identical work rates engendered less lactate (4.5 versus 7.2 mEq/L) and less VE (48 versus 55 L/min) after training; the low work rate training group had significantly less lactate and VE decrease (p less than 0.01). Further, endurance time for the high constant work rate increased 73% in the high work rate training group but only 9% in the low work rate training group. At identical work rates, VE decrease average 2.5 L/min per mEq/L decrease in lactate (r = 0.75). We conclude that most COPD subjects studied increased blood lactate at low work rates. Many of these patients were able to achieve a physiologic training effect. Though total work was the same, training at a high work rate was more effective than was training at a low work rate. The lower VE requirement to perform exercise was in proportion to the lower lactate level, but the VE decrease for a given decrease in lactate was smaller than that seen in normal subjects (7.2 L/min/mEq/L), apparently because patients with COPD fall to hyperventilate in response to lactic acidosis (PaCO2 does not drop). These findings provide a physiologic rationale for exercise training of patients with COPD. Endurance training is an effective component of pulmonary rehabilitation in COPD. Controversy exists regarding whether different modalities of supervised exercise training (continuous (C) or interval (I)) or self-paced (S) programs are equally beneficial.
                Seventy-one patients with COPD (average FEV(1)=55% predicted) were assigned to 8 weeks of C, I or S training, 45 min/session, 3 times/week. Group C (n=22) exercised at 80% of pre-training peak work rate in an incremental cycle ergometer test. In group I (n=17), training consisted of 30 min of cycling 2 min at 90% followed by 1 min at 50% peak work rate bracketed by 7.5 min at 50% peak work rate. The S group (n=32) was instructed to cycle, climb stairs and walk in their home with the same periodicity and time intervals.
                Improvement in incremental test peak work rate was significant in both C and I groups, but not in S. Peak oxygen uptake and lactic acidosis threshold improved significantly in the supervised groups, but differences among groups did not achieve significance. Scores in an activity questionnaire improved in all groups without significant differences among groups.
                In COPD patients, continuous and interval training have similar physiologic effects; by some measures of endurance exercise performance, they are superior to self-paced training. However, all were effective in improving patient-perceived activity.
Comparisons between the higher and lower training intensity were limited due to the small number of included studies and participants. Consequently, there are insufficient data to draw any conclusions on exercise capacity, symptoms and HRQoL for this comparison. For comparisons between continuous and interval training, both appear to be equally effective in improving exercise capacity, symptoms and HRQoL.