Vogiatzis I, Terzis G, Nanas S, Stratakos G, Simoes DC, Georgiadou O, Zakynthinos S, Roussos C
Chest. 2005;128(6):3838-3845.
Study objectives:
To investigate response to interval exercise (IE) training by looking at changes in the morphologic and biochemical characteristics of the vastus lateralis muscle and to compare these changes with those incurred after constant-load exercise (CLE) training.
Design:
Randomized, controlled, parallel, 2-group study (IE vs CLE training).
Setting:
Multidisciplinary, outpatient, hospital-based, pulmonary rehabilitation program.
Patients:
Nineteen patients with stable advanced chronic obstructive pulmonary disease (mean +/- SEM FEV1, 40 +/- 4% predicted).
Interventions:
Patients (n = 10) assigned to IE training exercised at a mean intensity of 124 +/- 15% of baseline peak exercise capacity (peak work rate), with 30-second work periods interspersed with 30-second rest periods for 45 min/d. Patients (n = 9) allocated to CLE training exercised at a mean intensity of 75 +/- 5% peak work rate for 30 min/d. Patients exercised 3 d/wk for 10 weeks.
Measurements and results:
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 [mu]m2; after, 4,934 +/- 467 [mu]m2 [P = .004]; type IIa: before, 3,695 +/- 372 [mu]m2; after, 4,486 +/- 346 [mu]m2 [P = .008]), whereas the capillary-to-fiber ratio was significantly enlarged (from 1.13 +/- 0.08 to 1.24 +/- 0.07, P = .013). Citrate synthase activityincreased (from 14.3 +/- 1.4 to 20.5 +/- 4.2 [mu]mol min-1 g-1), albeit not significantly (P = .097). There was also a significant improvement in peak work rate (by 19 +/- 5%; P = .04) and in lactate threshold (by 17 +/- 5%; P = .02). The magnitude of changes in all the above variables was not significantly different compared with that incurred after CLE training. During training sessions, however, ratings of dyspnea and leg discomfort, expressed as fraction of values achieved at baseline peak work rate, were significantly lower (P < .05) for IE training (73+/- 9% and 60 +/- 8%, respectively) than for CLE training (83 +/- 10% and 87 +/- 13%, respectively).
Conclusions:
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.
Commentary:
Patients with chronic obstructive pulmonary disease who exercise at high intensity (eg, 60%-80% of Wmax) can achieve physiologic gains in aerobic fitness, including increases in VO2max, delay in anaerobic threshold, and decreased lactate levels during exercise, that are associated with improved breathing pattern and reduced ventilatory requirement. However, some patients are unable to train at high intensity or may experience uncomfortable levels of dyspnea while exercising at high workloads. Interval training, wherein the patient alternates brief periods of high-intensity exercise with periods of rest or lower-intensity exercise, is an alternative option for exercise training for such persons. Previous studies have shown that interval training can also lead to improved exercise tolerance for patients with chronic obstructive pulmonary disease (Vogiatzis et al. Eur Respir J. 2002;20:12-19; Coppoolse et al. Eur Respir J. 1999;14:258-263). In this randomized, controlled, parallel group study comparing the outcomes of interval training to those of continuous, high-intensity exercise training, Vogiatzis and colleagues demonstrate that patients who undergo interval training can achieve significant gains in exercise tolerance that are comparable with those seen following conventional, constant workload exercise training. Moreover, the investigators demonstrated improvements in peak work rate and significant delay in anaerobic threshold after IT, which were associated with improved oxidative enzyme capacity, increased capillary-to-fiber ratio, and increase in type I (endurance) and IIa muscle fibers in the vastus lateralis muscle. This study provides further supportive evidence for the use of interval-type exercise training for patients with chronic obstructive pulmonary disease who may have difficulty performing continuous high-intensity exercise training.
CR