Upper-limb intervalversusconstant-load exercise in patients with COPD: a physiological crossover study

Abstract

ObjectiveUpper-limb exercise is recommended for patients with COPD, albeit there are limited data concerning the optimal modality to implement. We compared interval (INT-EX) to continuous (CONT-EX) upper-limb exercise in terms of exercise tolerance, ventilatory and metabolic responses when both conditions were sustained at an equivalent work rate.Methods26 stable COPD patients undertook three upper-limb exercise sessions to initially establish peak work rate (PWR)viaan incremental exercise test and subsequently two equivalent work rate tests to the limit tolerance in balanced order: 1) INT-EX consisting of 30-s work at 100% PWR interspersed with 30-s work at 40% of PWR; and 2) CONT-EX at 70% PWR.Results20 patients (76.9%) had longer tolerance during INT-EX, while six out of 26 (23.1%) exhibited longer tolerance during CONT-EX. The average endurance time was 434.1±184.7 and 315.7±128.7 s for INT-EX and CONT-EX, respectively. During INT-EX at isotime (i.e.when work completed was the same between INT-EX and CONT-EX), the majority of patients manifested lower oxygen uptake, minute ventilation, pulmonary hyperinflation, heart rate, symptoms and higher CO2blood concentration. Patients with longer INT-EX had a lower comorbidity score (Cumulative Illness Rating Scale: 1.58±0.30versus1.88±0.29, p=0.0395) and better-preserved lung function (forced vital capacity 84.7±15.31%versus67.67±20.56%, p=0.0367; forced expiratory volume in 1 s 57.15±14.59versus44.67±12.99% predicted, p=0.0725) compared to patients with longer CONT-EX.ConclusionINT-EX is more sustainable than CONT-EX for the majority of COPD patients with moderate obstruction, leading to lower dynamic hyperinflation and symptoms at isotime. Further studies need to define the benefits of its application during pulmonary rehabilitation.