Submaximal Eccentric Cycling in People With COPD: Acute Whole-Body Cardiopulmonary and Muscle Metabolic Responses

Abstract

Background: Eccentric cycling (ECC) may be an attractive exercise method in COPD because of both low cardiorespiratory demand and perception of effort compared with conventional concentric cycling (CON) at matched mechanical loads. However, it is unknown whether ECC can be performed by individuals with COPD at an intensity able to cause sufficient metabolic stress to improve aerobic capacity.

Research question: What are the cardiopulmonary and metabolic responses to ECC in people with COPD and healthy volunteers when compared with CON at matched mechanical loads?

Study design and methods: Thirteen people with COPD (mean ± SD age, 64 ± 9 years; FEV₁, 45 ± 19% predicted; BMI, 24 ± 4 kg/m²; oxygen uptake at peak exercise [V̇O_2peak], 15 ± 3 mL/kg/min) and 9 age-matched control participants (FEV₁, 102 ± 13% predicted; BMI, 28 ± 5 kg/m²; V̇O_2peak, 23 ± 5 mL/kg/min), performed up to six 4-min bouts of ECC and CON at matched mechanical loads of increasing intensity. In addition, 12 individuals with COPD underwent quadriceps muscle biopsies before and after 20 min of ECC and CON at 65% peak power.

Results: At matched mechanical loads, oxygen uptake, minute ventilation, heart rate, systolic BP, respiratory exchange ratio (all P < .001), capillary lactate, perceived breathlessness, and leg fatigue (P < .05) were lower in both groups during ECC than CON. Muscle lactate content increased (P = .008) and muscle phosphocreatine decreased (P = .012) during CON in COPD, which was not evident during ECC.

Interpretation: Cardiopulmonary and blood lactate responses during submaximal ECC were less compared with during CON at equivalent mechanical workloads in healthy participants and COPD patients, and this was confirmed at a muscle level in COPD patients. Submaximal ECC was well tolerated and allowed greater mechanical work at lower ventilatory cost. However, in people with COPD, a training intervention based on ECC is unlikely to stimulate cardiovascular and metabolic adaptation to the same extent as CON.

Keywords: COPD; eccentric; exercise; oxygen uptake.