Acute Effects of the 6-Minute Pegboard and Ring Test in COPD

There are few reports in the literature supporting the understanding of the physiological mechanisms of intolerance in patients with COPD to perform unsupported upper limb activities. The aims of this study were to quantify the electrical activity and oxygenation of inspiratory and upper limb muscles, and to investigate whether electromyographic manifestations of muscle fatigue are related to upper limb function as assessed by the 6-min pegboard and ring test (6PBRT) in subjects with COPD and in healthy subjects.

Thirty subjects with COPD (FEV₁ 42.1 ± 16.4% predicted; 68.0 ± 7.6 y old) comprised the COPD group, and 34 healthy subjects (66.8 ± 8.0 y old) comprised the control group. Both groups were assessed for body composition with dual-energy radiograph absorptiometry and spirometry. The 6PBRT was performed with simultaneous assessment of electromyography, near-infrared spectroscopy, and gas analyses (expiratory minute volume).

Differences were observed between groups for performance (number of rings) in the 6PBRT, with the COPD group achieving lower values than the control group (P < .001). The ventilatory demand (expiratory minute volume/maximum voluntary ventilation) and root mean square amplitude of the sternocleidomastoid muscle were higher in the COPD group than in the control group (P < .04). Lower values for oxyhemoglobin and total hemoglobin were found in intercostal muscles of the COPD group compared to the control group. The root mean square amplitude of the intercostal muscles was lower in the COPD group, while it was similar between groups for anterior deltoid and trapezius muscles. Median frequency of anterior deltoid muscles presented a decreased in both groups.

Our results indicate that the 6PBRT was performed at a higher electrical activity in the accessory inspiratory muscles, such as the sternocleidomastoid muscle, and a lower oxygenation profile in the intercostal muscles in subjects with COPD compared with healthy controls, but without muscle fatigue signs. These findings suggest that the higher ventilatory demand presented in subjects with COPD could have contributed to the worse performance in this group without signals of peripheral muscle limitation.