Reliability of quadriceps muscle power and explosive force, and relationship to physical function in people with chronic obstructive pulmonary disease: an observational prospective multicenter study.

Background: Muscle power declines with age and is a stronger determinant of physical function than strength. Muscle power using computerized dynamometry has not been investigated in COPD.Objectives: To determine: 1) test-retest reliability of quadriceps power using a standardized protocol with computerized dynamometry; and 2) associations between quadriceps strength and power, and functional capacity.Design/Setting: Prospective observational study in four Canadian research labs.Participants: People with mild to very severe COPD.Methods: Tests were conducted on two days. Quadriceps muscle maximal strength was evaluated during a static maneuver using maximal voluntary isometric contractions (MVIC). Rate of torque development (RTD) during MVIC was used to assess explosive force. Muscle power was measured using a dynamic, isotonic protocol from which peak and average power and peak velocity were derived. Functional capacity was assessed with the Short Physical Performance Battery (SPPB). Reliability was assessed using intraclass correlation coefficients (ICC), standard error of measurements (SEM), and Bland Altman plots. Spearman and Pearson correlation coefficients were used for associations.Results: 65 patients (age 69 ± 8 years; FEV1 48 ± 21% of predicted) were included. ICC was 0.77 for RTD and 0.87-0.98 for isotonic power measures (95%CI 0.63-0.99, p < .001); SEM < 10% for average/peak power and peak velocity, and > 30% for RTD. SPPB had moderate correlation with average power, but not with MVIC or RTD.Conclusion: The standardized isotonic protocol with computerized dynamometry was reliable in assessing quadriceps power in COPD. Our data highlights that average power correlates best with functional capacity, indicating higher relevance than static measures when investigating determinants of function.

Measuring and monitoring skeletal muscle function in COPD: current perspectives.

Skeletal muscle dysfunction is an important systemic consequence of chronic obstructive pulmonary disease (COPD) that worsens the natural cause of the disease. Up to a third of all people with COPD express some form of impairment which encompasses reductions in strength and endurance, as well as an increased fatigability. Considering this complexity, no single test could be used to measure and monitor all aspects of the impaired skeletal muscle function within the COPD population, resulting in a wide range of available tests and measurement techniques. The aim of the current review is to highlight current and new perspectives relevant to skeletal muscle function measurements within the COPD population in order to provide guidance for researchers as well as for clinicians. First of all, standardized and clinically feasible measurement protocols, as well as normative values and predictive equations across the spectrum of impaired function in COPD, are needed before assessment of skeletal muscle function can become a reality in clinical praxis. This should minimally target the quadriceps muscle; however, depending on the objective of measurements, eg, to determine upper limb muscle function or walking capacity, other muscles could also be tested. Furthermore, even though muscle strength measurements are important, current evidence suggests that other aspects, such as the endurance and power capacity of the muscle, should also be considered. Moreover, although static (isometric) measurements have been favored, dynamic measurements of skeletal muscle function should not be neglected as they, in a larger extent than static measurements, are related to tasks of daily living. Lastly, the often modest relationships between functional tests and skeletal muscle function measurements indicate that they evaluate different constructs and thus cannot replace one another. Therefore, for accurate measurements of skeletal muscle function in people with COPD, specific and formal measurements should still be prioritized.

The Relevance of Limb Muscle Dysfunction in Chronic Obstructive Pulmonary Disease: A Review For Clinicians.

"Chronic obstructive pulmonary disease (COPD) is often accompanied by extrapulmonary manifestations such as limb muscle dysfunction. This term encompasses several features, including atrophy, weakness, and reduced oxidative capacity. Clinicians should become accustomed with this manifestation of COPD because of its relevance for important outcomes such as exercise tolerance and survival. Measuring muscle strength and mass can be performed with simple and valid tools that could be implemented in clinical practice. One identified, limb muscle dysfunction is amenable to therapy such as exercise training that has been repeatedly shown to improve muscle mass, strength, and oxidative capacity in COPD."

Fixed Handheld Dynamometry Provides Reliable and Valid Values for Quadriceps Isometric Strength in People With Chronic Obstructive Pulmonary Disease: A Multicenter Study.

BACKGROUND: Quadriceps weakness is associated with poor clinical outcomes in chronic obstructive pulmonary disease (COPD). However, quadriceps isometric strength assessment has not been routinely adopted in clinical practice because of the lack of homogeneity in the devices and protocols and the lack of reliability studies. OBJECTIVE: The objectives of this study were to determine the test-retest reliability and the criterion validity of a commercially available handheld dynamometer for evaluating the quadriceps isometric maximal voluntary contraction (iMVCquad) using a standardized protocol and to investigate the relationship between iMVCquad and functional capacity in people with COPD. DESIGN: This was a prospective, observational, multicenter trial. METHODS: Participants with mild to severe COPD from 4 Canadian sites were tested on 2 separate days. Five iMVCquad measurements were obtained following a standardized procedure with a fixed handheld dynamometer (iMVCquad-HHD), and then 5 iMVCquad measurements were obtained with a computerized dynamometer (iMVCquad-CD; the gold standard). Functional capacity was assessed with the Short Physical Performance Battery. Intraclass correlation coefficients, standard errors of measurement, Bland-Altman plots, and Spearman correlation coefficients were used for analyses. RESULTS: Sixty-five participants (mean age = 69 years [SD = 8]; forced expiratory volume in 1 second = 48% of predicted value [SD = 21]) completed the study. The mean iMVCquad-HHD values on visits 1 and 2 were 102.7 (SD = 51.6) and 105.6 (SD = 58.8) N·m, respectively; the standard error of measurement was 11.4 N·m. The between-visits intraclass correlation coefficient for iMVCquad-HHD was 0.95 (95% confidence interval  = 0.92-0.97), with a mean bias of 2.0 (Bland-Altman plot). There was a strong correlation between iMVCquad-HHD and iMVCquad-CD (Spearman correlation coefficient = 0.86). There was no correlation between iMVCquad-HHD and Short Physical Performance Battery total score. LIMITATIONS: Participants had stable COPD with few comorbidities and were more physically active than the general population of people with COPD; results might not be applicable to patients with acute exacerbations of the disease or more comorbidities. Assessment order between handheld and computerized dynamometers has not been randomized, but analyses did not highlight any systematic bias or learning effect. CONCLUSIONS: Quadriceps strength assessment can be implemented in a reliable and valid way in people with COPD using a fixed handheld dynamometer and standardized procedure. This protocol should be established in clinical practice to facilitate the assessment of muscle strength in people with COPD.

Functional Tests in Chronic Obstructive Pulmonary Disease, Part 1: Clinical Relevance and Links to the International Classification of Functioning, Disability, and Health.

Chronic obstructive pulmonary disease is a major cause of morbidity and mortality worldwide and an important cause of disability. A thorough patient-centered outcome assessment, including not only measures of lung function, exercise capacity, and health-related quality of life, but also functional capacity and performance in activities of daily life, is imperative for a comprehensive management of chronic obstructive pulmonary disease. This American Thoracic Society Seminar Series is devoted to help clinicians substantiate their choice of functional outcome measures in this population. In Part 1 of this two-part seminar series, we describe the various domains of functional status to elucidate terms and key concepts intertwined with functioning and to demonstrate the clinical relevance of assessing functional capacity in the context of activities of daily living in agreement with the International Classification of Functioning, Disability, and Health. We hope that a better understanding of the various defining components of functional status will be instrumental to healthcare providers to optimize chronic obstructive pulmonary disease evaluation and management, ultimately leading to improved quality of life of patients afflicted by this condition. This first article also serves as an introduction to Part 2 of this seminar series, in which the main functional tests available to assess upper and lower body functional capacity of these patients are discussed.

Functional Tests in Chronic Obstructive Pulmonary Disease, Part 2: Measurement Properties.

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality worldwide and an important cause of disability and handicap. For a thorough patient-centered outcome assessment and comprehensive management of the disease, measures of lung function, exercise capacity, and health-related quality of life, but also of functional capacity in activities of daily life, are necessary. In Part 2 of this seminar series, we discuss the main functional tests to assess upper and lower body functional capacity in patients with COPD to help clinicians substantiate their choice of functional outcome measures in COPD. In agreement with the International Classification of Functioning, Disability and Health to assess functional capacity representative of daily life activities, this review focuses on functional tests that include components such as changing and maintaining body positions, walking, moving, and climbing, as well as carrying, moving, and handling objects. We review the validity, reliability, and responsiveness of these tests. With 11 links to the International Classification of Functioning, Disability and Health framework addressing several upper and lower body components of functional activities, the Glittre Activities of Daily Life test seems to be the most promising and comprehensive test to evaluate functional capacity in activities of daily life. The links between functional capacity tests and real participation in daily life, as well as with important clinical outcomes such as morbidity and mortality, need further investigation. More studies are also recommended to document minimal detectable changes, minimal clinically important differences, and normative values for these functional tests.

Adaptations in limb muscle function following pulmonary rehabilitation in patients with COPD - a review.

Even though chronic obstructive pulmonary disease (COPD) is primarily a disease of the respiratory system, limb muscle dysfunction characterized by muscle weakness, reduced muscle endurance and higher muscle fatigability, is a common secondary consequence and a major systemic manifestation of the disease. Muscle dysfunction is especially relevant in COPD because it is related to important clinical outcomes such as mortality, quality of life and exercise intolerance, independently of lung function impairment. Thus, improving muscle function is considered an important therapeutic goal in COPD management. Pulmonary rehabilitation (PR) is a multidisciplinary, evidence-based and comprehensive approach used to promote better self-management of the disease, minimize symptom burden, optimize functional status, and increase participation in activities of daily life. Exercise training, including cardiovascular and muscle exercises, is the cornerstone of PR and is considered the best available strategy to improve exercise tolerance and muscle function among patients with COPD. This paper addresses the various components of exercise training within PR used to improve limb muscle function in COPD, providing clinicians and health-care professionals with an overview and description of these various exercise modalities and of their effects on limb muscle function. Guidance and recommendations to help design optimal limb muscle training regimens for these patients are also presented.