<p>Measuring and monitoring skeletal muscle function in COPD: current perspectives</p>

Abstract

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.

Targeting Limb Muscle Dysfunction in COPD

“…Assessment of limb muscle mass and function should always be a priority within clinical praxis of COPD management, due to its clinical and prognostic relevance [4,54,55].…”

“…Considering the complexity of limb muscle dysfunction in COPD, no single test could be used to assess and monitor all aspects of the limb muscles within the COPD population, resulting in a wide range of available tests and measurement techniques [14,[54][55][56].…”

“…When deciding on how to assess limb muscles in clinical practice, several factors should be considered and will influence the choice of technique and strategy used. Table 1 highlights some factors that physiotherapists need to take into account when making this decision [55].…”

“…Furthermore, the availability of measurement equipment will likely vary between clinical settings and contexts, thus impacting the choice of the assessment strategy. The physiotherapist needs to acknowledge that measurement equipment and assessment strategies are not interchangeable and may provide different information even if the goal of the assessment would be the same [55,57].…”

“…before an assessment), equipment (e.g., free weight/weight-machines/ dynamometers), instructions (e.g., written/oral/visual), familiarization (to minimize learning effect), warm-up (e.g., general vs. specific warm-up of targeted muscles), positioning, the range-of-motion (e.g., start and end positions), velocity (e.g., seconds in concentric/ eccentric phase of movement), and rest (between contractions/sets, etc.). For further details on what to consider to standardize assessments, we refer to previously published work [42,54,55].…”