Purpose: Reduced maximal, peripheral muscle strength is associated with exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). Therefore, it is important to accurately evaluate muscle strength to identify patients with muscle weakness and to prescribe adequate loads for resistance training. The objective here was to systematically identify and summarize the literature on measurement of peripheral muscle strength in individuals with COPD and to make recommendations for strength testing in clinical and research settings.
Methods: A literature search was conducted of electronic databases between 1999 and 2009 of all English language articles utilizing muscle strength measurements.
Results: The search resulted in retrieval of 178 articles, of which 66 were reviewed. Isometric muscle strength was measured using handgrip (n = 30), strain gauge (n = 15), computerized dynamometer (n = 13), magnetic stimulation (n = 8), handheld dynamometer (n = 6), or manual testing (n = 3). Isotonic muscle strength was measured using a hydraulic system (n = 3) or 1-repetition maximum (n = 9), and isokinetic muscle strength was measured using computerized dynamometer (n = 16). Methodological issues such as limb position, number of trials, subject familiarization, test instructions, rest periods, and muscle group tested were all identified as important variables to consider when developing a strength-testing protocol.
Conclusion: Muscle strength has been measured in people with COPD using similar methods as in other clinical populations. Each method presents advantages and disadvantages that need to be considered when selecting the most relevant measure. Standardization of the test procedures is essential in both clinical and research settings to obtain valid and reliable measurements of muscle strength.