Classification(s): Exercise Testing; Pulmonary Rehabilitation
Introduction: One of the goals of pulmonary rehabilitation is to improve functional ability through improvements in muscular strength. Traditional strength measurement techniques are more appropriate for laboratory than clinical settings. Functional fitness tests have been proposed as surrogate measures for strength testing in clinical settings, yet the validity of functional fitness tests as surrogates for strength has not been clearly established.
Purpose: This study evaluated the relationship of functional fitness field tests to objective laboratory measures of strength in 40 older (70 +/- 1 years), frail (FEV1 1.0 +/- 0.08, FEV1/FVC% = 60.2 +/- 3.0) adults enrolled in pulmonary rehabilitation.
Design: This was a correlation study using data collected from two time-contiguous studies in a single pulmonary rehabilitation program to determine the ability of functional fitness tests to predict absolute strength.
Methods: Participants completed two trials of upper (incline chest press) and lower (seated leg press) body maximal strength (1RM) testing and a single trial of functional fitness testing (arm curl, lift and reach, chair stand, up and go). Intra-class correlations (ICC) were used to ensure test-retest reliability between strength trials. Pearson correlation analysis was used to estimate the strength of the relationship between maximal strength and functional fitness tests.
Results: ICC coefficients demonstrated a strong relationship between both trials of the chest press (r = 0.98, P < .001) and leg press (r = 0.94, P < .001). Among upper body functional fitness tests, the arm curl test had a moderately strong relationship with both chest press trials (trial 1: r = 0.55, P = .01; trial 2: r = 0.56, P = .01) while the lift and reach test did not. For lower body functional fitness tests, the chair stand test had a fairly strong relationship with both leg press trials (trial 1: r = 0.46, P = .1; trial 2: r = 0.38, P = .05) although the up and go test did not.
Conclusions: 1RM test results were found to be highly reliable measures of strength. However, only the arm curl and chair stand tests were found to be valid surrogate measures in these elderly, frail adults. Although it may be desirable to have multiple field tests that can be used to measure strength outside of a laboratory setting, these data support limiting functional testing to the arm curl for upper body and the chair stand test for lower body strength assessment.