Introduction and objectives Quadriceps muscle strength is commonly used to assess patients with chronic obstructive pulmonary disease (COPD). However a simple endurance test is not routinely available. We wished to evaluate a simple test of muscle endurance.
Methods We developed a quadriceps muscle leg lift test whereby seated patients extended their dominant leg from 90° flexion to 0° flexion for 5 s with a weight (2 kg for Men and 1 kg for women) strapped to their ankle. They repeated cycles of flexion and extension (with 5 s hold at each extension) until exhaustion. The duration of this test and number of lifts was compared to the duration and distance walked during an endurance shuttle walk test (at the speed equivalent to 85% of maximum oxygen uptake as determined from an incremental shuttle walk test), muscle strength (using an dynometer) and the dyspnoea and fatigue domains of the Chronic Respiratory Questionnaire (CRQ).
Results 43 (30 Males) patients with COPD with mean (standard deviation) of 68.9 (9.3) years and forced expiratory volume in 1 s (FEV1) of 42.5 (13.8) percent of predicted normal completed the tests. The mean (standard deviation) quadriceps strength was 16.1 (5.0) kg, number of lifts was 12.5 (7.1) in 85.2 (48.3) s, endurance shuttle-walk test (ESWT) distance was 177.3 (89.8) m in 184.7 (88.8) s and dyspnoea and fatigue domains of the CRQ were 2.4 (1.1) and 3.3 (1.2) respectively. The correlation coefficients comparing the measures are shown in Abstract P145 Table 1.
Conclusion The endurance leg lift test was closely associated with the fatigue domain of the Chronic Respiratory Questionnaire but poorly associated with the dyspnoea domain. This new test may have some clinical utility given that it more closely relates to fatigue than either muscle strength or the endurance shuttle-walk test.