Isokinetic muscle evaluation of quadriceps in patients with chronic obstructive pulmonary disease.

Rationale: Muscle debility has a significant impact on health-related quality of life in subjects with chronic obstructive pulmonary disease (COPD), and is correlated to exacerbation and even mortality. Assessing muscle strength is extremely relevant. Lack of standardisation in numbers of sets and rest interval in isokinetic test protocol can lead to distinct results, making com- prehension and comparisons among studies difficult.

Aim: To analyse the effect of two sets and three different rest intervals on isokinetic strength measurement of quadriceps tests, in order to define the adequate test protocol.

Methods: Subjects with severe or very severe COPD underwent three isokinetic tests to evaluate knee extensor muscle strength, at an angular velocity of 60°⋅s⁻¹, with rest intervals of 30, 60 and 120 seconds. Each test consisted of two sets of five repetitions, during which peak torque, total work and fatigue index were measured.

Results: In 20 studied subjects (66.1 ± 7.4 years, 70 ± 10.8 kg, 167.4 ± 6.2 cm, FEV₁ 36.5 ± 10.1%), there were no significant differences in peak torque, total work and fatigue index, independent of number of sets or rest interval between sets.

Conclusion: In subjects with severe or very severe COPD, quadriceps muscle strength can be evaluated by an isokinetic protocol with one set of five repetitions. If two sets are performed, a rest interval of 30 seconds is enough to ensure muscle recovery between sets.