Cutoff points for the 1-RM test and their association with mortality in COPD

Introduction: There is no available cutoff for the 1-repetition maximum (1RM) test of knee extensor muscles associated with prognosis in patients with chronic obstructive pulmonary disease (COPD). Aims: To determine 1RM cutoffs for the knee extensors and to verify their association with mortality in COPD. Methods: In a preliminary analysis of a multicenter study, 170 patients performed the 1RM test of knee extensors (52%♂; 66±8yrs; FEV1 46±15%pred). Cutoffs for 1RM and 1RM/Body Weight ratio (1RM/BW) were identified by ROC curve analysis in a subgroup of patients (n=114; 68 from Brazil; 46 from Portugal). They were classified as either normal (≥80%pred) or low ( Results: The best discriminative cutoffs (1RM♀: 22kg; 1RM♂: 34kg; 1RM/BW♀: 25%; 1RM/BW♂: 48%) were tested in Kaplan-Meier analysis (Figure 1). Respectively, 40% and 41% of patients classified as ‘low strength’ according to 1RM and 1RM/BW cut-offs died in 4 years, in comparison to 0% and 20% in those with normal strength (P>0.05). Cox regression adjusted for confounders was not statistically significant. Conclusion: New gender-based knee extensors 1RM cutoffs adjusted or not for body weight were provided, although they were not yet statistically associated with mortality in this preliminary analysis.