Assessing the robustness of muscle strength and physical performance measures in women older than 40 years: a test-retest reliability study

This study investigated the test-retest reliability and minimal detectable change of muscle strength and physical performance tests in women aged over 40 years. ObjectivesThis study investigated the test-retest reliability and minimal detectable change (MDC) of muscle strength and physical performance tests in women older than 40 years.MethodsA total of 113 women, aged 58 +/- 11 years (82% postmenopausal women), with a body mass index of 28.5 +/- 5.8 kg/m2, participated in this study. One-repetition maximum (1RM) tests were conducted for seven strength exercises: 45 degrees leg press, bench press, leg extension, pec deck, wide-grip lateral pull-down, leg curl, and seated cable row, with a retest after 48 hours. Timed Up and Go (TUG), 6-minute walk, and 30-second sit-to-stand tests were performed on the same day and retested after 72 hours. The tests and retests were administered by the same evaluators. Relative reliability (consistency of participant rank between test-retest) was assessed using the intraclass correlation coefficient for consistency and agreement, and absolute reliability (precision of score) was assessed using the MDC based on the standard error of prediction.ResultsThe 1RM and performance tests exhibited excellent reliability: 45 degrees leg press (consistency, 0.99; agreement, 0.98), bench press (consistency, 0.96; agreement, 0.96), leg extension (consistency, 0.93; agreement, 0.91), pec deck (consistency, 0.90; agreement, 0.88), wide-grip lateral pull-down (consistency, 0.91; agreement, 0.89), leg curl (consistency, 0.84; agreement, 0.83), seated cable row (consistency, 0.92; agreement, 0.94), TUG (consistency, 0.87; agreement, 0.87), 6-minute walk (consistency, 0.96; agreement, 0.95), and 30-second sit to stand (consistency, 0.85; agreement, 0.80). These tests showed meaningful MDC values, particularly for the 1RM test performed on the machine and the 30-second sit-to-stand test: 45 degrees leg press, 22.2 kg (15%); bench press, 4.9 kg (19%); leg extension, 9.2 kg (35%); pec deck, 8.8 kg (44%); wide-grip lateral pull-down, 9.4 kg (31%); leg curl, 9.2 kg (51%); seated cable row, 11.4 kg (29%); TUG, 1.4 seconds (20%); 6-minute walk, 50.9 m (10%); and 30-second sit to stand, 4.6 reps (30%).ConclusionsAlthough the muscle strength and physical performance tests demonstrate excellent relative reliability in women older than 40 years, they exhibit low absolute reliability, particularly the 1RM test performed on the machine and the 30-second sit-to-stand test. Therefore, although these tests show good consistency in the positioning of women within the group after repeated measures, their precision measure is relatively low (high fluctuation). Changes in these tests that are smaller than the MDC may not indicate real changes in women at middle age and older.