Validade e confiabilidade do teste do degrau incremental modificado para avaliação da capacidade funcional em indivíduos com diabetes tipo 2

Abstract

Individuals with Type 2 Diabetes (T2D) may exhibit reduced cardiorespiratory fitness due to a combination of changes in peripheral muscle fibers, cardiac dysfunction, and autonomic impairment. The gold standard for this evaluation is the cardiopulmonary exercise test (CPET), but this is a costly procedure and, therefore, not widely accessible to the general population. The six-minute walk test (6MWT) is a validated field test for assessing functional capacity in T2D; however, the physical space required for its implementation may limit its widespread use. The modified incremental step test (MIST) is a simple, low-cost field test that requires minimal physical space and has good practical applicability. Nonetheless, it has not yet been validated for assessing functional capacity in individuals with T2D. Therefore, the primary aim of this study was to investigate whether the MIST is valid and reliable for assessing functional capacity in individuals with T2D. The secondary objectives were to compare cardiovascular responses and perceived exertion between the CPET and field tests, including the 6MWT. This was a methodological, multicenter study conducted in Juiz de Fora and Belo Horizonte, involving volunteers of both sexes aged ≥18 years with a self-reported diagnosis of T2D. Participants underwent a detailed anamnesis for the collection of sociodemographic and clinical data and were subjected to a CPET (only in the Belo Horizonte center) and two repetitions each of the 6MWT and MIST. The criterion validity of the MIST was assessed by analyzing Pearson correlation coefficients between the number of steps achieved in the MIST and (1) peak oxygen consumption (VO₂ peak, L/min) measured during CPET and (2) the distance covered in meters during the 6MWT. Test-retest reliability of the MIST was evaluated using the intraclass correlation coefficient (ICC) calculated for the total number of steps climbed during the first and second tests. Fifty volunteers participated in the study (50% women; age 56.9 ± 11.4 years; T2D duration 10.2 ± 7.6 years). The criterion validity of the MIST was confirmed by identifying moderate to high correlations between the number of steps climbed in the MIST and (1) VO₂ peak (L/min) achieved in CPET (n = 18; r = 0.53; p < 0.001) and (2) distance covered in the 6MWT (meters) (n = 50; r = 0.65; p < 0.001). The ICC indicated adequate test-retest reliability of the MIST (ICC [95% CI]: 0.64 [0.44–0.78]). Compared to the CPET, the MIST exhibited lower deltas in heart rate (HR) (ΔHR-MIST = 40.7 ± 15.6 bpm vs. ΔHR-CPET = 70.5 ± 22.5 bpm, p < 0.001), systolic blood pressure (SBP) (ΔSBP-MIST = 29.3 ± 19.4 mmHg vs. ΔSBPCPET = 57.0 ± 22.6 mmHg, p < 0.001), diastolic blood pressure (DBP) (ΔDBP-MIST = -1.2 ± 7.3 mmHg vs. ΔDBP-CPET = 11.1 ± 10.5 mmHg, p < 0.001), final perceived exertion (PE) (PE-MIST = 4.3 ± 2.6 vs. PE-CPET = 8.6 ± 1.7, p < 0.001), and percentage of maximum HR achieved (MIST = 40.7 ± 15.6% vs. CPET = 70.5 ± 22.5%, p < 0.001). Compared to the 6MWT, the MIST showed higher deltas in HR (ΔHR-MIST = 41.6 ± 16.0 bpm vs. ΔHR-6MWT = 33.2 ± 12.6 bpm, p < 0.001) and final PE (PE-MIST = 4.5 ± 2.1 vs. PE-6MWT = 3.5 ± 1.6, p < 0.001), as well as a higher percentage of maximum HR achieved (MIST = 73.2 ± 9.9% vs. 6MWT = 68.4 ± 9.9%, p < 0.001). The MIST proved to be a valid and reliable test for assessing functional capacity in individuals with T2D. Furthermore, the MIST exhibited more intense cardiovascular and perceived exertion responses compared to the 6MWT.