Association between maximal and submaximal field tests in cystic fibrosis with impaired glucose tolerance

<bold>Background:</bold> Use of incremental shuttle walk test (ISWT) in cystic fibrosis with impaired glucose tolerance (CF-IGT) is infrequent. <bold>Aim:</bold> To compare ISWT and six-minute walk test (6MWT) findings in CF-IGT and to investigate relationship between exercise parameters, clinical characteristics, lung function, and muscle strength. <bold>Methods:</bold> Twenty-six patients with CF-IGT (mean age=14.5±2.2 years, mean FEV₁=82±23%) were included. HbA1c (6.36±1.44%), fasting and postprandial glucose and insulin levels (109.7±48.8 mmol/l, 136.2±50.7 mmol/l, 7.5±8.2 µU/ml, and 46.9±43.8 µU/ml, respectively) were recorded. Lung function, maximal inspiratory and expiratory (MEP) muscle strength, and handgrip strength (HGS) were measured. Exercise capacity was assessed using 6MWT and ISWT. Changes in heart rate (HR), blood pressure (BP), and oxygen saturation (SpO₂) were measured and dyspnea and fatigue perception (modified Borg Scale) were recorded before and after the tests. <bold>Results:</bold> 6MWT and ISWT distances were 564.6±138.3 m and 612.6±260.5 m, respectively (p=0.20). Intraclass correlation coefficient between tests was 0.794 (p<0.001), and Cronbach's alpha was 0.802. Changes in HR, dyspnea, and fatigue, and peak HR were higher in ISWT (p<0.05). 6MWT distance was associated with FEV₁ (r=0.576), MEP (r=0.391), and HGS (r=0.452, p<0.05). ISWT distance was related to FEV₁ (r=0.611), MEP (r=0.425), HGS (r=0.526), and 6MWT distance (r=0.729, p<0.05). <bold>Conclusion:</bold> ISWT distance showed good correlation and consistency with 6MWT. It was associated with lung function, MEP, and HGS in patients with CF-IGT. ISWT can be used to assess exercise capacity in CF-IGT.