To characterize physiological responses to a 1-minute sit-to-stand test (STS) and assess correlations with cardiopulmonary exercise test (CPET) variables, nutritional status, pulmonary function, and quadriceps muscle strength in cystic fibrosis (CF) patients. Subjects aged 6–18 years with a genetic diagnosis of CF were enrolled in this cross-sectional study. After collecting demographic, anthropometric, and clinical data the following tests were performed: pulmonary function (spirometry), aerobic fitness (CPET), STS, and isometric quadriceps muscle strength (hand-held dynamometry). Data collection was performed on the same day. The study sample comprised 17 children (9.8 ± 1.6 years) and adolescents (13.7 ± 1.5 years) with a mean forced expiratory volume in one second (FEV₁) of  − 0.80 ± 1.61 (z-score). In the CPET, peak exercise oxygen consumption (VO₂peak) was 35.1 ± 4.2 mL.kg⁻¹.min⁻¹, while in the STS mean number of repetitions was 32.5 ± 6.2 and total work (repetitions × body mass) was 1326.9 ± 379.6. At peak exercise, CPET elicited higher heart rate (p = .001) and subjective sensation of dyspnea (p = .001) compared to STS, though no significant differences were observed in peripheral oxygen saturation. Moderate and significant correlations were identified between total workload (CPET) and repetitions adjusted for body weight (r = 0.684; p = .002) and between STS repetitions and muscle strength corrected for body weight (r = 0.531; p = .034). No significant correlations were found with nutritional status (BMI), pulmonary function (FEV₁), or other aerobic fitness variables (VO₂ at ventilatory threshold or VO₂peak). In children and adolescents with CF, compared to CPET, the STS test elicits a submaximal cardiorespiratory response that is mostly dependent on quadriceps muscle strength.

To characterize physiological responses to a 1-minute sit-to-stand test (STS) and assess correlations with cardiopulmonary exercise test (CPET) variables, nutritional status, pulmonary function, and quadriceps muscle strength in cystic fibrosis (CF) patients. Subjects aged 6–18 years with a genetic diagnosis of CF were enrolled in this cross-sectional study. After collecting demographic, anthropometric, and clinical data the following tests were performed: pulmonary function (spirometry), aerobic fitness (CPET), STS, and isometric quadriceps muscle strength (hand-held dynamometry). Data collection was performed on the same day. The study sample comprised 17 children (9.8 ± 1.6 years) and adolescents (13.7 ± 1.5 years) with a mean forced expiratory volume in one second (FEV₁) of  − 0.80 ± 1.61 (z-score). In the CPET, peak exercise oxygen consumption (VO₂peak) was 35.1 ± 4.2 mL.kg⁻¹.min⁻¹, while in the STS mean number of repetitions was 32.5 ± 6.2 and total work (repetitions × body mass) was 1326.9 ± 379.6. At peak exercise, CPET elicited higher heart rate (p = .001) and subjective sensation of dyspnea (p = .001) compared to STS, though no significant differences were observed in peripheral oxygen saturation. Moderate and significant correlations were identified between total workload (CPET) and repetitions adjusted for body weight (r = 0.684; p = .002) and between STS repetitions and muscle strength corrected for body weight (r = 0.531; p = .034). No significant correlations were found with nutritional status (BMI), pulmonary function (FEV₁), or other aerobic fitness variables (VO₂ at ventilatory threshold or VO₂peak). In children and adolescents with CF, compared to CPET, the STS test elicits a submaximal cardiorespiratory response that is mostly dependent on quadriceps muscle strength.