Reference equation for the incremental shuttle walk test in Portuguese children and adolescents

The incremental shuttle walk test (ISWT) is one of the most widely used field tests to assess cardiorespiratory fitness in clinical and research settings. Reference equations to predict ISWT distance in different populations and age cohorts have been established. However, an equation for the Portuguese pediatric population is not available. This study aimed to develop a reference equation for predicting ISWT in Portuguese children and adolescents.

Healthy children and adolescents aged between 5 and 17 years old were recruited. Sociodemographic (sex, age), anthropometric (height, weight) and physical activity (Physical Activity Index) data were collected. Lung function was assessed through spirometry and quadriceps muscular strength through hand-held dynamometry. The ISWT was performed twice. A reference equation was established with a multiple linear regression.

130 (60 male; 13.66±2.61y) participants with normal lung function (forced expiratory volume in one second 102.73±15.09% predicted), body mass index (BMI) (20.27±3.59kg/m²) and quadriceps muscular strength (19.75±6.84kgf), completed the assessment. 50.8% (n=66) of the participants were moderately active. Participants walked on average 1165.08±327.19m in the ISWT. Sex, age and BMI were independent contributors to the ISWT, explaining 54% of its variability (p<0.001). The derived reference equation was: ISWT=342.06+(283.07×sex)+(83.61×age)-(22.22×BMI), with female=0 and male=1.

Sex, age and BMI were found to be contributors to the ISWT predictive equation for pediatric population, providing a simple reference to assess their cardiorespiratory fitness.