Background

The 6-minute walk test (6MWT) is extensively utilized to evaluate function of patients with morbid obesity and is a safe, straightforward assessment. However, existing reference equations overlook patients with morbid obesity. This retrospective study aimed to create a 6MWT reference equation tailored for this population and compared it to an existing model by Capodaglio et al., which included patients with an average BMI of 43 kg/m² and a mean age of 35.Subjects295 patients with morbid obesity were included, each evaluated by a single Physical Therapist between 2017 and 2023. The study comprised 252 females and 43 males, with an average BMI of 48.2 kg/m² and an average age of 43.

Methods

We conducted a multiple linear regression analysis to develop a new reference equation for predicting 6MWT performance using 85% of the study sample. The remaining 15% of the sample was employed for cross-validation. Subsequently, our model was compared to Capodaglio et al.'s equation using the Wilcoxon test.

Results

Our regression model yielded the equation: 6MWT=958.5620−(4.2143×Age;years −(5.4342×BMI;kg/m2)−(43.2640×Gender;0=male;1=female). Our predicted values were statistically lower than those reported by Capodaglio et al (p-value < 0.001) with an average difference of 6.52%. This difference was most significant in patients over age 60, with a 16.31% deviation, while those aged 40 and younger showed only a 1.55% deviation.

Conclusions

A 6MWT reference equation for patients with morbid obesity was formulated. Our study yielded statistically lower predicted values than Capodaglio et al.'s model, with the greatest difference in patients aged over 60.