Table 5.

Reference equations for 6MWD (m) in young, middle-aged and elderly healthy subjects

Predicted 6MWDa	LLNb
Females
8.10*age + 1.61*height−0.99*weight + 22.58*active−0.10*age2 + 222.55	Subtract 96 mb
Males
26.80*age + 8.46*height−0.45*weight−2.54*active−0.06*age2−0.13*age*height−890.18	Subtract 122 mb

Age is expressed in years, height is measured in centimeters (cm) and weight in Kilograms (Kg). Active is a dichotomous variable: its value is 1 when the subject is physically active, it is 0 otherwise; subjects who performed physical activity with a frequency of ‘‘2–3 times a week’’ or more and with a duration of ‘‘about 1 h a week’’ or more were classified as ‘‘active’’, the remaining subjects as ‘‘not active’’

^aThe reference equations for females and males presented in this table were calculated considering that the coefficient estimates were obtained with centered variables

^bLLN = predicted mean—1.645 * RSD, where RSD is the residual standard deviation of the estimated regression and −1.645 is the z-score used to detect if the measured value of the 6MWD is lower than the 95% of the subjects with the same age, height, weight and level of physical activity