Screening For Physical Inactivity In Adults: The Value Of Six-minute Walk Distance

Purpose:: Objectively measured physical inactivity (PI) has been described as predictor of mortality in adults. However, the assessment of physical activity in daily life by activity monitors is not feasible in clinical practice. We aimed to identify physical fitness tests able to predict PI in adults.

Methods: : A total of 120 participants (38 ± 14 years; 45 men) wore an activity monitor (Actigraph GT3x+) for seven days. Physical inactivity was defined as less than 150 min.wk-1 of moderate to vigorous physical activity in daily life. We assessed cardiopulmonary exercise testing, body composition (bioelectrical impedance), quadriceps and biceps isokinetic muscle function, handgrip strength, postural balance (force platform), and six-minute walk test (6MWT) and its physiologic responses (k4b2, COSMED). We fitted ROC curves for determining best physical fitness tests able to diagnose PI according to values of sensitivity (S), specificity (Sp), and area under the curve (AUC). We also evaluated this associations in multiple logistic regression adjusted by age, sex and the main physical fitness variables.

Results: The prevalence of PI in the present study was 25%. As expected, steps/day (≤ 5577) was the strongest predictor of PI (S = 100%; Sp = 84%; AUC = 0.956). The best physical fitness test for predicting PI was the 6MWT ≤ 522 m (S = 65%; Sp = 93%; AUC = 0.817) and ≤ 96% of predicted (S = 71%; Sp = 82%; AUC = 0.799). Body fat > 25% was also a signifi cant (S = 85%; Sp = 54%; AUC = 0.712). After multiple logistic regression, steps/day (Odds ratio, 0.998; CI95%, 0.997 – 0.999) and 6MWD (0.989; 0.979 – 0.999) remained as predictors of PI.

Conclusions: Among several physical fitness variables, the functional exercise capacity (i.e., 6MWT) may be an alternative strategy for screening for PI in adults. The 6MWT might be included in epidemiological studies as a more simple and cheaper tool for screening for PI in general population.