The 6-minute walk-test in type 2 diabetics predicts to some extent maximal aerobic capacity but not its training-induced improvement

Abstract

Objective: Six- minutes’ walk-test (6MWT) is a measure of physical fitness widely studied and validated in chronic pathologies with sedentary lifestyles. It is an aerobic fitness test, correlated with maximum oxygen consumption (VO2max) in some studies, but this correlation is not well established in diabetes. We assessed the extent to which it predicts VO2max and its training-induced changes in type 2 diabetics. Materials and methods: Twenty-five type 2 diabetics were randomized and divided into two groups: 13 completed a physical training program (eight hospital education sessions continued at home through two weekly 30-45-minute sessions at an intensity corresponding to the first ventilatory threshold VT1) and the remaining 12 continued their usual treatment unchanged. Results: After 1 year training maintained maximum aerobic capacity, while it decreased significantly in the untrained group (p=0.014). Voorrips’ activity score was correlated with VO2max (r= 0.44, p= 0.05) and with the distance walked at 6MWT (r=0.446, p=0.05). The distance walked during 6MWT is correlated with VO2max before (r= 0.456 p= 0.05) and after (r= 0.714 p<0.001) and on all values measured before and after (r= 0.571 p= 0.01). The change in MWT does not predict that of VO2max to which it is not correlated (r=0.318; NS), but it is weakly correlated to that of the VT1 (r= 0.435 p-0.05) while the absolute values of VT1 and 6MWT are not correlated at all. 6MWT was not correlated with HbA1c. Conclusions: as in other sedentary populations, 6MWT is an indicator (approximate but easy and economical) of aerobic fitness. However, it does not measure training-induced changes in aerobic fitness, its variations being rather a marker of those of the first ventilatory threshold.