Influence of repeated effort induced by a 6-min walk test on postural response in older sedentary women

According to the latest recommendations, adults should exercise regularly at moderate intensity to improve aerobic fitness and body composition. However, it is unknown whether aerobic exercise at submaximal intensity has detrimental effects on balance in older sedentary adults. We explored the effects of two 6-min walk tests (6MWTs) on the postural responses in 49 sedentary women between 60 and 76 years old. We assumed that an increase in the center of pressure (COP) fluctuations or a loss in the complexity of the COP time series would be a sign of a deleterious effect on balance. We used kinematic stabilometric parameters, recurrence quantification analysis (RQA) and the central tendency measure (CTM). We refer to the measures obtained through RQA and CTM methods by dynamical measures. Repeated-measures analysis of variance showed no significant differences between the three sets of postural kinematic measures (before vs. after the first vs. after the second 6MWT). However, we observed significant differences between the three sets for the CTM measure in the antero-posterior direction (p < 0.002), RQA determinism in the medio-lateral (ML) direction (p < 0.0001), and RQA entropy in the ML direction (F = 5.93; p < 0.004).Our results indicate that the effects of moderate-intensity walking exercise on posture are not revealed by classical postural kinematic measures but only by dynamical measures. The loss of complexity in the COP time series observed after both the first and second 6MWTs may indicate presymptomatic deterioration in the postural adaptive capabilities of sedentary older women.