"It ain't what you do, it's the way that you do it": does obesity affect perceptual motor control ability of adults on the speed and accuracy of a discrete aiming task?

Obesity impairs performing and learning a timing perception task regardless of the body position

Obesity has been associated with poorer sensorimotor performance. However, it remains unclear whether these obesity-related impairments can be mitigated by practice. In the present study, we sought to investigate the effects of practice on performing and learning a temporal estimation task, in women with and without obesity. The experimental task consisted of synchronizing the arrival of two rectangles at a target point. Limited to the pressing of a switch, the task was intended to minimize possible muscular fatigue, self-generated perturbations to balance and the need to accelerate/decelerate body segments. Participants were allowed to choose the displacement velocity of the rectangle they controlled and were informed that they would not be offered any choice over it during a test to come. To control for the effect of different body positions on sensorimotor performance and learning, the 19 women with obesity (BMI = 40.0 + 7.33, age = 44.2 + 6.6) and 20 without obesity (BMI = 22.3 + 1.95, age = 43 + 6.9) were assigned into 4 groups, according to their BMI and body position assumed during practice (standing upright with feet together or sitting). As no significant differences concerning body position were found, the data were reanalysed disregarding this factor. Results revealed that while both groups reduced errors during the Acquisition, participants with obesity showed poorer performance (Acquisition) and sensorimotor learning (Transfer). Given the experimental task and adopted procedures, our results tend to support the hypothesis that hindered perception and/or integration of sensory information is associated with obesity.

Older but not younger adults rely on multijoint coordination to stabilize the swinging limb when performing a novel cued walking task

Motor flexibility, the ability to employ multiple motor strategies to meet task demands, may facilitate ambulation in complex environments that constrain movements; loss of motor flexibility may impair mobility. The purpose of this study was to determine the effects of obesity (a specific model of mobility impairment) and advanced age on motor flexibility during a task that constrained foot placement while walking. Twenty-one community-dwelling obese (OB) and 25 normal weight (NW) older adults (46 total older adults-OA) and 10 younger adults (YA) walked normally on a treadmill (baseline) then walked while stepping on lighted cues projected onto the treadmill at locations corresponding to average foot placement during normal walking (cued). The uncontrolled manifold (UCM) analysis was used to partition total variance in a set of seven lower-limb segment angles into components that did ("bad" variance) and did not ("good" variance) affect step-to-step variance in the trajectory of the swing foot. Motor flexibility was operationalized as an increase (baseline to cued) in total variance with an increase in good variance that exceeded the change in bad variance. There was no significant group × walking task interaction for total and good variance for OB vs NW, but there was a strong and significant interaction effect for OA vs YA (p < 0.01; Cohen's d > 1.0). Whereas YA reduced both good and bad variance, OA increased good variance beyond the change in bad variance. In OA, these changes were associated with several functional measures of mobility. Cued walking may place greater demands on OA requiring greater reliance on motor flexibility, although otherwise healthy older obese adults may be able to compensate for functional and cognitive declines associated with obesity by increasing motor flexibility under such tasks. The extent to which motor flexibility is employed during novel or constrained tasks may be a biomarker of healthy aging and a target for (re)habilitation.