Quantifying the effects of body mass index on safety: reliability of a video coding procedure and utility of a rhythmic walking task.

OBJECTIVES To evaluate the association between body mass index (BMI) and motor actions related to safety risks (primary aim), and to examine the reliability of a video coding procedure and the utility of a rhythmic walking task in identifying safety risks (secondary aims). DESIGN Using a cross-sectional design, participants were filmed during a rhythmic walking task at slow, normal, and fast audio metronome paces. A video coding procedure was used to quantify signs of safety risks from the videotaped sessions. SETTING Motor development laboratory in a university. PARTICIPANTS Adults (N=32) with normal (n=15) and overweight (n=17) BMI scores participated. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Chi-squared analyses were conducted to compare the occurrence of coded motor actions (forward and lateral tripping) between participants with normal and overweight BMI scores. A kappa coefficient was computed as a measure of interrater reliability on the video codes. RESULTS Participants who were overweight exhibited more safety risks compared with participants with normal BMI scores at the slow (χ(2)(1,N=32)=3.94, P<.05, d=.75) and fast (χ(2)(1,N=32)=3.85, P<.05, d=.74) metronome paces. Interrater reliability was high (κ=.90, P<.01). CONCLUSIONS In support of the primary aim, the findings show a relationship between overweight BMI scores and safety risks. Toward the secondary aims, the results demonstrate that a video coding procedure can be reliably used to assess safety risks and that creating tasks appropriate for assessing safety risks in overweight adults is needed.