Mobile phone use impairs stair gait: A pilot study on young adults

Human movement control requires attention to accurately tune motor commands in response to environmental changes. Dual task paradigms are used to test the role of attention on motor performance. Usually the tasks used have little resemblance with every day experience. Here we ask: Does a common cognitive task, such as a mobile phone conversation, compromise motor performance on stairs? Eight young participants negotiated an instrumented seven-step staircase. Stair negotiation while talking on a mobile phone was compared to normal stair negotiation. Stepping parameters, jerk cost (measure of smoothness of locomotion) and step clearance were measured. When talking on a mobile phone, participants' overall body velocity (mean(sd): Ascent 0.534(0.026) vs 0.511(0.024) m/s, Descent 0.642(0.026) vs 0.511(0.024) m/s, No phone/Phone respectively) and cadence decreased significantly (Ascent 75.8(5.8) vs 65.6(4.4) steps/min, Descent 117.4(4.2) vs 108.6(6.0) steps/min, No Phone/Phone respectively). Pelvis and feet jerk cost also changed significantly, mostly decreasing with phone use. Foot clearance did not show significant changes between No Phone and Phone conditions. These pilot results show that, even for young, healthy and cognitively intact individuals, talking on a mobile phone whilst negotiating a staircase induces measurable changes in motor performance. Participants moved slowly but more smoothly, reducing the motor control cost, possibly at the expense of movement accuracy. The reduction in motor performance is likely to be due to the difficulty in integrating the two sub-tasks. These results suggest that even young, healthy individuals show stair gait impairment when simultaneously negotiating stairs and performing another cognitive task, such as talking on the phone.