Bipedal hopping timed with a metronome to detect impairments in anticipatory motor control in people with mild multiple sclerosis

Abstract

Background: People with mild multiple sclerosis (MS) often report difficulty in balance and cognition but display no measurable deficits on many clinical assessments. We examined whether hopping to a metronome beat has the potential to detect anticipatory motor control deficits among people with mild MS (Expanded Disease Severity Score ≤ 3.5). Methods: Participants with MS (n=13), matched controls (n=9), and elderly subjects (n=13) completed tests of cognition (Montreal Cognitive Assessment (MoCA)) and motor performance (Timed 25 Foot Walk Test (T25FWT)). Participants performed two bipedal hopping tasks: at 40 beats/minute (bpm) and 60-bpm in random order. Hop characteristics (length, symmetry, variability) and delay from the metronome beat were extracted from an instrumented walkway and compared between groups using a one-way ANOVA. Results: The MS group became more delayed from the metronome beat over time whereas elderly subjects tended to hop closer to the beat during 40-bpm (F=3.58, p=0.04). Delay of the first hop during 60-bpm predicted cognition in people with MS (R=0.55, β=4.64 (SD 4.63), F=4.85, p=0.05) but not among control (R=0.07, p=0.86) or elderly subjects (R=0.17, p=0.57). In terms of hopping characteristics, people with MS performed similarly to the matched controls during 60-bpm, but shifted towards the elderly subjects’ ability during 40-bpm. Conclusions: This new timed hopping test may be able to detect both physical ability and feed-forward anticipatory control impairments in people with mild MS. Hopping at a frequency of 40-bpm seemed more challenging. Two aspects of anticipatory motor control can be measured: response time to the first metronome cue and the ability to adapt and anticipate the beat over time.