Bipedal hopping to a metronome to detect impairments in anticipatory motor control in people with mild multiple sclerosis
Megan Kirkland, Dr. Michelle Ploughman, Alice Chen
Memorial University of Newfoundland
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 Disability Status Scale≤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. Results: The MS group became more delayed from the metronome beat over time whereas elderly subjects tended to hop closer to the beat (F=4.52, p=0.02). 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, as both were significantly different from the elderly group. However, during 40-bpm, the MS group was no longer significantly different from the elderly group, even though matched controls and elderly still differed significantly. 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. Several aspects of anticipatory motor control can be measured: including motor response to the first metronome cue and the ability to adapt and anticipate the beat over time.