Investigators found that over time, lower cardiorespiratory fitness predicts increased variability in stride time and could represent a biomarker for subtle neuromuscular decline in patients with MS.
Cardiorespiratory fitness “may exert neuroprotective effects on the central nervous system,” study investigator Syamala Buragadda, neurophysical therapist and PhD candidate, Memorial University, St. John’s, Nfld..
She reported her research at the annual meeting of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS).
Gait changes
Gait is a complicated process involving coordination of multiple systems, but steps are almost always consistent and symmetric, said Ms. Buragadda. Patients with MS can experience subtle declines in gait quality even without relapses. Considering the neuroprotective properties of exercise, having higher fitness levels could prevent brain atrophy and protect against subtle gait changes.
Calculating stride time variability is a sensitive method to map changes in gait quality.
Ms. Buragadda, with co-investigator Michelle Ploughman, PhD, also with Memorial University, evaluated stride time variability over time in people with MS and explored whether cardiorespiratory fitness predicts stride time variability.
They recruited 49 adults with relapsing-remitting MS (63% women) and mild disability (Expanded Disability Status Scale [EDSS] score < 4; median, 2.0) from MS clinics in Canada. None required walking aids, and none had experienced relapses in the prior 3 months.
Gait quality was assessed on an instrumented walkway, and variability was measured as the coefficient of variation of stride time. Cardiorespiratory fitness was measured as maximal oxygen uptake (VO2max) during a graded exercise test using recumbent stepper. Tests were conducted 2 years apart.
There were no significant changes in EDSS scores over the study period. However, stride time variability increased from 7.3% at baseline to 8.3% at 2 years.
Cardiorespiratory fitness at baseline significantly correlated with stride time variability 2 years later (P = .016) and was a significant predictor of stride time variability at 2 years, accounting for 10% of its variance, Ms. Buragadda reported.
Stride time variability, measured on an instrumented walkway, could be a biomarker for subtle changes to walking and balance, she said.
Limitations of the study include a convenience sample that may not represent the diversity of MS. Also, assessments were made at only two time points, and more time points would likely yield better predictive power. In addition, the lack of MRI images limits correlating structural changes with clinical observations of gait changes.
A buffer against disability?
In a comment, Valerie Block, physical therapist and adjunct instructor, department of physical therapy and rehabilitation science, University of California, San Francisco, and UCSF Weill Institute for Neuroscience, said the findings in this study are not surprising and align with what she has observed, subjectively, in her work.
“In the general population, cardiovascular fitness has a wide array of benefits. Depending on what means the person uses to maintain or improve cardiovascular fitness (that is, running, walking, swimming, etc.), this would have the potential for neuroplastic effects on gait – even in MS and other neurological disorders,” Ms. Block said.
Also offering perspective, Brain Sandroff, PhD, senior research scientist, Kessler Foundation, West Orange, N.J., said the study provides “more evidence on the multisystemic benefits of exercise training and having better physical fitness in persons with MS. The evidence seems to be converging more and more on this, as research groups across countries and continents are reporting on similar themes,” said Dr. Sandroff.
He noted that the findings from this study coincide with some other data that showed that premorbid physical activity is associated with reduced mobility decline over time in persons with MS.
“Collectively, the data suggest that perhaps engaging in exercise training early in the disease (or having better cardiorespiratory fitness at diagnosis) provides a buffer against disability progression over time,” Dr. Sandroff said.
He said it would be interesting to see whether “physical fitness/premorbid physical activity provides such a buffer in those who already demonstrate mobility problems.”
The study had no specific funding. Ms. Buragadda, Dr. Ploughman, Ms. Block, and Dr. Sandroff have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.