The study led by Victoria Leavitt and James Sumowski, from Kessler Foundation, US, provides the first evidence for beneficial effects of aerobic exercise on brain and memory in individuals with MS.
Hippocampal atrophy seen in MS is linked to the memory deficits that affect approximately 50 per cent of individuals with MS, researchers said.
Despite the prevalence of this disabling symptom, there are no effective pharmacological or behavioural treatments.
"Aerobic exercise may be the first effective treatment for MS patients with memory problems," said Leavitt, research scientist in Neuropsychology & Neuroscience Research at Kessler Foundation.
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Researchers said no beneficial effects were seen with non-aerobic exercise.
Leavitt noted that the positive effects of aerobic exercise were specific to memory; other cognitive functions such as executive functioning and processing speed were unaffected.
The study's participants were two MS patients with memory deficits who were randomised to non-aerobic (stretching) and aerobic (stationary cycling) conditions.
Baseline and follow-up measurements were recorded before and after the treatment protocol of 30-minute exercise sessions 3 times per week for 3 months.
Data were collected by high-resolution MRI (neuroanatomical volumes), fMRI (functional connectivity), and memory assessment.
Non-aerobic exercise resulted in minimal change in hippocampal volume and no changes in memory or functional connectivity.
"These findings clearly warrant large-scale clinical trials of aerobic exercise for the treatment of memory deficits in the MS population," said Sumowski, research scientist in Neuropsychology & Neuroscience Research at Kessler Foundation.