New research hints that even a simple exercise routine just might help older Americans with mild memory problems.

Doctors have long advised physical activity to help keep a healthy brain fit. But the government-funded study marks the longest test of whether exercise makes any difference once memory starts to slide — research performed amid a pandemic that added isolation to the list of risks to participants’ brain health.

Researchers recruited about 300 sedentary older adults with hard-to-spot memory changes called mild cognitive impairment or MCI — a condition that’s sometimes, but not always, a precursor to Alzheimer’s. Half were assigned aerobic exercises and the rest stretching-and-balance moves that only modestly raised their heart rate.

Another key component: Participants in both groups were showered with attention by trainers who worked with them at YMCAs around the country — and when COVID-19 shut down gyms, helped them keep moving at home via video calls.