Six Months of Hard Intervals Improved the Hippocampus for Five Years
The interval group matched steady walkers on fitness but had much better hippocampus structure and function, with harder effort linked to larger gains.
Andrew Huberman · Accelerate Learning & Increase Cognitive Capacity | Dr. Tommy WoodOlder adults were split into three groups: an easy activity group, a steady treadmill walking group three times a week, and a hard interval group. The hard group did the Norwegian 4x4, four rounds of four minutes pushing near peak pulse with three minutes of rest, three times a week for six months.
Both exercisers got equally fitter, but brain scans told a different story. The interval group had much better improvements in function and maintenance of structure in the hippocampus, the brain's memory center, and kept that benefit five years after training stopped.
In several analyses within the study, greater effort and higher cortisol release were linked to larger brain gains. Dr. Tommy Wood, a Seattle physician who studies brain health, said he does not think the specific treadmill protocol is required. He thinks hard effort releases muscle factors and lactate in particular, which easily reach the brain and stimulate production of BDNF, a growth factor that supports plasticity.
Questions people ask
Does steady walking still help the brain at all?
Yes. In an earlier yearlong trial, brisk walking for 40 minutes three times a week increased hippocampus volume, raised fitness, and improved memory. The new result is that hard intervals did substantially more for hippocampus structure and function, not that walking did nothing.
Is this kind of all-out interval training safe for older adults?
It can be, but it requires screening and buildup. Medical groups advise older adults or people with heart disease, high blood pressure, or joint problems to get checked first, start gradually, and use supervised programs with warmups and heart rate monitoring. Breathlessness, chest pain, or dizziness means stop and seek care.
Do I need to do hard intervals three times a week forever?
Researchers generally suggest one hard session per week plus easier aerobic work, resistance training, and balance or skill activity for long-term maintenance. Consistency, sleep, blood pressure control, and hearing and vision care also strongly affect later dementia risk.