Research and videos
Cardio (aerobic exercise, incl. Zone 2): the research and Kevin's videos
Which cardio is best for carriers (Zone 2, HIIT, VO2 max), and how much?
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This page has no results from Phoenix members yet. It shows what published research says, and what Kevin and the experts say in his videos.
See what Phoenix members have measuredWhich cardio is best for carriers (Zone 2, HIIT, VO2 max), and how much?
Regular aerobic exercise probably lowers dementia risk: active people have about a fifth less dementia, and in trials it improves heart and metabolic health and, in some, thinking and brain blood flow, including in APOE4 carriers with high blood pressure. Trials have not shown that Zone 2 beats other intensities for the brain; one large trial found harder training did no better than stretching. The kind you will keep doing is the best kind.
What the research says
Grade BAPOE4-specific evidence: limited
Aerobic exercise probably protects the brain and clearly improves heart and metabolic health; no specific intensity, Zone 2 included, is proven best for the brain.
Key studies
Iso-Markku 2022, Br J Sports MedGrade B
Cohort meta-analysis: physically active people had about 20% lower dementia risk.
Read on PubMed (opens in a new tab)Northey 2018, Br J Sports MedGrade B
39 trials in over-50s: exercise of at least moderate intensity improved thinking (small-to-moderate effect).
Read on PubMed (opens in a new tab)Young 2015, Cochrane Database Syst RevGrade B
12 short trials in healthy older people: aerobic exercise alone showed no cognitive benefit.
Read on PubMed (opens in a new tab)
4 more key studies
Baker 2025, Alzheimers Dement (EXERT)Grade B
296 adults with MCI: harder aerobic training did no better than stretching; both groups stayed stable for a year.
Read on PubMed (opens in a new tab)Erickson 2011, PNASGrade C
Randomized: a year of aerobic exercise grew the hippocampus about 2% in older adults and improved spatial memory.
Read on PubMed (opens in a new tab)Kaufman 2021, J Cereb Blood Flow Metab
Randomized, 44 people with high blood pressure: a year of aerobic exercise raised hippocampal blood flow in APOE4 carriers only.
Read on PubMed (opens in a new tab)Mattioni Maturana 2021, Med Sci Sports Exerc
55 trials comparing interval with steady cardio: interval was better for fitness and artery function, steady for HbA1c, with no difference in blood pressure, lipids or inflammation.
Read on PubMed (opens in a new tab)
What Kevin and experts say
9 passages for, 2 also discussed
Now showing: Dr. Kevin Tran · 0:00
Open on YouTube (opens in a new tab)For9 passages
Kevin says pushing harder in cardio is not better for the brain.
“Harder is not better.”
Dr. Kevin Tran, Founder of The Phoenix Community, Doctor of Pharmacy, APOE4/4 carrier
Aerobic exercise boosted memory-center blood flow in carriers with high blood pressure.
“[hippocampal] blood flow improved significantly while [non-carriers] actually saw a slight decrease.”
Dr. Kevin Tran, Founder of The Phoenix Community, Doctor of Pharmacy, APOE4/4 carrier
Correction: this 2021 trial (44 adults) enrolled only people with high blood pressure, and the blood-flow gain was seen in carriers, so it may not apply to carriers with normal pressure.
Read the study (opens in a new tab)Correction: this 2021 trial analysed only carriers with high blood pressure, so the blood-flow gain may not apply to all carriers.
Read the study (opens in a new tab)Aerobic exercise can reverse one to two years of hippocampal shrinkage.
“exercise training increase [hippocampal] volume by 2% effectively reversing age related loss in volume by 1 to two years.”
Dr. Kevin Tran, Founder of The Phoenix Community, Doctor of Pharmacy, APOE4/4 carrier
For carriers, exercise may be essential, not optional.
“for us, exercise isn't just beneficial. It may be essential for maintaining adequate brain [perfusion].”
Dr. Kevin Tran, Founder of The Phoenix Community, Doctor of Pharmacy, APOE4/4 carrier
Aerobic exercise is a top priority for a resilient brain.
“the most important things from my perspective for allowing the brain to be more resilient as we get older, regardless of pathology, is exercise, aerobic exercise”
Dr. Gayatri Devi, Neurologist, Park Avenue Neurology; Clinical Professor, Zucker School of Medicine at Hofstra/Northwell
Morning cardio deepens sleep; avoid it near bedtime.
“in the morning or the early afternoon and not within 3 hours of bedtime, these type of exercise have increased slow wave sleep stability and duration in many different studies”
Dr. Kevin Tran, Founder of The Phoenix Community, Doctor of Pharmacy, APOE4/4 carrier
Simple zone 2 plus intervals raised Kevin's VO2 max a lot.
Dr. Kevin Tran
Watch the Short on YouTube (opens in a new tab)
Aerobic exercise grew the memory center by 2%.
Dr. Kevin Tran
Watch the Short on YouTube (opens in a new tab)
Full sentences while exercising means you're likely in zone 2.
Dr. Kevin Tran
Watch the Short on YouTube (opens in a new tab)
Also discussed2 passages
Zone 2: you can talk, but with effort.
“at true zone 2 you should be able to hold a conversation not easily”
Dr. Kevin Tran, Founder of The Phoenix Community, Doctor of Pharmacy, APOE4/4 carrier
Moving matters more than hitting a specific heart rate zone.
“it's so much important to just get out of the chair and go move around”
John Yoder, Phoenix member, retired physician, APOE3/4 carrier
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