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A guide to Tortoise Time: educational articles and field-test calculators on fitness, strength, walking, and healthy ageing.
Created by Bernard Aoun, MD, a physician working in primary care and geriatrics. The newsletter is published on Substack.
Keep the limits in view. The tools are for education, not diagnosis. The Fitness Meter’s combined score is experimental, not a validated clinical risk or life-expectancy score. Read each test’s instructions and safety advice before using it.
Walking and strength tools
Chair stand test
How to do the 30-second chair stand or five-times sit-to-stand test, record your result, and understand what it says about leg strength and mobility.
Fitness Meter
An experimental, evidence-informed fitness index combining estimated VO₂ max and grip strength against contemporary age- and sex-specific reference standards.
Grip strength
Record right and left grip strength, see how it compares with research thresholds for low muscle strength, and track your grip over time.
Six-minute walk test
How to do the six-minute walk test at home or on a track, record your distance, and compare it with a published reference equation.
VO₂ max: the Rockport walk test
Estimate your VO₂ max with the Rockport one-mile walk test. Physician-written instructions, a free calculator and plain-language interpretation.
Articles and explanations
Can you get down to the floor and back up without your hands?
The sitting-rising test checks strength, balance and flexibility in one move. A 2025 study found it predicted survival over 12 years.
Can you stand on one leg for 10 seconds?
A simple balance test turns out to say a lot about health after 50, and balance is one of the easiest abilities to train.
Cardiovascular fitness, by the numbers
What large fitness studies, a walking trial and activity guidelines actually tell us about aerobic capacity.
Exercise and cancer: 13 cancers linked to lower risk
In 1.44 million adults, the most active people had lower risk of 13 different cancers. Here’s the full list, and the two surprises.
Fit and heavier, or thin and unfit? What matters more for long life
A 2024 review of nearly 400,000 people found that fitness predicted survival far better than body weight. Here’s what that means for you.
Fitness and strength: the two vital signs most checkups miss
Your blood pressure gets checked at every visit. Two of the strongest signals of how well you will age usually do not. Here is what the research shows, in plain language.
Frailty is not inevitable: what a major European trial found
In the SPRINTT trial, older adults with weak muscles who exercised regularly were less likely to lose the ability to walk. Here’s what the program looked like.
Grip strength: a two-minute window into how you are ageing
Why a simple squeeze test predicts so much, what the numbers mean, and what actually improves them.
Healthspan: adding life to your years, not just years to your life
Americans now spend an average of 12.4 years in poor health at the end of life. Five everyday habits are linked with a decade or more of extra healthy years.
How many steps a day do you really need?
Forget the magic 10,000. The largest study of step counts yet points to a friendlier target, and shows that every extra thousand steps helps.
How to read a health headline (without a PhD)
“Walking cuts your risk of death in half!” Here is how to tell what a study really shows, using real examples from exercise science.
Never too late, never too short: the new science of staying active
Started late? Only have a minute? Squeeze it all into the weekend? The latest research says all of it counts.
Protein and muscle: what older adults need to know
Strength training builds muscle, but muscle needs building blocks. Here’s how much protein the research suggests, and why it matters more as we age.
Strength training: the hour a week that pays off
You don’t need to live at the gym. Research suggests 30 to 60 minutes of muscle-strengthening a week brings most of the benefit, and it works at any age.
The after-dinner stroll: small walks, big effect on blood sugar
A few minutes of light walking after eating blunts the spike in blood sugar. It may be the easiest healthy habit there is.
The wall sit: blood pressure’s surprise champion
A review of 270 trials found that ‘holding still’ exercises like the wall sit lowered blood pressure more than any other type of exercise.
VO₂ max, explained without the hype
What VO₂ max measures, why it is linked with longevity, and how ordinary walking can move it.
About the publication
About Tortoise Time
Tortoise Time was created by a physician in internal medicine and geriatrics to help people measure and improve the abilities that shape healthy ageing.
Contact
Get in touch with Tortoise Time.
Medical disclaimer
Tortoise Time provides education and fitness assessment tools, not medical diagnosis or treatment.
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How Tortoise Time handles your information. Assessment results are stored only on your device.
Stay strong. Keep moving.
A five-minute weekly physician-led newsletter turning evidence on fitness, strength, mobility and healthy ageing into one practical next step.
Terms of use
Terms for using the Tortoise Time website and assessment tools.