Sit-to-stand test: Why leg strength already matters at 40

How easily you get up from a chair says more about your health than many people think. In a Chinese cohort study of 8,405 adults free of cardiovascular disease (Experimental Gerontology, 2026), good muscle health in the arms and legs was linked to lower cardiovascular risk over 9 years, mainly while heart, kidney and metabolic health were still in early stages. Muscle quality also matters for leg power, and a 30-second sit-to-stand test makes your leg strength easy to measure.

Key points at a glance

• In a Chinese cohort study of 8,405 adults, normal arm and leg strength was linked to a roughly 20 percent lower risk of new cardiovascular disease while heart, kidney and metabolic health were in early stages.
• In a later stage, this link was weaker and less certain in the same study, which supports building and measuring muscle strength early.
• In 70 older adults, the loss of leg power over 3 years was more closely tied to fat inside the muscle than to shrinking muscle mass.
• In an analysis of 34,457 UK Biobank participants, age-related muscle loss (sarcopenia) was linked to weaker cognitive performance.
• A single strength value is a snapshot; only a re-test shows whether training changes your strength.

Why does muscle strength matter in midlife?

Muscle strength is linked to lower cardiovascular risk, and this link is clearest at an early stage. Experts now view the heart, kidneys and metabolism as one connected system, the Cardiovascular-Kidney-Metabolic (CKM) syndrome. It progresses in stages, from unremarkable to advanced.

The Chinese cohort study, drawn from the China Health and Retirement Longitudinal Study, measured arm strength as grip strength relative to body weight and leg strength by standing up from a chair 5 times. In stages 0 to 2, normal arm strength was linked to a 20 percent lower risk and normal leg strength to a 22 percent lower risk of new cardiovascular disease. In stage 3, the links were attenuated and less precise. People with weaker grip strength at the start were also more often in a more advanced stage.

This fits the picture of scheduled maintenance: a plane is serviced before parts fail. Muscle strength appears to be linked to protection mainly while little risk has accumulated.

Why does muscle quality say more than muscle size?

Fat that builds up inside the muscle is more closely tied to falling leg power than the loss of muscle mass alone. That is what a 3-year MRI study of 70 community-dwelling older adults with an average age of 75 found (Archives of Gerontology and Geriatrics, 2026).

The researchers measured 19 hip and thigh muscles. Over 3 years, muscle volume decreased and the share of intramuscular adipose tissue (fat lying between and within muscle fibres) increased. A pattern in which this fat rose together across many muscles was independently linked to a greater loss of leg power, measured by jump height and the 30-second sit-to-stand test. The pattern of muscle shrinkage alone was not.

Also striking was how differently people aged: a clearly coupled course of muscle shrinkage and fat build-up appeared in only 4.3 percent of participants. For you, this means: how big a muscle looks reveals little about what it can do. A functional test measures performance directly.

What does the sit-to-stand test reveal about health?

The sit-to-stand test measures leg strength, balance and coordination in an everyday movement. Alongside the Chinese cohort study, a Spanish observational study of 137 people with chronic obstructive pulmonary disease (COPD) (Archivos de Bronconeumología, 2025) shows how much information this simple test carries.

Among high-risk patients, 5-year mortality was 60.5 percent with poor performance in the five-repetition sit-to-stand test and 11.1 percent with better performance. Poor performance remained linked to a 4.7-fold higher risk of death after accounting for heart disease and breathlessness. The group averaged 66 years of age, was 87.6 percent male and had lung disease. These figures cannot be transferred to healthy people.

Here is how to do the 30-second version at home: place a sturdy chair without wheels against a wall, cross your arms over your chest, and count how many times you fully stand up and sit back down in 30 seconds. Note the number, the date and the chair, so you can repeat it later under the same conditions. If you feel unsteady on your feet, only do the test with someone present.

Is muscle strength linked to cognitive performance?

Muscle strength is also linked to cognitive performance. An analysis of 34,457 UK Biobank participants using Mendelian randomization (JMIR Aging, 2025) found that sarcopenia was linked to lower fluid intelligence scores. The average age was 56, right in midlife.

Mendelian randomization uses genetic variants as a kind of natural experiment. In this analysis, genetically higher grip strength was linked to better cognitive function, and part of this link ran through physical activity. The authors therefore consider sarcopenia a potential causal risk factor for cognitive impairment and physical activity a modifiable lever.

One limit applies to all 4 studies: they observe associations in specific groups (Chinese adults, older Japanese adults, COPD patients, UK participants), and Mendelian randomization also rests on assumptions. The shared picture is solid: strength and muscle function are tied to heart and brain.

Why does only the trend show whether your training works?

A single strength value depends on the day; only repeated measurements show your direction. The MRI study shows how differently muscles age from person to person. Comparing yourself with others therefore helps less than your own trend.

The UK Biobank analysis names physical activity as a modifiable lever. Whether a training plan moves anything for you only becomes visible if you have a baseline beforehand and re-measure after some weeks under the same conditions. Movement, nutrition, sleep and medical guidance are the levers; the re-test is the feedback.

When to see a doctor?

Talk to your doctor if standing up or climbing stairs has become noticeably harder than a few months ago, if you fall or feel unsteady, if pain limits you, or if you or people close to you notice changes in your memory. If you have a known heart, lung or kidney condition, check with a doctor what suits you before starting new strength training. The decision on further examinations rests with the doctor.

How Chirayou can help

CHIRAYOU is a doctor-led online program for preventive health. In the 90-day program, we record the sit-to-stand test, grip strength and an objective cognitive test as short functional tests, plus body fat percentage and visceral fat via a smart scale.

The at-home blood test completes the picture, including vitamin D, apolipoprotein B (ApoB, the count of cholesterol-carrying particles that build up in artery walls), fructosamine (average blood sugar over the prior 2 to 3 weeks) and hsCRP (a marker of low-grade inflammation). The sit-to-stand test and grip strength are part of the program; the standalone blood test does not measure them.

Doctors discuss your results with you. From this comes a plan of 3 to 5 interventions, such as a strength and protein protocol. After 90 days, you measure again: Test, Plan, Act. This shows whether your values have moved. Your next step: start the 90-day program and set your baseline for leg and grip strength.

The bottom line

Muscle strength is not a topic that only begins in old age: it is linked to heart and brain health, and most clearly early on. Muscle quality also matters for leg power, and the sit-to-stand test measures that power directly. A baseline today and a re-test after 90 days show you which direction you are heading.

This article is for general information only and does not replace medical advice, diagnosis or treatment.