In a world where longevity clinics offer pricey scans and diagnostics, the humble tennis ball might be one of the best tools to assess your muscle health. According to Joshua Davidson, a strength researcher at the University of Derby, grip strength is a surprisingly accurate measure of overall health.

Instead of using a medical-grade hand dynamometer — a device designed to gauge the force exerted by your hand and forearm — Davidson says a basic "squeeze test" with a tennis or stress ball is good enough for a general check-in. Simply squeeze it as hard as you can and time how long it takes until fatigue sets in. If you can hold the squeeze for 15 to 30 seconds, that’s a good benchmark.

Why Does Grip Strength Matter?

Mark Peterson from the University of Michigan says a weak grip might not interfere with your daily tasks too much — maybe just opening a stubborn jar. But the implications go deeper. Researchers use grip strength as a proxy for your entire musculoskeletal health. It reflects your activity levels, hints at sedentary lifestyles, and even helps identify frailty.

One global study involving nearly 140,000 adults found that grip strength was more predictive of early death than blood pressure. Another long-term study tracked participants for over four decades — those with the strongest grips were 2.5 times more likely to live past 100 compared to those with weaker hands.

Your Muscles Reflect Your Life

Darryl Leong, a medical professor at McMaster University, explains that your grip is more than just a hand thing — it reflects nutrition, physical activity, and disease status. Essentially, it's a snapshot of your body's current condition and future potential.

For instance, lower grip strength — defined in one study as below 25.5 kg for men and 18 kg for women — was linked to sarcopenia, the progressive loss of muscle mass. This condition increases the risk of falls, fractures, and mobility issues in later life.

Guillaume Paré, also from McMaster, says he can often spot sarcopenia during a handshake. If someone’s fingers can’t close around his hand or their muscles feel sunken, it’s a red flag.

A Metabolic Mirror

Your grip might also hold clues about your internal health. Muscle plays a vital role in regulating blood sugar. Weak muscles are less effective at absorbing glucose, raising the risk of insulin resistance. That’s why lower grip strength has been tied to conditions like type 2 diabetes, poor bone density, malnutrition, and even depression.

Back in 2022, Peterson led a study linking grip strength with biological ageing. They found that people with weaker grips had altered DNA methylation patterns — chemical changes that affect how genes are read. These patterns often reflect stress, pollution, and lifestyle choices, further connecting grip to broader health.

The Connection to Chronic Illness

Grip strength doesn’t just predict physical capability — it offers insights into resilience against illness. Studies show that cancer patients with poor grip strength are more likely to experience rapid weight loss and worse survival outcomes. Weak grip can also predict poor recovery from infections like pneumonia, where strong muscles are needed to clear mucus and sputum from the lungs.

The trend isn’t limited to the elderly. A Brazilian study found that teenagers who spent more time glued to screens had significantly weaker grips. Paré says that low grip strength in youth often links to poor metabolic health even at an early age. And get this — countries with stronger average grip strength often win more Olympic medals.

How to Improve Your Grip Strength

Davidson suggests you don’t need fancy equipment. The tennis ball test is also a training tool — try squeezing it for longer each day. For a more structured approach, wrist curls are great. Sit down, hold a can with your palm facing up, and curl your wrist toward your body. Try five sets of 20 reps.

Leong advises full-body resistance training to boost muscle strength overall. More movement means better muscle health — and better grip as a result. Older adults can try the "get-up-and-go" test: rise from a chair, walk three meters, turn, and sit down again. It’s a reliable way to check leg strength and mobility.

If you’ve got equipment at home, try wrist curls or bicep curls with light weights or kettlebells. Davidson recommends 2–3 sets of 10–20 reps per arm to start.

So, while a strong handshake might not be the first thing you think of when assessing your health, it could actually be one of the most revealing. Your grip strength reflects your overall muscular health, metabolic resilience, and even your odds of fighting off chronic illness or living a longer life. And the best part? Improving it is within your grasp — literally.