Several of these are tests researchers actually use to predict how the next decade goes. None requires a gym and all of them can be improved.
Read This Before You Try Any of Them

These are population-level associations, not diagnoses. Failing one does not predict anything about you personally. Do not attempt maximum-effort tests cold, and if you have heart disease, chest pain, joint problems or have been inactive for years, talk to a GP before testing anything below.
Stand on One Leg for Ten Seconds

A 2022 study in the British Journal of Sports Medicine following 1,702 adults aged 51 to 75 found that those who could not hold a ten-second one-legged stance had roughly an 80 percent higher risk of death over about seven years. In absolute terms, 7.5 percent of those who failed died compared with 4.6 percent who passed.
Get Off the Floor Without Using Your Hands

The sitting-rising test, developed by the Brazilian physician Claudio Gil Araujo, scores you out of ten with points deducted for each hand or knee used going down and coming up. It measures strength, balance and flexibility at once, and lower scores have been linked to higher mortality in follow-up research.
Have a Decent Grip

Grip strength turned out to be a surprisingly powerful predictor in the international PURE study, where lower grip was associated with higher mortality and cardiovascular risk. A dynamometer costs very little, and the practical version is whether you can carry heavy shopping from the car in one trip without your hands giving out.
Do Push-Ups in Reasonable Numbers

A 2019 study of male firefighters published in JAMA Network Open found that those able to complete more than forty push-ups had markedly lower rates of cardiovascular events over ten years than those managing fewer than ten. The population was fit men, so do not over-read it, and it remains a useful benchmark.
Walk at a Brisk Pace

Gait speed is used clinically as a marker of ageing. Comfortably walking at around a metre per second or better, which is roughly the pace that gets you across a pedestrian crossing without hurrying, is the level associated with good outcomes.
Get out of a chair ten times without your arms

The thirty-second chair stand test counts how many times you can stand and sit fully without pushing off. Around twelve to fourteen repetitions is a reasonable target for a man in his fifties. It is a good test of leg power, which declines faster than general strength.
Carry something heavy for a minute

Loaded carries test grip, core and posture at the same time and mirror ordinary life better than most exercises. Two heavy bags for sixty seconds without your form collapsing is a decent standard and a good thing to train directly.
Reach behind your back with both hands

One hand over the shoulder, the other up from the waist, fingertips meeting or close. Shoulder mobility deteriorates quietly in men who sit at desks, and it is the thing that later makes putting on a coat or reaching a top shelf awkward.
Sleep through most of the night

Consistently waking exhausted after a full night, snoring loudly, or gasping awake, points toward sleep apnoea, which is considerably more common in men over fifty and is properly treatable. This is one to raise with a doctor rather than to fix with a gadget.
Have a Waist Under Half Your Height

Waist circumference predicts metabolic risk better than BMI, and the simplest rule is that your waist should measure less than half your height. It is easier to check than any weight-based measure and it accounts for the fact that muscle and fat are not the same thing.
Recover Quickly After Effort

How fast your heart rate drops in the minute after hard exercise is a well-established fitness marker. A quick drop suggests good autonomic function. Slow recovery is one of the earliest things to improve when someone starts training again.
Stand Up From the Floor After Playing With a Grandchild

The unglamorous real-world version of all of the above, and the one that matters most day to day. Every test on this list is really asking the same question, which is whether you can still do the things that keep you independent.
The Good News on All of It

Every single one of these responds to training, at any age, including into the eighties. Strength work twice a week, walking most days and some balance practice while you brush your teeth will move most of these markers within a few months.