For many people, 50 is a time when exercise can finally get back on the agenda after work and family commitments settle down.
But getting back on the treadmill to fitness is different at every age, so don't expect to do what you've always done, advises Les Mills' Head of Fitness Ish Cheyne.
"As you get older, you need to make smarter choices about how much impact an exercise has, because injuries can take longer to heal and joints aren't as springy," he says.
"Sedentary jobs can also take their toll over the years, so there's a need to ease back into fitness rather than expecting to do what you did in a different phase of life."
He says the 20s and 30s are when people are generally bullet-proof when it comes to fitness and training.
Even in your 40s you can still pretty much do what you used to, but when the 50s hit, fitness should be fine-tuned to anticipate future health problems, rather than just concentrating on athleticism.
"It's about asking, 'what's right for me in the new phase?'" says Cheyne, who has been with Les Mills for more than two decades.
"In your 50s, fitness should be less about high intensity, competitive sports and having a six-pack, and more to do with flexibility, yoga, strength, conditioning and endurance."
The aim is to keep a level of fitness that will work as a prevention to future health problems and give people a chance to have a range of movement in the later years, something that becomes very important in your 70s, when putting your shoes on can be difficult if fitness hasn't been maintained.
"Once, you might have wanted to run for fitness, or to look better, but once you're in your 50s, exercise is more about quality of life and quality of movement," Cheyne says. "Unfortunately, it's often injury that forces us to realise we need to change the way we exercise."
Les Mills has options for older gym-goers in most of its classes -- even in its high-intensity programmes - and Cheyne says it's about pushing yourself at your own ability.
Injury prevention and restorative classes are also available with little impact.
Whatever workout you choose, over-50s need to warm up more than their younger selves did. Stretching exercises should be a part of the fitness routine.
"Stability and flexibility should be the base of all movement," he says.
"That's where you'll have less injuries if you have a good core flex base."
If you've had a break from fitness, Cheyne recommends not trying to do too much, too soon, but rather to think of the long-term healthy attitude to avoid short bursts of fitness.
Nutrition is another area that needs to be adapted in your 50s.
"What you get away with when you're younger, you likely won't get away with when you're over 50," Cheyne says. "It's about a balanced, healthy diet and it's best to get a nutrition expert to help you."
For women, the 50s can also bring weight gain, fatigue and tiredness from hormonal changes from menopause. Bone health can also become an issue, so increased calcium will be needed for strong bones.
For men, regular bowel and prostate checks are recommended, as is a diet high in fibre.
"The worst thing you can do is jump on a diet bandwagon," Cheyne says.
"As you get older, get expert advice on what you want to work on -- whether it's diet or exercise."
Stress is also an important factor in fitness over 50, and Cheyne says stress can take its toll after a lifetime of dealing with life's ups and downs.
"Your resilience to stress gets better as you age, because of life experiences, but it sometimes mounts up and overflows in other ways, such as not sleeping well," he says.
"Exercise and nutrition has proven to be a good way for stress management and control."
The benefits of exercise, nutrition and a general healthy outlook at any age are important.
In your 50s, they're no longer an optional extra if you want to enjoy life into your 60s and beyond.
Ish Cheyne's top tips
*Get expert advice. Too often we ask advice from people that we want to be like, but everyone is different and it's better to ask for advice from experts, such as a personal trainer or nutritionist, so a programme can be tailored just for you.
*Join a gym, they're really good places to be for the best advice and the safest equipment.
*Don't jump on an exercise trend just because it's popular. Instead, do some research and talk to experts to find out if it's right for your specific needs.
*Don't underestimate flexibility and training as you age, because you'll want to keep your range of movement later on. For example, older people can struggle with the basics, such as getting up off the floor, so keep working on flexibility as a priority.
*The gym, exercise and healthy eating is a lifelong commitment. If you say you're going to get fit, think long-term rather than in bursts of activity. And remember that prevention is better than the cure.