• Exercise is crucial for longevity, but fitness priorities change as you age through your 30s and 40s.
• A personal trainer said training for your age can help maintain a healthy, active life over decades.
• Strength training is the foundation of healthy aging, along with stability, recovery, and cardio.

Stop putting off fitness for a longer life — if you want to be strong, athletic, and active in your 80s and beyond, now is the time to start.

One of the biggest fitness mistakes is failing to prioritize long-term fitness goals, according to Ollie Thompson, a UK-based personal trainer who specializes in longevity. He said working with clients in their 40s and older changed his own approach to fitness.

“People aren’t thinking about it until they’re too late,” Thompson told Business Insider.

A bit of planning ahead by combining smart strength training exercises, cardio, and good recovery habits can help you stay spry for decades to come, according to Thompson.

“It’s about living better, how can you stay capable and healthy throughout the years,” he said.

Prioritize strength training in your 20s

Thompson said the foundation of longevity fitness is strength training as early as possible.

Forget about maxing out on the bench press. While challenging yourself and progressing over time is key, overtraining a few movements can backfire by causing repetitive injuries over time.

“What happens when you go to do something else and you’re only strong in that position and you’re weak in positions that the body is supposed to move in?” Thompson said.

Instead, more varied exercises, a range of intensities, and weightlifting plus cardio can offer more bang for your buck in terms of longevity.

Try functional movements like lunges and weighted carries, along with dynamic exercise like kettlebell swings for well-rounded fitness.

Focus on keeping healthy habits in your 30s

It can seem more difficult to stay in shape or get fit in your 30s, but it doesn’t have to be, according to Thompson.

“We tend to overemphasize those changes,” he said. “The biggest thing is that life starts to get more serious. Maybe you put health and fitness on the backburner.”

Physiologically, there’s no special way to exercise differently in your 30s, since you still want to aim for building muscle and doing some cardio.

Thompson said the major difference is figuring out how to fit exercise into your busy schedule. Spending time in your 30s to make a consistent fitness habit is an investment in making and maintaining gains as you get older.

“It’s a peak time to build up strength and resilience around the joints as well as muscle mass so as you start to get older, you’ll have a bit of a safety net,” Thompson said.

Add more stability exercises in your 40s

Once you hit 40, there’s no need to reinvent your workouts. Regular strength training is crucial, and more cardio is a good idea to bolster your health, Thompson said.

You may want to slightly adjust the type of strength training you do by adding more core and stability-focused movements like planks, step-ups, and single-leg deadlifts.

Better stability can help keep you mobile, protect your joints, and prevent injury.

“It’s quite common for people to overcomplicate things by thinking they need to do a certain thing in their 30s and then change things again in their 40s,” Thompson said. “It’s not about changing the big picture, it’s about being a bit more sensible.”

Your 50s and beyond are all about maintenance and recovery

Once you start getting older, the biggest priority is making sure you can stay active while giving your body more time to recover from workouts.

Sleep and good nutrition are more important than ever. You should keep working out, but make sure the intensity is manageable. The goal is maintaining healthy pain-free movement, Thompson said.

It’s never too late to get started in fitness, or to return to it after some time off.

To get into the gym as an older adult, look for workouts that make you feel good or that have a social component like a strong community that will keep you coming back for more.

“It’s finding a mode of exercise you can find some enjoyment and repetition in,” Thompson said.