A 79-year-old who started running in her 40s has done 28 triathlons. She has 4 tips for young people wanting to be as fit as her.

Through school, college, and a successful career in management at a tech company, the idea of being an athlete never crossed Gruenfeld’s mind. But as soon as she started running, she discovered a love and talent for long-distance sports that seemed to build exponentially. In 31 years, Gruenfeld has completed the Ironman 28 times, even continuing to train through treatment for cancer.

“You can do things that were thought impossible for 80-year-olds,” she told BI, by “staying healthy and strong and having a commitment to living every day to the fullest.”

Being fit is great for your health — one 2019 study suggested that highly active people aged between 40 and 79 years old were 42% less likely to die prematurely. But you don’t have to already be active, because getting fit is beneficial at any age. The same study also suggested that people who were inactive at the beginning of the study, but who increased the amount of exercise they did over time, decreased their likelihood of dying from any cause by 24%.

Gruenfeld shared her tips for people wanting to be as fit as her at 79.

Get and stay strong

Gruenfeld said that she has found strength training helpful for her fitness, to maintain muscle as she has aged.

As you age, you naturally lose muscle — 5% to 10% of muscle mass per decade after the age of 50, according to a 2022 review of studies, which can make you less mobile and more prone to falls.

To maintain her muscle, Gruenfeld lifts heavy weights, to “really stress those muscles.”

BI has previously covered getting started with weightlifting, as well as how to build strength by doing the bare minimum.

Add activities you enjoy

You don’t have to only do strength training to get fit. Gruenfeld recommends adding “biking or hiking or running or swimming or golf or whatever physical activity you enjoy and fits into your lifestyle.”

Gruenfeld’s exercise regimen is already varied since her training consists of running, swimming, and cycling for the triathlon, and she also works with a personal trainer for strength training.

Varying what you do to keep fit is great to keep yourself motivated, and is also beneficial for health — BI previously reported on one 2022 study that found that doing cardio as well as weightlifting was linked to a 41% lower risk of mortality.

Make sure to rest

Gruenfeld rarely has a day without exercise, but she says she knows it’s important to take a rest from intense workouts.

The body actually needs recovery time to build muscle, and rest days reduce the likelihood of injury, according to UCLA Health. It’s best to do active recovery, where you rest from intense workouts but still incorporate some light movement into your day.

Sometimes, Gruenfeld will do something active, but gentler than her regular workouts.

“Go out for an easy walk or an easy swim, just anything that’s not really stressing the body but still keeps you moving,” Gruenfeld said.

Be vigilant about what you’re eating

“My best tip for nutrition is just simply to be vigilant about what you’re putting into your mouth,” Gruenfeld said.

She eats a balanced diet that contains a mix of fruit and vegetables, whole grains, fish, beans, eggs, and nuts, with limited sodium and sugar. When she’s training, she prioritizes carbohydrates before a workout to fuel her body, and protein afterward to build and maintain muscle.

Being conscientious about what you’re putting in your body is important for fitness. BI’s nutrition reporters love the 80/20 rule — where you eat healthily 80% of the time, and are flexible for the other 20% — because it’s a great way to fuel your body for exercise while maintaining balance and a healthy attitude toward food.