The 3-part fitness formula for longevity, according to a top sports doctor

Three hours a week might be all you need to boost your longevity — if you pick the right workouts.

Dr. Kevin Sprouse, owner of Podium Sports Medicine and medical advisor for longevity clinic Eternal, has worked with elite athletes for more than a decade, helping them to achieve peak performance.

He told Business Insider that the same science can help anyone live a longer, healthier life — by targeting factors like VO2 max and lactate threshold, key measures of fitness and endurance.

His prescription for the best results — even on a tight schedule — is a mix of strength training, steady cardio, and interval training.

"You're hitting different effort levels and getting a different stimulus with each one of them to really round it out," he said.

Zone 2 builds stamina and heart health

The foundation of longevity fitness is the ability to keep up a slow, steady effort over time.

The key here is Zone 2 cardio — exercising at 60-70% of your max effort, or a pace at which you can hold a conversation without getting out of breath.

Zone 2 can help boost your VO2 max — the measure of how efficiently your body can use oxygen — a key indicator of heart health and fitness linked to better longevity.

"You need to have a Zone 2 base," Sprouse said, to "build the machinery that allows you to get fitter."

If you're short on time, aim to spend about 50% of your exercise time doing Zone 2 cardio so you're not missing out on the benefits. If you've more hours a week to exercise, aim for 80% at Zone 2 and 20% at a higher intensity.

Interval training raises your lactate threshold

Shorter, higher-intensity bursts of effort challenge your heart and muscles differently, Sprouse said.

That can help you raise your "lactate threshold" — the point at which fatigue sets in.

In other words, if VO2 max is the engine, lactate threshold controls how much you can gun it when you're working out.

When you hit that threshold, your body runs low on oxygen and taps into glycogen (sugar reserves) stored in the muscles. Your limbs get heavier, and holding the pace becomes a slog.

"That's when you're on a running clock of how long you can sustain that effort," Sprouse said. "Lactate threshold is the true measure of fitness in the moment."

For best results, vary your training. Try 30 seconds of all-out effort, then rest and repeat. The next session, switch it up to three to five minutes of hard effort, or even 10 minutes at a race pace.

Weightlifting for muscle and strength

Cardio isn't enough on its own. Lifting weights strengthens muscles, controls blood sugar, and prevents injuries — all key for longevity.

"To build VO2 max, you have to have muscle size. Lower fat means higher VO2 max," Sprouse said. "All these things come together in this one number, and it's great for benchmarking against the population where you stand."

You don't need hours-long, daily gym sessions.

Aim to hit the weights a couple of days a week, depending on your schedule.

With the right strength training routine, you can be in and out of the gym in 30 minutes and still make progress. For more efficient strength workouts, focus on compound movements like squats, deadlifts, and presses that work multiple muscle groups at once.

Don't forget nutrition and recovery

Another example to follow from top athletes: recovery is as important as the workout.

"The thing that the world's best do better than the rest of us is recover," Sprouse said.

If you're not resting or eating well, it can make it harder to meet your goals even if you're doing everything right in the gym. Aim to eat enough protein, carbs, and calories to fuel your activities, without overdoing it on refined sugars and processed foods.

"We'll move the needle partially with exercise and partially with nutrition. If you just address one or the other, you're only getting half of the bang for the buck," Sprouse said.