Cardio Isn't One Size Fits All: How to Pick Yours

Most people pick cardio one of two ways. They do what they like, or they do whatever the machine says burns the most calories. Both are fine starting points. Neither asks what you need the cardio to do, and that decides whether it helps. When I build a client's plan, I pick the job first, then the tool.

Start with the job

Cardio can do several different things, and they pull in different directions.

• Health. Your heart, blood pressure and blood sugar respond to regular moderate work. The Physical Activity Guidelines put the target at 150 to 300 minutes a week of moderate activity, or half that if it's vigorous, plus two strength days.
• Weight loss. Cardio adds to the calorie deficit that food creates. It helps, and it's still the smaller lever.
• Supporting your lifting. A stronger heart and better conditioning let you recover between sets and handle more training.
• A warm-up and movement practice. Short, full-body work that gets joints moving before you lift.

A person with a sore knee who wants to lose 30 pounds needs a different answer from a person who lifts four days a week and wants to keep their muscle. Write the job down before you pick the machine.

Pick the tool for the job

If running hurts your knees, hips or back, running is the wrong tool for now, and that's allowed. A rower, a bike, an incline walk, jump rope or a short circuit of bodyweight movements gives the heart the same work without the impact.

If the job is health or weight loss, the research is kind to you. In a review of 13 trials comparing interval training with steady moderate cardio in overweight adults, both cut fat mass and waist size by similar amounts. The intervals took about 40 percent less time per week. Pick the one you'll show up for. For most of my clients that's brisk walking, because it fits between meetings and needs nothing.

If the job is supporting your lifting, the type matters a little more. A 2022 review found that adding cardio to a lifting program had a small negative effect on muscle fiber growth, and the effect showed up mainly when the cardio was running. Cycling didn't show it. If you lift hard and want to keep every bit of muscle while you lose fat, bike, row or walk on the days between lifting sessions rather than piling on running.

Progress it like you progress a lift

Cardio gets treated as a box to tick, and that's why it stalls. We track load, sets and reps in the weight room. The same rule applies on a bike. Track time, distance or average pace, and nudge one of them up every week or two.

If you rotate between machines, METs can help. A MET is a unit of effort relative to sitting still, so a 6 MET activity burns about six times what you burn at rest. The reference list for this covers 821 activities, so a stair climber on Monday and a rower on Thursday can be compared on the same scale. Two warnings come with it. The machine's readout is only as good as the weight you entered, so update it, and the number on the screen is an estimate with a wide margin. Use it to compare sessions with each other. It's far too rough to decide what you earned for dinner.

Do the kind you avoid

If you only lift, you need some cardio for your heart, and twenty minutes on a bike twice a week won't shrink your muscle. If you only do cardio, you need to lift, because a calorie deficit without strength work costs muscle along with fat, and the guidelines ask for two strength days for a reason.

Your body responds to what it's asked to do, whatever you happen to prefer. I'd rather a client do ten minutes of the thing they avoid than another hour of the thing they already like.

A plan that fits a normal week

Three or four lifting sessions, 20 to 30 minutes of easy cardio on two of the other days, and a step count you can hit without rearranging your life covers the guidelines and the weight loss job for almost everyone. If you want to see how the cardio fits around your lifting without wrecking recovery, read how to fit cardio into a weight loss program.

Sources

1. Piercy et al., JAMA, 2018. The Physical Activity Guidelines for Americans. Adults: 150 to 300 minutes a week of moderate activity, or 75 to 150 vigorous, plus muscle-strengthening on 2 or more days.
2. Wewege et al., Obesity Reviews, 2017. HIIT vs moderate-intensity continuous training on body composition in overweight and obese adults. 13 trials: both styles cut fat mass and waist size by similar amounts; intervals took about 40 percent less time.
3. Lundberg et al., Sports Medicine, 2022. Concurrent aerobic and strength training and muscle fiber hypertrophy. Adding cardio to lifting had a small effect on muscle fiber growth, mostly when the cardio was running.
4. Ainsworth et al., Medicine and Science in Sports and Exercise, 2011. Compendium of Physical Activities, MET values. The reference list of MET values for 821 activities.