Why Your Body Isn't Changing Despite All That Cardio

You show up. You put in the miles, the bike rides, the time on the machine. And your body still isn't changing the way you expected.

If that's you, the cardio probably wasn't wasted. It may just be doing only part of the job.

The cardio wasn't wasted

Cardio does real work. It supports your heart health, and it can help with fat loss. Those are good reasons to keep doing it, especially if you enjoy it.

So this isn't a post about quitting cardio. It's about what cardio doesn't do on its own.

Strength training does a different job

Cardio and strength training aren't two versions of the same thing. They ask different things of your body, and they tend to give you different results.

Resistance training is especially important for building and maintaining muscle, and muscle influences how your body looks, feels and performs after 40.

A well-known trial shows the difference. Researchers at Duke followed sedentary, overweight or obese adults through eight months of supervised training in one of three groups: aerobic training, resistance training, or both (Willis et al., 2012). Fat mass went down in the aerobic group and in the combined group, but not in the resistance-only group. Lean mass went up in the resistance group and in the combined group, but not in the aerobic-only group.

Two caveats are worth knowing. The people in that study were sedentary adults aged 18 to 70, not specifically people over 40 who already train, and only about half of those enrolled finished the trial with complete data. It's one study, not the final word. But it fits what the Reel says: cardio and strength do different jobs, and if your body isn't changing, cardio may be doing only part of the work.

Three ways to fit both into your week

1. Keep the cardio you enjoy. You don't need to give it up. The walks, rides and runs you actually look forward to are the ones you'll keep doing, and they're doing real work for your heart.

2. Add strength training at least twice a week. The CDC's adult guidelines call for muscle-strengthening activity on two days each week, working all the major muscle groups: legs, hips, back, abdomen, chest, shoulders and arms (CDC, Adult Activity: An Overview). That can be machines, free weights, bands or bodyweight work. If you're new to it, starting with two simple sessions beats waiting for the perfect program.

3. Pay attention to what you're eating, too. Training is only part of what changes your body. If the results aren't showing up, look at your food along with your workouts instead of adding more of the same exercise.

What keeps this realistic

This doesn't mean cardio is bad or that strength training is a shortcut. It means each one does a different job, and a plan that has both covers more of what you want.

If you're new to strength training, or you have a health condition, an injury or take medication, it's worth talking with your doctor before you change your routine.

Want a plan that adds the strength?

Our guide Get Strong, Lean & Energized After 45 lays out a 12-week blueprint with structured strength training, protein targets, and a simple way to track your progress.

For women: The Woman's No-BS Guide to Fitness After 40 covers training and nutrition for women over 40.

And if you'd rather not figure out the balance alone, that's what we built The Fit Velocity for. We match you with a vetted coach and a dedicated Fitness Journey Manager, so your plan keeps changing as you do.

Frequently asked questions

Why isn't cardio changing my body? Cardio supports your heart and can help with fat loss, but it's only one of the jobs your body needs done. Resistance training is especially important for building and maintaining muscle, so if you do a lot of cardio and little strength work, cardio may be doing only part of the job.

Is cardio or strength training better after 40? They do different jobs, so it's not either-or. Keep the cardio you enjoy and add strength training at least twice a week.

How much strength training do I need? The CDC recommends muscle-strengthening activity two days a week for adults, covering all the major muscle groups. Start with what you can keep doing consistently.

Keep the cardio. Add the strength.

References

• Willis LH, Slentz CA, Bateman LA, et al. Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults. Journal of Applied Physiology. 2012;113(12):1831-1837. PubMed 23019316.

• Centers for Disease Control and Prevention. Adult Activity: An Overview. Physical activity guidelines for adults. cdc.gov (accessed 10-30-2026).

Sources used only in this week's graphics (add to the reference list if you want one list for the week):

• Fradkin AJ, Zazryn TR, Smoliga JM. Effects of warming-up on physical performance: a systematic review with meta-analysis. Journal of Strength and Conditioning Research. 2010;24(1):140-148. (Thursday infographic, R-078)

• National Institutes of Health, Office of Dietary Supplements. Dietary Supplements: What You Need To Know. ods.od.nih.gov. (Saturday infographic, R-080)

About the Author

Alfonso Hammond is a 30-year fitness industry veteran, founder of The Fit Velocity, and a firm believer that lasting fitness is built on purpose, accountability, and relationships, not shortcuts. He created The Fit Velocity because he saw too many men and women over 40 following programs that were never designed for the lives they actually live. They didn't need another workout. They needed a Journey worth staying on. His philosophy is simple: People don't start from nothing. They start from everything they already are. Whether working with competitive athletes or someone taking their first walk in years, Alfonso's approach remains the same: strengthen the person, strengthen the Journey, and the results will follow

Every article, guide, and resource published through The Fit Velocity is built upon the same principles found throughout the TFV Testament, practical, honest, and grounded in the belief that meaningful progress comes from reclaiming who you are, strengthening the person you are building, and continuing to thrive throughout life.