Cardio vs. Strength Training: What Each Does for Your Body
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In this article
Cardio and strength training serve different purposes. Understand what each type of exercise does and how combining them supports overall health.
Key Takeaways
- Cardio primarily strengthens the heart and lungs and supports endurance and calorie burning during exercise.
- Strength training builds muscle mass, increases bone density, and raises resting metabolic rate over time.
- Both forms of exercise have been linked to improved mood, reduced anxiety, and better cognitive function.
- Most health guidelines recommend including both cardio and strength training each week for well-rounded fitness.
- Neither approach alone is universally superior — your goals, age, and health status all shape the right balance.
What Cardio Does for Your Body
Cardiovascular exercise — commonly called cardio — refers to any sustained activity that elevates your heart rate and keeps it elevated for an extended period. Walking briskly, cycling, swimming, jogging, and dancing all qualify. The defining feature is that your cardiovascular system (heart, lungs, blood vessels) is doing the heavy lifting.
Over time, regular cardio makes the heart a more efficient pump. It can lower resting heart rate, improve blood pressure, and increase the volume of blood the heart moves with each beat — a measure called stroke volume. The lungs also adapt, improving how efficiently oxygen is delivered to working muscles.
Cardio is often associated with calorie burning during the session itself, which can support weight management when paired with appropriate nutrition. Research also consistently links aerobic exercise to reduced risk of cardiovascular disease, type 2 diabetes, and certain cancers. For more on how exercise affects mood and stress, see our article on exercise and mental health.
| Criterion | Cardio Training | Strength Training |
|---|---|---|
| Primary system targeted | Heart, lungs, circulatory system | Muscles, bones, connective tissue |
| Main adaptation | Improved cardiovascular efficiency | Increased muscle mass and strength |
| Calorie burning | Higher during the session | Higher at rest over time |
| Bone density impact | Moderate (weight-bearing types) | Strong, well-documented benefit |
| Heart health benefit | Direct and well-established | Present, but more indirect |
| Examples | Walking, cycling, swimming, jogging | Weight lifting, resistance bands, bodyweight |
| Equipment needed | Minimal to none for many activities | Varies; bodyweight requires none |
What Strength Training Does for Your Body
Strength training — also called resistance training — involves working muscles against an external load. This includes free weights, resistance machines, resistance bands, and even bodyweight exercises like push-ups or squats. If you're weighing equipment options, our guide on free weights vs. resistance machines covers the trade-offs in detail.
When muscles are challenged beyond their current capacity, they adapt by growing stronger and, with adequate protein intake, larger. This process — called hypertrophy — also contributes to increased resting metabolic rate, meaning your body burns more calories even when you're not exercising. That effect accumulates meaningfully over months of consistent training.
Strength training also stimulates bone remodeling, helping maintain or increase bone density — a significant concern as people age. It supports joint stability, improves posture, and underpins everyday functional movement like lifting, carrying, and climbing stairs.
2x/week
Recommended muscle-strengthening frequency
U.S. Department of Health and Human Services Physical Activity Guidelines recommend muscle-strengthening activities on two or more days per week for adults.
150 min
Weekly moderate aerobic activity target
The same guidelines suggest at least 150 minutes of moderate-intensity aerobic activity per week for substantial health benefits in healthy adults.
~1% per year
Rate of muscle mass decline after age 30
Research estimates adults begin losing muscle mass at roughly 1% per year after age 30 without resistance training, a process called sarcopenia.
How They Compare — and Why You Likely Need Both
Neither cardio nor strength training is categorically better. They target different physiological systems and produce different adaptations. A useful way to think about it: cardio tends to improve your engine (the heart and lungs), while strength training builds the chassis (muscles, bones, and connective tissue).
Major health organizations, including the U.S. Department of Health and Human Services, generally recommend that adults aim for both moderate-intensity aerobic activity and muscle-strengthening activities each week. The specific targets vary based on individual health status, so consulting a healthcare provider before starting a new routine is a sensible step.
It's also worth noting that the two approaches aren't entirely separate. Circuit-style strength training can elevate heart rate significantly, and sustained cardio does engage muscles. The distinction matters most when you're designing a program around a specific goal. For most people, a balanced weekly routine that includes both is supported by the broadest body of evidence. Read more on building durable habits in our piece on why consistency matters more than intensity.
The Two Approaches Work Best Together
While it's tempting to choose one type of exercise over the other, most fitness and public health guidance supports doing both. If time is limited, even short sessions of each can provide meaningful benefit. Where and how you exercise matters less than doing it consistently — see our comparison of home vs. gym workouts for practical options.
This article is for general informational purposes only and does not constitute medical advice. Speak with a qualified healthcare professional before beginning any new exercise program, especially if you have a chronic condition, injury, or other health concern.
Author
Health & Wellness Editorial Team
Health & Wellness Editorial Team is the collective byline for our editorial team and contributor network. Articles published under this byline or an editorial pen name are researched, written, and reviewed according to our editorial standards for clarity, consistency, and independence before publication.
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