Cardio vs. Strength Training: What Each Does for Your Body
Cardio and strength training offer different benefits. Here's how each affects your heart, muscles, metabolism, and overall health.
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Key Takeaways
- Cardio primarily strengthens the heart and lungs while improving endurance and caloric burn during exercise.
- Strength training builds muscle, increases resting metabolic rate, and supports bone density over time.
- Both forms of exercise contribute to mental health benefits, including reduced anxiety and improved mood.
- Physical activity guidelines from the CDC recommend adults incorporate both types each week.
- Most people benefit most from combining cardio and strength training rather than choosing one exclusively.
What Cardio Does to Your Body
Cardiovascular exercise — commonly called cardio — refers to any sustained, rhythmic activity that raises your heart rate and keeps it elevated. Walking, cycling, swimming, and jogging are classic examples. The primary adaptation target is your cardiovascular system: your heart, lungs, and blood vessels.
With consistent cardio training, the heart muscle itself becomes more efficient, pumping more blood per beat (known as increased stroke volume). Over time, this lowers your resting heart rate and reduces the workload on your heart during everyday activity. Research consistently links regular aerobic exercise to lower risk of cardiovascular disease, improved blood pressure, and better cholesterol profiles.
Cardio also burns a significant number of calories during the session itself, which can contribute to body weight management when paired with appropriate nutrition. However, it produces relatively modest changes to resting metabolic rate compared to strength training, since it does not build substantial muscle tissue.
150 min
Recommended weekly moderate aerobic activity
According to CDC Physical Activity Guidelines for Americans, adults should aim for at least 150 minutes of moderate-intensity cardio per week.
2–3x
Weekly strength sessions recommended
The same CDC guidelines recommend muscle-strengthening activities targeting all major muscle groups on two or more days per week.
~3–5%
Muscle mass lost per decade after age 30
Research in exercise physiology suggests adults can lose roughly 3–5% of muscle mass per decade without resistance training, a process called sarcopenia.
Beyond the physical, aerobic exercise has well-documented effects on mental health. It stimulates the release of endorphins and supports neuroplasticity — the brain's ability to form new connections — which is linked to reduced symptoms of depression and anxiety. For a closer look at how to time your sessions for maximum benefit, see what the research says about workout timing.
What Strength Training Does to Your Body
Strength training — also called resistance training — involves working muscles against an opposing force, whether that's free weights, resistance machines, bands, or your own bodyweight. The goal is to create controlled mechanical stress on muscle fibers, which prompts the body to repair and rebuild them larger and stronger.
One of the most significant long-term benefits is its effect on resting metabolic rate. Muscle tissue is metabolically active, meaning it burns more calories at rest than fat tissue. Building and maintaining lean muscle mass therefore raises the number of calories your body uses even when you're not exercising — an advantage that compounds over years and decades.
Strength training is also one of the most effective tools for maintaining bone density. Weight-bearing resistance exercise stimulates bone-forming cells (osteoblasts), which is particularly important for adults at risk of osteoporosis. Older adults may find this especially relevant — exercise considerations for people over 50 covers this and related topics in detail.
| Criterion | Cardio | Strength Training |
|---|---|---|
| Primary benefit | Heart and lung efficiency | Muscle growth and strength |
| Calorie burn during exercise | High (sustained sessions) | Moderate, with post-workout elevation |
| Resting metabolic rate | Modest long-term increase | Meaningful increase via muscle gain |
| Bone density support | Mild (weight-bearing cardio) | Strong evidence of benefit |
| Mental health benefits | Well-established | Well-established |
| Equipment needed | Minimal (walking, running) | Weights, bands, or bodyweight |
| Best frequency (per week) | Most days (moderate intensity) | 2–3 sessions with rest days |
For those without gym access, these benefits are still achievable. Strength training at home can be done effectively using bodyweight movements and minimal equipment.
Choosing One or Combining Both
The research is clear: the greatest overall health benefit comes from doing both. The U.S. Centers for Disease Control and Prevention (CDC) recommends that adults aim for at least 150 minutes of moderate-intensity aerobic activity per week, alongside muscle-strengthening activities on two or more days per week.
This doesn't mean every workout must be a lengthy two-part session. Many exercisers alternate days — cardio on some, strength on others — or use shorter sessions of each in the same week. What matters most is consistency over time, not a single perfect workout.
Both Types Count Toward Your Weekly Goals
You don't have to choose between cardio and strength in a single session. Many fitness approaches combine the two across a weekly schedule, alternating focus days. What matters is accumulating enough of each type over the week to meet general health benchmarks. Even small, consistent amounts of activity produce measurable benefits compared to a sedentary lifestyle.
If you're new to exercise, it's worth approaching both types with realistic expectations. Progress is gradual, and the body needs adequate rest to adapt. Avoid common misconceptions that can derail your efforts — exercise myths that keep people from making real progress addresses many of the most persistent ones. If you're exploring strength work specifically, free weights vs. resistance machines can help you choose the right equipment approach.
This article is for general informational purposes only and is not a substitute for personalized medical or fitness advice. Consult a qualified healthcare provider or certified fitness professional before beginning a new exercise program, especially if you have any existing health conditions.
Health Editorial Team
Health 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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