Key Takeaways
- Strength training builds muscle and increases resting metabolic rate; cardio primarily strengthens the heart and lungs.
- Both exercise types reduce risk of chronic disease, but through different physiological mechanisms.
- Most health guidelines recommend a combination of resistance and aerobic exercise each week.
- Neither approach is universally superior — the best choice depends on individual goals and health status.
- Consistency over time matters more than which type you choose.
Option A
Strength Training
The muscle-building, metabolism-shaping approach.
Best for: People looking to build muscle, improve bone density, and boost resting metabolic rate over time.
Option B
Cardio
The heart-health and endurance powerhouse.
Best for: People focused on cardiovascular health, endurance, calorie burn during exercise, and stress relief.
If your primary goal is building muscle and improving body composition
Strength Training
Resistance exercise is the most effective stimulus for muscle protein synthesis and long-term increases in lean mass and resting metabolic rate.
If you want to improve heart health and aerobic endurance
Cardio
Aerobic training consistently improves VO2 max, lowers resting heart rate, and reduces cardiovascular disease risk markers.
If you're over 50 and concerned about bone density and fall prevention
Strength Training
Weight-bearing resistance exercise is one of the most evidence-supported strategies for maintaining bone mineral density and muscle mass with age. See how training needs shift after 50 for more context.
If you want a well-rounded routine that supports overall health
Both
Current guidelines from organizations like the CDC and WHO recommend both aerobic and muscle-strengthening activities each week for optimal health outcomes.
If you're just starting out and want the most accessible entry point
Cardio
Walking, cycling, or swimming require minimal equipment and technique knowledge, making cardio easier to begin safely for most people.
What Each Type of Exercise Actually Does
When you lift weights or use resistance bands, your muscles experience small amounts of mechanical stress that trigger a repair-and-grow process. Over time, this leads to increased muscle fiber size (hypertrophy), greater force production, and a modestly elevated resting metabolic rate — meaning your body burns slightly more energy even at rest. Strength training also places stress on bones, which can help maintain or improve bone mineral density, a key concern as we age.
Cardiovascular exercise — running, cycling, swimming, brisk walking — works differently. It primarily challenges your heart, lungs, and circulatory system. Regular aerobic training improves the heart's stroke volume (how much blood it pumps per beat), lowers resting heart rate, enhances the body's ability to use oxygen efficiently (measured as VO2 max), and improves how muscles use glucose. These adaptations are strongly associated with reduced risk of heart disease, type 2 diabetes, and stroke.
For a closer look at how specific aerobic formats compare, see cardio formats compared.
| Criterion | Strength Training | Cardio |
|---|---|---|
| Primary adaptation | Muscle growth, strength | Heart/lung efficiency |
| Bone density impact | Strong positive effect | Moderate (weight-bearing only) |
| Calorie burn (during session) | Moderate | Higher per minute |
| Post-exercise calorie burn | Elevated (EPOC effect) | Returns to baseline faster |
| Resting metabolic rate | Increases with muscle gain | Minimal long-term change |
| Cardiovascular risk reduction | Moderate benefit | Strong, well-documented benefit |
| Equipment needed | Weights, bands, or bodyweight | Often none (walking, running) |
| Learning curve | Technique matters; moderate | Generally low barrier |
Calorie Burn, Metabolism, and Body Composition
A common misconception is that cardio always burns more calories than strength training. During a session, moderate-to-vigorous cardio typically burns more calories per minute. However, strength training creates what's known as excess post-exercise oxygen consumption (EPOC) — an elevated calorie burn that can persist for hours after a workout as muscles repair.
More importantly, because strength training increases lean muscle mass over months and years, it can raise your baseline metabolic rate. Muscle tissue is more metabolically active than fat tissue, so a higher proportion of muscle means more calories burned around the clock — even while sedentary.
~3 lbs
Average muscle gained with consistent strength training
A 2022 meta-analysis in the British Journal of Sports Medicine found adults averaged roughly 1–2 kg of lean mass after structured resistance programs lasting several months.
30–35%
Reduction in cardiovascular mortality risk
The WHO notes that regular aerobic physical activity is associated with approximately 30–35% lower risk of cardiovascular disease mortality compared to inactivity.
2x/week
Minimum strength sessions recommended by major health bodies
The CDC and WHO both recommend muscle-strengthening activity targeting all major muscle groups at least twice per week for adults.
For body composition goals, research generally shows that combining both training types produces better outcomes than either alone. If you're interested in building sustainable habits around exercise frequency, consistency matters more than intensity over the long run.
Mental Health and Stress Effects
Both strength training and cardio have documented mental health benefits, though the mechanisms differ somewhat. Aerobic exercise is well-established as a mood regulator — it stimulates the release of endorphins and, with regular practice, supports lower cortisol levels and improved sleep architecture. Research also links regular cardio to reduced symptoms of anxiety and mild-to-moderate depression.
Resistance training has its own psychological benefits. Studies show it can improve self-efficacy, reduce symptoms of anxiety, and support cognitive function. A 2017 meta-analysis published in JAMA Psychiatry found that resistance exercise was associated with significant reductions in depressive symptoms across a range of populations.
It's worth noting that exercise of any kind can help buffer against chronic stress. For a deeper look at how stress affects the body, see what stress actually does to your body and mind.
This article is for general informational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting a new exercise program, particularly if you have an existing health condition.
What Current Guidelines Recommend
Major health bodies — including the CDC, WHO, and the American College of Sports Medicine — do not ask people to choose between cardio and strength training. Their guidelines recommend both. For most adults, this means:
- At least 150–300 minutes of moderate-intensity aerobic activity per week (or 75–150 minutes of vigorous activity), and
- Muscle-strengthening activities involving all major muscle groups at least two days per week.
These recommendations exist because the health benefits of each type are largely complementary, not redundant. Cardio and strength training affect different physiological systems, and evidence consistently shows that people who do both have better health outcomes than those who do only one.
If you're newer to exercise, walking is an often underestimated entry point. Walking's documented benefits for cardiovascular and metabolic health are more robust than many people expect. And if you're wondering whether a gym is necessary to get started, working out at home versus a gym involves real trade-offs worth understanding before committing.
A Note on Special Populations
Adults over 50, pregnant individuals, those with chronic conditions, and anyone recovering from injury have specific exercise considerations that general guidelines may not fully address. If you fall into one of these groups, consulting a healthcare provider or certified exercise professional before changing your training is strongly recommended. For age-specific context, see exercise guidance for adults over 50.