Key Takeaways
- Cardio primarily strengthens the heart and lungs, while strength training builds muscle and bone density.
- Both exercise types reduce risk of chronic disease, though through different biological mechanisms.
- Research consistently supports combining cardio and strength training for the broadest health benefits.
- Neither approach is inherently superior — the best choice depends on individual goals and health context.
- Even modest amounts of either type of exercise produce measurable health improvements.
Our Verdict
Both cardio and strength training deliver real, well-documented health benefits, and decades of research show they complement rather than compete with each other. Most people benefit from incorporating some of both into a regular routine, rather than treating the two as mutually exclusive. The question isn't which is better — it's which combination fits your goals, schedule, and current fitness level.
| Best for | Recommended |
|---|---|
| Those whose primary goal is cardiovascular health and endurance | Cardio-focused training with some strength work added |
| Those focused on muscle preservation, bone density, or metabolic health | Strength-focused training with cardio for heart health |
| Most generally healthy adults seeking broad health benefits | A balanced combination of both cardio and strength training |
| Complete beginners unsure where to start | Low-intensity cardio initially, adding strength training gradually |
What Each Type of Exercise Actually Does
Cardio exercise — sometimes called aerobic exercise — refers to sustained physical activity that raises your heart rate over time. Running, cycling, swimming, and brisk walking all qualify. The primary adaptations happen in the cardiovascular and respiratory systems: your heart becomes more efficient at pumping blood, your lungs improve oxygen exchange, and your body gets better at using fat and glucose for fuel during prolonged effort.
Strength training, also called resistance training, involves working muscles against load — whether that's free weights, machines, resistance bands, or bodyweight. The primary adaptations are muscular and skeletal: muscle fibers grow and strengthen, connective tissue becomes more resilient, and bone density tends to increase in response to the mechanical stress. These adaptations also improve insulin sensitivity and resting metabolic rate over time.
Neither category is monolithic. Walking and running produce different cardio adaptations, and light resistance work differs meaningfully from high-intensity lifting. Understanding these nuances matters when setting realistic goals.
What the Research Shows on Health Outcomes
| Cardio Training | Strength Training | |
|---|---|---|
| Primary system targeted | Cardiovascular & respiratory | Muscular & skeletal |
| Calorie burn during workout | Generally higher per session | Generally lower per session |
| Resting metabolic rate effect | Modest long-term effect | Greater long-term effect via muscle mass |
| Bone density benefit | Modest, weight-bearing types mainly | Strong, especially with load |
| Heart health evidence | Very strong | Strong, complementary |
| Blood sugar regulation | Significant benefit | Significant benefit |
| Equipment typically needed | Minimal (walking, running) | Weights, bands, or machines |
Large population studies — including analyses drawing on data from hundreds of thousands of adults — consistently show that both forms of exercise reduce all-cause mortality risk. A widely cited analysis published in the British Journal of Sports Medicine found that adults who did both aerobic and muscle-strengthening activity had lower mortality risk than those who did either type alone.
Cardio exercise has particularly strong evidence for reducing cardiovascular disease risk, improving blood pressure, and supporting mental health outcomes including reduced depression and anxiety symptoms. Strength training has robust evidence for preserving lean muscle mass (which naturally declines with age), improving blood sugar regulation, and reducing injury risk by strengthening connective tissue.
~30–35%
Reduced mortality risk with combined exercise
Adults doing both aerobic and muscle-strengthening activity show lower all-cause mortality risk than those doing either type alone, per British Journal of Sports Medicine analyses.
2+ days/week
Strength training recommended by U.S. guidelines
The U.S. Department of Health and Human Services recommends muscle-strengthening activity on at least two days per week for healthy adults.
It's worth noting that much of this research is observational, meaning it identifies associations rather than proving direct causation. Still, the convergence of evidence across study types is substantial enough that major health organizations — including the CDC and the American Heart Association — recommend including both types of activity in a regular fitness routine.
The Case for Combining Both
The framing of cardio versus strength training is somewhat misleading, because the two aren't physiologically competing — they target different systems that both need attention. Several fitness myths have reinforced this false binary, including the idea that lifting makes you "bulky" or that cardio alone is sufficient for metabolic health.
A combined approach tends to produce better outcomes across multiple markers simultaneously: cardiovascular fitness, muscular strength, body composition, bone density, and metabolic function. For people managing weight, research suggests that cardio burns more calories during the workout itself, while strength training may support a higher resting metabolic rate over time — making them genuinely complementary for that goal.
Starting Small Still Counts
Research shows that even small increases in physical activity — adding 10 to 20 minutes of moderate movement several days a week — produce meaningful health improvements in previously sedentary adults. You don't need to start with lengthy or intense sessions. Building a consistent habit gradually is more effective long-term than attempting an aggressive program and burning out. Focus on showing up regularly before worrying about volume or intensity.
If time is a constraint, research on concurrent training (doing both in the same session or week) shows that benefits from each are largely preserved even when combined. Order may matter slightly — many exercise physiologists suggest strength work before cardio in the same session to avoid pre-fatiguing muscles — but the most important factor is consistency over time, not session architecture.
If you're new to resistance work, see our beginner's guide to strength training for a practical starting point.
Finding a Sustainable Starting Point
Current U.S. public health guidelines (from the Department of Health and Human Services) suggest adults aim for at least 150 minutes of moderate-intensity aerobic activity per week, plus muscle-strengthening activities on two or more days. These are population-level recommendations, not personal prescriptions — talk with a healthcare provider about what's appropriate for your specific health situation, particularly if you have a chronic condition or have been inactive for an extended period.
Sustainability matters more than optimization. A routine you maintain for months produces far greater health benefit than a more intense plan abandoned after two weeks. Whether you prefer group classes or solo training, the goal is building a habit that fits your life. Starting with shorter, lower-intensity sessions and gradually increasing volume is generally safer and more effective than dramatic initial effort.
Understanding different cardio intensities can also help you structure aerobic work more effectively without overexerting yourself early on.
This article is for general informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before beginning or significantly changing any exercise program, especially if you have an existing health condition.