All About Cardio: How It Fits With Strength Training
If you strength train, you've probably wondered where cardio fits in. Do you need more of it? Is your strength training enough? Do you have to run?
Cardio matters - but it's often overcomplicated. For most busy adults training 2-3 times per week, a straightforward approach covers most of what the research actually recommends.
Do you need cardio if you strength train?
Yes - but cardio should support your training, not compete with it. Most people do well with strength training 2-3 times per week, regular low-intensity movement like walking most days, and a small amount of higher-intensity work occasionally. That structure covers the major health benefits of both without requiring hours of additional training or workouts you don't enjoy.
What is cardio?
Cardiovascular training - also called aerobic training or cardio - is any exercise that raises your heart rate and breathing rate, challenging your heart and lungs to meet the oxygen demands of the activity.
Common forms: walking, hiking, running, biking, swimming, rowing, elliptical, and circuit training. Intensity can range from a slow walk to an all-out sprint, and the zone you're training in affects what kind of benefit you get.
Why cardio matters (the benefits go beyond calories)
Most people think of cardio primarily as a calorie-burning tool. That undersells what it actually does.
Regular cardiovascular training is linked to:
Lower blood pressure and cholesterol
Better blood sugar control and reduced diabetes risk
Decreased risk of cardiovascular disease
Improved recovery between strength training sets
Better sleep quality
Improved mood and mental health
Stronger mitochondrial function - which supports energy, longevity, and disease prevention
That last point is worth noting. Zone 2 cardio specifically supports mitochondrial health in a way that has meaningful long-term implications for how well your body functions as you age.
And even if your only goal is getting stronger, cardio helps. Improved cardiovascular fitness increases blood flow to muscles, improves endurance between sets, and makes recovery faster. A better aerobic base means you can train harder and recover better from strength work.
Understanding cardio intensity - a simple framework
You don't need to obsess over heart rate numbers to train effectively. A practical way to think about intensity:
Low to moderate intensity (Zones 1-2): You can hold a comfortable conversation. Feels sustainable for a long time. Examples: walking, easy biking, a relaxed hike. This is where most of your cardio time should be.
Moderate to hard (Zone 3-4): Talking is possible but harder. Breathing is noticeably elevated. Examples: a steady jog, moderate-pace cycling.
High intensity (Zone 5): Talking is difficult or impossible. Feels like close to maximum effort. Examples: sprints, hard intervals. This should be a small portion of total training time.
For a rough heart rate estimate, the classic formula is 220 minus your age. At 40 years old, estimated maximum heart rate is around 180 bpm. Zone 2 typically falls around 60-70% of that number. These are approximations - a heart rate calculator gives you a more precise range. If you have cardiovascular concerns or risk factors, consult your physician before testing near maximum intensity. Here’s a calculator that can help you estimate your heart rate ranges.
Zone 2 cardio - why it matters more than most people realize
Zone 2 has gotten significant attention in recent years, and the attention is warranted.
Training at low-to-moderate intensity builds your aerobic base - the foundation that supports both higher-intensity cardio work and strength training. It improves how efficiently your body uses fat for fuel, enhances mitochondrial health, and speeds up recovery between strength sessions. For longevity and long-term health, consistent Zone 2 work is one of the most evidence-supported things you can do.
For most people, Zone 2 is achievable through brisk walking. As your fitness improves, you'll be able to do more work at the same heart rate - which is a direct sign that your cardiovascular fitness is improving.
The practical target for most people: 100-200 minutes of Zone 2 work per week. That sounds like a lot until you realize a couple of 45-60 minute walks covers a significant portion of it.
Does strength training count as cardio?
Partially - with an important caveat.
Strength training provides meaningful cardiovascular benefits when you're first starting out. Your heart rate elevates, breathing increases, and your aerobic system gets challenged. For beginners, this crossover is real.
But as your fitness improves, the cardiovascular benefit from strength training plateaus. Your body adapts, sessions become more manageable, and the aerobic challenge decreases. At that point, dedicated Zone 2 work becomes necessary to keep building your aerobic base. The two forms of training develop different systems and are better treated as complements rather than substitutes.
Should you separate strength and cardio?
Generally yes, if you want to get the most out of both.
High-Intensity Interval Training (HIIT) has become popular, and true HIIT - very high effort over short periods - has legitimate benefits. The problem is when gyms build 45-60 minute workouts at near-HIIT intensity throughout. That approach tends to land in a zone that's too intense for the aerobic benefits of Zone 2 but not intense enough for the specific benefits of Zone 5, while also compromising strength work.
If you're training at high enough intensity that your heart rate is maxed out, heavy strength work becomes difficult and form suffers. The two types of training are better done separately or structured so that strength work isn't compromised by cardiovascular fatigue.
For strength workouts, the priorities are: good form with appropriately heavy weights, moderate pace that doesn't spike heart rate, and enough rest to maintain technique.
For dedicated cardio sessions, the priorities are: Zone 2 for the bulk of it, with short bursts of higher intensity occasionally.
What a practical weekly structure looks like
For most adults training at bStrong:
2-3 full-body strength workouts per week - this is the foundation
100+ minutes of Zone 2 work weekly - walking covers most of this for most people; 150-200 minutes is the better target
10-20 minutes of higher-intensity Zone 4/5 work weekly - this can be the conditioning finisher at the end of your strength sessions, or a few sprint efforts on a bike, rower, or trail
That totals roughly 3-4 hours of movement per week including strength sessions - achievable for most busy adults and covers the major bases for health, strength, and longevity.
For endurance athletes or people training for a specific event, the structure looks different. A useful rule of thumb for endurance training is the 80/20 guideline: roughly 80% of cardio time in Zones 1-2, 20% in Zones 4-5.
What most people get wrong about cardio
Doing too much intensity too soon. Jumping into frequent high-intensity sessions before building an aerobic base usually leads to burnout, excessive soreness, and inconsistency. Most people need more easy movement and less hard effort than they think.
Treating cardio as the only tool for fat loss. Cardio burns calories during the session. Strength training builds muscle that affects how your body uses calories throughout the day. Both matter - but they play different roles and neither fully replaces the other. For more on this, read our strength training vs cardio for fat loss post.
Skipping Zone 2 entirely in favor of HIIT. Zone 2 is where the long-term aerobic adaptations happen. If most of your cardio is high-intensity without the Zone 2 base underneath it, you're building on an incomplete foundation.
Undervaluing walking. Walking is one of the most effective and sustainable forms of cardio for most adults. It's low injury risk, easy to fit into a day, and highly effective for Zone 2 accumulation. Consistent walking beats occasional intense cardio for long-term health outcomes.
How to fit Zone 2 into a busy schedule
Zone 2 doesn't have to feel like a workout. For most people at conversational intensity, it's genuinely sustainable and enjoyable.
Practical ways to accumulate Zone 2 time:
Walk your dog, walk with a partner, or walk during a phone call
Use a cardio machine at the gym with a podcast or show
Walk during lunch breaks
Take the stairs and park farther away consistently
Active recovery walks on non-training days between strength sessions
If you're training at bStrong 2-3 times per week, Zone 2 on the days between strength sessions serves as active recovery - it keeps you moving, aids recovery, and builds your aerobic base without adding meaningful fatigue.
What this looks like at bStrong
At bStrong in Bellevue and Redmond, strength training is the foundation. Most members train 2-3 times per week and add cardio around that - not instead of it.
The conditioning finisher at the end of each session covers a portion of the weekly Zone 4-5 target. Walking and light movement on non-training days covers most of the Zone 2 target. For most members, that structure is enough to support health, recovery, and strength progress without adding complicated programming on top of an already busy life.
For more on how strength and cardio work together, read our why cardio isn't enough post and our benefits of strength training guide.
Frequently asked questions
Do I need to run to get cardio benefits?
No. Many people build strong cardiovascular fitness without ever running. Walking, biking, swimming, rowing, and hiking all provide Zone 2 benefits. Running is one option among many - choose what you'll actually do consistently.
Is walking enough for cardio?
For most adults, yes - especially when done consistently and at a pace that keeps heart rate in Zone 2. 150-200 minutes of brisk walking per week covers the major cardiovascular health recommendations and contributes meaningfully to recovery and longevity.
Will cardio hurt my strength gains?
Not when it's balanced appropriately. Low-intensity Zone 2 cardio typically improves recovery and doesn't interfere with strength training. Very high volumes of intense cardio can compete with strength adaptations - which is why the structure matters. For most people training 2-3 times per week, adding moderate amounts of cardio has no negative effect on strength.
Should I do cardio on non-training days?
That works well for most people, particularly low-intensity Zone 2 movement. Active recovery on rest days - walking, easy biking, a relaxed swim - aids muscle recovery, keeps the aerobic system active, and doesn't add meaningful fatigue.
How much cardio do I actually need?
The practical weekly targets for most adults: 100-200 minutes of Zone 2 work, 10-20 minutes of Zone 4-5 work, and 2-3 strength sessions. Walking covers most of the Zone 2 requirement for many people. The conditioning finisher in strength sessions covers much of the higher-intensity requirement.
What's the difference between Zone 2 and HIIT?
Zone 2 is low-to-moderate intensity - you can hold a comfortable conversation, and you could sustain it for a long time. HIIT is high-intensity interval training - very hard effort for short periods, near or at maximal capacity. Zone 2 builds aerobic base, mitochondrial health, and long-term cardiovascular fitness. HIIT builds peak capacity and anaerobic fitness. Both have a place, but most people need significantly more Zone 2 than HIIT.
Cardio doesn't need to dominate your schedule or involve workouts you dread. For most people training 2-3 times per week, a simple structure - strength as the foundation, walking and light movement filling the Zone 2 requirement, and the conditioning finisher covering the high-intensity piece - is enough.
If you want a coached program that builds this structure in for you, our 3-week trial is a practical place to start. A consultation call, an Intro / Ramp Up session, 6 coached small group personal training workouts, an InBody scan, and practical nutrition resources - all for $99 at our Bellevue and Redmond locations.