Why Zone 2 Is the Missing Piece in Your Chicago Fitness Routine

Tired of grinding in the gray zone? This guide explains Zone 2 cardio, how to find your true Zone 2, and how to blend it with strength training for smarter fitness in Chicago.

If you hang around runners or cyclists on the Lakefront, on the 606, or people training in West Loop and Gold Coast condo gyms, you’ve probably heard “Zone 2” thrown around like a magic longevity code.  In simple terms, Zone 2 is steady, easy aerobic work, which is usually a pace where you can talk in full sentences, breathe a little heavier, but you’re nowhere near gasping (CDC, 2023).  Under the hood, it lines up with the intensity just below your first “threshold”, where your body is still comfortably clearing lactate, relying mostly on your aerobic energy system, and burning a higher proportion of fat for fuel (Meixner et al., 2025; Sitko et al., 2025).  This is why endurance coaches, cardiologists, and exercise physiologists love Zone 2…it’s sustainable, joint-friendly, and builds a huge base for performance and health.

From a physiology standpoint, regular Zone 2–style endurance work increases your skeletal muscle mitochondria (your “energy factories”) and capillary density, improving how efficiently your body uses oxygen and delivers blood to working muscles (Bishop et al., 2025; Mølmen et al., 2025).  Those changes show up as improvements in VO₂max and overall cardiorespiratory fitness (CRF).  Large meta-analyses consistently show that people with higher CRF have a much lower risk of cardiovascular events and all-cause mortality, independent of other risk factors (Kodama et al., 2009; Lang et al., 2024). 

In plain English: building your aerobic base with easy, consistent work can make your “fitness age” younger than your driver’s license suggests.  For my Chicago personal training clients in the West Loop, Gold Coast, and western suburbs, Zone 2 is usually the backbone of any endurance or longevity-focused plan.

So how do you actually find your Zone 2 without a lab test?  

A practical starting point is heart rate.  For many adults, Zone 2 lands roughly around 60 – 70% of maximum heart rate, or about 40 – 60% of heart-rate reserve (ACSM, 2021; Mayo Clinic Staff, 2023).  But there’s a lot of individual variability as recent work in cyclists shows big differences in where true Zone 2 sits when you compare simple percentage formulas versus physiological markers like lactate or ventilatory thresholds (Meixner et al., 2025).  That’s why I also lean on the talk test and RPE.  Zone 2 should feel like a 3-4 out of 10 effort: breathing faster than rest, but you can comfortably talk, not sing, while walking, jogging, or spinning on a bike (CDC, 2023).  Common mistakes include chasing your friend’s heart-rate zone, ignoring how stress or poor sleep raise your heart rate, and forgetting that beta-blockers or other meds can blunt heart-rate responses, which is something I pay close attention to with my personal training clients.

The reason Zone 2 feels “too easy” is exactly why it works.  Most busy adults in their 30s – 50s drift into the “gray zone”, which is a bit too hard to truly recover, but not hard enough to really push fitness.  It feels productive because you’re sweaty and breathing hard, but you can’t accumulate much volume without burning out.  Research on “polarized” endurance training shows that athletes make their best gains when ~80% of training time is at low intensity (like Zone 2) and only ~20% is hard (Seiler, 2010).  Zone 2 lets you stack a lot of minutes and weekly mileage while keeping fatigue manageable and joints happy.  When my Chicago office-worker clients finally commit to truly easy Zone 2, whether that’s brisk walks along the river, treadmill incline in a West Loop high-rise, or easy spins on a Gold Coast condo bike, their recovery, sleep, and energy often improve before their pace does.

Here’s a simple 6-week Zone 2 progression I use as a template.

Runners might start with 3 sessions per week of 20 to 30 minutes continuous Zone 2 in Week 1 – 2, build to 35 to 40 minutes in Week 3 – 4, then 45 – 50 minutes in Week 5 – 6.  Cyclists can use the same structure on a spin bike or road bike, keeping cadence relaxed and heart rate or talk test in check.  If you’re more of an “I just walk” person, start with 25 – 30 minutes of brisk walking (you can talk, but you wouldn’t want to sing) 3 – 4 days per week, then slowly nudge either duration or incline up.  Evidence suggests that meaningful mitochondrial and capillary adaptations can begin within 4 – 6 weeks of consistent endurance training, even in previously untrained adults (Mølmen et al., 2025).  The key is consistency: two to four Zone 2 sessions per week, week after week, will beat the occasional “hero workout” every time.

Finally, Zone 2 doesn’t replace strength training, it complements it.  

For a typical busy Chicago professional, a balanced week might include 2 – 3 total-body strength sessions (for example, Monday, Wednesday, Friday) and 2 – 3 Zone 2 sessions slotted on alternate days or tacked on as 20 – 30 easy minutes after lifting, as recovery allows.  That structure builds muscle, protects joints, and boosts metabolism while steadily raising your aerobic capacity and “fitness age.”  I’m more cautious chasing aggressive Zone 2 volume when someone is very deconditioned, recovering from illness, or already doing a lot of high-intensity work.  In those cases we build a basic movement and strength foundation first, then layer in structured Zone 2.  If you’re training in the West Loop, Gold Coast, or anywhere in Chicago and feel like you’re always working hard but not getting fitter, dialing in true Zone 2 might be the “boring” missing piece that changes everything.

References

How does the exercise prescription affect mitochondrial adaptations to training? Annual Review of Physiology, 87, 107–129.   https://www.annualreviews.org/content/journals/10.1146/annurev-physiol-022724-104836

Centers for Disease Control and Prevention. (2023). How to measure physical activity intensity.   https://www.cdc.gov/physical-activity-basics/measuring/index.html

Kodama, S., Saito, K., Tanaka, S., Maki, M., Yachi, Y., Asumi, M., et al. (2009). Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events: A meta-analysis. JAMA, 301(19), 2024–2035.  https://pubmed.ncbi.nlm.nih.gov/19454641/

Lang, J. J., Oh, H., Xi, B., & Ortega, F. B. (2024). Cardiorespiratory fitness and risk of incident cardiovascular disease, cancer, and all-cause mortality: A systematic review and meta-analysis. British Journal of Sports Medicine, 58(1), 18–26.   https://bjsm.bmj.com/content/58/10/556

Mayo Clinic Staff. (2023). Exercise intensity: How to measure it. Mayo Clinic.  https://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/exercise-intensity/art-20046887

Meixner, B., Lotzerich, H., & Figueiredo, P. (2025). Zone 2 intensity: A critical comparison of individual variability in different submaximal exercise intensity boundaries. Sports, 13(2), 42.   https://pmc.ncbi.nlm.nih.gov/articles/PMC11986187/

Mølmen, K. S., et al. (2025). Effects of exercise training on mitochondrial and capillary growth in human skeletal muscle: A systematic review and meta-regression. Sports Medicine. Advance online publication.   https://link.springer.com/article/10.1007/s40279-024-02120-2

Seiler, S. (2010). What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance, 5(3), 276–291. https://pubmed.ncbi.nlm.nih.gov/19454641/

Sitko, S., et al. (2025). What is “Zone 2 training”? A Delphi study on the concept of low-intensity endurance training. International Journal of Sports Physiology and Performance.  https://journals.humankinetics.com/view/journals/ijspp/20/11/article-p1614.xml

Chicago & Western Suburbs Personal Trainer

Looking to transform your fitness journey with personalized training and expert guidance?

Welcome to your next step toward a healthier, stronger you!  My name is Michael Padua and I offer personalized in-home personal training, functional strength & conditioning classes, and online programs designed to fit seamlessly into your lifestyle. Whether you’re in Chicago or the Western Suburbs, my mission is to help you build sustainable habits for long-term health and fitness success.

Ready to start your journey? 

Click the Let’s Chat button and let’s discuss your goals.  You can also sign up for my free newsletter for exclusive fitness tips, workouts, and motivation straight to your inbox, or keep exploring to learn more about how we can work together to reach your goals!

Follow Me

Michael Padua Fitness Personal Trainer Resume