The One Fitness Number Chicago Professionals Ignore (and How VO₂max Can Rewind Your ‘Fitness Age’)

Learn what VO₂max really is, why it predicts your ‘fitness age,’ and how smart personal training in Chicago’s West Loop and Gold Coast can improve it in just 6 – 12 weeks.

VO₂max is one of those terms that sounds very “lab coat,” but it describes something simple and powerful, how much oxygen your body can use when you’re working as hard as you possibly can.  

Technically, it’s the maximum amount of oxygen your heart, lungs, blood, and muscles can deliver and use per minute during intense exercise, usually expressed in milliliters of oxygen per kilogram of body weight per minute (mL·kg⁻¹·min⁻¹) (Kaminsky et al., 2015).  In a clinical exercise physiology lab, VO₂max is measured with a mask on a treadmill or bike, but in the real world, whether you’re training in a Chicago condo gym, a West Loop personal training studio, or out on the Lakefront Trail, we can estimate it from well-designed fitness tests or even from wearables like WHOOP or Garmin.  The higher your VO₂max, the more “engine” you have for everything from climbing stairs to running a 10K.

Where VO₂max really earns its reputation is in long-term health and longevity.  Large meta-analyses show that people with higher cardiorespiratory fitness (CRF), often measured as VO₂max or METs, have a much lower risk of dying from any cause compared with those who are unfit (Kodama et al., 2009; Laukkanen et al., 2022; Lang et al., 2024).  For example, every 1-MET (about 3.5 mL·kg⁻¹·min⁻¹) increase in fitness is associated with roughly an 11 – 13% lower risk of all-cause mortality (Kodama et al., 2009; Laukkanen et al., 2022).  The American Heart Association now argues that CRF should be treated like a clinical “vital sign” because it predicts cardiovascular disease, cancer, and other health outcomes beyond traditional risk factors (Ross et al., 2016).  That’s what people mean by “fitness age”, if your VO₂max is high for your age, your body is effectively younger on the inside than the calendar says.

The good news for busy adults is that VO₂max can improve meaningfully in as little as 6 – 12 weeks with the right training. 

Controlled trials show that structured programs combining continuous aerobic work and high-intensity intervals can raise VO₂max and overall fitness in previously sedentary adults over 12 weeks (Amaro-Gahete et al., 2019).  Meta-analyses also find that high-intensity interval training (HIIT) which is short bursts of hard effort with recovery, reliably increases VO₂max across healthy, overweight, and athletic adults (Wen et al., 2019).  One study even found that 12 weeks of very brief sprint intervals produced similar VO₂ improvements to traditional longer endurance training, despite much less total workout time (Gillen et al., 2016).  Practically, that might look like two days per week of intervals (for example, 4 – 6 × 2 – 3 minutes hard with equal easy recovery) and one to two days of steady “Zone 2” work where you can still talk in full sentences.

So what counts as a “good” VO₂max for someone in their 30s to 50s who has a career, family, and maybe a dog that hates the Chicago winter?  Large fitness registries using thousands of treadmill and bike tests show that VO₂max naturally declines with age, but there is a wide range at every decade (Kaminsky et al., 2015; Peterman et al., 2020).   For many men in their 40s, a VO₂max in the mid-30s to low-40s mL·kg⁻¹·min⁻¹ is around average, while women often sit in the high-20s to mid-30s range (Kaminsky et al., 2015; Peterman et al., 2020).  Being “above average” for your age group is already associated with meaningful reductions in health risk.  For most Chicago professionals, a realistic target over time is to move from “low” to “moderate” or from “moderate” to “high” fitness for their age bracket and you necessarily don’t need to chase marathoner-level VO₂max scores.

When I build a VO₂max-focused block for a personal training client in Chicago,  I usually think in 8 – 10 week phases.

A simple template is:

• two interval days (for example, Tuesday and Friday),
• one to two Zone 2 days (brisk walking, easy jogging, cycling),
• and two to three strength sessions to protect muscle and joints.

Early weeks might use shorter, moderate intervals (like 6 × 1 minute hard / 2 minutes easy), progressing to longer efforts or slightly higher intensities as their recovery, sleep, and life stress allow.  For clients using wearables or devices like WHOOP or Garmin, we also watch recovery metrics and resting heart rate trends to make sure we are nudging VO₂max up, not just grinding them into fatigue.

There are also times when I do not chase VO₂max directly.  If a new client is sleeping poorly, under-eating, highly stressed, or deconditioned, the first priorities are consistency, basic movement, and strength.  In those cases, we start with walking, simple cardio intervals at a comfortable pace, and foundational strength work, and VO₂max improves as a side effect.  High-intensity intervals and aggressive VO₂max goals make more sense once someone has a base of 3 – 4 active days per week, good technique, and enough recovery.

The big picture is this:

You do not need to live in the pain cave to extend your “fitness age”, you need smart, repeatable training that fits your actual life in Chicago.

References

Amaro-Gahete, F. J., De-la-O, A., Sanchez-Delgado, G., Robles-Gonzalez, L., Jurado-Fasoli, L., Ruiz, J. R., & Castillo, M. J. (2019). Changes in physical fitness after 12 weeks of structured concurrent exercise training, high-intensity interval training, or whole-body electromyostimulation training in sedentary middle-aged adults: A randomized controlled trial. Journal of Clinical Medicine, 8(3), 278. https://pubmed.ncbi.nlm.nih.gov/31105580/

Gillen, J. B., Martin, B. J., MacInnis, M. J., Skelly, L. E., Tarnopolsky, M. A., & Gibala, M. J. (2016). Twelve weeks of sprint interval training improves indices of cardiometabolic health similar to traditional endurance training despite a five-fold lower exercise volume and time commitment. PLOS ONE, 11(4), e0154075. https://pmc.ncbi.nlm.nih.gov/articles/PMC4846072/

Kaminsky, L. A., Arena, R., & Myers, J. (2015). Reference standards for cardiorespiratory fitness measured with cardiopulmonary exercise testing: Data from the Fitness Registry and the Importance of Exercise National Database. Mayo Clinic Proceedings, 90(11), 1515–1523. https://pmc.ncbi.nlm.nih.gov/articles/PMC4919021/

Kodama, S., Saito, K., Tanaka, S., Maki, M., Yachi, Y., Asumi, M., Sugawara, A., Totsuka, K., Shimano, H., Ohashi, Y., Yamada, N., & Sone, H. (2009). Cardiorespiratory fitness as a quantitative predictor of all-cause mortality and cardiovascular events in healthy men and women: A meta-analysis. JAMA, 301(19), 2024–2035. https://jamanetwork.com/journals/jama/fullarticle/1108396

Lang, J. J., Prince, S. A., Merucci, K., Cadenas-Sanchez, C., Chaput, J.-P., Fraser, B. J., et al. (2024). Cardiorespiratory fitness is a strong and consistent predictor of morbidity and mortality among adults: An overview of meta-analyses representing over 20.9 million observations from 199 unique cohort studies. British Journal of Sports Medicine, 58(10), 556–566. https://pubmed.ncbi.nlm.nih.gov/38599681/

Laukkanen, J. A., Isiozor, N. M., & Kunutsor, S. K. (2022). Objectively assessed cardiorespiratory fitness and all-cause mortality risk: An updated meta-analysis of 37 cohort studies involving 2,258,029 participants. Mayo Clinic Proceedings, 97(6), 1054–1073. https://pubmed.ncbi.nlm.nih.gov/35562197/

Peterman, J. E., Kaminsky, L. A., Arena, R., Myers, J., Marzolini, S., Ross, R., Lavie, C. J., Wisløff, U., Stensvold, D., & FRIEND Consortium. (2020). Development of global reference standards for directly measured cardiorespiratory fitness: A report from the Fitness Registry and Importance of Exercise National Database. Mayo Clinic Proceedings, 95(2), 255–264. https://pubmed.ncbi.nlm.nih.gov/31883698/

Ross, R., Blair, S. N., Arena, R., Church, T. S., Després, J.-P., Franklin, B. A., Haskell, W. L., Kaminsky, L. A., Levine, B. D., Lavie, C. J., Myers, J., Niebauer, J., Sallis, R., Sawada, S. S., Sui, X., & Wisløff, U. (2016). Importance of assessing cardiorespiratory fitness in clinical practice: A case for fitness as a clinical vital sign: A scientific statement from the American Heart Association. Circulation, 134(24), e653–e699. https://www.ahajournals.org/doi/10.1161/cir.0000000000000461

Wen, D., Utesch, T., Wu, J., Robertson, S., Liu, J., Hu, G., & Chen, H. (2019). Effects of different protocols of high-intensity interval training for VO₂max improvements in adults: A meta-analysis of randomised controlled trials. Sports Medicine, 49(10), 1469–1487.  https://www.sciencedirect.com/science/article/abs/pii/S1440244018309198

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