How to Measure and Increase Your Cardiorespiratory Fitness

Ways to Improve Your Aerobic Conditioning for Better Health

There can be nothing more crucial to your health and wellbeing than having a strong and healthy heart and lungs – sometimes referred to as good cardiorespiratory fitness. 

If you have increased heart disease risk factors or there’s been a regression in your fitness levels (all too easy when life gets in the way), making some step-by-step changes will improve your chances of living a longer, healthier life and avoiding chronic disease.

If your heart and lungs are already in good shape, there are ways you can build on this to optimize your cardiorespiratory fitness and ensure your training stays in balance. 

In this article, we’ll explore some of the most effective ways to optimize your cardiorespiratory fitness and endurance, home exercise tests that can measure your status and progress, how to balance strength training with cardio, and more. 

Cardiorespiratory fitness: couple running outdoors

What Is Cardiorespiratory Fitness?

According to the American Heart Association, cardiorespiratory fitness (CRF) is “the capacity of the circulatory and respiratory systems to supply oxygen to skeletal muscle mitochondria [the powerhouses found in each cell] for energy production needed during physical activity” [1 Trusted SourcePubMedGo to source].

In other words, cardiorespiratory fitness is the measure of how well your body performs during exercise without getting fatigued (it’s also referred to as cardiovascular fitness and cardiovascular endurance).

Improving Cardiorespiratory Fitness: A Snapshot 

Before going into more detail, let’s take a quick overview of the steps that will help improve cardiorespiratory fitness:

  • Start with the heart health basics: 
    • Eat a supportive, heart-healthy diet with plenty of whole, unprocessed foods.
    • Aim to get better quality sleep and manage stress. 
    • Avoid excess alcohol. 
  • Build your fitness base: 
    • If you don’t already have a regular fitness routine, start small with short, regular exercise sessions. 
    • Choose aerobic exercises like running, cycling, or swimming where you can control your pace. 
  • Measure your cardiorespiratory fitness: 
    • Perform an at-home test like a Cooper run or treadmill test, and plug your score into a VO2 max calculator to see where you’re at. 
    • You can repeat these tests down the road to help measure your progress and keep you motivated. 
  • Optimize your cardiorespiratory fitness: 
    • Gradually increase your level of aerobic exercise. 
    • Incorporate some weight-training (resistance) and high intensity interval training (HIIT) exercises. 
    • Make sure to balance strength training with cardio exercise for the best results. 

Benefits of Improving Your Cardiorespiratory Fitness

Your cardiorespiratory fitness isn’t just about your ability to go run further or faster, or to bike up a steep hill without needing to get off and walk. Research shows there are much wider health outcomes associated with having high cardiorespiratory fitness levels, not all of which are physical fitness related. These include:

In young people specifically, higher cardiorespiratory fitness is also a predictor of:

If you have low cardiorespiratory fitness, resting heart rate is higher, driving the sympathetic (fight or flight) arm of your autonomic system to work harder. In turn this can cause more fatigue and more intolerance to exercise (and, ostensibly, other forms of stress). 

On the other hand, exercise stimulates the sympathetic nervous system, which helps the body maintain stability when faced with increased physical, metabolic, respiratory, and cardiovascular demands [9 Trusted SourcePubMedGo to source].

Home Exercise Testing

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The most well-validated way of estimating how good your cardiorespiratory fitness is a VO2 max exercise test, which calculates the oxygen consumption of your body during high-intensity activities.

For full accuracy, this test must be done in a lab, while you are exercising to capacity as you wear an exercise mask. The gases you breathe in are collected and measured, and this gives a very accurate measurement of your oxygen uptake and VO2max.

The good news — two much easier at-home tests still give a very good estimate of your VO2 max, and correlate closely with the lab test.

The first is the Cooper 12-minute run test. Ideally, you should do this on a running track, but you can do it on flat ground or as a treadmill test.

The idea is that you run as fast as you can for 12 minutes and see how far you go. (This is now very simple to do accurately with the help of any GPS fitness tracker or app). You then plug your time into a VO2 max calculator to see how your cardiorespiratory fitness rates compared with others in your age groups. 

Another option is to use a rowing machine and see how quickly you can row 2000 meters. Here too, you’ll enter your details (age, time and weight in this case) into a calculator to estimate your VO2 max. 

The great thing about these exercise training tests is that you can follow up over time to see how your aerobic capacity improves.

Build Your Fitness Base 

If you want to improve your cardiorespiratory endurance from a low base, it’s easier if you start with small, frequent sessions and gradually build up your physical activity levels and energy expenditure. Over 8-12 weeks, you should increase until you are doing regular exercise in line with the Physical Guidelines for Americans recommendations, which means being active at least 2.5 hours a week. 

Going too hard too soon with endurance training can mean you overreach or find it too hard and give up. So measuring your heart rate and staying in the moderate zone is ideal when you start out. Even if it feels a little easy, stick with it, as the health benefits will still come. 

To work out your moderate intensity heart rate, subtract your age from 180. 

If you are 40 years of age, this means that keeping your heart rate at a maximum of 140 (180 – 40) beats per minute when you are first starting out.

These are all great aerobic exercises to begin improving your cardiorespiratory fitness, as you can do them at a pace/heart rate intensity that fits your current fitness level:

  • Running/jogging
  • Cycling
  • Swimming
  • Power walking
  • Aerobic/dance classes 

Optimizing Cardiorespiratory Fitness 

When you’ve worked up to a good basic level of fitness as outlined above, you’ll be able to lift your cardiorespiratory fitness still further by:

  • Starting to exercise for longer and/or at a higher heart rate. 
  • Incorporating HIIT training (short bursts of maximum efforts inserted into longer bouts of moderate/high-intensity exercise). Studies suggest this may be particularly effective at improving cardio-pulmonary (heart and lung) function [10 Trusted SourcePubMedGo to source].

For those short, all-out efforts, some options to try include:

  • Burpees
  • Sprinting
  • Cycle sprints
  • Jumping rope
  • Mountain climber planks

Balancing Strength and Cardio Exercise

Person doing a bicep curl

If you’ve gotten into lifting weights lately, that’s great, especially as anaerobic or resistance training (strength training, HIIT, etc.) has all these benefits [11 Trusted SourcePubMedGo to source]:

  • Promotes the production of C-natriuretic peptide, which protects the elasticity of blood vessels and promotes their dilation, thereby keeping the heart young
  • Helps to reduce body fat and body mass index, or BMI (helping to fight obesity) 
  • Improves overall body composition (fat to muscle ratio)

However, if you don’t accompany strength training with the appropriate amount of cardio, you might not have the baseline aerobic conditioning to meet the muscle gains you want to achieve.

For a deeper dive on this topic and why cardiovascular conditioning is so important for everyone, including those who often lift weights, listen to my podcast with exercise scientist Dr Mike T Nelson

Can Too Much Strength Exercise Harm the Heart?

Some evidence also suggests that if you are unbalanced with your training and focus only on resistance (strength) training, there could be some actual structural changes to the heart that may not be favourable. The claim is this imbalance can cause concentric hypertrophy (an unhealthy thickening of the left ventricle of the heart).

As of now, there’s not much evidence to support this, with one 2013 systematic review / meta-analysis of 92 observational studies (offering low to moderate evidence) reporting that resistance athletes did not have concentric hypertrophy [12 Trusted SourcePubMedGo to source]. 

However, this review showed endurance athletes did better heart-health wise. They had significantly greater diameter and volume of the left ventricle when relaxed than resistance athletes, indicating that the heart is pumping blood to the body more efficiently.

Another review found that too much anaerobic exercise (without enough aerobic exercise) may indirectly harm heart function through reducing the body’s production of human growth hormone (HGH). Too little HGH is known to reduce the normal thickness of the back wall of the left ventricle, its overall mass, and the amount of blood it can eject upon contraction [11 Trusted SourcePubMedGo to source]. 

While the research is far from complete in this area, what emerges clearly is that combining aerobic plus strength exercises provides more comprehensive cardiovascular disease benefits than aerobic-only or strength-only exercise [13 Trusted SourcePubMedGo to source].

The Bottom Line

Practicing good cardiorespiratory fitness will not only help you exercise better with less fatigue. It also has benefits that extend to reduced risk of cardiovascular disease and improved mental function.

Starting low and slow is the key to building up your fitness, only incorporating HIIT and other more intense workouts once you have a solid base of 2.5 hours moderate exercise a week. Strength workouts are also important, but not at the expense of your aerobic ones.

For more personalized help with any health or fitness goal you can book an in person or online appointment at the Ruscio Institute.

➕ References
  1. Raghuveer G, Hartz J, Lubans DR, Takken T, Wiltz JL, Mietus-Snyder M, et al. Cardiorespiratory fitness in youth: an important marker of health: A scientific statement from the american heart association. Circulation. 2020 Aug 18;142(7):e101–18. DOI: 10.1161/CIR.0000000000000866. PMID: 32686505. PMCID: PMC7524041. Trusted SourcePubMedGo to source
  2. Ross R, Blair SN, Arena R, Church TS, Després J-P, Franklin BA, et al. 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. 2016 Dec 13;134(24):e653–99. DOI: 10.1161/CIR.0000000000000461. PMID: 27881567. Trusted SourcePubMedGo to source
  3. Sui X, Sarzynski MA, Lee D-C, Lavie CJ, Zhang J, Kokkinos PF, et al. Longitudinal patterns of cardiorespiratory fitness predict the development of hypertension among men and women. Am J Med. 2017 Apr;130(4):469-476.e2. DOI: 10.1016/j.amjmed.2016.11.017. PMID: 27986522. PMCID: PMC5362290. Trusted SourcePubMedGo to source
  4. Wong CN, Chaddock-Heyman L, Voss MW, Burzynska AZ, Basak C, Erickson KI, et al. Brain activation during dual-task processing is associated with cardiorespiratory fitness and performance in older adults. Front Aging Neurosci. 2015 Aug 12;7:154. DOI: 10.3389/fnagi.2015.00154. PMID: 26321949. PMCID: PMC4532928. Trusted SourcePubMedGo to source
  5. Lang JJ, Belanger K, Poitras V, Janssen I, Tomkinson GR, Tremblay MS. Systematic review of the relationship between 20m shuttle run performance and health indicators among children and youth. J Sci Med Sport. 2018 Apr;21(4):383–97. DOI: 10.1016/j.jsams.2017.08.002. PMID: 28847618. Trusted SourcePubMedGo to source
  6. Ortega FB, Ruiz JR, Castillo MJ, Sjöström M. Physical fitness in childhood and adolescence: a powerful marker of health. Int J Obes (Lond). 2008 Jan;32(1):1–11. DOI: 10.1038/sj.ijo.0803774. PMID: 18043605. Trusted SourcePubMedGo to source
  7. Santana CCA, Azevedo LB, Cattuzzo MT, Hill JO, Andrade LP, Prado WL. Physical fitness and academic performance in youth: A systematic review. Scand J Med Sci Sports. 2017 Jun;27(6):579–603. DOI: 10.1111/sms.12773. PMID: 27714852. Trusted SourcePubMedGo to source
  8. Lubans D, Richards J, Hillman C, Faulkner G, Beauchamp M, Nilsson M, et al. Physical activity for cognitive and mental health in youth: A systematic review of mechanisms. Pediatrics. 2016 Sep;138(3). DOI: 10.1542/peds.2016-1642. PMID: 27542849. Trusted SourcePubMedGo to source
  9. Patel PN, Zwibel H. Physiology, Exercise. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2021. PMID: 29489294. Trusted SourcePubMedGo to source
  10. Weston KS, Wisløff U, Coombes JS. High-intensity interval training in patients with lifestyle-induced cardiometabolic disease: a systematic review and meta-analysis. Br J Sports Med. 2014 Aug;48(16):1227–34. DOI: 10.1136/bjsports-2013-092576. PMID: 24144531. Trusted SourcePubMedGo to source
  11. Patel H, Alkhawam H, Madanieh R, Shah N, Kosmas CE, Vittorio TJ. Aerobic vs anaerobic exercise training effects on the cardiovascular system. World J Cardiol. 2017 Feb 26;9(2):134–8. DOI: 10.4330/wjc.v9.i2.134. PMID: 28289526. PMCID: PMC5329739. Trusted SourcePubMedGo to source
  12. Utomi V, Oxborough D, Whyte GP, Somauroo J, Sharma S, Shave R, et al. Systematic review and meta-analysis of training mode, imaging modality and body size influences on the morphology and function of the male athlete’s heart. Heart. 2013 Dec;99(23):1727–33. DOI: 10.1136/heartjnl-2012-303465. PMID: 23474689. Trusted SourcePubMedGo to source
  13. Schroeder EC, Franke WD, Sharp RL, Lee D-C. Comparative effectiveness of aerobic, resistance, and combined training on cardiovascular disease risk factors: A randomized controlled trial. PLoS ONE. 2019 Jan 7;14(1):e0210292. DOI: 10.1371/journal.pone.0210292. PMID: 30615666. PMCID: PMC6322789. Trusted SourcePubMedGo to source

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