Cardio Series: Living Longer

Over the years I have helped many clients to improve their health and body composition through a focus on resistance training and improved nutrition. In my one-on-one sessions with clients I almost never have them perform any cardio during the hour we have together. This has led to some clients asking me whether I think cardio is useless for health and fat loss. Nothing could be further from the truth.

Many gym-bros make the claim that lifting weights is all you need to improve your cardio. While it is true that any form of exercise can improve cardiovascular fitness when the base-line is low enough, the adaptations from aerobic training and resistance training are quite different, and tend to be specific to the activity. 

Increasing cardiorespiratory fitness (CRF) is one of the single most effective ways to improve health and reduce the risk of developing various diseases. CRF is the ability of the respiratory and circulatory systems to deliver oxygen to tissues during physical activity. In order to improve CRF in the long term an individual will need to actually perform some aerobic training. 

A longitudinal study by Mandsager & colleagues (2018) which assessed the relationship between CRF and long term outcomes found an inverse dose-response relationship between CRF and mortality risk. In other words, the greater your CRF, the longer you are likely to live.

The researchers had thousands of participants perform a graded exercise protocol on a treadmill as part of a stress test at a health clinic, and their health outcomes were then monitored over time. One particularly striking observation was that "when compared with the lowest performers, elite performance was associated with an 80% reduction in mortality risk" (Mandsager et al., 2018).

Even after adjusting for potential confounding variables such as smoking and alcohol use, the health benefits of higher levels of cardiovascular fitness are obvious. A final note is that the researchers did not observe a threshold at which higher levels of performance were associated with worse outcomes. It is sometimes claimed that the stress of very high aerobic training volumes might lead to a higher risk of certain cardiovascular conditions, but if this effect exists, the researchers did not observe it (Mandsager et al., 2018).

A key indicator of CRF is VO2-max, which is a measure of the total volume of oxygen your body can utilize during exercise, measured in terms of mL/kg/min (Strasser & Burtscher, 2018). Although there are clinically validated methods of assessing VO2-max in a laboratory setting, individuals who are not interested in maximizing their performance in an endurance event do not need to go to the trouble of lab testing.

Most wearable tech devices, like the Apple Watch, or Whoop, do a decent job of measuring heart rate during exercise at different intensities, and this information can generate a reasonable proxy measure of VO2-max. However, another great way to assess whether your cardiovascular fitness is improving is to simply see if your performance...improves.

If it previously took you 40 minutes to comfortably run 5km, but 4 weeks later you can complete that 5km in 30 minutes, that is a pretty clear indication that your cardiovascular fitness and VO2-max have improved.

Although VO2-max can be viewed as a general measure of aerobic capacity, it is also affected by the specific training an individual does. An elite long-distance runner may have an exceptionally high VO2-max, but they may not demonstrate their elite status if tested on a stationary bike. The opposite scenario would be true for an elite cyclist performing a test on a treadmill. While both athletes are exceptionally fit, they will be able to express their highest level of fitness in whatever activity they engage in regularly. 

So, what can we take away from all this information? Well, we know that improving VO2-max and overall CRF improves health status and reduces disease risk. Although maximizing VO2-max for a sport requires a well formulated program, and the accumulation of hours upon hours of training, improving CRF more generally is actually quite simple. The majority of benefit comes from being physically active regularly.

A cohort study by Hamaya & colleagues (2018) followed the health outcomes of a sub-group of participants from the Women’s Health Study who tracked their daily step counts via an accelerometer between 2011-2015. The researchers found that accumulating sufficient physical activity via step-counts of 8,000-10,000 led to similar reductions in cardiometabolic disease and all-cause mortality risk as meeting the physical activity guidelines for moderate, or vigorous activity.

Current physical activity guidelines recommend that adults get either 150-minutes of moderate-intensity physical activity, 75-minutes of vigorous intensity physical activity, or some combination of the two- for example, 75-minutes of moderate intensity activity, and 35-minutes of vigorous activity. While performing some type of targeted training can give a more pronounced benefit in terms of improving VO2-max than low-intensity exercise like walking, simply putting on a podcast and going for a walk or two can lead to profound health benefits for many individuals.

It is always worth remembering that the most impactful effects on health come from modest but consistent effort over time. Although improving aerobic performance can absolutely continue to contribute to improvements in health and quality of life (Mandsager et al., 2018; Strasser & Burtscher, 2018), going from lower levels of physical activity to moderate and slightly higher levels via low-intensity training will get you a lot of bang for your buck.

Maximizing performance in a sport is a totally different undertaking to simply living a healthy lifestyle (Strasser & Burtscher, 2018), and will require a more specific approach. Different sports, and events within the same sport or class of sports, can have very different aerobic and anaerobic demands. A dedicated Olympic weight-lifter might need to restrict their volume of moderate intensity cardio. Meanwhile, a soccer player will need to develop a huge aerobic capacity via high volumes of moderate intensity training interspersed with higher intensity training to deal with the demands of the sport. 

For clients who have specific cardio goals, or who want to challenge themselves in addition to just getting healthier, I love getting into the details of a cardio prescription. This approach works very well with online clients. We can zoom out from a single session, and instead look at how different forms of conditioning can contribute to improved performance over time.

This article has mainly dealt with the impact of cardio for health, without exploring its effect on weight loss. In the next article, I will delve a little further into how cardio impacts weight loss and energy expenditure. You might be surprised at how contentious a topic the role of cardio on weight loss can be, but you should never underestimate how much the fitness industry can argue over this stuff.

Thank you for reading, and try to get your steps in!

References

Hamaya, R., Shiroma, E. J., Jr, Moore, C. C., Buring, J. E., Evenson, K. R., & Lee, I. M. (2024). Time- vs step-based physical activity metrics for health. JAMA Internal Medicine, 184(7), 718–725. https://doi.org/10.1001/jamainternmed.2024.0892

Mandsager K, Harb S, Cremer P, Phelan D, Nissen SE, Jaber W. (2018) Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Network Open. 1(6):e183605. doi:10.1001/jamanetworkopen.2018.3605

Strasser, B., & Burtscher, M. (2018). Survival of the fittest: VO2max, a key predictor of longevity?. Frontiers in Bioscience (Landmark edition), 23(8), 1505–1516. https://doi.org/10.2741/4657