Exercise Capacity and COVID-19

By: Tana Mardian

We receive new research and information about the coronavirus pandemic every day, as seen in the evolution of recommendations throughout the months regarding mask-wearing, social distancing, gathering size, etc. Now that the pandemic has been going on for much of 2020, scientists have had the opportunity to do a deeper dive into various factors that could impact an infected individual in the course of the illness, and one of these factors is fitness.

In a study by Brawner et al., the researchers looked at the relationship between exercise capacity before contracting coronavirus and hospitalization due to COVID-19. To rephrase it, what’s the connection between fitness level before contracting coronavirus and the odds of ending up in the hospital due to coronavirus infection? 

The article begins by highlighting the importance of high cardiorespiratory fitness, or in other words, a high exercise capacity. Even though age, genetics, and chronic disease have certain implications on fitness, physical activity is essential in developing high fitness, especially if the activity is structured training. Structured training is intentional and planned exercise, as opposed to the natural physical activity we get through everyday things like cleaning, doing laundry, etc. Exceptional cardiorespiratory fitness is associated with a better potential to fight off harm to the body, such as a respiratory infection like coronavirus, and aerobic-style exercise, in particular, can increase immune function, decrease ongoing low levels of inflammation, and overall reduce the risk of respiratory infections. 

At this point in the pandemic, we know of certain things that put a person at greater risk of complications from the disease, like pulmonary disease, heart disease, smoking, and obesity, but how does exercise fitness play a role in the recovery from COVID-19?

First, the investigators found participants that fit the criteria of their study. They needed individuals that had completed an exercise stress test within the past few years, as well as people that had a coronavirus test in the first couple of months of 2020. They were then able to track hospitalizations. In all, the study gathered data on 1,181 adults (Brawner, et al., 2020). 

To interpret the results of the research, it’s important to understand what an exercise stress test looks at. Most of the participants in the study had completed a Bruce or modified Bruce protocol for their exercise stress test, which involves walking on a treadmill in 3-minute increments, with each increment requiring a faster walking speed and steeper slope (Vilcant, & Zeltser, 2020). Their exercise capacity was then measured in METs or metabolic equivalents. To conceptualize a MET, we think of 1 MET as the energy required when someone is completely at rest; anything more than that requires additional energy (additional METs) to power the body. For example, a vigorous activity like climbing could require 10 METs or 10x the amount of energy you need just sitting and doing nothing (Boccalandro, 2009).

Now going back to the study, the researchers found an inverse relationship between maximal exercise capacity and the chance of being hospitalized for COVID-19. That is to say, a greater exercise capacity is connected with a lower chance of hospitalization from the disease. Further, one MET greater was linked to a 13% lower probability of ending up in the hospital. 

While all research has its limitations, this study has important implications in encouraging us to stay active and healthy during this time. Our cardiorespiratory fitness is an essential indicator for general health, as well as the capacity to respond to natural stresses we experience every day, one of which could be COVID-19. This isn’t to say each exercise session needs to be hours of high-intensity interval training in hopes that we increase our exercise capacity; the benefits for our immune system and our ability to fight off infection can come from regular moderate to vigorous aerobic exercise (Brawner, et al., 2020). Additionally, it’s essential to find a workout routine that is simultaneously enjoyable and challenging to keep you motivated. 

The great thing about this information is that we know exercise capacity is modifiable, meaning that we can improve our fitness with training (Brawner, et al., 2020), and exercise can provide a much-needed break from everything going on around us. All in all, adding in some structured physical activity can benefit us in so many ways, and this research demonstrates the importance of exercise, especially during this time.

Reference List:

Boccalandro, F. (2009, October 30). Exercise Stress Testing. Cardiology Secrets (Third Edition). https://www.sciencedirect.com/science/article/pii/B9780323045254000071. 

Brawner, C. A., Ehrman, J. K., Bole, S., Kerrigan, D. J., Parikh, S. S., Lewis, B. K., … Keteyian, S. J. (2020, October 5). Maximal Exercise Capacity is Inversely Related to Hospitalization Secondary to Coronavirus Disease 2019. Mayo Clinic Proceedings. https://www.mayoclinicproceedings.org/article/S0025-6196(20)31130-7/fulltext. 

Vilcant, V., & Zeltser, R. (2020, July 26). Treadmill Stress Testing. https://www.ncbi.nlm.nih.gov/books/NBK499903/.