Can Extreme Exercise Damage Your Health?


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Throughout February, various news websites and health blogs have been busy discussing the results of a research study conduced by the Copenhagen City Heart Study. Titled modestly as Dose of Jogging and Long-Term Mortality, the findings have inspired a plethora of headlines. And from most of the headlines, the prevailing theme is that too much exercise can be as bad for your body as not exercising at all. Already it’s clear why the study has sparked interest the world over!

Finding the Ideal Exercise Dosage

To draw from a credible range of data, the Copenhagen City Heart Study (CCHS) established a sample that consisted of 3,950 non-joggers (lowered to 413 for long-term analysis), who were deemed to be healthy, and 1,098 healthy joggers. The entire sample has been studied at regular interviews since first participating in the research back in 2001, with the study running over 12 years until concluding in 2013.

The simple basis for the research was that CCHS was already aware that people who are regularly active are at a 30% lower risk of death than people who remain inactive. CCHS wanted to expand on the research by determining the ideal dosage of physical activity for increasing lifespan.

For the previous study, the researchers solely focused on the health benefits of jogging for 2.5 hours a week over three sessions, but this time the researchers defined three jogging categories for analysis:

health and fitness

Source: Dose of Jogging and Long-Term Mortality by the Copenhagen City Heart Study, 2014

Additional characteristics that impacted the research were gender, smoker status, alcohol intake, diabetes, and education. After making adjustments in the analysis based on those characteristics, the core death findings were as follows for each of the groups in the study:

health and fitness

Source: Dose of Jogging and Long-Term Mortality by the Copenhagen City Heart Study, 2014

The above chart shows many participants were alive at the end of the study, denoted in red, while those who died are displayed in blue. From the inactive category, it was alarming to see that approximately 30% of participants died. Had they engaged in light jogging, perhaps the risk of death could have been decreased.

Within the light category, just 1.22% of joggers died during the study. That rate then increased to 3.17% for moderate and 5.56% for the strenuous groups. Setting aside the inactive control group, there was a clear correlation between the growing intensity of exercise and an elevated risk of death.

Looking back to the complete results, the findings were interesting when determining the hazard ratio for each group. As a side note, hazard ratio is a formula used to determine risk, which, in this case, would be death.

Source: Dose of Jogging and Long-Term Mortality by the Copenhagen City Heart Study, 2014

After working out the hazard ratio for each group, the J-curve showed that the level of risk increased based on the intensity of the exercise. Essentially, the participants who exercised with the highest level of intensity and in multiple sessions each week were at the greatest risk.

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Possible Limitations of the Study

There’s no denying that the study raised some interesting questions in regard to the potential health risk of an extreme exercise routine. However, NHS analysis has pointed out that the sample size of the strenuous group was extremely low compared to the light group (40 vs. 576). Such a large disparity does raise a question over the integrity of the sample size. A future study focusing on a strenuous group would lend greater clarity.

To a lesser extent, yet still relevant, is that the study did not evaluate the jogging patterns of the jogging groups. For instance, whether or not they maintained a steady pace over a long period of time or else changed pace regularly during sessions.

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Light Exercise Beneficial for All

Moving on from the possible limitations, the study did succeed in determining that even a little regular exercise can be extremely beneficial for your health, and Maureen Talbot from the British Heart Foundation echoed that conclusion: “This study shows that you don’t have to run marathons to keep your heart healthy.” So, while the debate will continue to discuss the potential damage of intense exercise, there can be no argument over the value of light exercise.

Based on advice from the British Heart Foundation, UK residents are recommended to engage in approximately 150 minutes of exercise each week to a moderate level of intensity. Not only will weekly exercise your improve your health, but also it could help secure lower insurance premiums from your provider. Visit the British Heart Foundation for more information on maintaining your heart health.