Moderate Intensity Exercise Improves Immune Function While High Intensity Interval Training (HIIT) Reduces Immunity

Just when you thought the only acceptable way to exercise these days is with high intensity intervals (HIIT) we have some new data that suggests good old moderate intensity cardiovascular training is not only just as good, it may be better for your immunity.

Just when you thought the only acceptable way to exercise these days is with high intensity intervals (HIIT) we have some new data that suggests good old moderate intensity cardiovascular training is not only just as good, it may be better for your immunity.

While there is plenty of data supporting the benefits of HIIT, as you dig through the research comparing HIIT to more moderate intensity training you can find studies that support HIIT, others that favor moderate intensity and still more that show similar effects. With the publicity that HIIT training has received over the past few years (including in this blog) and the facilities that are built around it you might be left thinking that despite the limited and mixed research on the topic, you have to be banging out heart wrenching workouts at the local boutique gym in order to make any gains.

Today we have a study that suggests when you are talking about the effect of your exercise routine on immunity, you may be better off with more moderate intensity workouts.

The authors had half of their subjects run high intensity intervals for multiple rounds of 30 seconds at 100% intensity and then 30 seconds at 50% intensity. The moderate intensity group did an equivalent amount of work, but it was performed continuously at 75% intensity.

At the end of 9 weeks all the various physiological factors that were measured showed similar results with one major exception, immune biomarkers. The specific biomarkers were all white blood cells leukocytes, lymphocytes, neutrophils and monocytes. The high intensity training group saw negative changes in all four of these key immunity markers while the moderate intensity training group saw positive improvements.

These findings fall in line with previous studies that have found a suppression of immunity with high intensity training and others that have shown improvements with more moderate intensity approaches.

As I always caution, with every study there are limitations. This study only had 16 subjects and they were all fit, active young men ages 18-20. While it would seem logical that if this population saw these types of changes everyone else would, there is no data to say the same results would be found with women or with other age groups or people with different health status. There is also the question of what would be different if the study was of a different length of time, the training frequencies were different, or the training volumes were greater.

What does this study mean for you, the average exerciser or fitness professional? Well we know that many people find high intensity workouts uncomfortable and unenjoyable. This means a much great chance of their stopping exercise, something we obviously don’t want to happen. So, anytime we find some evidence suggesting that more moderate intensity training is just or good or better than the highly publicized high intensity approaches that supports ignoring the buzz and letting people skip the HIIT.

Certainly there are still times that certain fitness training objectives require higher training intensities, but for the average exerciser they can probably skip the intervals if they don’t enjoy or tolerate them. And if someone is dealing with any sort of illness or medical condition in which optimizing their immunity is a key factor, skipping the high intensity work in favor of other approaches just may be the safest and best approach.

 

Khammassi, M., Ouerghi, N., Said, M., Feki, M., Khammassi, Y., Pereira, B., Thivel, D. and Bouassida, A. (2020) Continuous Moderate-Intensity but Not High-Intensity Interval Training Improves Immune Function Biomarkers in Healthy Young Men. Journal of Strength and Conditioning Research. January, 34:1:249-256.

Mountain View, CA, USA

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