Does interval training affect immune function?

What is it about?

Our study aimed to answer two questions. Firstly we were interested in whether the way cyclists perform hard interval training sessions might affect their risk of getting sick (common colds, etc). We know, for example, that long and hard sessions such as running a marathon can increase the risk of common colds. We wanted to know if there was any difference in training effect or illness risk between doing long, intervals (8 minute efforts) versus a higher number of short intervals (40 seconds). We didn't see any differences in common cold symptoms between the groups, suggesting that interval duration doesn't make a difference to our immune system. Secondly we wanted to know if any biological markers can help us to predict who is most at risk of getting sick during a hard training period (involving doing 3 interval sessions per week for 4 weeks). We saw that the participants who were most fit at the start of the study reported the most symptoms. But there weren't really any strong relationships between factors such as Vitamin D, iron, or stress hormones and illness risk.

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Why is it important?

This study gives us an understanding about how interval training affects the immune system, that could help to inform coaches and athletes about how to plan their training. However, because we only took samples before and after the 4-week training period, we might have missed some interesting responses in the body in the interim. One interesting observation was that many of the participants got sick in the first week of the 4-week training intervention. This could suggest that sudden increases in training volume and intensity, or even just switching to a new regime could disturb immune function. This observation is worth of further exploration in future studies.

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