This is what this new study from Germany sought to answer (link to study below).

They took a group of healthy young men and had them do 2 different types of exercises:

- Endurance exercise (cycling at moderate effort), or

- Resistance training exercises (lifting weights).

They then measured the activity of the immune system (activity of various immune cells as well as "systemic inflammation").

What they discovered is that the "endurance" exercise caused a much higher increase in immunity activation compared to resistance exercise.

What does that mean for you? It means 2 things:

1. If you want to strengthen your immune system, then doing moderately hard endurance exercise followed by PLENTY of recovery will help you build your immunity.

2. Since endurance exercise stresses the immune system more: doing a lot of endurance exercise (especially without enough recovery) means you're at a HIGHER risk of infection, because your immune system is stressed.

So:

- If you feel you're at risk of infection, focus on resistance exercise which stresses your immune system less;

- If you feel you're "safe" from infection and want to focus on building your immunity, focus on endurance exercise with PLENTY of recovery (sleep & nutrition).

Resistance exercise has a lot of other benefits of course, and should always be part of your training regimen.