Randomized crossover clinical trial in which a group of runners are ask to complete a 15 minutes standardized physical test on a treadmill. The same group of participants are randomized to the order in which they use a facemask (surgical mask, polyester reusable cloth mask) or no mask, while running.

Each test, according to the type of mask or no mask, are held on different dates. Heart rate, oxygen saturation and shortness of breath are measured every 3 minutes during the test.

Between 15-20 recreational runners are included in a crossover trial to run under three different conditions the same 15-minutes treadmill running test. They Will run wtih surgical mask, polyester reusable cloth mask or without mask. The order in which they use or not the mask is randomized. Each test is done on a different day.

Heart rate, oxygen saturation and shortness of breath are measured every 3 minutes during the test.

The primary outcomes are the differences in heart rate, oxygen saturation and shortness of breath at the end of the test, between groups.

Inclusion Criteria:

• Recreational runners.
• Age between 16-65 years.
• Workers or students from the health area.

Exclusion Criteria:

• None.