"Exercise Performance in Healthy Individuals"

Did that include pregnant women?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8050876/

Cloth face masks led to a 14% reduction in exercise time and 29% decrease in VO2max, attributed to perceived discomfort associated with mask-wearing. Compared with no mask, participants reported feeling increasingly short of breath and claustrophobic at higher exercise intensities while wearing a cloth face mask. Coaches, trainers and athletes should consider modifying the frequency, intensity, time and type of exercise when wearing a cloth face mask.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8212079/

When using double SM, oxygen saturation is significantly reduced compared to pre-mask values. Nevertheless, it seems difficult to say that these decreases have clinical significance.

We could cite studies to each other all year. I doubt we'll change anyone's minds. If she doesn't want to wear a mask that's her choice.

"Exercise Performance in Healthy Individuals"

Did that include pregnant women? Do you know this womans health?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8050876/

Cloth face masks led to a 14% reduction in exercise time and 29% decrease in VO2max, attributed to perceived discomfort associated with mask-wearing. Compared with no mask, participants reported feeling increasingly short of breath and claustrophobic at higher exercise intensities while wearing a cloth face mask. Coaches, trainers and athletes should consider modifying the frequency, intensity, time and type of exercise when wearing a cloth face mask.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8212079/

When using double SM, oxygen saturation is significantly reduced compared to pre-mask values. Nevertheless, it seems difficult to say that these decreases have clinical significance.

We could cite studies to each other all year. I doubt we'll change anyone's minds. If she doesn't want to wear a mask that's her choice.