Depends on the time period. Corset fashion had a period from the early-mid 19th century in which extremely constraining corsets were made of metal, whale bone, and like rigid materials. By the late 19th century, they were mostly fabric and as breathable as any other tight garment, but there was a period in which corsets were genuinely health hazards.
I’m more concerned with physical effort in that corset
I thought that corsets didn’t really constrain breathing and that idea was mostly from men deriding women’s fashion?
Depends on the time period. Corset fashion had a period from the early-mid 19th century in which extremely constraining corsets were made of metal, whale bone, and like rigid materials. By the late 19th century, they were mostly fabric and as breathable as any other tight garment, but there was a period in which corsets were genuinely health hazards.