All kinds of clothes and accessories are normally considered as personal expenses, even if they are only intended to be used for business purposes. There are exceptions for protective clothing and branded clothes with company logotypes, and stage clothes within the cultural industry unless the clothes could be worn also for personal use and if they are stored in the home of the company owner.
Frequently asked questions about clothing:
Normally not, if it is about clothes that you could possibly choose to use privately, whether you do or not. An old and classic example of this is Swedish dance bands who often dress so extravagantly to avoid that the Swedish Tax Agency would consider that the clothes could be used privately.
It is exactly the same rules that apply here, so as we see it, the Swedish Tax Agency would most likely not allow deductions. If you want to make a deduction, buy workout clothes with the company’s logo on it.