Sayyed Mohammad Al-Musawi, Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to... Answered 1 month ago

Any work or act or business which causes or leads or results in sinful act is not permissible. Making both genders mix with out proper Hijab is not allowed in Islam. Usually gyms in western countries don't care for proper Hijab, that it why Muslim should not indulge himself in such business which can lead to sinful acts, otherwise he will be responsible and his income from such sinful business will not be lawful.