Gym memberships for that purpose are not deductible. For gym
memberships, see, for example, IRS Rev. Rul. 78-128.
The Revenue Ruling discusses the case of a law enforcement officer who
was required, as a condition of employment
to be in excellent physical condition. It held he/she could not deduct
membership fee in health club because it was a personal, nondeductible, expense
for his/her general health. Your situation of appearing physically fit would
not be any different than the police officers requirement to be physically fit.