what
@Alexx said. also dry shampoo/baby powder/corn starch will be your friend. Not saying you need to jump from every day to once a week, but even every other day is good for a lot of people's hair, especially if yours seems dry. Initially you're going to be disgusted because your hair will look so oily, but your scalp is just producing that much oil frantically trying to replace what you wash off everyday. If you wash it less, it'll realize you don't need as much oil and the production will decrease. I wash mine on Thursday nights and then don't wash it again until Monday morning since my hair is in a bun majority of most weekends anyway.
I go to the gym 3-4 times a week and just wrap my hair in a tight bun on top of my head and shower after every workout. If the suggestion was for dryness, you could even wet your hair and leave it or wet and condition it, just skip the shampoo.