I don't sweat as much as others because I'm always cold (reptile blooded) but I do do a pretty heavy cardio workout every other day. (In the days between I do lighter exercises that won't get me sweaty like yoga.) It's intense so I always wash my hair afterwards. My routine is co-wash, co-wash/sometimes tea tree scalp treatment then water wash, then low-poo once a week. But if I'm feeling especially grimy I may low-poo twice a week or whatever I feel like. I also have a clarifying shampoo on hand to use as needed. You could always pre-poo the length of your hair if you needed to in order to prevent your hair from drying out. I think washing with a baby shampoo with gentle sulfates once to twice a week is really good though.
3A - C, HP, ME, HD. (Coarse, High Porosity, Medium Elasticity, High Density.)

CG since Nov. 2012

Poos: SM Moisture Retention + Yucca Baobab, TJ's Tea Tree Tingle
Condish: TJ 'sTea Tree Tingle*, SM Moisture Retention* + Curl & Shine + Yucca Baobab, Yes to Blueberries
Stylers: KCKT*, SM Curl Enhancing Smoothie* + Curl & Style Milk*, KCCC*, FSG*, CJ Pattern Pusha, Curl Keeper
Sealers: Jojoba* or Grapeseed* oil

* = HG