To cool down during intensive cardio HIIT sessions, ACE-certified trainer Kelly Morgan, PhD, relies on the Chill Pal PVA Cooling Towel ($13). You simply soak the towel, store it in the pouch while you work out, and drape it over your shoulders, neck, or even in your sports bra (Kelly's pro tip) when you need to cool down. "This towel goes with me for all workouts," she told POPSUGAR. "It totally changed how I feel while working out: in the heat, in the gym, and anywhere."