Trim your toenails very short. When the nails are long, they are more likely to experience pressure from pushing against the front of your sneakers.
Wear sneakers with adequate room in the toe box. When you stand up, there should be at least half an inch of space between the end of your toes and the shoes.
Insert nonslip insoles or wear gripping socks if you feel you're moving around slightly in your shoes during exercise. Unless the problem is a shoe that's too big, nonslip insoles and socks can prevent excess movement, which can lead to nail trauma.
Wash and dry your feet immediately after exercise. Don't sit around with your feet in sweaty socks.
Wear synthetic, moisture-wicking socks to minimize the moisture your toenails are exposed to during workouts.
Wear shower thongs if you shower at the gym and never walk barefoot in locker rooms, as fungal infections are easily transmitted this way.
Sprinkle antifungal powder on your feet or inside of your sneakers before exercise.
Avoid wearing nail polish, as this can trap moisture underneath and create the perfect environment for fungal growth.