So far this week, we’ve featured a push-up challenge, a squat challenge, and a burpee challenge.  Today, we’re doing a 500-repetition core challenge with Maddie Lymburner from MadFit.  The last three days of challenges have worked the core as a secondary part of the exercise, but this routine targets all parts of the abdominal wall.  Some ask whether it’s okay to work your core every day.  The answer is nuanced, according to Livestrong.com: More isn’t always better. Generally speaking, … most people shouldn’t do ab workouts more than six times a week. Not only do your abs need a break, but so does the rest of your body. Without at…