6. Do crunches or sit-ups in the afternoon or evening
Your body is at its most vulnerable in the morning. At this time, your disks are full of fluid, making your risk of injury higher. Added pressure from an early morning sit-up can cause more damage than doing the same exercise in the afternoon. So, best save your sit-ups for a later time in the day. If you must exercise in the morning, make sure to perform lots of stretching and some other exercises before continuing to the back ones.