Performing dynamic stretches before you do situps increases the flow of oxygen and blood to your abdomen, improves range of motion and reduces the risk of injuring your lower back or stomach during your routine. The good news is that many dynamic stretches for the core also tone and strengthen it at the same time.
Warm muscles are more effective than cool ones. Similar to starting a car in cold weather, a heating period helps muscular performance. Warming up the stomach muscles will make it easier to do your crunches. In fact, you may experience an increase in output and capability. For example, it may be easier to hit your target goal of crunches after your warm-up, rather than immediately hopping into a set of crunches. It is important to do dynamic stretches, not static ones. Static stretches involve lengthening and holding a muscle in its extended position. This signals relaxation -- and can hurt your muscle if you force it to lengthen when it's cold -- and is better to do after your workout.
The American College of Sports Medicine (ACSM) recommends doing flexibility exercises two or three times a week. They also recommend doing abdominal exercises two or three times a week, so combining the two is a way to check off fitness requirements during your week. ACSM suggests doing each stretch two to four times for 20 to 60 seconds at at time. Doing enough sets to complete a minimum total of 60 seconds is a way to ensure maximum benefits.
Get Ready for Crunches
The bridge warms up the lower-back and the rectus abdominis, a set of muscles that runs down the front of the abs and powers standard crunches. Lie on your back, bend your legs and put your feet on the floor beneath your knees. Tighten your stomach, lift your hips and lower back into a straight line with your shoulders and knees. Hold and then lower for one bridge.
Don't Forget Your Sides
Torso twists warm up the lower back and the obliques, the sides of the abs. The obliques play an active role in certain crunches, specifically bicycle crunches. Stand up straight, bend your knees slightly and place your hands on your hips. Twist your torso and shoulders to your right without moving your hips and then twist to the left.
In Case of Crunch Variation
Leg drops warm up the rectus abdominis and the hip flexors. While the hip flexors don’t do that much during standard crunches, they are challenged during bicycle crunches and reverse crunches. Lie on your back, tighten your abs and press your lower back against the floor. Lift your legs above your hips and point your toes toward the ceiling. Lower your right leg toward the floor, stopping before your heel touches it. Stop sooner if your lower back arches. Arching indicates that you are going too far and may cause injury. You will be able to lower more after you build abdominal strength. Lift your right leg above your right hip, then lower your left leg. Continue alternating for 20 to 60 seconds. You can also bend one knee and place one foot on the ground if your back needs extra support.