When you look at your stomach, do you wish it were tighter and firmer? A strong core can determine posture and balance. These core exercises will tighten your abs and improve your posture.

Do the good old sit up and crunch routine. These two oldies but goodies will make a difference. As you lift and lower your body (full extensions for sit ups, small lifts for crunches), use your fingertips to cradle your neck and always use slow, controlled movements to lift and lower without straining your body.

When you’re sick of sit ups, move into the position to do the bicycle. Start out in the same position as a traditional sit up, but lift your legs in the air and bend them at 90-degree angles. Lift your upper body and touch your opposing elbow and knee. Then twist and touch the other opposing elbow and knee. Continue this movement in a smooth pattern.

Tighten your abs by using your core muscles to lift and lower your legs in a controlled motion. Lie on your back with your arms and legs extended. Keeping your lower back solidly on the ground, lift both legs, slowly, until they point to the ceiling. Using maximum control, smoothly lower your legs again, using your stomach muscles to control the movement of your legs.

Get solid abs by acting like a plank. Flip over onto your stomach. Start out by using your arms to lift you into a push up position, but then freeze, engaging your ab muscles and making sure your back is straight. Hold the position as long as you can; then slowly release down to the ground again.

The last exercise can be done all day; simply sit on your exercise ball. The ball will require you to engage those core muscles so you can stay upright, even while you’re working.