Dumbbell ab crunch (abs):

Lie on your back with your knees bent, feet flat on the floor, holding a dumbbell with both hands (one hand over each end of the dumbbell) close to your chest just below your chin. Keeping your butt and lower back on the floor, slowly roll your upper back off the floor, keeping your neck neutral. Pause and hold for a second or two and then return to the starting position and repeat.

Low dumbbell crossover (chest):

This awesome move can completely isolate and pump up your pecs. It’s like the Low Cable Crossover but done with dumbbells to further isolate the pectoral muscle. With one foot forward for stability, grasp the dumbbells (hands facing forward), spread your arms until they’re at about a 45-degree angle and your hands are a few inches behind your hips. Lean forward slightly. Bring the dumbbells up and together, using a sweeping arc motion, stopping right in front of your lower chest. Pause for a full second, return to the starting position and repeat. Keep your arms slightly bent to be sure that you’re fully isolating the pecs.