Take on this intense ab challenge to strengthen and tone your core before the new year! Complete 200 mountain climbers, 100 sit-ups, 100 Russian twists, and 100 side-to-sides in this full-core workout ...
• Sit-ups target your abdominal muscles, back muscles, and hip flexors, while crunches only target your abdominal muscles. • Neither sit-ups nor crunches alone burn abdominal fat. Overall activity and ...