Crunches: Lie on your back with your knees bent and feet flat on the floor. Place your hands behind your head or crossed over your chest. Lift your shoulders off the floor by contracting your abdominal muscles, then slowly lower back down.
Plank: Get into a push-up position with your elbows bent and resting on the floor. Keep your body in a straight line from head to heels, engaging your core muscles.
Russian Twists: Sit on the floor with your knees bent and feet flat. Lean back slightly and lift your feet off the floor, balancing on your tailbone. Hold a weight or medicine ball in front of your chest and rotate your torso from side to side.
Mountain Climbers: Start in a push-up position with your hands directly under your shoulders and your body in a straight line. Drive one knee towards your chest, then quickly switch legs, alternating back and forth as if you're running in place.
Bicycle Crunches: Lie on your back with your hands behind your head and your legs lifted, knees bent at a 90-degree angle. Alternate bringing your right elbow towards your left knee while straightening your right leg, then switch sides in a pedaling motion.
Burpees: Start standing, then squat down and place your hands on the floor in front of you. Jump your feet back into a plank position, then immediately jump them back towards your hands. Stand up and jump into the air, reaching your arms overhead.
Leg Raises: Lie on your back with your legs straight and your hands under your lower back for support. Lift your legs towards the ceiling, keeping them straight and together, then slowly lower them back down towards the floor without letting them touch.
High Knees: Stand with your feet hip-width apart. Lift one knee towards your chest, then quickly switch legs, alternating back and forth as if you're running in place, pumping your arms for added intensity.