Why? These old-school favourites have gone the distance for a reason. A study by the American Council of Exercise looked at crunches alongside the effectiveness of popular core-busting kit such as the Ab Roller, Ab Lounge, and Circle Pro, and the humble crunch showed the greatest muscle activation overall. If it ain't broke...
Why? Having just talked about compound moves engaging your core, the spiderman press-up is designed to do exactly that. While it's targeting your chest and triceps like any other press-up, since you're only being supported on three points of contact when you move your leg forward, this means that your abdominals and other core muscles have to work harder to maintain stability.
Hanging Leg Raises
Why? One of the hardest ab exercises around is also one of the most effective. It does need a pull-up bar to work, but can still be done in the comfort of your own home. Variations such as the hanging twisting knee raise keeps the exercise fresh.
Arms Extended Plank
Why? This tricky variation on your average plank engages your entire body as your core works to centre yourself. Your whole body needs to be held in place by your core for the duration of the exercise. Brutal.
Why? As well as providing a new angle for the classic plank, the muscles targeted by this move end up supporting the lower back and preventing back pain in later life. Researchers at Kuopio University in Finland found those with stronger hip and back extensor muscles suffered less from lower back pain. Straighten up by lying down.
Why? The only other exercise on our list that requires any equipment, the Russian Twist works with either a weight plate or a medicine ball. Much more effective than static rotations standing up, your core must be continually engaged to keep you balanced while the twist works either side of your body. Both sides? That's one rep.
Why? Our final exercise will feel like a real killer. After all the punishment you've been through, we're asking you to hold that "v" position for three seconds each time for ten reps, testing your level of control over your core. Made it to the end? We're impressed.