You don't need a gym membership, dumbbells, or expensive equipment to get stronger. Since the beginning of time, we've had access to the one piece of equipment that is essential for strength training – our own bodies. Strength training without the use of external forces and equipment is called "bodyweight training". From push-ups and squats to planks and chin-ups, bodyweight training has become one of the most popular ways to exercise because it can be done anywhere – and it's free. So, what is