The simple answer is yes. Weight training at a lower intensity but with more repetitions may be as effective for building muscle as lifting heavy weights. Using bodyweight exercises like pushups, for example, you can definitely build muscle and strength. However, if your goal is to have massive arms and tree-trunk legs, you will have to use heavier resistance training and do isolation exercises. If your goal is to increase your general strength and your level of physical fitness heavy weights aren’t necessary. Actually, if you’re just starting to become more physically active, adding weights to your training right away might get you injured.
Other resistance protocols, beyond the often discussed high-intensity training, can be effective in stimulating a muscle building response that may translate into bigger muscles after resistance training. These have important implications from a public health standpoint because skeletal muscle mass is a large contributor to daily energy expenditure and it assists in weight management. Additionally, skeletal muscle mass, because of its overall size, is the primary site of blood sugar disposal and thus will likely play a role in reducing the risk for development of type II diabetes.
High-intensity muscle contractions derived from lifting heavy loads were not the only drivers of exercise-induced muscle development. In resistance-trained young men a lower workout intensity and a higher volume of repetitions of resistance exercise, performed until failure, was equally effective in stimulating muscle proteins as a heavy workout intensity at lower repetition rates. An additional benefit of the low-intensity workout is that the higher repetitions required to achieve fatigue will also be beneficial for sustaining the muscle building response for days.
If you are not using heavy resistance like you get from weight training it will be hard to increase force, but you can increase the distance you move during each repetition and increase the amount of work your muscles are doing. Start slowly and get a feel for your body before you start jacking up your exercises. Also, do not unload your pantry or get all crazy your first time out. If you jump to something too advanced you’re basically stealing from future gains and robbing yourself of the training that will help you right now. Always remember that when it comes to training, know what your goals are and ask yourself if they are attainable. Educate yourself, and find out what you need to achieve them.