Resistance bands are tools used to develop muscular strength and endurance. They come in two forms. The first type of resistance band, like the ones in the picture above, look like giant rubber bands. The other type, like the one in this article about How To Make A Home Gym With 6 Cheap Pieces Of Equipment, come with handles on each end.
These bands can be used to strengthen literally every muscle in the body. They can be used in warm-ups and stretching. Both types of bands come in varying tensions to provide different levels of resistance. They can be used by athletes at every level.