Band training has been a staple of the training of elite powerlifters for the last 25 years.
Louie Simmons has to be credited for popularizing it in the Iron Game.
However, the first time I saw was in a French book by Lucien Demilies written in the thirties… Attaching bands to curling implements also known as the Jettison technique also gained popularity in the seventies. Here are five things you need to know about band training:
1 It is one of the best ways to improve powerIn the sporting world, maximal strength is pointless in most cases, if not applied in the shortest amount of time. The exception being the sport of powerlifting, which is in fact a misnomer. For this reason, athletes in other strength and power-dominant sports are more concerned with power which we know is the product of strength times speed.
In biomechanical terms, it is known as the rate of force development (RFD). Attaching bands to barbells in extensors lifts helps match the strength curve by accommodating the resistance for the stronger joint angles. In other words, the bands provide extra resistance where the shoulder flexors, and elbow extensors are at their strongest in the range of motion.
It basically teaches the trainee to keep accelerating with the load, which is not the case with a simple loaded barbell. Bands are therefore great at teaching the concept of acceleration which is key in improving power.
2 It is best applied to the extensor chain movementsThat means band training is best for movements such as squats, presses, and deadlifts as these exercises have an ascending strength curve in the concentric range. Meaning, that the more you displace the load, the greater your mechanical advantage. For example, you are much stronger at the end range of a squat/press/deadlift than at the bottom range.
They also work very well when combined to dumbbells in training all the forms of chest flyes. Josh Bryant is a big fan of those.

Example of extensor chain exercises
Chins and curls share an ascending-descending strength curve, hence, it makes no sense to use the bands for the full range. You are weak in chins and curls at the top range, where the bands exerts the most resistance. Therefore, you would use bands for these movements only at the bottom range.
4 Band training is severe work on the tendonsBoth John Meadows and I have made this observation, hence we agree to only recommend them for one workout out of two for the same body part.

John Meadows doing banded presses
Bands attached to hack squats, pendulum squats and leg presses units can be very beneficial to overload the strength curve. Especially in rehab cases, for example terminal knee extension is the hardest to regain after a quadriceps tendon tear.
In conclusion, band training when used wisely will accelerate gains in strength, power and hypertrophy.
Enjoy the results,
Coach Charles R. Poliquin