Exercise bands and I have a long history.
I used to use them religiously while I was traveling and when I would work out in college. There is no doubt that bands hold a number of advantages. They are portable, inexpensive and it's had to match them for versatility. They are also great for therapy and other applications where a muscle needs some extra tender loving care.
The question at hand is if working out with bands is just as effective as using regular weight?
I used to think bands were just as good as weight. I often surprised why someone might spend $ 500 on a free weight set up when I can do the same movements and more with my $ 30 band setup. Some of the marketing behind bands is that resistance is resistance, no matter where it comes from. To a point this is true, but it's important to understand that how the resistance is delivered is very vital.
The thing with bands is that as they stretch, the amount of resistance they supply increases. Some say this increase is a good thing because with some lifts, you do get stronger as you reach the top of the lift. So it makes sense then to use a tool that will work you harder as you get stronger. It looks attractive to go from lifting 10 pounds to 30. It gives you the impression that the band will give you a far better challenge.
The reality is that if I can lift a band to an end resistance of 30 pounds; why not use a 30 pound weight to start off with?
If I use a 30 pound weight I will have 30 pounds of weight at the start, middle and end of the lift instead of just having optimum resistance at the end of the lift. The truth is a band does give more resilience at some points in the range of motion. It also has less resistance at other points. Does not it make more sense to simply have optimum resistance through the full range?
Of course there is no such thing as a lift that has exactly the same resistance through the range of motion. Through the use of moving the resistance to gravity you can change how much pull the weight has (like in a bicep curl) and even the body will put more or less stress on a muscle as it moves. So in the end, does a change in resistance really matter?
For the most part a slight change in resistance might not matter, but usually bands do not give a slight change. The change in resistance is quite drastic for most movements and in the end; I do not believe that such changes are optimal for most applications for strength and muscle conditioning.