Resistance bands - e.g. these - are always an interesting option for training, especially if the aim is muscle fatigue rather than grunting up the weights.
Here is a study I spotted about the use of bands:
A Comparison of Elastic Tubing and Isotonic Resistance Exercises
The aim of this study was to assess effects of a short-term resistance program on strength in fit young women using weight machines/free weights or elastic tubing. 42 physically fit women (21.79±0.7 years) were randomly assigned to the following groups: (i) the Thera-Band® Exercise Station Group (TBG); (ii) the weight machines/free weights group (MFWG); or (iii) the control group (CG). Each experimental group performed the same periodised training program that lasted for 8 weeks, with 2-4 sessions per week and 3-4 sets of 8-15 submaximal reps. A load cell (Isocontrol; ATEmicro, Madrid, Spain) was used to test the evolution of the Maximum Isometric Voluntary Contraction (MIVC) in 3 different exercises: Vertical Rowing (VR), Squat (S) and Back Extension (BE). A mixed model MANOVA [group (CG, TBG, MFWG) x testing time (pre-test, post-test)] was applied to determine the effect of the different resistance training devices on strength. The only groups to improve their MIVC (p<0.005) were TBG and MFWG, respectively: VR 19.87% and 19.76%; S 14.07 and 28.88; BE 14.41% and 14.00%. These results indicate that resistance training using elastic tubing or weight machines/free weights have equivalent improvements in isometric force in short-term programs applied in fit young women.
Interesting conclusions:
These results indicate that resistance training using elastic tubing or weight machines/free weights have equivalent improvements in isometric force in short-term programs applied in fit young women.
So, bands worked just as well in this experiment
Comments
There is one big difference between using elastic bands and weights, biomechanically: bands increase their resistance through the movement (the further you stretch it, the more strength you need to stretch it even further). Weights, or any other objets for that matter, don't do that.
That's why, generally, I (subjectively) don't like the feeling of elastic band resistance. There is something that feels wrong. Now, that does not mean it is not effective or usefull. As a physical therapist, I've seen some shoulder patients who have used bands for rotator cuff strengthening, but who make things worse, and changing to weights/gravity giving improvement.
It would be interesting to see what Mr. De Simone says about this.
I know Taylor Lautner used on the set of Twilight so they have their place
Raymond
Bands increase the resistance to stretching, but the moment arm CAN change (it depends on the exercise). Imagine, as an example, shoulder flexion with a band attached to your foot. The moment arm will be greatest when your arm is perpendicular to your body. As you raise your arm from that position, even as the band is stretched, the moment arm on your shoulder joint decreases. The higher you raise your arm, the more the force of resistance of the band is trying to compress your arm bones. It takes very little force to counteract that. So even though in that particular exercise, the resistance of the band changes, you ALSO need to consider the changing moment arm, which will (near the end range) be so small as to essentially require no force from the shoulder flexors.
This is one of THE most common mistakes that people make. It's about force at the joint, which means you need to consider torques and vectors, not just forces. It's not about the force in the band. It's about the force at the joint.
Simple physics...
Although I agree that using different anchor positions for different kind of movements is usefull, I have to disagree with your example.
Actually, the greatest moment arm in shoulder flexion with band attached to foot, will be around 75°, when the angle between your arm and the band is 90°.
By the way, I would never do a shoulder flexion (with straight arm) as a strength exercise. I much more prefer a press/push
Another possible disadvantage of elastic resistance is that it is rather un-physiologic (if that is a word), or unnatural. There is real precedent in our natural history. Our bodies are probably better suited for handling objects.
But again, your point about using mechanics to make the exercise better. But do not only think about muscle mechanics, don't forget joint mechanics...
Why test isometric force, for goodness sake?
Bands are OK-ish for rehab - after that it is just another way of avoiding training.
None the less, when people who deadlift 500lbs+ routinely make almost unanimous use of an instrument I DO take notice.