[QUOTE=Knifefighter;965225]All of these statements are incorrect.
Some simple movements have more crossover to real life than do their complex movement counterparts. The average person is much more likely to perform an elbow flexion (as is done in a standing arm curl) lifting motion in his daily activities than he is to perform a shoulder flexion, adduction (as is done in a pull down).
Rather than increasing injury risk, single joint exercises are also a good way to prevent injuries, as they can be used to balance out muscle imbalances that occur in sports and every day activities.
Isolation exercises also assist in sports such as grappling that require several isolation movements.[/QUOTE]
[QUOTE=Knifefighter;965229]Specificity is the key. You have to look at what the goal is and what movements are specific to that goal. If you are training for a sport, you need to mimic the motions of that sport. If you want to avoid injury, you also need to mimic the opposing motions, as well as to train specifically weak areas that are prone to injury.
Multijoint and single joint (which usually aren’t really single joint, but also involve another joint as a stabilizer or partial mover) can both be part of a good strengthening program.[/QUOTE]
[QUOTE=taai gihk yahn;965246]exactly; there is really no such thing as a “single joint” movement: for example, anytime you move at all, you engage spinal joints at the very least as stabilizers,
in fact from a clinical perspective, it is sometimes easier for people to do “complex” movements that operate in context of their particular dysfunctional patterns of movement than it is for them to do isolated “single” joint movements that operate outside of that; for example, someone might have no problem at all doing a sit to stand with their left leg forward (a complex, multi-joint movement), but can’t do it at all with the right leg forward, and then when you have them try do isolated gluteal contraction on the right leg, which is a simple / single-joint muscle, they can’t do it, and fire hamstrings instead (which are a multi-joint one); so in this case, you need to train the single joint, simple action of gluteus max doing hip extension, and you may need to go back to prone and do it, because if you tried it in standing, they would never be able to do it;
simple-stuff is needed to do the complex stuff - but once you get it and put it all together, you will naturally tend to emphasize the complex because it mimics daily living functional patterns;[/QUOTE]
These make sense. Thanks guys!