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This email which I wrote for another user group may also be of interest here. The discussion began with this remark: >> . . . . It seems people have forgotten that the seated leg ext. machine was designed to rehab the knee. Why anyone would do leg extensions in a seated position is a good question. ***This letter raises a very important issue: why, indeed should one try to perform many exercises in attempts to restrict joint involvement and 'isolate' certain muscles? Sure, sure, we have heard from traditional bodybuilders that this offers better development than allowing several joints to move in any multi- articular movement, a forbidden action which is supposed to decrease isolation and the training effect. Sure, physical therapists sometimes isolate joints if other joints contributing to a movement are injured. The fact remains that many muscles are multi-articular (involve several joints) for a very good reason, namely to offer the smoothest and most efficient possible control over the body as a linked system of bones. There is also the fact that, if one prevents movement about any one joint, then the stress increases at the next free joint in that chain. So, if one immobilises the hip, as is the case during seated knee extensions, then stress will increase across the knee joint. That is why more and more physios are now discovering that closed chain squats are more effective and less stressful than knee extensions for rehabilitating knee injuries. Nevertheless, we still see them and many bodybuilders swearing by prone leg curls to 'develop the hamstrings'. If you raise the hips, this is regarded as dangerous or cheating, so the well-meaning instructor insists on pushing down on the hips or using a leg curl device which is angled upwards to keep the butt of the user fixed in place. The idea here is that, even though the hamstrings are biarticular muscles, one is supposed to obtain a superior training effect if one forces them to behave like a one-joint (uniarticular) muscle. The same thing applies to preacher curls, sit-ups, tricep push-downs, calf-raises and many other traditional isolationist exercises. Invariably one can raise greater loads if one allows the muscles to behave in their naturally intended multi-articular manner, so that it is difficult to understand scientifically the rationale behind isolation training in the uninjured person. Practically speaking, one needs to look at the magnificent muscularity developed by gymnasts who always use multi-articular exercises to develop their great strength and capabilities. It is irrelevant to state that since they are not as big as bodybuilders, their training methods are inferior for enhancing hypertrophy - their goal is functional and very skilled strength. The point is that some of their type of multi-articular training exercises (or simple variations of these) could serve as a very useful adjunct to traditional bodybuilding methods, especially those based on machines and 'strictness' of execution. In the days before the popularity of machine training, the vast majority of exercises methods used joints in their naturally dominant mode of multi- articular action, so it might be inferred that the 'muscle isolation' philosophy is largely a consequence of the machine training philosophy and that marketing has more to do with most isolation exercises than applied anatomy or kinesiology. Certainly, we have 'isolation' exercises like concentration curls with dumbbells and many others, but the isolationist philosophy tends to cloud the vital role that is played by non-isolation exercises, free weight and free standing (without weights) training. All too often, the term 'strict' says nothing whatsoever about correctness - it simply means that the exercise is meant to isolate a given muscle. This, of course, is frequently a lot of nonsense, because what they really mean is that a given joint action is isolated, not a given muscle action! It is very difficult indeed to isolate muscles, especially as the load increases and tends to cause overflow and synergistic involvement of adjacent muscle groups. So, as was commented originally: "Why anyone would do leg extensions in a seated position is a good question". Indeed! Why on earth would anyone regularly choose to do ANY isolated or 'strict' exercise? Surely, physios should have realised many years ago that simple actions such as walking or stair climbing (later with added loads) which offer concurrent biarticular action of the knee and hip extensors and flexors (plus some functional adduction) would have offered superior and more functional early stage rehabilitation of the knee than seated knee extensions? It seems as if the bodybuilding profession was not the only one to be seriously afflicted with this "isolation über alles" (isolation above all) disease! In the world of aerobics and general fitness and shape, the pre- eminence of ab crunches and all those weird and wonderless sit-up devices shows that this isolationist creed is alive and flourishing! Yes, isolation exercises can play a role in some aspects of training, but they are among the most overused methods of training in the entire world of strength and shape training. Dr Mel C Siff Littleton, CO, USA [log in to unmask] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%