iamgeekfit

Let's take the more global one first: stand or go prone rather than sit. Stewart McGill, a back guru/researcher, in The Ultimate Back Fitness book shows how just sitting is about the worst posture a human can adopt in terms of stresses on their low back in particular. He shows that doing loaded exercises in this position rather standing or prone is pretty much even worse. Given this, what is the most common position for machines in the gym? Yup. Seated.

The second reason for going to free weights? Use of free weights involves more of our muscular system to deal with balance and control of those masses throughout a movement. And that involvement means also involving more of our nervous system, in particular mechanoreceptors. These are the sensory neurons in our muscles and around our joints that contribute to telling us where we are (our muscles, bones and joints anyway) in space. This awareness is sometimes referred to as proprioception.

So, we are training more of our whole body system to carry out a particular weighted, taxing move, rather than simply forgetting about form and letting the machines work that balance/form for us. This difference between making the effort to control a move ourselves rather than accepting the path set by a machine relates to a third reason: range of motion . The way our bodies move through space is complex. What looks like moving straight ahead for instance, frequently involves rotation, too. A recognized issue with machines is that their fixed positions do not necessarily support our own individual range of motion. An impact of this deficiency is that our joints get less action that they otherwise would with having to move weights freely. A machine may also enforce a range of motion that is uncomfortable, whereas doing the move with free weights would be manageable - especially if one has restricted range of motion due to an injury. Free weights more clearly tell us about the quality of our form and our use of our muscles to manage real motion.

Finally, a fourth reason for considering free weights is something called compound movements. Compound movements engage more muscles to carry out a task than so called "isolation" moves. They're so called because there's no such thing really as a move that only involves one muscle, but there are moves that put specific emphasis on a muscle. The biceps curl is a famous example of an isolation move: the focus is on the biceps. These are the main muscles working, even though other muscles are called into play as antagonists and stabilizers, the biceps pretty much alone are driving the movement. Even here, though, the flexors along the forearm are supporting the grip it takes to hang onto that weight. As mass increases, those flexors may give out before the biceps. There are ways around this: strap the weight to the wrist, and isolate the work of the biceps even more. Is there any athletic reason to do this? Maybe not, but bodybuilders, working on proportion for sculpting their shape will.

We can see that moves like a bench press, push up, pull up or squat all involve a number of muscle groups for them to work. Arguments have been made that compound work is more supportive of athletic training because it supports real movements: deadlifts work chains of muscles used in sprints for breaking force, for example. Indeed, that term "chain" is commonly used in discussing open and closed kinetic (movement/energy) chain movements, of which there are two types: open and closed.

Technically, closed kinetic change exercises are defined by Steindler in 56 as those where the force applied is not sufficient to overcome resistance (nicely described in this note). So in a squat, force goes through the ground but doesn't move the ground. In a pull up, force is acting on the bar, but doesn't move the bar. More commonly closed kinetic chain has therefore been translated to mean where one part of the body - the would be moving part - is fixed: squats feet on the ground; pull ups, hands on the bar; push ups, all fours are on the floor.

Some of the discussion around closed kinetic chain work has been that it involves more of the body than its opposite - open chain. Compound movements are also more often than not closed chain movements.

Open chain means that force can overcome resistance, but these also sometimes get joints moving in ways that aren't exactly natural. A typical example of this kind of open chain move is the knee extension machine, which some have argued causes the knee to create a shear force along the joint it's not designed to support. It's also carried out seated on a machine, where the thigh action is isolated and the knee action up is really forcing the rectus femorus of the quads to get that knee up. That said, research is not yet conclusive around superiority/inferiority of one type over the other. Open/Closed are raised here as a way of categorizing movement and muscle involvement.

It may be worth noting that it's rather tough to find an example of a closed chain exercise that isn't standing or prone - what we might think of as more natural or athletic positions: crawling, climbing, resting, running. Seating doesn't come into it.

SUMMARY If you want to do the best by your body, you may want to consider work that

primarily uses free weights rather than machines

involves standing or prone positions rather than sitting

privileges compound rather than isolation style movements

in order to respect and enhance muscular involvement, proprioception, optimal physical positioning for range of motion and natural movement patterns.