I’ve read that lifting weights very slowly makes for a more efficient workout. Also, in T’ai Chi, when “posting” we maintain a static posture for many minutes, for example, just standing with knees bent and arms outstretched. Both slow lifting and T’ai Chi posting feel like a lot of work, and they seem to increase the power of muscles.
But work is force over distance, and power is work per unit time. If you’re just standing statically, how can you be working? If you’re lifting slowly, how can that make muscles more powerful?
To put it more scientifically, how does one figure how much energy and power are being used by the human body in a mechanical way?
See how long you can stand with your arms raised to your sides, and tell me you’re not working. You are doing work–just enough to counter gravity.
The reason that lifting weights slowly is a more efficient workout than lifting them quickly is because when you lift quickly enough, you’re letting momentum do some of the work.
There are three types of muscular strength: concentric, isometric, and eccentric. Concentric strength refers to your ability to raise weights. Isometric strength refers to your ability to hold the weight in place once you’ve lifted it. Eccentric strength refers to your ability to lower a weight slowly.
So when you hold a position against gravity (like the pose you described), you’re building isometric strength.
Actually, when you’re holding a pose (with or without extra weights), you aren’t doing any work: mutatron has it right on that count. But you are expending energy. Since, like any machine, the human body is not 100% efficient, your muscles are always turning some of their energy into waste heat. When you’re not moving, they’re turning all of the energy they’re spending into heat.
Just how much energy that is, I don’t know. Is there a physiologist in the house?
I was under the impression that the reason it still takes energy to hold a limb stationary against gravity is that your muscle fibers are actually repeatedly contracting and relaxing many times a second.
But I’m not one of those muscle-things-knower-abouter-people, so…
If you are holding a limb stationary against gravity you are performing isometric work. The limb is working against the force of gravity to maintain its lift. Isometric=same weight, but no movement.