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Lecture Notes

The second broad category of resistance training is dynamic resistance, and we'll talk about three different types of dynamic resistance training. First is dynamic constant external resistance, the second is isokinetic exercises, and the third are plyometrics. So the first one we'll talk about in this slide is dynamic constant external resistance, also called isotonic exercises, "Iso" standing for constant and "tonic" for tension, so you have constant tension throughout the range of the motion here. And we're talking about resistance exercises that can occur with free weights and some weight machines also, and here the weight does not change throughout the range of motion, and we'll see a couple examples on the next slide; that's one of the key aspects. The second key aspect of this type of exercise is that there's both a concentric, or lifting phase, or shortening phase of each rep, and also a lowering, or eccentric, and lengthening phase during each repetition. So if you think about a bicep curl with a free weight, you have the concentric as you lift your hands up toward your shoulders, the eccentric phase as you move your hands down, and that weight is not changing as you go through the range of motion. That doesn't mean that it's the same difficulty to move the weight at each joint angle as you go through the range of motion, but the actual weight that you're lifting is not changing, so that is staying constant in these types of exercises.