 Now as far as the intensity itself, Doug had mentioned about a lot of people reaching that point where the exercise is beginning to get hard, they start to panic, they hold back. There's a couple reasons that people do this. One, the genetic aspect Doug talked about, just the panic at exerting yourself to the point where you are literally almost incapable of further movement. It is, again like you said, as far as your body can tell, a life or death event. The only time in the course of normal day to day activities when any animal would exert themselves to that degree would be if it was a life or death situation. Your body does not know the difference between you struggling against a heavy barbell in your back doing a squat or fighting off something that's either trying to kill you or that you're trying to kill to eat it. It's natural to get to that point to hesitate to want to hold back, usually again because of the panic Doug had talked about as well, is because of a lot of people's minds fear of injury. A lot of people associate training hard with the potential for damaging themselves during the exercise. It's kind of an idea that the harder something is or the heavier the weight, the more likely you are to damage yourself in the process. But the weight has nothing to do with it. It's not how heavy the weight is but the manner that you try to lift it that determines whether or not you're going to injure yourself in the process. For example, and get a little bit off track here but I'll come back to the intensity. If you were to go out in the parking lot right now and attempt to lift somebody's car or truck, it's not going to happen. It's a much, much heavier weight than anybody's ever going to touch during a workout. But whether you're injured in the process has nothing to do with how much it weighs but rather the manner in which you attempt to lift it. If you grab the bumper and you just yank at it as hard and fast as you can, you're likely to pull or strain something. On the other hand, if you grab the bumper and you begin to pull gradually and over a period of a couple seconds, a little bit harder and a little harder until you're contracting as hard as you possibly can and then you gradually ease off, you're not going to wreck yourself in the process, you're not going to pull or strain anything. In either case, it's a tremendously heavy weight but whether you hurt yourself depends on the manner in which you attempt to lift it. When you want to move similarly during an exercise, you have to lift heavy. If the weight is not adequately heavy, it's not going to do you any good. No amount of lifting with light weight is going to produce any kind of meaning for results and it comes down to that intensity, the level of effort that you put into the exercise. It's an absolute but if you're going to do this for the long run, if you're going to be doing this when you're in your 40s, 50s, 60s, I know some people in their 70s and 80s that train in this fashion, you have to do so in a manner that's not going to wreck your joints in the process. So you need to keep in mind when you're doing these exercises that you have to always be moving under control. Again with the example of picking up or attempting to pick up a car, if you take the weight and you try to yank or jerk at it as fast as you can, you're going to pull or strain something. If on the other hand, you attempt to lift it gradually and as you approach the end of the lifting movement, you gradually sort of stop, you reverse direction, you bring it back down, you anticipate reaching the start, you slow down for that so that you're able to reverse direction smoothly. You'll be able to lift as heavy a weight as your muscles are capable of but you're not going to pull strain, wreck or damage anything in the process. And a healthy person, your tendons, your ligaments, your other connective tissues, everything will be able to more than adequately handle the heaviest weight that your muscles are capable of contracting against as long as you're moving in a strict and controlled fashion.