When I was first writing about strength training back in 1992 I coined the terms alpha strength and beta strength to differentiate between the two manifestations of human muscle strength. It’s important to understand these two forms of muscle strength and how to train to improve them.
Alpha strength is our ability to perform a great amount of work in a short period of time. We see this ability in a 10-second sprint of 100 meters or a world-record bench press of a single repetition. Some people refer to this as explosive strength but I avoid that term because there are trainers who try to get people to do “explosive” exercises with heavy weights and that is a huge invitation to injury. I prefer the term momentary intensity.
Momentary intensity or alpha strength is easily measured. It’s the total weight you can lift in one minute or in 20 seconds or in 5 seconds or whatever time frame you choose to measure. Originally I used the Power Factor measurement to calculate momentary intensity. If you did 10 reps with 200 lbs in one minute it meant you lifted 2,000 lbs per minute or had a Power Factor of 2,000 for that exercise. So to ensure progressive intensity all you had to do was improve that 2,000 number next time.
Alpha strength is a pretty easy concept to understand; it’s the rate of lifting.
Beta strength is a more subtle concept. It’s the ability to sustain a relatively high intensity of muscular output. Nobody can maintain his absolute peak output for very long. The best runners in the world are already slowing down significantly between 200 and 400 meters of distance which is less than a minute of exertion for them. The world record holders for bench press or any other lift cannot hoist their record-weight three times in a row. This is true for 100% of humans.
The fact is there is an inverse relationship between how intense an exercise is and how long it can be maintained. Once we had a Power Factor measurement of intensity this phenomenon showed up graphically. For example, a person could generate a Power Factor of 1,500 lbs per minute for two minutes last week but generate a Power Factor of 1,500 lbs per minute for three minutes this week. So his average momentary intensity did not improve whatsoever yet he was able to sustain it for 50% longer. That means he got stronger, right? So how do you measure that?
The Power Index measures sustained intensity and beta strength because it takes the total weight into consideration (P.I. = W^2 / time x 10^-6). This way we can spot improvements in the ability to sustain high intensity, or beta strength. In the above example, while the person’s Power Factor stayed the same, his Power Index would go from 4.5 to 6.75 showing us immediately that improvement was made. If this person wanted to improve his beta strength his next workout would need to generate a higher Power Index. Trainees wanting more muscle endurance power and/or more workout volume should train by improving their Power Index.
These issues are a piece of cake when you have some black and white measurements to guide you instead of trying to guess how much ‘burn’ you experienced today or how ‘pumped’ your muscle is, or how ‘confused‘ it is. Haha.
Another great benefit of having an objective way to measure alpha strength and beta strength is that it shows up the lies that fly around gyms and websites about this or that exercise or this or that technique or training system that has miracle muscle building properties. If your momentary or sustained intensity decreases there is no way you will build more muscle. The human body doesn’t work that way. Sit in the shade and you won’t deepen your suntan, do a goofy exercise with a lower P.F. and P.I. than your current exercise and it will not – can not – build more muscle for you.
When you use meaningful measurements you are training with your brain.
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