Take 2
Knuttgen and Komi, in Strength and Power in Sport (1992), define intensity as the level of muscular activity that can be quantified in terms of power output.
In Essentials of Strength Training & Conditioning, Wathen says the "intensity of exercise is often synonymous with the training load (amount of weight per repetition). Scientists describe intensity as the power output of an exercise."
The quantification of intensity of exercise will differ during different activities (see prev. post). W/o an accelerometer, its pretty tough to guage power output (specifically velocity or speed) during resistance exercise, so load is commingly used, as Wathen says.
For a western scientist, the purpose of defining "intensity" would be to describe a quantifiable variable that can used in studies where statistical analysis is the guide for decision making. Intensity must be a variable, usually a continuous number, a rating, a binary value, etc.
A generic definition might be:
Intensity of resistance exercise is equivalent the load (kg) being lifted.
The above fits with the definition of absolute intensity, where the lifters capabilities are not taken into consideration.
Relative intensity, which is what most folks focus on when designing training programs (e.g., I can't really follow Ed Coan's squat training regime, but have to use weights appropriate to my ability), could be defined as:
Relative intensity of resistance exercise is the load (kg) being lifted, expressed relative to the maximum load that could be lifted (1RM).
BIG HEINZ, perhaps you can provide a reference for your definition?...
"A healthy person [performs] an exercise to the point of momentary muscular failure (100% intensity), you can be assured that you have attained a level of intensity that will stimulate increases in muscular size and strength." What if I do maximum rep sets with 20% of my 1RM, i.e., for several hours? Atha (circa 1980, published in Exercise Science and Sport Reviews) reviewed the literature even then and, using the commonly accepted scientific definition of "intensity," found that a load of at least 60%1RM is required for substantial strength gains in previously trained individuals.
It seems your definition (you refer to "degree of difficulty") refers to what you might call "psychological intensity," which is quantified in western science as a rating of perceived exertion (RPE). Unfortunately, you can do many different kinds of exercise that would have the same RPE rating, but required dramatically different physiological attributes. (E.g., riding a bike at max. velocity for 30 min might elicit an RPE of 10, the same as the RPE during the last rep of a 10 rep maximum set.
One might also expect maximum exercise intensity to increase as one becomes more trained. This would be reflected in the 1RM. On the other hand, RPE in the trained state will be less (compared to untrained) for any absolute load lifted (lifting 100lb is easier when you can lift 200lb compared to when you can only lift 150lb).
Some powerlifters never take sets to failure (at least not intentionally), thus they never reach a maximum RPE. However, they realize that they must increase they weight (load or intensity) they train with in order to have higher totals in competition.
I personally think that a definition of intensity should be one that defines a variable that can be manipulated to vary the training stimulus, as well as one which can be used to quantify strength, standardize muscular endurance tests, etc. Intensity as I have described it above does that. "Psychological Intensity" or an RPE seems a very poor way to ensure progressive overload. If you always train to maximum RPE, how could you know if you are increasing the training stimulus if you never know how much weight you are lifting?... RPE would never change - it would always be maximum. If your RPE when lifting 100lb goes from a 6 (0-10 scale) to a 4, does this mean you got 33% stronger?...
Hope this answers the questions better(?)... Probably stirs up some more, too...
-Randy
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