What is an acceptable score for a maximal assessment of strength?
There are many factors is determining an acceptable performance level for strength. First we have to collect tens of thousands of assessments on both sexes and among all age groups, (i.e. reference population). The reference population data comes from individuals who wanted their strength and fitness evaluated.
The strength measurements will employ compound multi-muscle group exercises like a squat, bench press, pull-down or shoulder press. These more complex motor patterns better translate to real-life lifting skills seen in real life. This is in contrast to single muscle group exercises that cannot evaluate the effects of summation and coordination of forces involved in more complex skilled lifting tasks.
Maximal lifting, with free weights (barbells and dumbbells), could introduce a high risk for injury, especially if the individual is not well trained. A safe protocol has been developed where the subject is stretched, warmed up and tested using isokinetic equipment. In isokinetic strength testing, the investigator introduces a set speed the lever arm will move (20 in/sec), and the subject pushes against the lever arm as maximally as possible. Since there is no eccentric phase of the lift (letting a heavy weight down), there is less trauma and damage introduced to joints and muscle tissues. A five-repetition maximum effort is used to elicit a full depletion of the ATP Creatine-phosphate high-energy substrates in the working muscles.
A one repetition maximum effort is estimated from the average weight lifted for 5 repetitions. Using the 3% rule: 3% of the average weight lifted times the repetitions and add this back to the average weight lifted. In essence, the average weight lifted for five repetitions is multiplied by 115% to get your one rep max.
Once we have established your one rep max, we need to compare your strength to that of the reference population. It would not be fair to grade based solely on the weight lifted as larger individuals would have a decided advantage. If we use strength to weight ratio of the lift, smaller subjects would have an advantage. A law of physics states that strength-to-weight ratio, falls on a 2/3 exponential ratio to mass. If the individual is twice as big, they cannot lift twice the weight, but 2/3rdsof twice the weight. The Exercise Science Center has patented these formulas, termed â€œAllometric Scalingâ€, so any individual can be compared equitably to an entire reference population regardless of differing body dimensions.
Once strength performance is properly scaled, a statistical determination of where you fall in comparison to a reference population is made on a 0.00 to 4.00 GPA format. A 2.00 GPA your score is the average for a person your age, sex and weight. If you scored a 3.00 GPA you would be one standard deviation better that the reference population (84thpercentile), and a 1.00 GPA you would be one standard deviation lower in that values obtained by the reference population (16thpercentile). So from your GPA score we can statistically find exactly where you fall on the distribution curve for a subject your age, sex and weight.