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Here is a quick and easy way to compare strength levels between individuals of different body weights….it’s commonly referred to as the 2/3’s power rule and is an improvement on the more commonly used methods out there.
I first came across this reading through some of Dan Bakers work, all of which I would highly recommend (www.danbakerstrength.com), and more recently work on monitoring by Dr Greg Haff from the US brought it back to my attention.

Generally speaking aside from the obvious absolute strength comparison (eg you lifted 120, I lifted 100 therefore you are stronger), the only other widely used comparison is the relative strength values which is calculated by weight lifted/bodyweight, eg 200kg/100kg = 2 vs 150kg/70kg = 2.14. In this case the lighter individual would be classed as relatively stronger than the heavier individual as they can lift more weight per kilogram bodyweight. But this is obviously the case, lighter people will always be stronger relative to their bodyweight. But is this actually the case, are they actually stronger? We know that the capacity for producing force exponentially decreases with additional bodymass. The world record clean and jerk in the 105kg class is 263kg, this equates to an impressive 2.5x bodyweight. But when compared to the 56kg class record which is 168kg you can see that the lighter man has the better relative strength, over 3x bodyweight! In my gym when we do max testing the lighter guys always win the contest when you look at the results from a relative point of view even though the heavier guys always lift more weight. But who do the bragging rights really belong to? Well hopefully this method will help to settle the argument once and for all!

The 2/3’s power formula is a handy method for comparing the two lifters to decide who is actually the stronger.

Here’s an example: In the first instance the lighter individual is relatively stronger than the heavier individual with a 2.14x bodyweight lift versus a 2x bodyweight lift.
But we know that lighter individuals are always going to be relatively stronger than heavier individuals, so using the 2/3rd’s power formula we can determine who is actually the strongest.

Firstly the formula is as follows:

Now don’t get concerned about the maths element to this, you really don’t need to have a maths degree to figure it out, all you need is a calculator with a power to button which all scientific calculators have!!

Using the example above the figures are inserted into the formula (I have started with the heavier individual first):

This gives us the value of 9.14 which is the multiplier for the comparison between the lifts.

Using this multiplier we can see that the formula for the 70kg individual:

So the value that the 70kg individual needs to lift is unknown, but the formula can be rearranged very simply to calculate this figure:

The value comes to 157kg, So in actual fact in the example shown, the heavier individual is the strongest, as the lighter individual would need to lift 7kg extra to be equally as strong.

For maximal strength lifts this is the way you would compare lifts with more accuracy than the relative strength comparison. This formula is also really handy for S&C coaches when comparing workloads during training blocks both between the same individual and between athletes of different bodyweights. You just insert the number of reps and sets into the formula and work it out the same way.
You can compare men with women as well with this formula but it may be slanted slightly due to gender differences.
Don’t be put of buy the maths, its like an S&C version of brain training to keep you younger for longer whilst at the same time improving your programmes!

Thats all for now, my brain is fried from all this…….keep training hard guys and let me know if you found this useful.

BC

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