Adjusting High-Reps Percentages for Lower Body Lifts
A little piece of me dies every time I see someone prescribing same percentage for high reps sets (i.e. 70% x 10reps) for upper (e.g. bench press) and lower body (e.g. back squat) lifts. This is much harder to be completed for the lower body exercises, and in my opinion because we don’t take into account the bodyweight lifted.
This is pretty similar to comparing pull-up and lat pull-down. Let’s assume I can lift 30kg for 3 in the pull-up, and that’s approximate 33kg 1RM (30 x 3 x 0.033 + 30). I want to do sets of 10 with 70%, and that’s 33 x 70% = 23kg. Can I do it? Of course not!
I need to take my body weight into account. Since I am lifting my full body, I need to take 100% of my BW. Hence the formula now becomes:
30kg (external) + 100kg (BW) = 130kg (total system weight)
1RM = 130 x 3 x 0.0333 + 130 = 143kg
Now, when I am calculating 70% x 10, I get 70% x 143 = 100.1kg. Since this is total system load, I need to deduct 100% of BW (in this case 100% x 100kg = 100kg) to get 0.1kg, or basically I can do sets of 10 with bodyweight only. Compare this to the above extra 23kg (70% of 33kg) – can you see why this can be applied to squat?
Lat pull-down on the other hand have 0% of BW involved, so 1RM (external) is 143kg.
When we squat, we lift approximately 65% of our bodyweight (more or less, bit this is a rule of thumb), since we are not lifting our legs. Hence, the 1RM needs to be increased for 65% of BW, and 65% needs to be deducted from total system load when calculating how much we need to put on our backs when prescribing using percentages (see the Pull-up example).
You can read more about this blog post.
To keep long story short, I am explaining how to do this in Strength Card Builder. Enjoy and let me know what you think.