I have a 2 day alternate split that either has the main exercise (Squats) or the important isolation exercises to directly improve the muscle associated with the main lift. In this case, the main isolation muscles that I work on for the squats are the hip thrusts to maintain the glute strength and the quads. I lie doing unilateral variations because it enables me to be able to do eccentrics after the regular concentric set is done. So after doing my max amount of concentric reps (pushing the weight up), then I would use both legs to raise the pad up and then have the working leg lower the weight for 1-4 reps depending on the amount of reps were in the regular set.
Anyway, I happened to have a Quadriceps Isolation exercise and the Back Squats, where the rep amount was the same, and it was within 7 days to make the potential conversion valid enough to work with.
Case #1
Date
3/14/26
3/19/26
3/19/26
Exercise
Single Leg Extensions (weakest limb)
Back Squats
Barbell Hip Thrust
Lifting Parameters
110lbs x 10 reps; 146lbs 1 RM
225lbs x 10 reps; 300lbs
435lbs x 4 reps; 472.8lbs
I know that my glutes are way stronger than my quads when it comes to the strength contribution of the lift because the initial part is easy and I usually struggle on the top half. The ratio between Single Leg Extensions and Back Squats is 2.04 (300 / 146).
Case #2
I saw a staff member at the gym squatting 355lbs for 4 reps which was impressive. At some point, I also saw him doing some single leg extensions, and it seemed like a no-brainer to ask him about the parameters of these two lifts. He was nice enough to share his lifting parameters which I share here:
Exercise
Single Leg Extensions
Back Squats
Lifting Parameters
155lbs x 6 reps; 180.2 1RM
355lbs x 4 reps; 385.9 1RM
The ratio between those 2 lifts is 385.9 / 180.2 = 2.14.
Things to Keep in Mind
There are several reasons why our ratio has a .1 difference:
- The starting placement for the leg pad
- Differing lifting tempos
- Amount of sets done per exercise
- The guy doing squats more often
- Having different sticking points
- Core strength, including the lower back for stability
All in all, with these 2 cases: a working conversion for now is:
Single Leg Extensions * 2.09 +- .05 = Barbell Back Squats
This formula will be more useful when it’s clear that the glutes aren’t the weak point.