Yesterday he had me do the exercise using just one leg at a time. He said to set the machine at 10lbs. I was like, what? I can do 100lbs with both legs, why not 50lbs with one leg? But he was right, 10lbs using one leg at time was pretty tough.
Why is that? Why is 10lbs using one leg so hard when I can do 100lbs using both legs? Is it because I'm using more of my core muscles when I use both legs?