Isometric Hold Leg Extension

Select a weight that is about 60-70% of your normal working weight.

Forcefully extend both legs to the top position, just like in a normal repetition.

Stay at the top and hold the full contraction in your quadriceps for 5-10 seconds. Breathe steadily during the hold.

Lower the weight back to the starting position very slowly (a 3-5 second descent). Take a short rest and repeat.

You can also combine this with a normal set: perform 8-10 reps and hold the last rep at the top for as long as you can.