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globecanvas Probably eccentric contractions on the hike down hill. The other day I was doing a leg workout alternating box jumps and leg presses. I have done this before. I added an isometric hold at the end of the leg press set for 30 seconds. I felt a little strain / cramp in my quads during the hold and stopped. They felt stiff but okay. I went for another set of jumps and on the first jump my quads seized. It was amazing how much pain one can get in both inner and outer legs. I laid on the mat and stretched and rolled but when I got home, they were sill really sore. Fortunately, they were better the next day.
BTW, I noted last night how high I actually jumped and the angle of my knees on landing. I am at a different gym that does not have plyo safe boxes so I used a 12 inch metal plyo bench. I jump 12 inches of vertical and my legs are straight and feet slightly above the box. I land soft and step off. I suspect when I jump 24 inch box, my knee angle is less than 135 degrees. So I suspect that 15 to 18 inch box is about right for me.