Standing knee extension strength DR (level 2) (Knee extension drag resisted (level 2), leg 90/90 forward, standing, fin on foot)

Stand upright with a wall to your side.
Hold onto the wall with your nearest hand, you will be exercising your opposite leg.
Place a fin onto your foot.
Keeping your back straight, slowly bend your knee.
Quickly kick your foot forwards, straightening your knee.
Bend your knee and repeat the exercise.