Leg stiffness is a measure used in physiology and exercise science to determine how much deformation occurs as a result of various amounts of force. In other words, it is for the most part a measure of how much leg bend occurs during the stance phase of the gait relative to how much vertical force is applied. For efficient runners the amount of leg bend at faster paces (more force) will be less than that of inefficient, less fit runners at those same speeds. Having optimal leg stiffness is a direct link to running faster with less effort and staying more injury-resistant, and thus exercises that develop it should be a staple for dedicated runners.

A sample progression of exercises to develop leg stiffness might look something like this:

1. Isometric Strength
– wall sit: 2 min
– quarter squat hold (lower body down 4-6” only): 4 min
– full squat hold (thighs just above parallel): 90 sec
– full squat hold with heels off the ground: 90 sec

2. Strength Endurance
– single leg RDLs: 2 sets of 15 reps/reps @ 8 seconds/rep pace
– single leg squats: 2 sets of 15 reps/reps @ 8 seconds/rep pace
– eccentric calf raises: 2 sets of 40 reps/leg @ 5 seconds/rep pace

3. Power Development
– barbell squats: 3*4-8 reps w/ 125-250 lbs
– straight leg deadlifts: 3*4-8 reps w/ 125-250 lbs
– single leg hip bridges: 3*4-8 reps w/ 45-135 lbs

4. Leg Stiffness Development
– hops double leg: 200 @ 3 hops/sec rate
– hops single leg: 2* 100/leg @ 3 hops/sec rate
– box jumps off knee height step: 3*20 with < .2 sec on ground (quick transition)
– tuck jumps (jump up with knees to coming to chest and hands sweep under shins): 3*10 w/ < .2 sec on ground in between each jump

During the build-up of strength and leg stiffness, making sure your legs are staying loose and pliable is critical. This will not only help avoid over-use injury, but it will also raise the ceiling of your end-limits and subsequently increase the super-compensation.