Plyometrics

Plyometrics can improve Running Economy for runners and I've covered the supporting research under The Science of Running Economy. Unfortunately, there are no scientifically based recommendations for the structure or progression of plyometric training. The available research uses various plyometric routines, but none compare different structures or progressions. The best I can do is to put together some common empirical recommendations.

• Typically, 2-3 plyometric sessions are used, separated by 48-72 hours of recovery.
• Athletes should be healthy and uninjured before starting plyometrics. Injury free includes no pain, no limited range of motion, or swelling. Healthy includes things such as good balance (30 seconds on one leg) and no more than 20% muscle strength side-to-side. Being able to squat 1.5-2.5x body weight without pain is also a recommended prerequisite.
• I couldn't find recommendations for volume, but one paper suggested using number of foot contacts, with 80-100 as beginner, 100-120 as intermediate, and 120-140 as advanced.
• The National Strength and Conditioning Association's position on plyometrics indicated that athletes over 220lb/100Kg should not do depth jumps from higher than 18"/45cm. It's unclear where this recommendation comes from, but I'd take it to mean that the heavier you are, the more caution you should have in your starting point and progression.
• You can look on YouTube for videos of various plyometric moves. This is the best source I found for explaining how a given move should be performed.
• While plyometrics are explosive movements, a key aspect is the sequence of stretching the muscles before the explosive movement. This can be a simple countermovement, such as squatting down before jumping up, or more extreme, such as dropping from a box before the jump (depth jump).
• Jumping up onto a box is lower impact than jumping on level ground, which in turn is lower impact than doing a depth jump. The original training program, called "shock training" focused on depth jumps, which may be the most effective, though difficult type of plyometrics.
• Single leg exercises are more than twice as hard as the double leg equivalent. Not only do you have twice the force, but there's more stabilization effort required.
• Having an overhead goal you're reaching for can help improve the jump height, and this probably improves the effectiveness of the plyometric exercise.
• I suspect that a key to the benefit of plyometrics for runners is to recruit all the muscle fibers in the activated muscles.