Plyometrics, Ground Contact Time, and Sprinting (Part 4)

Last Updated on February 22, 2012 by Jimson Lee

This is Part 4 of a multi-part article.

The purpose of the article Plyometrics, Ground Contact Time, and Sprinting was simply to demonstrate the faster the movement, the shorter the ground contact time.  Dunking a basketball is much different than sprinting, so the Plyometrics you do should have a positive impact on improving (or optimizing) ground contact, while getting the muscles and tendons stronger to increase the force while on the ground.  CNS is also worked as an added benefit.

Part 2 of this series was covered in How to Weight Train without Weights and it focused on speed strength.

Part 3 of this series was titled Driving Resistance Band Training with a video from Remi Korchemny.

The term “plyometrics” is a loose term, because it can workout different aspects of “strength training”, and I’ll get to each of them.

I’ll break down the term “strength” into 5 areas:

1. Absolute strength, or Maximal strength
2. Power, or speed-strength
3. Explosive strength (Plyometrics is a good example)
4. Reactive strength, or elastic strength
5. *Strength endurance (not really part of this discussion, but check out Matt’s Pull 1 minute WR)

For Part 5 of this series, I’ll go in detail with explosive training next week with a guest lecture video from Tim Egerton of www.sprintstrong.com (exclusive for the readers on Speedendurance).

Absolute and Relative Strength

Before we talk about strength training, we need to make sure your athlete doesn’t gain too much muscle mass.  See article on non-functional hypertrophy.  You can never bee too strong but never at the expense of flexibility.  Then again, you can’t be too big either, especially 400m sprinters.

This may sound weird, but I have the genetic ability to gain muscle mass fairly easily while staying lean at under 10% body fat. (see photo of me on Facebook or my athlete bio page weighing over 190 pounds (86 Kg) at 6’ (1.82m) tall)  95% of men in the world today would die for this condition.

So there are two considerations you need to be aware of:

1. Absolute strength – The maximum force one can exert with his body weight or muscle size

2. Relative strength – The maximum force exerted in relation to body weight or muscle size.

Speed Strength

I covered speed strength in this previous article How to weight train without weights.

Basically, speed strength is the ability of the neuromuscular and CNS system to produce the greatest number of impulse in the shortest possible time. Of course, the two aspects to speed strength are (1) starting strength and (2) explosive strength (more from Tim Egerton later). Starting strength is the force developed in about 30ms from the onset of the concentric contraction. The key is explosive strength (~150ms) having the ability to continue the initiated force as long and fast as possible.

To sum it all up, it is the maximum rate of force development (RFD) in a maximum isometric contraction. Sounds easy, but how do you apply it to the real world? In our case, faster times in sprinting?

Plyometrics

There are lots of “proof” that Plyometrics work.  That’s easy.  It’s the volume and recovery part that is hard to quantify for the variety of athletes on your team.

In this study: (PDF)

Effects of a Plyometrics Intervention Program on Sprint Performance (EDWIN RIMMER AND GORDON SLEIVERT from the Journal of Strength and Conditioning Research, 2000, 14(3), 295–301

The control group showed no changes in sprint times. There were no significant changes in stride length or frequency, but ground contact time decreased at 37 m by 4.4% in the plyometrics group only.

It is concluded that a sprint-specific plyometrics program can improve 40-m sprint performance to the same extent as standard sprint training, possibly by shortening ground contact time.

Plyometrics or Weights?

One of the earliest discussions was Carl Lewis (and several others), and how he didn’t do weights.

Carl Lewis didn’t do weight training (at least he hasn’t admitted it yet)

It’s hard to classify Plyometrics or Weights, but at the end of the day, it’s all “strength” training.

There are 4 types of strength training

1. general strength (i.e. maximal strength) such as bench press and squats.
2. strength endurance
3. explosive strength – Olympic lifts
4. elastic strength (and speed strength) – hurdle hops, stadium stairs, depth jump or box jumps, resistance training with bands

Elastic strength is important because this type of strength is required for a muscle to move quickly against a resistance. Thus this combination of speed of contraction and speed of movement is sometimes referred to as power.

Plyometrics is the last group, the elastic strength component of training.  This can be broken into 3 phases for the beginner where phase 1 you do “Jump Up” exercises (vertical jump, SLJ, etc), phase 2 you do “Jump Over” exercises (hops, bounds, etc), and in phase 3 you do “Jump Down” exercises (depth jumps from box, etc).

For an idea of test correlations, see 100 meters elastic power and strength test correlation.

To add some variation, and to identify weaknesses, you can vary it with single leg hops and double leg hops.

I know from personal experience when I do multiple single leg hops (i.e. 10 hops), my left leg is significantly weaker and sometimes “collapses”.  This is from years of long jumping and triple jumping.

BEFORE you start plyos and depth jumps, read my old article How to increase vertical jump with plyometric exercises.