Monday, September 21, 2015

Phases of Sprinting

As we continue our dive into all things sprinting, this part will look at the different phases of sprinting and what does/should happen during those instances.

As we breakdown the phases of sprinting, we'll do so in 2 ways.

1) Acceleration Speed vs Top End Speed

2) Phases of the Sprinting Cycle

Each of these will present similarities, differences, and carryover that will clear up some ideas and discussion about training for enhancing speed.

Acceleration vs Top-End Speed

When talking about sport performance, acceleration speed is king.  Most team sports live in the 0-15-yard range, and it's rare for many athletes to reach top-end speed.  For this reason, focusing most speed training on acceleration speed is a smart idea.

That being said, this doesn't mean top-end speed is un-necessary. In sports like football, soccer, rubgy, lacrosse, many of the big, game-breaking plays are a result of an athletes great top-end speed.  So while it may occur less often than acceleration, when top-end speed is needed it's often for a big play.  

Also, when we talk about top-end speed, we must realize these are not track and field athletes.  What I mean by that is track and field take roughly 50-60m to reach top-end speed, and they do this on purpose.  

Team sports athletes have been shown to reach top-end speed as quickly as 20-yards.  Now if you look at many team sports, there will be more instances than you think when athletes will have to run 20-yards in a straight line.  So while it occurs less frequently than acceleration, it does occur quite a bit and athletes adapt strategies to reach top-end speed more quickly.

All in all, the interplay of mechanics, timing, rhythm, high velocity muscular contractions and simultaneous muscular relaxation, elasticity, coordination, eccentric-isometric-concentric actions, etc make sprinting incredibly unique.  

I often say if there was only one exercise to do for the rest of time - it would be sprinting.  

When breaking down acceleration and top-end speed, there are different technical, mechanical, and coaching that make each unique.  Knowing this will allow a coach to better communicate, cue, and evaluate each phase.  

Acceleration - Characteristics

Ninety percent of sprints in soccer and 68% of sprints in rugby are 20m of shorter.  Also in many sports, acceleration speed is preceded by movement.  For example, a player is walking, jogging, shuffling - and all of a sudden they must shift gears and accelerate.

What does this mean?

Strictly performing acceleration drills from a standing start isn't accurate to what many sports actually experience.  It's a different skill set to accelerate from a stand still, than it is from a moving start - so performing both is a must.

Let's look at some basic acceleration characteristics...
  • Ground Contact Times = ~.18-.20sec
  • Forward Body Lean = ~45-Degrees
  • Low Heel Recovery
  • Foot Lands Behind COM
  • Big Split in Hands

Acceleration - What To Look For

The biggest thing to look for during acceleration is the athlete is getting a full push.  We want a committed push, not a rushed, shortened turnover.
We tell our athletes all the time - don't be the roadrunner - spinning your wheels but not going anywhere.

Each stride should be purposeful with the intent to put as much force into the ground as possible. As a coach you should look for...
  • Straight Line Heel to Head
  • Triple Extension - Ankle, Knee, Hip
  • Positive Shin Angles
  • Swing Leg Stepping Over Opposite Ankle - Calf 

Acceleration - What To Say

As the coaching world continues to grow and expand, it's becoming more and more evident that what we say, and how we say it matters!  It's not just X's and O's, it's about communication and stimulating motor learning, and a lot of this is done by the words we use.

It's clear that external cueing is king and it's much more effective than internal cueing in improving performance and motor functioning.  Porter el at (2015) showed that external cueing led to a decrease of .12sec in a 20m sprint.

Remember what we say and how we say it directly influences movement behavior.  Here are some ideas on external cueing during acceleration.

  • Push the Ground Behind You
  • Drive Out Like A Jet Plane Driving Down The Runway 
  • Explode Off The Ground Like A Rocket

Top-End Characteristics

Top-end differs from acceleration in a few key ways, mainly body positioning and ground contact times.  In fact, ground contact times are half of what is seen during acceleration phases.

This means less time on the ground to produce force and more need for elastic components and impulses.  To maximize these things posture and mechanics are key, and as a coach here are some important characteristics of top-end speed...
  • Ground Contact Times = ~.07-.10sec
  • Upright Body Position
  • High Heel Recovery
  • Ground Reaction Forces = 5xBW
Top-End - What To Look For

The actions of top-end sprinting occur so quickly it is advisable to record and break it down frame by frame.  Things happen just to fast for the un-trained eye, that video will give you a much better understanding of what's really happening.

When looking at sprinting, these things are a must...
  • Stacked Head, Spine, Hips
  • Neutral or Dorsiflexed Ankle
  • At Ground Contact
    • Vertical Shin
    • 100% of Height
    • Figure 4 Position - Swing Knee Even or In Front of Grounded Knee
Top-End - What To Say

As we touched upon earlier, the ground contact times during sprinting are under a tenth of a second.  This is not enough time to actually consciously think about something or elicit change while on the ground.

This means our coaching needs to move away from words and cues that try create images of force production, and instead focus on being like a spring or pogo.  Words like the following create the correct image and motor response needed for the demands of top-end sprinting.
  • Relax
  • Bounce
  • Push Yourself Tall
  • Be Like A Whip
  • Snap Off The Ground

Phases of the Sprinting Cycle

To better understand what is happening during sprinting, it is important to understand the different phases of the sprint cycle.  Now many people may classify the phases differently or assign them different names, but the important part is to understand, that during these times, certain actions needs to be occurring.  If they are not, speed and efficiency will be limited.

1) Ground Preparation

Each phase is vitally important, but ground prep might be the most important as it dictates success during the other phases.  

During ground prep, the leg is actively driving into the ground.  THIS IS A MUST.  An athlete cannot produce force once their foot is on the ground, there is simply not enough time.  They must actively be extending and driving while the foot is still in the air.  
The ankle/foot should ideally have some dorsiflexion and it cannot be plantarflexed.  Dorsiflexion allows for greater stored elastic energy and shorter ground contact times.  

2) Ground Contact
Ground contact occurs as the foot touches the ground.  During this time, we see huge amounts of isometric strength in the whole leg as the goal is to become stiff and resist deformation.  

Remember, at ground contact, the body experiences forces as much at 5xBW.  The goal is to not collapse under these forces and instead act like a spring.  
During acceleration, we want to see ground contact take place behind the COM and have a positive shin angle.  During top-end sprinting, we want to see ground contact as close to under the COM as possible and have an upright shin.  
At ground contact, the athlete should be 100% of their height, and their hips shouldn't overly sink or sag towards to grounded leg.  As the athletes leaves the ground, they should maintain this height and actually look as though they are floating across the ground.  Low, sinking runners are a sign of poor elastic abilities and the ability to create rigidness, and instead try to muscle through running which leads to loud steps and longer ground contact times.

3) Toe-Off

I actually classify the 2nd half of ground contact as toe-off.  This is a different phase because during the 2nd half of the whole ground contact phase, the athlete needs to be actively preparing for flight.  
The athlete should NOT be trying to push or continue to drive the foot behind the body.  Instead they should already be dorsiflexing their ankle/foot to elicit the crossed extensor reflex and getting their leg preparing for the flight phase. 
"Sprinters do not actually reach full extension because they are already actively
recovering the leg before the foot is actually off the ground"
- Ralph Mann
4) Flight
Flight phase occurs as the leg leaves the ground and gets back into position for ground preparation.  During this phase we want as little backside mechanics as possible.  The goal is to have the knee take the shortest path as possible to get back to the front side of the body.  

As the opposite leg drives into the ground and reaches ground contact, we want to see the flight leg knee be even or in front of the grounded leg.  I call this the figure 4 position.  

If this position does not occur, we know the athlete is spending too much time on backside mechanics and losing valuable time. 

Stay tuned for Part 4 of our sprinting series.

Go Get 'Em!

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