Monday, August 17, 2015

Deceleration: Cheetahs, Sprinters, and Weightlifters
Credit hookgrip

When I was in college, one of the prerequisites for undergraduates was a writing course. Before each assignment, we read two passages from books then formed a thesis for our paper. The bulk of the paper was drawing upon our readings and finding the similarities between both works. This wasn't always easy and forced me to closely examine the stories.

While I never enjoyed writing - which is strange considering this site - it became a valuable skill in exercise. Coaching, programming, and exercise choices require a sharp eye for picking up the subtle details. That is the aim for this post where we'll take a look at sprinters, cheetahs, and Olympic weightlifters. They appear different from one another, but in fact they share similarities.

Sprinter [source]

Researchers at Southern Methodist University of Dallas analyzed the running mechanics and action of sprinters compared to a group of soccer, lacrosse, and football players. It was previously believed that running fell under the influence of a spring-mass model described as:
The spring-mass model assumes the legs work essentially like the compression spring of a pogo stick when in contact with the ground. In this theory, during running at a constant speed on level ground, the body falls down out of the air. Upon landing, the support leg acts like a pogo stick to catch the body and pop it back up in the air for the next step.
It's been generally assumed that this classic spring model applies to faster running speeds and faster athletes as well as to slower ones. Elite sprinters do not conform to widely accepted theories of running mechanics.
The article states that sprinters deliver a deliberate striking action to the ground versus the mixed athlete group.
"Our new studies show that these elite sprinters don't use their legs to just bounce off the ground as most other runners do," said human biomechanics expert and lead author on the studies Ken Clark, a researcher in the SMU Locomotor Performance Laboratory. "The top sprinters have developed a wind-up and delivery mechanism to augment impact forces. Other runners do not do so."
And I'll highlight this last excerpt.
We found that the fastest athletes all do the same thing to apply the greater forces needed to attain faster speeds," Weyand said. "They cock the knee high before driving the foot into the ground, while maintaining a stiff ankle. These actions elevate ground forces by stopping the lower leg abruptly upon impact." 
The new research indicates that the fastest runners decelerate their foot and ankle in just over two-hundredths of a second after initial contact with the ground.
Keep this information in mind as we review the next article.

Cheetah [source]

The cheetah is the fastest mammal on the planet and is known for its speed. Alan Wilson and his team from the University of London’s Royal Veterinary College discovered that the cheetah's speed is not its most important hunting trait.
Third, cheetahs can decelerate faster than they can accelerate, much as sports cars with powerful engines need beefed-up brakes. While both these processes require different sets of muscles and depend on different conditions, the rates of acceleration and deceleration beat those of any other land-dwelling animal. Based on the recorded data, Wilson calculates that the muscle power output of cheetahs is about four times that of Usain Bolt, three times that of polo horses, and nearly double that of greyhounds.

The top speed of a cheetah hunt had no correlation to the successful outcome of the hunt. Instead, Wilson found that success depended more on how fast the cheetah could slow down, rather than on how fast it could speed up. It is this last phase of a hunt that was critical for success, where the cheetah slows down. When these two observations are put together, Wilson thinks that it seems cheetahs don’t abandon hunts early to save energy or reduce risk of injury.

Finally, cheetahs are not built to be able to turn at their highest speed. In an artificial setting, which astronauts and fighter pilots are put into for training, the force felt by a cheetah trying to turn around at top speed could knock it unconscious. Instead they use their ability to slow down and their ridged footpads and claws to grip the ground well enough to turn quickly.
The cheetah's ability to slow down as well as its agility are key factors to hunting.

Let's pull all this together for training.

Olympic Weightlifter

Weightlifters and the classical lifts, snatch and clean & jerk, are often known for their power and speed. If you want to develop a fast athlete, you have them employ those movements or a derivative of them. Typically, there is an emphasis on accelerating in the second pull and having a forceful extension of the ankles, knees, and hips (triple extension).

This is where it all ties into one another. While a powerful extension is beneficial and desired, sometimes lifters and coaches overlook the next part - deceleration/force absorption. In weightlifting, this is also known as triple flexion and is the resulting action of triple extension. The weightlifter speeds under the bar and decelerates it in the receiving position.

Much like in the discussion above for the sprinter and cheetah, deceleration is critical. Similar to the actions of the former two, the pull under the bar is deliberate.

In the sport of weightlifting, the goal is to put up the highest numbers possible. Athletes accomplish that by lifting the bar to the lowest height possible and then pull their bodies under it to speed into the receiving position. This can only be done because of deceleration at the end of the movement. They absorb the impact.

If the body did not slow down, their would be incredible wear and tear to the joints. And to an extent, this is true for a lifter who is lifting more than they are capable of handling.


If deceleration is important, how is it trained?

For the beginner, squatting consistently with good eccentric (lowering) control is first and foremost.

Intermediate weightlifters can incorporate snatch balances into their programs.

Non-weightlifter can use various jumps such as broad jumps, vertical jumps, box jumps, and depth drops. Emphasis should be placed on perfect landings for the most benefit as well as not overdoing it on the advanced movements like the depth drop.

For weighted movements, the Triple Extension-Flexion article provides two exercises - jump squats and trap bar jumps. Low rep sets with light-to-moderate weight is enough to provide the necessary training stimulus.

As you can see, three seemingly unrelated areas have something in common. Remember that deceleration/force absorption is important and is an active and deliberate action that should be trained.
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