Acceleration and Power: Breaking Down the Start

 

This past summer, I was lucky enough to spend some time with JB Morin. I was excited because I am always interested in learning more about acceleration. In my typical fashion, I immersed myself in the topic to the point of borderline OCD. I bought a 1080 Sprint to experiment with my athletes. Then, about a year ago, JB published his paper on acceleration, “Sprint Acceleration Mechanics: The Major Role of Hamstrings in Horizontal Force Production.”

One part of his paper that caught my attention was the displacement difference between the best and worst runners. Or, in other words, how fast each athlete got to his first step. If you study Frans Bosch’s “Strength Training and Coordination: An Integrative Approach” (and it is a book to study, not read), muscle slack and co-contraction principles can really help with this. I will talk more about this in another article.

Another point that interested me was about power: It is not how much horizontal power an athlete can produce, but rather the effectiveness of the power he uses. Morin uses a unit that he calls the Drf, or the decrease of effectiveness of horizontal power. His claim is that a good starter only loses 5% of the effectiveness of his horizontal force production as he runs toward top end speed. A slower athlete will lose 10%. To improve the effectiveness of this force, he recommends heavy sled runs. However, sometimes the body may not be ready for a heavy sled run, or even a light one, either. The effectiveness may break down due to biomechanical issues.

I was sent a series of videos to review because the athlete in them seemed to stagnate on his progression. I don’t know him and I have never seen him run in person. As I watched the video clips I was sent, I thought about his Drf. If I weighed a sled for him to pull—heavy or light—I thought the results would be minimal, due to some of his movement patterns or lack thereof. I responded with a breakdown of what I saw in the start. After all of the feedback I received from my Building a Champion article, I thought I would do the same with this athlete.

Acceleration: Toe Off and Ankle Stiffness

I started with the side shots. His toe off is picture perfect and he gets good glide time. A telltale sign of that is when his toe comes off the ground, there is a delay on the landing with the next foot. Better yet, at toe off, the swing leg knee is still moving up. His foot placement is good. It is close to underneath his center of mass (hard to tell for sure at the angle). However, when his foot hits, his right ankle gives or lacks stiffness, and the problem it creates changes the angle of his shin. As the ankle sinks and he goes to push forward, the force becomes less horizontal and more vertical because, as the ankle softens, the shin becomes more vertical, resulting in less effective horizontal force.

This might be why that stride length is smaller than the next step. The same thing happens with his next right leg stride: He collapses and pushes vertical. If I were to have him pull either a heavy or light sled, would his ankle become more rigid? Or would it become softer, due to the force opposing his push, and cause a new compensation pattern?

Video 1: This is a left-side view of a sprinter toeing off. He demonstrates perfect toe off, good glide time, and good foot placement. But when his foot hits, the right ankle is not stiff enough and this changes his shin angle. The result is less horizontal and more vertical force, which may be the reason his stride length shrinks.

Video 2: This video shows good toe off. The sprinter shows very little break in the ankles as he accelerates. As he pushes back, his body/ankle is rigid. He would do better with a heavy sled. In fact, we used EXERGENIE for resistance and I used to anchor it to my four-way hip machine. When he accelerated, he pulled the whole machine on its side and dragged it down my driveway. He ran a 6.2 FAT 55.

This view is from the front and, again, he takes a great first step. But as he lands, you can see some rotation in the right leg that causes a push not only back, but to the right also. His knee shifts to the right. The force is now pushing to his one o’clock and his foreleg ends up on the wrong side of his body. This causes a balance issue and forces his right arm to throw farther, creating another balance issue. This could be because he missed his big toe and found another part of the foot to push from. However, that remains to be seen until we look at him from the back.

His left foot gets to the big toe, and that is why he has a better drive from that side. In fact, you can see the stiffness when he lands and goes through a moment of ankle rocker to get the momentum going forward and keeping his horizontal forces horizontal. The second right step again has a spin to it and his vector is not straight. The footage of when he is close to the finish line show his right foot clearly pushing to the right. As he becomes more upright, his left foot starts to roll to the outside and he doesn’t make it to his big toe. This can account for his block 10 and block 30 times. He has a decent block 10, but his block 30 does not correlate. So his Drf is probably not as good as it could be.

Video 3: A view of the runner from the front. While his first step is great, the landing leg is rotated, throwing him off-balance. He has better drive on his left side, pushing through his big toe, but the left foot starts to roll to the outside as he becomes upright. This decreases his horizontal power (Drf).

The back is an interesting angle. His first step is really good. He is coming off his big toe and, at toe off, his swing leg hip is reaching up to his armpit. At mid-stance of his first step, his hips are almost parallel to the ground and his swing stays under the corresponding hip. But, that toe off position from the right creates some lateral movement, which is shown by the drop in his right hip. He doesn’t get his left swing leg up to his armpit. From that point, he stays on the outside of his feet and never comes through to his big toe. This becomes cyclic as he moves down the track.

Video 4: This view of the back of the athlete shows a good first step. However, his toe off on the right creates lateral movement and, instead of coming through his big toe, he continues to stay on the outside of his feet.

What is interesting is that this athlete’s vertical jump video from the back will also show that he pushes through his feet in the same fashion as he does when he comes down the track. Maybe this is why there is a correlation between vertical jump and acceleration times. A good jumper will go through his big toes, like a good starter.

Video 5: This shows the same athlete jumping, from behind. Notice that he pushes through his feet in the way that he does when sprinting down the track. This may be the reason that there is a correlation between his vertical jump and acceleration times.

This video of the Asafa Powell vs. Tyson Gay comparison shows two different techniques. Powell was going through his toe drag phase, which is quite a clever technique. The drag causes a pretension in the opposing hamstring, which may cause it to be more reflexive. Both men keep their hips parallel to the ground, which allows for better balance. Both men show the ankle stiffness that rolls into an ankle rocker to improve their Drf. And both drive to their big toe to get a true triple extension.

Video 6: While runners Asafa Powell and Tyson Gay have two different acceleration techniques, they share some commonalities in form, too. Both get better balance by keeping their hips parallel to the ground. Both improve their Drf using stiff ankles rolling into an ankle rocker, and both drive to their big toe.

Outward Explosion From the Start

Again, we are looking for how effective an athlete’s acceleration can be. In the previous section, we saw the importance of getting to the big toe and ankle stability. An athlete can have all of the hip extension power in the world, but if the ankle is not rigid or the drive in the foot is not forward, they will not accelerate well. Or they will have a poor Drf.

Now, we have a different case. This athlete is different than the previous one. His needs are almost the opposite. While this athlete has a better vertical jump, he does not have the outward explosion that the previous athlete does. So, let’s take a look.

From the side, his first step has some explosion. To see this, I am looking at the hang time from toe off to contact of the opposite foot. But, his torso is curved quite a bit, which can reduce some power output. It is more difficult for the body to organize and release power when the spine is as curved as this athlete’s. The collapsed torso will also inhibit how high his knees come up as well, which means his foot strike is out in front of his center of mass. This will delay the time for the next push because the mass takes time to move forward.

This is the reason that explosion out of the blocks is critical. It gets the momentum moving faster, so foot strike underneath is more probable (JB Morin’s research about velocity differences before first contact). This athlete also lacks some ankle stiffness. Watch as his ankle hits the ground and his heel sinks downward and to the rear, which forces his shin to move to a more vertical angle. His horizontal velocity now becomes more vertical in nature.

Another reason for his vertical force is that his knee is extending without his hip extending. His hips seem to stay behind in his start as his legs do the work. His next step almost happens at the same time that his toe off occurs. This shows a lack of power, which could be either from the lack of toe off or from his curved posture. There is no insight as to why this happens at this point. Step No. 2 has an ankle give as well and he is becoming more vertical. Again, at toe off, Step No. 3 is about to hit the ground and contact is becoming more out in front.

Step No. 4 shows some good ankle rocker but lacks stiffness elsewhere. The front and side will show more, and the timing is critical at this point. The lack of hang time is not allowing for the swing leg to follow through and, with his center of mass not moving quickly, the foot contact will be premature. He is now “late in his gait.” The concept of Drf is that effectiveness of the acceleration. By Step No. 5, his shins are almost vertical. His horizontal force is all created by his lean and his arm drive.

Video 7: As we study explosion, we notice that the athlete in the video has some explosion in the first step. However, his torso is curved, which reduces power release and delays the next push. Additionally, his ankle isn’t stiff enough, which forces his shin to a more vertical angle and leads to vertical velocity instead of horizontal velocity.

Video 8: This view is of the same athlete, but a little more to the side/front, showing the points made in the previous video. The vertical force is also due to extension of his knee without corresponding extension of his hip, His toe off needs improvement, as it’s currently premature. His lean and arm drive are creating horizontal force, but not his legs.

From the front, we are looking for cues that will show that, despite his ankle rocker, something else is not rigid to allow ankles to work properly. In his stance, with no blocks to help align his feet, he is already off balance. His feet are lined up behind one another. Without balance, all else will fail. His main concern at this point is to not fall. Acceleration has now become secondary.

The initial push is through the big toe but, due to his stance, he is already moving to the side. Additionally, his posture doesn’t allow for space to let his hips and shoulders move. At toe off, it looks as if his hips are staying behind. Previous to contact, he is already rotating his pelvis and his right shoulder is falling behind and his left arm is crossing. This rotation continues throughout his start.

Video 9: The athlete starts out off-balance, with not enough rigidity despite his ankle rocker. The result is that he remains off-balance and moving to the side, with rotation through his pelvis, a falling right shoulder, and a crossing left arm. His focus is not on acceleration—as it should be—but on not falling.

From the back, at toe off, his right hip doesn’t come forward at all. In fact, to get distance, he drives his knee laterally. On steps 1, 3, and 5, his lateral chain collapses and he loses power from the additional rotation of the wind-up he uses to push forward. This may cause problems with his timing of his hips. His hips never seem to advance his body forward and he loses his ability to move his center of mass. Watch the back view in reverse—it looks like he is falling into a hole on his right side. This is the lack of stiffness on that side and it is a huge power leak.

Unlike the previous runner, this runner has good ankles and toe off, but the rest of his body is lacking in timing and stiffness, especially in the hips.

Video 10: The back view of this athlete shows that his hips are ill-timed, which means they don’t seem to advance his body forward. Instead, he relies on his knees. While he has good ankle stiffness and toe off, he still needs more stiffness in the rest his body, as well as better timing.

So, how do you improve on this? Come to the Track Football Consortium from December 2-3 in Hinsdale, Illinois. I’ll have a lot of cool stuff to share on acceleration.

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