Last Updated on September 11, 2017 by Jimson Lee
I was watching an interesting video from UKA Coaching. Due to excessive bandwidth costs, the coaching videos are only available to UK residents. I am fortunate to have clients in the UK so I can watch them!
The video was a 2 part series by Jon Goodwin.
It continues the whole debate on Stride Rate and Stride Frequency. We can go back to 2007 and talk about Ralph Mann’s research on how he wanted to reduce ground contact by 0.01 seconds. Take 43 strides, and that cuts your time by 0.43 seconds. (Hmm, can a 10.00 sprinter really improve to 9.57 if this was true?)
This video is another take on the Velocity theory but looking at another angle.
Contact Length (CL) is the distance covered during Ground Contact Time (CT).
As you can see from the formula:
Velocity = Contact Length / Contact Time
… even the minutest reduction in CT will increase the velocity.
In the slide below, taken from the video, a 5 cm difference in CL due to anthropometric leg length will yield more CT at the same velocity.
But the big difference is the same CT and longer CL will yield a higher velocity (13.1 compared to 12.5 m/s)
Since you can’t do anything during air time (flight time), a greater force during ground contact is your only chance to run faster. Greater force means greater length. Let stride rate and stride frequency take care of itself. Speed is all about how fast you can cover ground.
Higher top end speeds, and the ability to sustain it (i.e speed endurance), will win Gold medals any day!
So why does Usain Bolt run so fast? What’s his trick?
I’ll save that for another article. UK residents can watch the video to find out.
Eric Lepine says
Couldn’t agree more!!!! And, this is not unlike what Barry Ross has been preaching I suppose…
Now, all that’s left, is understanding how to increase that force via strength training in a time-efficient manner ;) And, as my comment from a few days ago, I have a few ideas as to how to do that best…
I think the words of Drew Baye, again, are worth mentioning here… (Comments in [“] are mine…)
“The terms “fast” and “slow” in fast and slow twitch muscle fibers refer to the twitch speed – how quickly the fibers can reach maximum tension – not the speed of movement they produce. [BIG misconception in the world of coaching/training!!!!] Fast twitch fibers reach maximum tension between around 50 and 80 milliseconds, slow around 100 to 200 milliseconds. On average this is a difference of only 85 ms – less than one tenth of a second. The biggest difference between fast and slow twitch fibers is the relative fatigue and recovery rates; fast twitch fibers fatigue more rapidly and recover more slowly, slow twitch fibers fatigue more slowly and recover more rapidly. [Explains the importance of working on speed endurance within the confines of the physiological limits of the energy system required for the specific activity. Increasing the work-capacity (in terms of time for the effort, and time required for recovery) of the specific energy system required for sprinting requires that the coach/athlete be aware of the inherent problem of insufficient rest between efforts, which would push the athlete into the next energy system, due to the nature of the imposed demand].
Contrary to popular misinterpretation of their names, your muscles’ slow twitch fibers are capable of producing very fast movements and your fast twitch fibers will be recruited during even the slowest movements if the resistance is high enough.
For example, an isometric contraction is about as slow as it gets during exercise – you don’t move at all. However, when performing very heavy isometrics training and other types of static holds you will recruit even the high threshold fast twitch motor units because the muscles need to recruit all of their motor units to produce the required amount of force. [This concept is too often forgotten or misunderstood].
Moving fast is neither necessary for recruiting the fast twitch motor units nor more effective for that purpose. The one thing moving faster tends to do is compromise form and increase the risk of injury. The idea one must “train fast to be fast” or that “slow training makes you slow” is nonsense.
Of course, if you want to become more powerful in a specific movement you must also learn and practice the skill of performing that movement in a way that makes efficient use of the strength of the involved muscles. However, skill improvement is very specific; to become more skilled at a movement you must practice that movement, not something that somewhat resembles it, not a similar movement while holding a weight or with something heavier than you would normally use, but the exact movement.
Many well-meaning but misinformed coaches and trainers will tell you doing power cleans will result in a transfer of explosiveness to just about any other activity. They’re wrong. The only thing power cleans are good for is improving your ability to perform power cleans. They are relatively ineffective for improving the strength of the involved muscles when compared to other exercises, have a greater risk of injury, and will do nothing at all to improve your skill in any other movement. If you are a competitive Olympic lifter you must perform cleans as part of your training for the clean and jerk, but there is no good reason for anyone else to do them.”
I think we have forgotten one very important factor about UB: the size of his foot, it is broad, the toes are ‘curly'(?), pointing upwards, when that kind of a foot pushes towards the ground, any ground, tartan etc, it gives more platform for the calf muscle to contract its muscles in the most devastating force. But then again, I might be wrong.
Jimson Lee says
@Harry, I was writing an article on why top sprinters are slightly “pigeon toed” as opposed to having the feel flare out like kicking a soccer ball. Ato Bolden was guilty of this. I’m still looking for high speed video to prove (or emphasize) my points. Stay tuned.
Jimson Lee says
@Eric, you make some good points above. The reason why we do power cleans is recruitment. When you wait in line for an hour, notice how your legs are constantly shifting as they get tired? It’s the same for track events, eventually, your muscles get tired, and you will have to recruit other muscles to keep doing the same movement (see article on hamstring imbalance and iliopsoas).
This brings up the topic of EMS. The human muscle can contract about 30% of the muscles with a human response by the nerves (voluntary). EMS can get that number much much higher. EMS is extremely popular here in Italy.
Most people shun away from talking about negative foot velocity. Mainly because this involves “gasp” limb velocity, which most people have discounted completely due to Weyand’s study. But surely the conditions created on the ground (high contact forces) are partially created by limb velocity. If people truly believe that these very high ground contact forces are created solely at ground contact from sheer contraction of the fast twitch fibers, there is a great misunderstanding of the physics involved. If a person tries to put a whole in the wall do they place their fist on it and push as hard as they can? Or do they generate velocity of the fist and at the moment of impact generate stiffness?
Sprinting is the same. You need high contact forces as you’ve mentioned, this is created through a hard hitting foot and the ability to generate stiffness at contact and avoid collapse. Contact length is highly anthropometric, but horizontal impulse is not.
Some things to consider.
Eric Lepine says
@Jimson… Interesting point. However, if recruitment is indeed a concern, and if you insist on using different exercises to counteract this (the pool of exercises used will obviously vary according to the athlete and the sport), wouldn’t you agree that it might be better to choose a “safer” exercise than cleans? In that respect, full ATG squats paired with stiff-legged deadlifts, or deadlifts with GHR would be more than enough to recruit the necessary fibers…
Motor unit recruitment is determined by the amount of force the muscles are required to produce in order of size, starting with the smallest motor units with the fewest fibers and ending with the largest with the most fibers. Regardless of the speed of movement if the weight is heavy enough (a minimum of about 60% of your one rep max) you will recruit all of the motor units in the muscles being worked within a few reps. After all of the motor units have been recruited and are fatiguing, further increases in force production are achieved by increasing rate-coding (the frequency of the signal to the motor units to contract).
EMS is certainly interesting, as you pointed out, if not only for the fact that it allows for the recruitment of MU in an inverse order. The reasons for the varying results in the scientific literature, however, render its application quite complex. This is also why the underlying mechanisms of action EMS are also very unclear. Does it increase muscle strength, reeducation muscle action, facilitate muscle conctaction, increase speed of recruitment, increase local blood supply, act as an effective massage, relieve pain, reduce msucle spasms, promote relaxation and recuperation, increase ROM, reduce swelling, improve metabolic efficiency, etc.? All of these? A combination? One thing is clear however: unless applied by professionals trained in medicine or physiotherapy, the results can be quite disappointing…
As for voluntary contractions not recruiting more than 30% of MU, that number seems a little low. Most beginners have be shown to exhibit, on average, recruitment of 50-60% of MU, while some elite level athletes make it all the way to 90% +!!!!
Markham Lee says
Here is an interesting take on the contact time discussion.
Due to a variety of issues (Birth defect + some bone damage), it takes me a fraction of a second longer to get my right foot off the ground than my left. Now none of this was discovered until I was in college, but the estimate is that the problems started around the beginning of my Jr. year in high school. The basis for the estimate?
From my indoor season to the outdoor season the overall trend was that my times were getting slower, but the “outlier” times would be faster. Think: on average my 200m times were slower, but I’d have a couple of amazing races that were way faster. Thing is all those good times came after I missed some practices or races (injury, family vacation, etc), as the foot (even though it didn’t hurt) was just less inflamed.
In college the problem became more pronounced, I’d run a 300 in 35-37 and then struggle to break a minute in the 4 x 400 when I had more than enough time to recover. I wouldn’t feel tired just like I was running in quick stand and couldn’t get my left leg to cooperate.
200s were interesting I would often blaze past people who beat me in the 100, reason being the inner (left leg) is moving faster than the outer one (at least that’s what my coach and I thought).
Either way it’s an interesting thing to think about: small differences in bio-mechanical efficiency could make a huge difference in the times of two different athletes. Just think about it, if I’m racing my twin who does everything I do as far as training and is just as determined, but he can get his right foot off the ground say 0.005-0.01 seconds faster than I can, and do it using less energy how much does that translate to as far as a 100m time? Especially since that problem slows down your left foot too (otherwise you’d run in circles).
Very very interesting comments. Think about what difference it will make if the other leg, foot is slightly different in size;length,broader, the flexibility in toes…I don’t know if it makes much difference in 30,40, 50 meters but from then on the cumulating effect should be negative(?).
Speed = Foce/mass * time (Impulse)
@ Eric Lepine:
I agrre with your argument on FT fibres. FT bibres can produce higher forces and produce it faster than ST fibres.
In top speed sprinting FT fibres are crucial, because there are ground reaction forces of 4-5x BW in ~ 0.05s in elite sprinting (fact). The eccentric phase is the key component. The better the RFD of the eccentric phase of the supporting legs muscles, the shorter the contact time and the higher the force! F=m*dv/dt
You need FT fibres for the eccentric work, because it’s the only moment where force and velocity is extreme high!
Concentric muscle work should NOT really happen in top speed sprinting. The energy of the eccentric phase should be stored and released in the tendons of the muscles. A long, stiff achilles tendon is crucial for that quick elastic energy release.
Thats why fast animals like cheetahs or cats have long tendons and short muscles. It’s economical.
In a perfect muscle tendon complex, the muscle would be so strong that it can apply the force isometrically (needs the least energy), and the tendon would be long and stiff with no hysteresis (energyloss by heat). Usain bolt bends his ankles less than other sprinters. That means his eccentric supporting phase is shorter OR his tendons are stiffer or both.
@ Mike: limb velocity against the ground isn’t the key in top speed sprinting. It the velocity of the whole body who matters. And this velocity is already near to it’s top level in TOP speed sprinting. “You have to rund fast before you are able to run faster”
Gravity is the main enemy. Wind resistance is less important.
You have to figth against gravity. The horizontal speed is already there.
That’s my opinion to ground contact time in top speed sprinting.
sry for my english.