Barry-
Please explain how are you able to know that the ground reaction forces of elite sprinters are not caused by the kinematics rather than the other way around.

Also, before you ask for peer-reviewed studies that show that kinematics do affect sprinting performance....please show us that kinematics do not affect performance. As the primary person leading the charge against long-held beliefs it is YOUR DUTY to prove your point, not ours to disprove yours. There are countless world record holders, Olympic champions, and their coaches who would tend to disagree with your points. And please don't come back with the Weyand study again because we both know that the only kinematic parameter that was examined was swing time, which tells us NOTHING about the actual joint kinematics.

Hi Mike,

What follows is my response to your recent blog comment:

“Also, before you ask for peer-reviewed studies that show that kinematics do affect sprinting performance....please show us that kinematics do not affect performance. As the primary person leading the charge against long-held beliefs it is YOUR DUTY to prove your point, not ours to disprove yours. There are countless world record holders, Olympic champions, and their coaches who would tend to disagree with your points. And please don't come back with the Weyand study again because we both know that the only kinematic parameter that was examined was swing time, which tells us NOTHING about the actual joint kinematics.”

Here is what I wrote in my recent blog:

“That being said, in the case of effecting kinematic changes through specific training validation should be via peer-reviewed research that shows: (1) Kinematic changes can be derived solely from specific technique training (absent the use of any strength training). (2) That kinematic changes derived from technique training alone shows statistically significant increases in running speed. (3) Evidence that kinematics taught by isolated drills mimic the kinematics during high speed running. (4) That swing mechanics can be altered by technique training to correctly apply ground force and improve speed.”

“Therefore, time spent on technique training to alter kinematics would be redundant at best and in all likelihood would be counterproductive.”

“Unfortunately, the practice of technique training still persists despite the lack of substantive basis and a growing body of contrary evidence.”

“The bottom line is that the use of technique training to alter kinematics, problematical from the beginning, is not justified by current research.”

“Therefore, any rationale for technique training specifically designed to alter kinematics and/or swing mechanics must provide the basis by which ground force application increases through such training”

Clearly I did not state that kinematics do not affect performance, as you claim. The issue is about specific training that alters kinematics. The long held beliefs are about training.

I have no challenge to Ralph Mann’s work unless you can show that his research specifically suggests the use of training protocols to alter kinematics. I doubt he would have published anything regarding specific training; therefore there is no need for you to continually defend Mann’s work as if it’s under attack.

The disagreement between us is based solely on the possibility of altering kinematics through specific training and, if it is possible, is it necessary. If you claim that you can alter kinematics through training and that it is necessary to do so, then the burden of proof is on your shoulders.

We can reasonably eliminate from a potential kinematic-altering training protocol the use of certain drills, especially A’s and B’s.

In Kivi and Alexander’s “A kinematic comparison of the running A and B drills with sprinting,” the authors state “The purpose of this study was to examine the kinematics of the running A and B drills, and to compare them to sprinting. Because the drills are used extensively in training, the hypothesis for this study was that no differences in the majority of the kinematic variables would exist among the running A drill, running B drill, and sprinting.”
At the completion of the study, Kivi and Alexander stated: “From the results of this study, it was concluded that the kinematics of the A and B drills were not similar to sprinting. Coaches must be aware of these differences when incorporating the A and B drills into a sprinter's training program.”

To be fair, many coaches still use these drills for other training purposes rather than for altering kinematics. That being said, there are many who still use them because they are not aware of Kivi and Alexander’s research.

Several times in our discussions you’ve made a point of mentioning elite athletes. Perhaps your intention is to show the possibility of an inherent difference between sprinters that separates the elites from the run-of- the-mills or perhaps you’re taking the nature side of the nurture/nature debate.
However, separating the elites from the ordinary complicates the case for attempting to alter kinematics via training.
Even without a head wind, the elite sprinter creates increasing drag at higher speeds—much more than an ordinary sprinter. Adding in the possibility of tail wind creates what would appear to be a nightmare of kinematic training possibilities. How does the coach teach the athlete to find the best vector alignment for each possible running speed/wind condition without actually training in the specific condition?

In essence, this is the same problem that affects the A and B drills: The kinematics used during training might not match the kinematics of racing. The infinite number of possible combinations of track surface, wind conditions and other factors make it unlikely that any coach would be able to direct the athlete’s specific training needs (altering kinematics) to any single race let alone a season full of them.

I noted earlier that the disagreement between us is based solely on the possibility of altering kinematics through specific training and, if it is possible, is it necessary.

Based on Kivi and Alexander’s work and the vagaries of outside factors that affect running, it’s highly unlikely that training via specific kinematic-altering drills would be the cause of any meaningful improvement in performance.

Yet, improvements in performance do occur, at all levels. We see them, you see them.
We know that ours did not occur from any attempt to alter kinematics through specific training. In fact, we believe that it is not necessary to spend training time on altering kinematics because the athlete can adapt kinematics on their own, just as other bipedal and quadrupedal runners can.

In a study by Young-Hui Chang, et al, “The independent effects of gravity and inertia on running mechanics” subjects ran under 3 different conditions: additional gravitational and inertial forces, with only additional inertial forces, and with only reduced gravitational forces.
It should be obvious that each of these alterations in the running environment is neither a condition that a runner normally encounters nor would they fall within the training experience of a coach.

The subjects were given the opportunity to familiarize themselves with what ever apparatus was necessary to simulate the conditions of test runs. They practiced at two levels of each of the three experimental treatments—for approximately 30 minutes.

Interestingly, changes in running kinematics were observed across the three experimental treatments yet they were relatively small.

The researchers stated “Despite a nearly threefold change in the magnitude of the resultant force vector generated across three different experimental treatments and 10 conditions, the orientation of the resultant force vectors at corresponding instants remained nearly constant during times of high force generation.
Changes in the magnitude of the vertical component of force are accompanied by proportional changes in the horizontal component of force to maintain the orientation of the resultant force vector.”

One might ask if this was an unusual case. Were the subjects previously trained by coaches of elite athletes?

“We suggest that the resultant force vector at these corresponding times of the step cycle remained nearly constant across the different trials to maintain the alignment with the leg. During legged locomotion, this alignment may be a universal mechanism for running animals to minimize net muscle moments about each joint and, therefore, muscle forces. Many running mammals align the resultant force vector with the long axis of the leg (Biewener, 1989, 1990).”

“Given the empirical and theoretical support, it is likely that our subjects were also aligning the resultant force vector with the leg to minimize muscle forces in both our control and experimental treatments in response to acute changes in weight and mass.”

It’s worth repeating: “…it is likely that our subjects were also aligning the resultant force vector with the leg to minimize muscle forces in both our control and experimental treatments in response to acute changes in weight and mass. “
It’s also worth repeating that they had about 30 minutes to acclimate themselves to the apparatus. Apparently, no one spent time in using specific drills to alter their kinematics.

One could make the case, if they were so inclined, that the conditions were such that runners might be able to alter their kinematics only for the particular changes in weight and mass. If this was the case, it would be more then likely that they did so without an elite coach—more than likely without any coach.

The paper suggests “In most situations, this unifying principle of resultant force vector alignment with the leg for running may be a valuable predictive tool for understanding the locomotion biomechanics of legged animals in different habitats and under different conditions. Studying the biomechanics of human running provides a tractable experimental model that can predict the responses of other legged animals to different force environments.”

The last line should suffice as an answer to your initial question: “Please explain how are you able to know that the ground reaction forces of elite sprinters are not caused by the kinematics rather than the other way around.” Predicting the response to different force environments means that force influences kinematics.
If you do believe that ground reaction force is caused by kinematics, you need to clearly prove by what mechanism the body, as a falling mass, can alter force.

From the same study: “We suggest that the alignment of the resultant force vector with the leg during times of high force generation may be a universal mechanism for minimizing net muscle moments, muscle forces and metabolic costs during running.”

Apparently, no one coached or drilled the subjects of the study. They were able to adapt in short order to unusual circumstances. It seems that other legged animals are capable of doing the same thing, and they don’t hire coaches.

The two issues I posited earlier, is it possible and is it necessary to alter kinematics via specific training, have been addressed by these studies—without using the JAP study.

As I've said before, I no longer care to convince you of points that you have your mind set on but I do want to point out that your suggestions that 1). kinematics are solely dictated by ground reaction forces and 2). technical modifications are either not possible or not beneficial are in stark contrast to the findings and suggestions of 25 years of Mann's research and also to the anecdotal evidence of the 1,000s of coaches. As a result, the onus does remain on you to prove that it your points are correct since you are in the overwhelming minority. In contrast to what your comment says, Mann clearly states that technical modification in sprinting is both possible and beneficial. So unless you agree with these points, you are in fact disagreeing with his line of research despite whatever you may say to the contrary.

As for your study about novice runners naturally aligning their force vectors in contrived environments.....perhaps you forgot how this was shot down on my own forum. You post the parts that suit your needs and ignore the parts that state otherwise. How about the fact that they were basically jogging ...running at 1/4 of the speed of an elite sprinter. I think we are both in agreement at the very least this would make the results somewhat of a stretch for a sprinting....an activity which differs greatly in both kinetics and kinematics. How about the fact that they say: "Our data suggest that it is important to consider both the vertical and horizontal forces taken together rather than as independent entities" ....something which you have largely overlooked when posting on my forum and others? How about the fact that when tested under the lowest bodyweight condition, the subjects actually did not follow the so-called rule that they would align force vectors naturally?

As I said before, it is in your court to show us that we are wrong in believing that kinematics can be changed and can result in improved performance. You are the overwhelming minority in your belief that they cannot be changed and that attempting to do so is either a waste of time or a detrimental. I am open to a good argument but haven't seen any strong points to sway my beliefs.