The high knee lift of elite sprinters is due to well conditoned iliopsoas muscles and passive components such as tendons, fascia, aponeuroses and connective tissue. I find issue with the study by Weyand bacause its too mechanical and superficial. Its not taking into consideration the thermodynamic qualities of muscle, passive components and the morphology of muscle, to name a few. Studying MSF will not solve the training requirements of all sprint athletes in fact all that can be infered from the study is the importance of reactive strength. The study does not take into consideration the bodys reaction to the hip extension flexion as a reflex action that can re-inforce either motion, the stonger the flexion the greater the reaction of hip extension and vice versa…
Your concept is exactly correct. The hip flexion that occurs during a maximal sprint is active, not a passive event as Weyand and ‘spring’ theorists would have us believe. There is much evidence to support the necessity for hip flexion strength (ie., dynamic, explosive strength, rather than pure lifting ability).
First, EMG (electromyography) studies demonstrate a large increase in iliopsoas muscle firing towards late acceleration and terminal velocity phases of a 100m sprint.
Second, the faster one sprints, the greater is the degree of maximal hip flexion (Such an increase in hip flexion cannot be a passive event)
Third, the hip flexors are part of the ‘kinetic chain’ of muscle contractions that occurs during a sprint (ie., the kinetic begins with the arm, then torso, then hip flexion and finally knee extension).
Fourth, exactly as you have written, the hip flexors are necessary in that they allow the contra-lateral hip extensors to generate a greater push-off at each ground contact. In other words, greater hip flexor strength equates to greater contra-lateral hip extension strength. Hip extension strength is the primary strength needed for forward acceleration after the initial start of a sprint. By strengthening hip flexors properly, one increases push-off strength, and hence increases both acceleration and terminal velocity.
The need for hip flexion strength does not negate the need to be able to generate greater ground forces at ground contact during terminal velocity.
Sport Specific Strength Training is needed to improve sprint speed. A simple increase in muscle mass does not equate to faster sprint times. Muscle mass is a reflection of muscle fiber size and muscle fiber type. Muscle fiber size is partially due to number of sarcomeres. It is also due to energy storage, such as fats, glucose, glycogen, creatinine, etc. If an athlete trains simply to increase size then this may be due to an increase in glycogen and/ or fat storage, which has no effect on sprint times in the well-trained athlete. If one trains to improve type IIB (type C) muscle fibers of the proper muscles then one has the potential to improve sprint speed.
The proper muscles and manner to train them depends on an analysis of the biomechanics of sprinting. The proper training in a biomechanically specific manner is too detailed a subject to include in a short space herein.
The hip flexion that occurs during a
maximal sprint is active, not a passive event as Weyand and ‘spring’
theorists would have us believe. There is much evidence to support the
necessity for hip flexion strength (ie., dynamic, explosive strength,
rather than pure lifting ability).
First, EMG (electromyography) studies demonstrate a large increase in
iliopsoas muscle firing towards late acceleration and terminal velocity
phases of a 100m sprint.
If active muscle power were the key to faster speeds, you would see faster repositioning of the limb correct? We don’t though? I think Ben’s hip flexor strength is probably a little better than most peoples right? Why not move them faster? If it were active like you claim, then the simple solution would be to move them faster.
At many walking and running speeds, the hip flexors are activated minimally to not at all. These muscles cannot in any way shape or form assist a runner in accelerating or applying ground force at top speed. Accelerating a runner forward requires pushing rearward against the ground (there is no other way to do it) - only the extensors move the leg in the direction required to do this. The flexors (If active) would hamper acceleration by counteracting the force the extensors apply to the ground. The same is accurate at top speed - all the ground force is delivered by the extensors and activating the flexors would only lessen the force applied to the ground.
Flexors are critical for swinging at top speed - I would agree, but neither force, nor fiber speed and accompanying power appear to make any appreciable difference in how rapidly this occurs at top speed. Please provide any remotely reasonable argument, somehow related to the mechanics of sprinting that hip flexor muscles and/or training matters?
Read Tidow et al read F Bosch etal, read Wiemann et al read jollenbeck et al, read mann et al.
Study/read about the stumble and inverse-extension reflex. I am sure you will think twice about what those studies are saying. Probably the reason why most people do not pay much attention hip flexion and its importance in sprinting is simply because the iliopsoas muscle is very hard / impossible to record its emg readings due to its location. Yes hip extension is important and critical, but the hip flexion action re-inforces and aids the reactive abilitiy of the hip extnesors through the stumble and inverse extension reflex.
During the floating phase, the hip and knee of the trailing leg are flexed, while the hip and knee of the leading leg are extended. The scissor-like movements of the two legs are involuntarily related as a reflex. This scissor movement is nothing more than a combination of the stumble and inverse-extension reflexes. In other words, bending the hip and knee of one leg strengthens extension in the other hip and knee, and vice versa. This involuntary, reinforcing effect is important. The pendu-lar action of the leading leg just before foot placement is carried out with more force because of such reinforcement
Here is a "remotely reasonable " explanation of how hip flexion swing phase can aid fast sprinting.
“It is necessary, certainly when running at speed, that the movement of the trailing swing leg ‘chases’ that of the leading leg involuntarily. This means that hip flexion in the trailing swing leg must be brought about as forcefully and rapidly as possible after toe-off. If the trailing swing leg is brought forward too slowly, the leading swing leg * must ‘wait’, so to speak, with the consequence that tension can no longer be built up in the muscles optimally. The result will be a soft landing, with a loss of landing energy as it ebbs away. Moreover, backward flexion in the hip just before foot placement will be too slow and the foot will touch ground in front of the hip, which works to decrease speed. The outward pendular motion of the leading swing leg will slow, so that preloading the hamstrings with elastic energy will be less than optimal. The ability to preload the hamstrings counts as an important, if not the most important, limiting factor for reaching the highest speed feasible.”
“Running” By F Bosch and R Klomp ISBN 0 443 07441 0
Wannagetfast (Dan), [On a personal note we met several years ago in Lisle, Illinois at Ken Jakalski’s speed conference where Peter Weyand gave a lecture.]
With respect to leg repositioning your statement that leg repositioining rates are not increased for better sprinters is not correct. I believe that your statement is based on conclusions from the Harvard/ Weyand paper (Faster top running speeds are achieved with greater ground forces not more rapid leg movements, J Appl Physiol, 89; 1991-1999, 2000.) That study found that leg repositioning TIMES are no different between fast (F) and slower (S) runners. Based on that finding they concluded that leg repositioning RATES were the same between F and S runners. But you cannot compare repositioning times and rates. Leg repositioning RATES are actually faster for faster sprinters, contrary to the study’s conclusion.
In order to better understand this one has to consider what it is that determines repositioning time. Repositioning TIME is dependent on one thing, and only one thing - VERTICAL DISPLACEMENT. Time for repositioning is only dependent on the vertical component of sprinting and has no bearing on the horizontal component (ie., how fast one is running.)
This fact is based on simple physics. For example, if you throw an object up and wait for it to come down, then the amount of time in the air (ie., air phase time) is dependent only on vertical displacement (which is the distance that it goes up and down). Nothing else determines air phase other than vertical displacement. We can carry out this example further to clarify my point even more.
Let’s say that you have two balls. Let’s then say that you throw one ball up and down and a little distance forward, and that it moves exactly 1 meter in vertical distance and it moves forward 1 meter. Then you throw the second ball 10 meters forward and you do it in a way that its vertical displacement during that throw is exactly 1 meter. With this scenario both balls have equal vertical displacements, 1 meter. Because they both have equal vertical displacements it will take equal amount of time (ie., equal air phase time) for them to go up and down.
But this tells you nothing of forward movement. The 1st ball moves 1 meter in x period of time, whereas the 2nd ball moves 10 meters in x period of time. The second ball has greater horizontal speed because it moves 10 meters in x period of time, whereas ball one only moved 1 meter in x period of time. Greater horizontal speed for ball 2 means that its COM (center of mass) has greater speed than ball 1 even though both balls have equal air phase times (equal vertical displacements). This is analogous to S and F sprinters. S and F sprinters have equal vertical displacements, but the F sprinters have greater SL (ie., SL in air phase], which means that they have greater horizontal movement. Because F runners’ horizontal movement is greater and it occurs in an equal time period it means that rate of movement of COM is greater for F sprinters. Because movement of the COM is dependent on, and determined by leg movement, one can only conclude that the RATE OF LEG MOVEMENT, or REPOSITIONING, is also GREATER for F sprinters during Swing phase, or air phase (and Stance phase also, as will be discussed shortly).
In other words, if two sprinters have different running velocities but they have equal aerial times, this is the same as saying that they have an equal vertical displacement of their CG. One can use the comparison of two bullets as an example - if two bullets from varying caliber guns are fired off of the ground, simultaneously, at two different trajectories, but their vertical displacements are exactly the same, then both bullets will reach the ground at the exact same time. Even though vertical displacement and time spent in the air are the same, the higher caliber bullet (that one with greater horizontally directed force at the onset) will travel a greater horizontal distance.
In a similar manner two runners who have equal vertical displacements, but where one runner is faster than the other, will have equal vertical displacements but unequal horizontal displacements (stride length). The faster runner has a greater horizontal distance (or, longer stride) because he generates greater horizontally directed ground forces during the ground contact phase.
We can look at leg repositioning rates from a different view in order to further demonstrate the fact that faster runners have faster repositioning rates.
Biomechanics of running/ sprinting demonstrates that the faster an athlete runs the greater is the total, or maximal, degree of hip flexion that occurs for each leg in swing phase.
Let’s first look at what occurs during stance phase. Because the maximum degree of hip flexion is greater in F runners this means that the total amount (ie., total angular degree) of hip extension (degree of motion from maximal hip flexion to maximal hip extension) that occurs during stance phase is also greater in F runners. Because F runners have shorter stance phase time, and because they also have a greater degree of hip extension (ie., from @90 to @ 0 to -10 degrees), the overall ‘rate’ of angular motion is greater for F runners (F runners’ hips move through a greater arc in a shorter period of time than do S runners’ hips).
Next, we can look at swing phase. During swing phase the hip first moves backward (hip extension), then forward hip flexion occurs, then hip extension begins, all prior to the next stance phase. The total or maximal degree of hip flexion for F runners is greater than S runners. Because F runners go through a greater degree of motion at the hip, and because this greater degree of motion occurs in an equal air phase time, one can conclude that F runners have a greater angular rate of motion at the hip than do S runners.
I am belaboring the above point because there is a misconception amongst sprint training coaches that leg repositioining rates do not matter for faster sprinting. I believe that this misconception is largely based on the Harvard/ Weyand study conclusions. I hate to be negative about anyone's study and hard work and I do not want to come across in the wrong way concerning my disagreements with the Harvard study. However, it needs to be known that leg repositining RATES are indeed important for sprinting ability.
I could send you even more detailed information by e-mail if you want more information concerning the above.At many walking and running speeds, the hip flexors are activated minimally to not at all. These muscles cannot in any way shape or form assist a runner in accelerating or applying ground force at top speed. Accelerating a runner forward requires pushing rearward against the ground (there is no other way to do it) - only the extensors move the leg in the direction required to do this. The flexors (If active) would hamper acceleration by counteracting the force the extensors apply to the ground. The same is accurate at top speed - all the ground force is delivered by the extensors and activating the flexors would only lessen the force applied to the ground.
You are correct when you state that the hip flexors are not activated during walking or even during jogging activities. However, one cannot compare muscle activity during a walk or even a long distance run to muscle activity during a sprint. The biomechanics are completely different. Because the biomechanics are different you cannot use any biomechanical data from walking and apply it to sprinting. IN this respect many ‘spring’ theory proponents make arguments against the need for propulsion during terminal velocity simply because hip flexor strength is not needed much in a long distance run. Such a comparison is not correct because, again, the biomechanics and muscle requirements are different for a ‘run’ as compared to a sprint.
The hip flexors act to increase the force that the contralateral hip extensors can generate during the ground phase.
What I would like to explain to you it this:
ONE CAN IMPROVE SPRINTING SPEED BY STRENGTHENING HIP FLEXION STRENGTH!
WHAT?
This last statement would generate much debate amongst sprint training ‘experts’. Before you disregard this statement realize that the reasons behind it are more detailed than simply ‘hip flexion strength’ per se. It is not only hip flexion strength that is important, as I will explain in following sections.
I agree with the belief by others that butt-kicks, skips, A & B drills will not improve sprint speed in the highly trained athlete. Why? Because these are the wrong types of strengthening exercises. In the past researchers have looked at hip flexion strength in the wrong way. I will try to explain to you why it is important. Important points:
- The general feeling about Hip Flexion is that it thrusts the thigh, hence the entire leg forward. Those who believe that Hip flexion is important generally believe that such a forward thrust acts to somehow thrust the body forward. I believe that such thinking is wrong.
If one looks at the biomechanics of sprinting one will find that Hip Flexion is important because it increases the ability of the contra-lateral Hip Extensors to propel the body forward during stance phase when the stance phase leg ‘pushes’ against the ground. It is the Hip Extensor muscles that ‘push’ the body forward during stance phase. The Hip extensor muscles need a counterforce to act against in order to maximize their effect. The counterforce that I am talking about is HIP FLEXION. In other words:
A GREATER HIP FLEXION FORCE WILL GENERATE A GREATER CONTRA-LATERAL HIP EXTENSION FORCE DURING STANCE PHASE.
In other words, STRONGER HIP FLEXOR MUSCLES WILL RESULT IN THE ABILITY TO GENERATE A GREATER CONTRA-LATERAL HIP EXTENSOR FORCE DURING STANCE PHASE.
[ Let’s look at another example in order to better understand this concept. When a karate puncher thrusts one arm forward in the act of a ‘punch’ that arm is being thrust forward because it is being pushed against the body, to which it is attached. If one wants to increase the forward thrust of that arm one can add an extension, or backward, thrust of the contra-lateral arm. Just as contra-lateral arm extension increases forward thrust of a punching arm, contra-lateral hip flexion will increase hip extension thrust during the stance phase of sprinting. ]
So, if you agree with the need to improve hip extension strength, which acts to push the body forward during stance phase, then I hope that you can now agree as to why hip flexion strength is needed.
2)When I refer to hip flexion strength it not just any kind of ‘strength’ (ie., how much weight one can lift) that will improve sprinting speed. It is also not just about moving the hip faster. It is about ACCELERATION of hip flexion. Accelerations means dynamic, or explosive strength. Only by improving explosive strength can one hope to improve hip flexion strength that can improve sprinting speed. The same goes for hip extension strength – only by improving explosive hip extension acceleration can one hope to improve sprinting speed.
Next, with regards to developing the ability to swing one’s leg faster vs. developing the ability to push the ground with larger force - what you will find is that, by improving an athlete’s ability to swing his/her leg faster it will result in a greater ability to push the ground with a larger force. It seems that there is the tendency to separate the two concepts (1- moving the leg faster and 2- force against the ground). But in reality, when you properly improve one aspect (1- faster leg swing or hip rotation, including both flexion and extension) you actually strengthen the other aspect (2- push-off strength against the ground).
I completely agree with the above. It reinforces the need to improve hip flexion and extension strenght in order to improve sprinting speed.
concerning your first point, please could you post the references for these studies?
concerning your second point : if we analyse a single sprinter running at various sprinting speeds or compare different level sprinters (jogging/running/sprinting, what is the criteria for put the limits?), we don’t find increases in hip flexion with increase in running speed. If you take pictures at various points during the stride cycle and compare body angles (like hip flexion) you won’t find a difference between two sprinting speeds for a given runner. Differences can only be found in limb speeds (angle/sec).
Hip flexion argument finds an end when looking at the incredible wind range in max hip flexion at top speed we find in elite sprinters, compare Pavlakakis and Aliu in men, Privalova and Lauryn Williams in women; Pavlakakis and Privalova lift their knee extremely high wether they run sub max (qualifying rounds, first half of 400m race) or max sprints (finals or PB races).
Alex,
I do remember! We went to dinner to!
Answer me these questions
-
I believe that such thinking is wrong. If one looks at the biomechanics of sprinting one will find that Hip Flexion is important because it increases the ability of the contra-lateral Hip Extensors to propel the body forward during stance phase when the stance phase leg ‘pushes’ against the ground.
Explain the length of time in this push, and at what third of the contact phase this hip movement will allow for a more contra-lateral hip extension?
Is this propulsion “similar” to that in acceleration, although you recognize the angles and position of the body are the same? Would force traces show an increase in the “push” phase?
-
GREATER HIP FLEXION FORCE WILL GENERATE A GREATER CONTRA-LATERAL
How are you measuring this in athletes who do it well vs. those who don’t? -
STRONGER HIP FLEXOR MUSCLES WILL RESULT IN THE ABILITY TO GENERATE A GREATER CONTRA-LATERAL HIP EXTENSOR FORCE DURING STANCE PHASE.
If that is correct, what exactly is the contribution so that we know how much training will be sufficient to produce this powerful hip extension of the grounded limb?
- Just as contra-lateral arm extension increases forward thrust of a punching arm, contra-lateral hip flexion will increase hip extension thrust during the stance phase of sprinting.
This analogy is a little bit confusion, since in running there is a grounded limb already rotating over the center of mass. That is not true in your karate punch. (That’s a very weak parallel you have proposed)
- So, if you agree with the need to improve hip extension strength, which acts to push the body forward during stance phase, then I hope that you can now agree as to why hip flexion strength is needed.
One simply cannot “push” when the center of mass is directly over the grounded limb. Therefore, this push must be occurring in the latter of the three phases of ground contact. But that’s when the forces are the lowest. Can you explain this?? So you propose stronger not swing faster?
- When I refer to hip flexion strength it not just any kind of ‘strength’ (i.e., how much weight one can lift) that will improve sprinting speed. It is also not just about moving the hip faster. It is about ACCELERATION of hip flexion. Accelerations means dynamic or explosive strength. Only by improving explosive strength can one hope to improve hip
flexion strength that can improve sprinting speed. The same goes for hip extension strength – only by improving explosive hip extension acceleration can one hope to improve sprinting speed.
Can you demonstrate this on Dartfish or Silicon Coach? I’d like to see you highlight exactly where this push via hip extension is occurring. The timing here is critical.
- Again, are you saying there are lots of horizontal forces involved in max velocity sprinting? This you have to show me! We know the net propulsive forces are 0
I have a very nice video if some one on this site can show me how to post it! Please send me a private email with the details of how to.
Dan
I have given you the information and the source of the information, it is up to you to disprove what has been observed by biomechanists, and experienced by athletes who I know personally have run 10.17 secs and faster.
With all due respect… this is the problem with discussions about sprinting, you can not look at photo sequences and the position of angles alone to determine which muscles or firing patterns are contributing. Its not the position of the hip flexors that are important but their explosive ability and function.
Technique and style are also distinct and what you find with alot of photo sequence comparisons is not the comparing of technique between two athletes but the style which is wrong.
Its the initial drive. “stepping over the knee” “Like stepping over tall grass” all these ques given by elite sprint coaches refer to the initiation of the hip flexion action as important.
If the initiation or the starting acceleration of this important que can be improved then its bound to help.
I may add that alot of elite sprint programs have alot of exercises that are already targetting the hip flexors, but less developed athletes are likley to ignore their importance…because they do not see how it all adds up. How many really follow through CFs advice on doing 500 sit-up exercises on speed day and 1000 on tempo day rule? Are the hip flexors not tragetted then and conditioned?
martn76, we agree that more or less what i said, it’s not enough to look at max hip flexion on a photosequence to determine sprinting speed or technique efficiency. However, i’m confused with the difference between style and technique. We can differenciate techniques in high jump (frontal, fosbury) shot put (translation, turn), long jump (extension, cisors), etc, but in sprinting you have not many choices in techniques. Style may be the non-limiting factors each athlete has (Flo-Jo’s left knee lift inside, Ato’s foot turn outward, etc). When sprinters are interviewed and asked to detail their races from a technical point, they usually talk about psychology rather than biomechanics. This tells much about what advices athletes are ready to hear/understand, and by extension the method to teach technique.
Could you give examples of exercises that you would advocate?
If hip flexion were that important we would have been born with our butts in front.
Sit-up with feet fixed. Cable hip flexion, decline si-up with feet fixed in place. Hip flexion machine…abdominal exercises that stress hip flexion along with the abdominals.
Most abdominal exercises with an emphasis on folding at the hip. Hanging leg raises. lying on back doing leg raise folding at the hip. High knee drills to develop strength endurance. Mach drills A and B.
Effects of hip flexor training on sprint, shuttle run, and vertical
jump performance.
J Strength Cond Res. 2005 Aug;19(3):615-21.
Deane RS, Chow JW, Tillman MD, Fournier KA.
Deane, R.S., J.W. Chow, M.D. Tillman, and K.A. Fournier. Effects of
hip flexor training on sprint, shuttle run, and vertical jump
performance. J. Strength Cond. Res. 19(3): 615-621. 2005.
-Although hip flexion is integral in sports, hip flexion exercises
are seldom emphasized in strength and conditioning for sports
performance. This study aimed to determine whether a hip flexor
resistance-training program could improve performance on a variety of
tasks.
Thirteen men and 11 women completed an 8-week hip flexion resistance-
training program. Eleven men and 13 women served as controls.
Isometric hip flexion strength, 40-yd dash time and the time for the
first 10-yds, 4 x 5.8-m shuttle run time, and vertical jump height
were evaluated at the beginning and end of the training and control
period. Improvements were observed in the training group but not in
the control group.
Individuals in the training group improved hip flexion strength by
12.2% and decreased their 40-yd and shuttle run times by 3.8% and
9.0%, respectively. An increase in hip flexion strength can help to
improve sprint and agility performance for physically active,
untrained individuals.
Just thought I’d throw this in to the mix…
http://www.charliefrancis.com/community/showthread.php?t=11495&highlight=hip+flexors
EMG studies:
Mann, Roger, etal., Comparative electromyography of the lower extremity in jogging, running and sprinting. Amer J Sports Med, 14(6); 501-510. 1986.
Montgomery, WH, et al., Electromyographic Analysis of Hip and Knee Musculature During Running. Amer J Sports Med, 22(2); 272-278. 1994.
Kolka, Leigh. From: research done at Middle Tennessee State and The Ultimate Leg Conditioning Speed Training System: Instruction Manual. distributed by Kolka Equipment. (This study demonstrates that energy expenditure is greatest for hip extensors up to @ 30m in a sprint, after which the hip flexors have maximal energy expenditure.)
Second, when an individual goes from a walk to a jog to a run to a sprint there is greater hip flexion. The hip flexion that occurs is active. The active hip flexion and greater hip flexion is necessary in order to sprint faster. Once an individual is close to maximal sprinting speed, for a single individual there may not be a measurable difference between different sprinting speeds. Between individuals there certainly would be a difference as each body habitus and design differs, so you couldn’t make a comparison between individuals.
While I may be mistaken… i always assumed that the majority of the work done to raise the knee (hip flexion) during running came not from the hip flexors but from the rebound of the foot off of the track…(?) The faster you are the more force you put into the ground (time dependant) and i assume the more powerful this reboud effect. I thought this rebound effect was also useful because it helped conserve energy. This goes back to the idea of inhibition and the athlete’s ability to relax muscles as being as/more important than the ability to contract them in the first place.
Would this mean that hip flexor development for the novice athlete would be more important than for the elite? Another reason for the greater (relative) importannce of general conditioning (low intensity hip flexor work during med ball/torso work).
Comments?