Pose Running. Is it for you?

Pose Running

The pose running method was developed by Dr. Nikoloas Romanov as a safer more efficient way to run.  The idea behind Pose is that we as humans do not run correctly, and this leads to less efficient running and more running related injuries.

Humans need to be taught how to run properly, and Pose believes their method is the ideal way to run. 

Every other skill is taught proper technique such as swimming, throwing, shooting, etc, but not running.

Why not?

This is the question Dr. Romanov asked himself when he first developed this running method. 

Pose running is characterized by 3 phases - pose, fall, pull.  These are the ques that Pose will engrave in all it's runners.

Pose

This is the posture Pose runners need to adapt to. It is characterized by a forward body lean in which the ankle, hips, and shoulders are all in a straight line.

The support leg knee is slightly bent and you'll hear Dr. Romanov say how he wants to see a S-shape between the legs and torso.

Fall

Because of the forward lean in the pose position, the body is pulled forward by gravitational force.  So basically the runner starts to fall forwards and downwards and the support leg will naturally come off the ground and the lead leg will naturally leave the ground to prevent from falling on ones face.

Because of the lean and allowing the cycle leg to just drop to the ground, it will land directly under the center of mass of the runner and on the ball of the foot.  So the foot will not be out in front causing a braking action, this allows for gravity to "pull" you forward and takes slack of the muscular system.

Pull

The pull teaches the runner to actively pull their foot up under their butt after their support leg leaves the ground.  This eliminates backside mechanics and less time spent on the ground.

Overall the Pose running method is characterized by

• Pose, Fall, Pull
• Foot landings under the center of mass and on the balls of the feet
• Shorter stride lengths
• Higher stride cadence
• Less stress put on the knee joint due to the slight bend in the knee and foot contact underneath the center of mass

Here's a video of Dr. Romanov teaching the pose, fall, and you can see the pull.

Benefits

Pose has been a big component of altering and looking at running mechanics in a magnified light.  Dr. Romanov deserves some acknowledgement for looking for a better way to run and coming up with a method he believes is a better way to run.

Most of us out there could use some improvements in our running technique, and the fact that running is natural to everyone isn't exactly true.  Learning how to run properly can help with speed, efficiency, and decreased chance on injury.

I think that the Pose method is on the right track when talking about landing underneath the center of mass.  Landing underneath your center of mass eliminates braking forces that would regularly occur when you land out in front of your body.

Braking forces, as the name applies, cause very slight and quick "stops" in your running in which you need to expend a little more energy to overcome.  Landing underneath your center of mass also allows for a cleaner and quicker transition because the runner spends less time on the ground during this touchdown to toe-off stage.

Pose makes it so you land on the ball of your foot.  Landing on the ball of your foot again allows for a cleaner transition and less braking forces, and maximized the use of stored elastic energy or the lower leg.  It also takes stress off the knees because landing heal first sends a lot of force up through the legs.  Finally landing on the ball of your foot vs your heal allows a quicker stance phase and can potentially allow for less energy leaks.

Concerns

While at first glance Pose might seem like a better way to run, I have some severe concerns.

First and foremost, I feel it is more designed for distance running than sprinting.  Everyone they work with is triathletes and distant runners, and not acceleration/sprinting types of activities.  I'm much more interested in acceleration and max velocity speed athletes and the pose method falls WELL short in terms of application for acceleration and max velocity.  In fact Pose even claims that Usain Bolt runs with Pose technique, but here is an article debunking that.

I also feel they don't quite understand what actually makes us run faster.  And that is force production.

The more force we apply into the ground, in the correct direction, and in the shortest amount of time is what allows one to run faster.

It's Newton's 3rd Law, for every action there is an opposite and equal reaction.  Now there is plenty of debate on what forces vertical (Peter Weyand, Mike Young) or horizontal (JB Morin, Dr. Yessis) are more important to speed, but it is accepted that the more force we can apply and in the shorter amount of time, the faster we will run.

Pose instead says that gravity just pulls the leg to the ground and the leg is basically there to be a point of support before falling over to the next stride becoming the next point of support.

So really running just becomes a transition of your legs becoming alternating points of support, not the runner putting forces into the ground.  Pose claims gravity, causing the body to fall, is where ground force application comes from.

This is debunked by science and it can't hold up to scrutiny.  Maybe it helps preserve energy in long ass races like a marathon, but like I said I'm not interested in that, I'm interested in sprinting, and in no form or fashion could this be beneficial.

The pull portion of the pose method is also not scientifically correct.  One does not actively pull their foot up to their butt when running, this is very common knowledge.

We talked about Newton's 3rd Law of Action/Reaction, and this is what is happening the the cycle foot.  The foot cycles up towards the butt as a reaction to the force and the direction of that force being applied to the ground.

Basically like a bouncy ball bouncing back up after hitting the ground, your foot bounces upwards after it's action with the ground.  The hamstring muscles are not active during this phase, look at any EMG of sprinting.

If you want less backside mechanics, then apply more force, in the correct direction with great posture.

Pose also promotes that this type of running takes a lot of stress of the knee joint and can allow runners to run without that hinderence.  What they don't tell you is that the forces taken off the knee have to go somewhere.

And where do they go? 

Your lower leg!

Because Pose lands with a bend and on the balls of your feet, it takes that stress from the knees to your achillis tendon, gastrocs, and foot.  Like I said before Pose is pushed more towards distance running, and if you take a runner and all of a sudden have him/her landing on the balls of their feet for miles at a time there will be consequences.  I said before landing on the ball of your feet are beneficial, but again if you're a sprinter running distances 400m or less, not running 26 miles.  So all they did was take pain away from the knee and put it on the lower leg. 

In fact, the study Pose always falls back onto when promoting itself is a study done in 2002 in Cape Town.  The studies results showed that after a week of being taught Pose running techniques, runners experienced

• Shorter stride lengths
• Higher Stride Frequency
• Less vertical displacements
• Lower rate of loading of he vertical impact force
• Lower knee power absorption and eccentric work
• Increased ankle power absorption and eccentric work

So of course all the benefits of this study were put to light, but the forces being transfered to the ankle were not.  In fact, this study was done with 20 participants, and 2 weeks after the initial results were posted 14 of the 20 participants broke down with either calf problems, achilles tendon sprains, or foot issues.  That's 70% of the participants experienced new pain from this technique!

Now what Dr. Romanov and other Pose instructors will say is that they were doing the technique wrong.  But in this study the participants were taught by Dr. Romanov himself and they went through a week of intensive coaching (here is a link to Ross Tucker and Jonathan Dugas article.  They were 2 of the participants in the study and are both sport scientists, very smart dudes).

Now if one cannot learn the technique from the creator himself after a week of intensive coaching, who can learn this technique.  Is it really worth it to try and alter mechanics, if it is this hard to learn, and can lead to other problems?

Finally there was another study done on Pose that took 8 triathletes through 12 weeks of Pose technique training, while another 8 kept their normal training.

Before and after the study each group were tested for stride length, stride frequency, vertical oscillation, and running economy at two different speeds (4:00min/km and 4:40min/km)

The results showed that for the Pose group, the subjects showed a decreased stride length (which was expected), decreased vertical oscillation, and reduced running economy.

What!

That's exactly the opposite that Pose running is supposed to do.  Pose running in this study actually increased the oxygen cost of running (def. of running economy).  When running for distance this is not a good thing.  Also this study was done for 12 weeks!  That's a lot of time to develop the correct techniques and become comfortable with the techniques of Pose.

But Pose seemed like it was really on to something?

Maybe it still is, but from what we just looked at, it doesn't look like it.  Maybe if it is developed at an early age and more instilled into the runner, it may be a better way to run.  But the previous study showed that 12 weeks of using the Pose method resulted in poor results. That's 3 months!  For many coaches out there that is more time than we'll ever have with an athlete for a straight period of time.

So Is It Worth It?

For me personally I would say no.

• First I have no interest right now in teaching/coaching distance running.
• This technique, I feel, would not be beneficial to acclerlation/top-end speed; which all the sports I would coach.
• This technique seems very hard to coach and to perfect. I am all for taking the time to coach proper technique, progressions, and overall just not being lazy; but when you only have a limited amount of time with athletes, Pose just doesn't fit in.
• Overall if I was into distance running I would look further and more detailed into the Pose running method, as well as others (chi, barefoot, kenyan)

So I hope you now know a little bit more about Pose running and what it exactly is.  If your interested in learning more, research deeper into Pose for yourself, or ask me and I'll give you some links to help lead you the way.  


Go Get 'Em!





http://bretcontreras.com/category/interviews/page/2/
http://www.elitetrack.com/article_files/longjumpemg.pdf
http://jn.physiology.org/content/95/6/3426.full
http://www.posetech.com/
http://canute1.wordpress.com/2010/02/14/problems-with-pose/
http://www.sportsscientists.com/2007/10/pose-running-reduces-running-economythe.html
http://www.sportsscientists.com/2007/09/running-technique-part-ii-scientific.html

 

Weekly Recap: Nutrition Edition- 10/20/12

Nutrition Edition

Like that ring?!  Nutrition Edition, I'm a real life rhyming machine.  No, but wanted to mix up this weeks recap with an emphasis on diet and nutrition.  Found quite a few new articles this week that I think you'll enjoy. 

Also be sure to check out Peanut Butter Protein Balls!  I'm telling you, you'll love these puppies.  So get your nutrition learnin' on.  Enjoy!

20 Food Facts – Mike Geary

The Healthiest Condiments – Mike Geary

Top 10 Spices to add to your foods – Catherine Ebeling

Truth About Saturated Fat – Mary Enig and Sally Fallon

Low Carb For Muscle Growth  – Mike T Nelson

Fat Loss Playbook – Nate Miyaki

Carbs Make You Lose Your Mind? – Conditioning Research

What Happens to Your Body After You Drink a Coke - Nutrition Researchers

7 Good Supplements For Your Health - Born Fitness

Geeky Fridays - Bojan Kostevski

Hockey Nutrition – Kevin Neeld

The Death of Sports Drinks – Kevin Neeld

Advocare - If your interested in nutrition, take a look into advocare.  It is a leading nutritional supplementation company, that is backed by research and science.  They offer everything from sports performance to weight loss to overall health/wellness to nutrition for children.  Check out their site and just look around.

That's all I got for ya this week.  Have a good weekend and Go Get 'Em!



5 Favorite Lower Body Posterior Chain Exercises

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Unless you've been under a stone for the past decade, you've heard of the posterior chain.  Posterior means back and chain basically links, more specifically links of muscles.  So posterior chain means the muscles that make up the backside of the body.  For the lower body this would mean your gastrocnemius, hamstring complex, and glutes. 

If you've ever heard from power lifters or olympic lifters, they'll often tell you they are most afraid of someone with a well developed backside not someone with a well developed front side.  Big, developed muscles of the posterior chain is associated with strength, power, and athleticism.  Look at any sprinter, field athlete, or really any athlete in a power/explosive sport and you will likely see well developed glutes and hamstrings. 

As many strength coaches will tell you, if you want to get faster, jump higher, and become more athletic start hitting these muscles.  And hit them in different vectors, angles, tempo's, intensities, and rep/set schemes.  The a strong posterior chain will accomplish all of these

The muscles of the posterior chain propel us forward during sprinting, give us explosive hip extension for jumping, tackling, blocking, etc, aid in quicker lateral/agility movements, give us better posture and a more appealing look to the opposite sex ;), and stabalize the legs during all of the movements to minimize energy leaks

During sprinting the hamstrings act not only as knee flexors and extensors, but also very important hip extensors.  The glutes work primarily as hip extensors and hip hyperextensors, but they are also very important in hip abduction/external rotation and hip stability. The gastrocnemius works as plantar flexors and a great deal of this is done isometrically. These same basic priciples hold true for most movements, and it is important to train these muscles in all these ways. 

It is very important to work these muscles in conjunction, and not so in isolation.  During sport and athletics these muscles work in unison with each other and it is very important to have great co-contractions and correct motor firing patterns.  Many different muscles are used in hip extension/hyperextension and the extensor recruitment varies depending on the load vector, knee action, hip angle, and other factors.  For example the 3 different hamstring muscles (biceps femoris, semitendinosis, semimembranosis) are more active/involved at different times during hip extension along with the adductor muscles playing a role and of course the glutes are also heavily involved..

Many times injuries occure to the Hamstring complex because the glutes aren't firing correctly or in the correct pattern.  You must develop this muscle coordination and timing throught the correct exercises and then starting overloading this pattern for greater results.

The first thing I would suggest before doing lower body posterior exercise is stretch the hip flexor.  The hip flexors tend to be shortened in most people due to our lifestyles.  Tight hip flexors inhibit the ability of the glutes/hamstrings to fire at their true potential because they cause the pelvis to tilted at a dis-advantaged angle. So statically stretching them opens up the hips and allows the backside to be more effective.  So here are my 5 favorite ways to strengthen your P-Chain.

Hip Thrust

First on the list is the hip thrust.  The hip thrust is an exercise made popular by Bret Contreras (Check out the interview we did with him HERE)  Basically what Bret did was say hey, a ton of programs use body weight glute bridges to activate the glutes before working out, so why not load these bridges and make them a main lift, and the hip thrust was born. 

Bret has done a ton of great work with EMG (elecomyography) to study the amount of muscle activation in the glutes, hamstrings, etc and the hip thrust is the king of glute exercises!  What I like about the hip thrust is the different angle/vector load it puts on the glutes.  We spend most of our lower body work moving vertically, moving weights up-and-down (ie squat, deadlift).  The hip thrust however loads yours hips horizontally and you move the weight from back-to-front.

When you do hip thrusts for the first time, you will feel the difference in this exercise from anything you've done before.  Hip thrusts work hip extension and hyperextension or basically the end range of motion of the glutes like nothing else.  You will definitely feel these bad boys, and will for sure add them as a staple to your program.

I recommend getting some sort of pad for your hips, because as you increase the weight on the bar, it can be uncomfortable on your hip crease, and despite what it looks like, it won't crush your junk.

Key technique is to squeeze your butt at the top of the movement, basically posteriorly tilting your pelvis (ducking it under).  Try and keep your lower back relaxed and let the glutes control the exercise.  Lower back pain can often be caused by weak glutes and many find adding this exercise into their routine eliminates their back pain.

Back Squat

Yup the back squat makes the list.  Many consider the back squat the king of lower body lifts, and they have a damn good reason for that.

The squat is hits just about all of the major lower body muscles, and if done correctly can really hit the glutes.  The key to the squat is to make sure you sit back, spread your knees apart (try spreading the floor with your feet) and get to parallel or beyond.  All of these ques will help you activate your glutes.

The squat allows you to really load the lower body, and this allows you to built some mass and strength.  It is also a great mobility exercise for your ankles, T-Spine, and Hips.  The wider stance you take the more posterior chain you'll hit, while vise versa, narrow stances will hit the quads more.

Deficit, Snatch Grip Deadlift

Take the deadlift, now twist it, mold it, and make it evil, and you have the deficit, snatch grip deadlift.

This is a deadlift that basically puts you in a harder position in order to put even more stress on your whole lower and upper posterior chain.

First step you add a block, box, or plate to stand on.  I choose anywhere from 1-3" depending on what's available.  So now the bar is lower on your shins, and then to compound that you take a snatch grip.

Essentially you're making yourself bend down even lower to grab the bar, and making your hips set higher, thus putting your hamstrings and glutes in a bigger stretch and harder angle.  Your backside really has to take over in this lift, as the angle takes your quads out of the exercise.  Another big reason I like this is because it is not quite so hard on the CNS as regular deadlifts are, mostly due to the lighter weight you'll have to use.

The wide grib forces you to really squeeze your back tight, and is great for your lats and overall back strength.  The deadlift is possibly the best lower body lift you can do, but it is just so hard on the body and nervous system, that I find this version more effective and can impliment it more frequently.

Valslide Leg Curls

Valslide leg curls are the same thing as stability ball leg curls except it is my opinion better to use a stable object rather than a stability ball.

The use of the valslides allow us to focus on the movement we want to achieve rather than limiting load, muscle actions, stability, and angle that you get with the stability ball.  The valslide leg curls are great because you get simultaneous hip extension and knee flexion.  This type of exercise trains the hamstrings through both extension and flexion, while also isometrically training the glutes in extension.

With your heels on the valslide, begin by squeezing your glutes and extending your hips into a bridge position. Do not extend your lower back, try and keep it neutral and relaxed.  Then slide your feet in, keeping your hips up the whole time.

When bodyweight becomes too easy, you can progress to attaching bands to your feet, or my favorite way is single leg (S/L).  The videos below show each variation.  Please start adding this exercise, it the BEST way to train simultaneous hip extension and knee flexion of the hamstrings while also training glute extension, and these actions are the how the P-Chain work together during athletic movements. 

Sprinting

Sprinting might be the overall best exercise/movement you can perform, and maybe the most under used or utilized aspect of training for some.  Sprinting in itself is the basis or a key quality of most athletics and really a basic fundamental movement of our species.

While most sports do rely more heavily on acceleration rather than top speed, it is still a very important quality to train, especially with the benefits it has.  EMG studies show that the hamstrings are the most active during forward propulsion muscle during sprinting as they contribute the majority of the terminal swing hip extension and knee flexion torques, while the glutes contribute most to the stance phase hip extension.

If you think about this, the hamstrings and glutes are working eccentrically to extend the leg to touchdown, and after touchdown, the glutes work isometically to keep transfering this force until take-off.  Just like the the valslide leg curls, this is an extremely important quality to train and improve.

Honorable Mention

It's very tough to choose only 5, so I'm making an honorable mention, heck theres an honorable mention for everything now, so why not this.  As you can see from above, I picked mostly big/compound lifts.  These are great for developing the correct motor firing patterns, overloading and progressing, carryover into athletic movements.  But I had to throw in these 4 honorable mention because these are always in my programming somewhere and I feel are very important to athleticism. Not don't get me wrong, some of these could be considered a main lift, but for me they are usually an assistant lift or activation lift.  But without these would subtract results and greater progression from my athletes.

Eccentric Natural Glute/Ham

The Eccentric Glute/Ham is great for working the eccentric strength of the hamstings, and is really a killer.  It works again knee flexion and hip extension in an eccentric fashion.  This exercise is a real tester to see how strong your hamstrings really are.  If you can perform a perfect Ecc. Glute/Ham, you have some strong hammies.  Also recent studies have shown that training the eccentric action of the hamstrings helps prevent hamstring pulls and recover faster from a hamstring pull. 

Single Leg RDL

The Single Leg RDL, is a great exercise because it works the P-Chain in a straight legged position.  If you watch the leg that's on the ground during the exercise it is very close to the same angle as a plant leg would be in during sprinting.

The single leg RDL, more than a traditional RDL, works the glute medius because it must prevent abduction of the hip due to being on one leg.  This is also a great exercise because it works the end range of motion of the hamstrings, or bascially it works the hamstrings at a stretch.

When performing any sort of RDL movement, you should think about pushing your hips/butt back and pull your chest forward.  I like to think that there is a rope tied around my waist and someone is pulling back on that rope.  There is also a rope around my upper back, and someone is pulling that rope forward.  These forces are happening at the same time, and you are getting a big vertical separation of your hips and upper back and the same tempo.  Kind of hard to explain, but you'll feel it when you do it.

DB/KB Swings

The dumbell or kettlebell swing is quickly becoming a favorite exercise for many coaches.  For some it is replacing Olympic lifts, due to it's simplicity.  If you really look at the movement, it is just a dynamic RDL.  You get a big hip hinge, with a flat back, hips pressed back, and the glutes/hamstrings pull the weight out of the hole and swing it out and up.

As you can see, swings get great hip extension, and for some this exercise comes naturally, but for others it must be taught more thoroughly.  First off the head must stay neutral.  There is a tendency for the head to look up when the weight swing between the legs.  You should strive for a straight line from the back of the head to the back of your butt in that position.  Then when coming out of that position really stress to change the direction of the weight by actively extending your hip, not by extending your back!  This is a great exercise that can be used in so many different way.  It's versatility definitely makes this an exercise a must for all.

Reverse Hypers

And finally rounding it all off is the reverse hyper.  The reverse hyper is a great exercise to target hip extension in the horizontal plane.  Just like the hip thrust it differs from most lower body exercises because it's not bottom to top, but front to back.  I love this exercise as a great activation and learning tool.  You can really feel how you must activate your glutes in this exercise, and not your lower back.  The only negative about this exercise is that it is an open chain movement, meaning nothing is in contact with the ground, and not many athletic activites work in this manner.  Also if you do not have a reverse hyper machine, it can be difficult to load.  You can use dumbells between the legs or bands, but it can be a pain depending on your situation.

References

http://www.elitetrack.com/articles/read/2341/

http://www.t-nation.com/free_online_article/sports_body_training_performance/dispelling_the_glute_myth

http://www.t-nation.com/free_online_article/most_recent/fantastic_hamstring_movements&cr

http://www.elitetrack.com/articles/read/2166/

http://www.t-nation.com/free_online_article/sports_body_training_performance/the_lost_art_of_hamstring_training;jsessionid=FBBFD739F6FC6E17ABB3DC9C3E072B89-mcd02.hydra

Lactic Acid: What's the Deal?

Lactic Acid: Urban Legend?

Imagine your running a 400m dash, you hit the home stretch with a lead, but then the awful happens. 

You tighten up, your legs feel like bricks, and you can't exert any force into the track. 

What's happened? 

It's the boogyman of sport, Lactic Acid! 

Everybody and their mother is quick to blaim lactic acid accumulation for muscle fatigue, loss of muscular force/power, and that hitting the wall feeling. 

You hear this from coaches, parents, and just about every couch coach there is. 

I was watching the Olympics the other day when Ryan Lochte finished a race and hurried to the "warm-down" pool.  The announcer then proceeded to explain the reason for doing so was because of lactic acid build up.

Gotta hit the the warm-down pool, hop in an ice bath, do a cool down, or stretch so that lactic acid doesn't build up and stay in your body long and ruin another workout.  But the reality is this could not be the case, and this whole lactic acid being the ultimate bad guy is false.

Must Be Lactic Acid, Right???

Intracellular acidosis due mainly to lactic acid accumulation has been regarded as the most important cause of skeletal muscle fatigue (Allen DG, Lännergren J, Westerblad H).

Let's say you partake in intense anaerobic exercise, this will lead to an intracellular accumulation of lactic acid.  Since lactic acid is a strong acid, it breaks down into lactate and H+.  The increase in H+ leads to reduced pH or acidosis and is the classic cause of skeletal muscle fatigue (Håkan Westerblad, David G. Allen, and Jan Lännergren). 

Decreased pH levels and acidosis caused by lactic acid have been found in fatigued muscles by source of skinned muscle fibers (muscle cells where the surface membrane has been chemically or physically removed).  Studies like skinned muscle fiber are on single muscle fibers and this provides the most direct way to address cellular mechanisms of fatigue  (Håkan Westerblad, David G. Allen, and Jan Lännergren).

The presence of lowered pH and acidosis are the main reasons lactic acid is believed to cause muscle fatigue, pain, and "heaviness" during intense exercise. Another substance often found in fatigued muscle samples in high concentrations is K+ (Ole B. Nielsen, Frank de Paoli, Kristian Overgaard).

Recent studies on mammalian muscle, however, show little direct effect of acidosis on muscle function at physiological temperatures (Håkan Westerblad, David G. Allen, and Jan Lännergren).

In fact, it has been shown when muscle forces are depressed by high concentrations K+, acidification by lactic acid actually produced a recovery of force.

As stated before, intense exercise is associated with an increase of K+, acidosis, and decreased pH, but this might indicates that acidosis may protect against fatigue rather than being a cause of fatigue (Juel, C., Pilegaard, H., Nielsen, J. J. & Bangsbo, J.). 

This relationship of acidosis actually improving muscular fatigue and power is getting more and more recognition of being the true case in muscles.  So, now the focus has been shifted to more on lowered pH levels and high K+ concentrations, as multiple studies have recently looked into this. (Links at the Bottom)

Don't Let This Happen To You



     

Recently the role of reduced pH as an important cause of fatigue is now being challenged, and several recent studies (Posterino GS, Dutka TL, and Lamb GD) show that reduced pH may have little effect on contraction in mammalian muscle at physiological temperatures.

Phsysiological temperatures mean temperatures similar to that which would be seen in muscles during exercise.  Many previous studies have based the idea of pH causing fatigue on studies of muscles at colder temperatures (less than 15 degrees C), however recent studies looking at muscles at around 30 degrees C and more (physiological temperatures of muscle), have found that the muscle fatigue and reduced muscle force are not present at these temperatures despite lowered pH's (Renaud JM and Light P). 

Another key finding has been when looking at muscle fatigue and recovery, it has been found that muscle force and fatigue recovers faster than pH levels after a strenuous workout (Sahlin, K and Ren, JM). This means that non-fatigued muscles have at times reduced pH levels, which obviously contradicts the idea of pH causing muscle fatigue.

  
This leaves the accumulation of K+ ions in the interstitial fluid as being a key cause of fatigue, by inhibiting the propagation of action potentials along the cell membrane.

This K+ accumulation depolarizes the fiber, preventing Na+ recovery, which causes a reduction of action potentials and reduction in force production (Bandschapp, Soule, Iaizzo). 

In a recent study done by Bandschapp, Soule, & Iaizzo, they wanted to test findings to see if they found similar results.  So they did a test on muscle biopsy on live pigs (muscle very similar to humans).  They first added K+ to these muscle biopsy's and then added lactic acid to test the findings.

The researchers found that when K+ was added to the muscle solution, muscle force/power decreased, but when lactic acid was then added, muscle force/power was restored.  The exact reason for this is not completely known, but a possibility explanation is that lactic acid helps in decreasing the permeability of chloride ions, which restores the excitability of the cell membrane (Bandschapp, Soule and Iaizzo).
    
The exact cause of muscular fatigue and loss of power due to intense exercise is unknown.  There are many factors that contribute, like metabolic factors, genetics, nutrition, peripheral muscular factors, central nervous system, temperature, oxidative factors, elevation, sleep, etc.

But it is becoming more and more evident that lactic acid is not a major cause of fatigue, loss of force, and might actually have the opposite effect on muscles (Pedersen TH, Nielsen OB, Lamb GD, and Stephenson DG). 

More research has to be done, but it looks like K+ is a big cause of fatigue, loss of power, and we might need to shift focus on how to reduce the accumulation of K+ and how to recover from this accumulation. 

Exercise Science is always shifting and what was thought as being a truth yesterday could be proven wrong tomorrow.  I don't know if this research will hold up, or if future studies will confirm or deny some of the work done by these scientist.  But I do know that the further we look at lactic acid, the less and less we are seeing it have the effects that most think of. 

I can't say for certain what goes on in a fatigued muscle, and really no knows for exact certain what causes that fatigued, hit the wall feeling.  But I think these studies need to be held up to brighter light, as lactic acid is about as big a "myth" out there as anything. 

And as always hope you enjoyed and Go Get 'Em!

References

            Sahlin K and Ren JM. Relationship of contraction capacity to metabolic changes during recovery from a fatiguing contraction. J Appl Physiolgy 67:648-654, 1989.

            Allen DG, Lännergren J, Westerblad H. Muscle cell function during prolonged activity: cellular mechanisms of fatigue. Exp Physiol 80: 497–527, 1995

             Posterino GS, Dutka TL, and Lamb GD. L(+)-lactate does not affect twitch and tetanic responses in mechanically skinned mammalian muscle fibres. Pflügers Arch 442: 197–203, 2001

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Links

http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.2004.078014/full,  http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7793.2001.t01-1-00161.x/full,  http://www.aleixo.com/biblioteca/MUSCULA/Topicos2e3/Revis%E3o%20fadiga%20muscular.pdf