The Anterior Chain

I wrote this article and submitted it to Rupert, but he hasn’t gotten back to me yet. As such, I decided just to post it here. Hope everyone likes it and takes away something new.

All Aboard the A-Chain
Roger Nelsen

Louie Simmons once said something along the lines of, “A strong man is strong on the back of his body.” And whether it was intended to or not, it was these words, along with his training advice, that sparked off a wave in the S&C industry. Following in the steps of the famous Westside gym leader, people everywhere began to turn their focus away from their sweeping quads and redirect it towards the less mirror-friendly group of muscles commonly referred to as the posterior chain.

Consisting of the spinal erectors, glutes, and hamstrings, the muscles of the P-chain work to stabilize and generate force across the hip, and knee. Over the past few years, the words “posterior chain” have become all but synonymous with athletic speed and power thanks to Louie Simmons and those who have successfully adapted  his methods to popular sports (such as trainer Joe Defranco). But in this torrent of box squats, glute-ham raises, reverse hypers, and good mornings, some people have lost sight of the P-chain's equally important, but much less glamorous counterpart, the anterior chain.

Positioned directly opposite of the posterior chain, the anterior chain consists of the abdominal muscles, the illiopsoas, and the rectus femoris. And where the posterior chain works to create spinal and hip extension, the anterior chain works to create spinal and hip flexion. 

At first glance, spinal and hip flexion might not seem too important in most sports, but a closer look reveals the exact opposite, especially where sprinting speed is concerned. Though the P-chain is responsible for generating the force that propels us forward in a sprint or upwards in a jump (along with the quads of course), the A-chain works in a couple of different, though no less important, ways.

The first purpose the A-chain serves is as a pelvic stabilizer during athletic movement, primarily whilst running. The abdominals and hip flexors work in concert with the glutes, hamstrings, and spinal erectors to control the positioning of the pelvis and ensure the optimal transfer of force across the hip. Weakness through either the abdominals or the hip flexors (the rectus femoris and illiopsoas) can cause the pelvis to rotate either anteriorly or posteriorly and reduce the leverage of the propulsive muscles (the quads, glutes, and hamstrings) or put the body in the wrong position to generate force in a movement immediately following. 

Looking at running specifically, if the abdominals aren't strong enough then the pelvis rotates anteriorly and the trail leg will tend to flail too far behind the body after each stride. If the trail leg is allowed to travel excessively far back before it's brought forward to get ready for the next stride, then the athlete's illiopsoas and rectus femoris will rarely be strong enough to bring it back around in time to assume the optimal position during the support phase (ground contact phase) of the opposite leg. If the leg isn't brought around in time and doesn't find the optimal position then the athlete won't be able to generate optimal power in their next ground contact (Bosch and Klomp, 2001). And since sprinting is a cyclical activity, the problem will perpetuate itself during the following leg cycles, essentially handicapping force production, and therefore speed, with each stride.

As you can clearly see, abdominal strength is huge in determining sprint speed, but surprisingly enough, so is powerful hip flexion. Though it's somewhat counterintuitive, studies have shown that hip flexion strength is a better predictor of sprint speed than is hip extension strength amongst trained athletes (Blazevich & Jenkins, 1998). Similarly, other studies have demonstrated significant decreases in short sprint (3.8%) and shuttle times (9.0%) after a period of hip flexor training (Dean et al, 2005) and have found a link between larger illiopsoas (when compared to the quadriceps) and 100M speed (Hoshikawa et al, 2006). But how do strong hip flexors make you faster, you ask. There are two ways.  

The first way in which the hip flexors help generate speed is through faster and more complete repositioning of the leg after it has left the ground. By moving the leg back into position faster and having the strength to move it higher, the athlete will demonstrate greater frontside mechanics when they run. What this means is that the legs will spend more time in each cycle in front of the body rather than behind it (backside mechanics). If one takes a look at top sprinters and compares them to average , slower athletes, the first thing they'll notice is the different in mechanics. 

When sprinters run, they display a neutral or posteriorly rotated pelvis, high and fast knee lift, and their legs spend more time in front of their body than behind it during each sprint cycle. The reason for this is not because of the time they spend on technique, but because they have strong enough abdominals and hip flexors to hit such positions. 

In stark contrast, when a slower athlete runs, their pelvis will oftentimes be anteriorly rotated, their knees won't reach nearly as high, and their legs will flail back behind them after each stride. They can try to hit the same positions as a sprinter, but won't be able to do so effectively because they simply lack the strength in the relevant muscle groups (the anterior chain). 

The second way in which powerful hip flexion strength can aid in speed is through something called the inverse-extension reflex. The inverse-extension reflex is an involuntary mechanism which causes the hip flexion of one leg to facilitate hip extension of the opposite leg (Bosch and Klomp, 2001). A more powerful flexion of one leg will lead to a more powerful reflex-potentiated extension of the opposite leg. In this way, the strength of the anterior chain will actually direct increase that posterior chain. Pretty cool, huh?

So, as you can see, if you're an athlete who's sport requires them to run, regardless of the distance, then training for the anterior chain is a must, and I don't just mean doing high rep crunches in between sets either. As is the case when training for any sport, muscles are best trained the way they will be needed to function on the field, and the A-chain is no different.

Taking a look at conventional A-chain training, there's really not much “chain” work going on at all. Crunches are a long time favorite exercise of the casual gym goer, but they're completely ineffective for two reasons. One, they take the hip flexors entirely out of the movement and therefore aren't of much more functional use than a leg extension. Two, the abs are muscles too, they need load in order to get stronger and grow. And don't think squatting will cut it either, because it won't.

All too often people get to talking about how squats and deadlifts are the best core exercises, but in this case, they'd be sadly mistaken. Though the abdominals are called in to stabilize, the brunt of the load of both exercises is taken by the quads and p-chain, most notably the spinal erectors. So while you can build a strong back with two of the classic powerlifts, and in an integrated movement pattern no less, you won't be doing much for the front of your body.         

In order to best train the A-chain, you've got to train it just like you would any other part of your body, in sequence with the relevant muscle groups (in this case we're referring to training the abdominals and hip flexors together) and under a heavy load (sorry, but there are no 50 rep 'burn' sets here). 

Also, since it's fairly common to develop problems with overly shortened or tight illiopsoas, all of the prescribed exercises will work them at an extended length and over the range of motion in which they'll be called upon to perform in sport. Since muscular the tension and length of the muscles (aka flexibility) is controlled primarily by neuromuscular processes (Siff, 2003), training the muscle group in a lengthened state will promote better active flexibility gains than stretching alone (Iashvili, 1982). Meaning, if you train them in a lengthened state, you'll never have to worry about tight hip flexors again.

Now that we're done with that, let's get to the training recommendations. I'm not going to outline an actual program, but I am going to suggest several very useful exercises for building up your certainly lagging A-chain and explain just what they do and why/how.

Split Squat
The split squat is like a almost exactly like a lunge, except that once you get your feet planted they stay there for the rest of the set and you merely rise up and down instead of taking a step forward or backwards. In order to do the exercise optimally, it’s necessary that you position your feet so that four things happen:
1) At the bottom, your front shin is perpendicular to the ground and your weight is on the heel.
2) You’re able to maintain a neutral (not arched) back. (This will take some abdominal control.)
3) The weight is distributed evenly between the hip extensors of the front leg and the hip flexors of the rear leg.
4) You can keep your legs in line throughout the movement (no knees or ankles externally rotating).

If done correctly, the split squat trains the hip extensors of one leg in concert with the hip extensors of the other and it does so at the length they'll be used at while running. Similarly, the act of keeping a neutral pelvis throughout the set will help to coordinate the abdominals with the hip flexors and extensors. This increased coordination will show up on the playing field as greater speed and stability while moving. 

The movement does have a problem though, and that's that it's performed over a relatively small ROM. This can be dealt with quite easily though. To get the most out of the movement, I suggest doing sets of 5-8 reps per leg with a paused isometric hold of 3-5 seconds at the bottom of each repetition. Either a barbell or dumbbells can be used to add load. 

Ab Bench Holds
When sprinting, the primary type of strength required by the A-chain is isometric in nature. At the moment the leg transitions from going back to being brought forward it’s isometric strength that determines the speed of the movement, and this isometric strength needs to be displayed over a very specific range of motion. To develop this strength, we turn to the decline ab bench.

Usually used to perform sit ups, the ab bench can be a culprit in producing overactive and tight hip flexors, but we're going to get around that by performing the exercise with the illiopsoas in a lengthened position while simultaneously coordinating them with the abdominals.

In order to do this exercise properly, get in an ab bench or decline ab bench just like you normally would and put your pelvis into a neutral position. Lean your torso back as far as possible while maintaining a neutral pelvis, stopping when your back starts to arch (go into extension). Now, once you've reached that position, just hold for time. I recommend sets of 20-30 seconds.

The above variation strengthens the abdominals more so than the hip flexors, but this can be fixed by performing the exercise with only one leg hooked into the bench and the other allowed to stay free. Performing the holds in this manner will primarily stress the illiopsoas and rectus femori while putting less stress on the abdominals. Think of it as single leg work for the front side of your body. 

Depending on where your weakness lies, you can pick and chose a variation. 

Here’s a video of the variations:

Leg Lowering Holds
The final strength exercise I’m going to recommend is the leg lowering hold. To perform this exercise, lie on your back and stick your legs straight up in the air while keeping them together with the knees locked. Bracing your upper body if necessary, slowly lower your straight legs towards the ground while focusing on keeping your lower back on the ground. To keep your lower back on the ground, you’ll need to prevent your pelvis from anteriorly rotating by contracting your abdominals. Only lower your legs as far as you can while keeping your lower back firmly on the ground.

Once you found how far you can go before form breaks down, just hold your legs there for 20-30 seconds. To make the exercise more difficult you can do two things. One, you can try to get your legs closer to the ground, but this will require higher levels of control and flexibility. And two, you can hold a DB between your feet. Don't add load until you can get your heels within 6-12” of the ground while maintaining form.

Like the ab bench holds, this exercise works the A-chain isometrically and helps to coordinate the firing of the abs and hip flexors.

Out of the Weight Room
Once you’ve built up your strength in the weight room, you can bring your new strength and movement patterns out on to the field of play by using a few higher velocity, lower load exercises. Here’s where you first get to witness the rubber meeting the road.
-Sprints (30-60M in length)
-Hill Sprints (again, about 30-60M in length)
-Broad Jumps
-Tuck Jumps
-Kicking a heavy bag
-A-skips and B-skips

By keeping the discussed principles in mind and applying the recommended exercises for the often ignored A-chain, you'll be able to balance out your body and take your sport performances to the next level. But don't go overboard. Balance is everything, and making sure to train your body from all sides (A-chain and P-chain) is more important than developing strength in a lopsided manner. 

So, while it's not glamorous, and won't get you many glances from the hot gym bunnies, hammering your A-chain is necessary if you want to reach your fullest potential.


Blazevich AJ, Jenkins DG (1998) Predicting sprint running times from isokinetic and squat lift tests: a regression analysis. Journal of strength and conditioning research Vol 12: 101-103

Bosch F, Klomp R (2001) Running: Biomechanics and Exercise Physiology Applied in Practice.Reed Business Information

Dean RS, Chow JW, Tillman MD, Fournier KA (2005) Effects of hip flexor training on sprint, shuttle run, and vertical jump performance. Journal of strength and conditioning research 19(3): 615-621

Iashvili A (1982) Active and passive flexibility in athletes specializing in different sports. Teoriya I Praktika Fizischeskoi Kultury 7: 51-52

Siff MC (2003) Supertraining 4th Ed. Supertraining International, Denver

Nice article RJ24, I guess with Charlies program you can perform the unweighted ab movements because he seems to have all of your “out of weight room movements” in his programs…

Really enjoyed this article. I feel that Hip Flexor strength is underrated in sprinting.

Do you think that Dragon Flags would be an even more effective exercise than the leg lowering for stability/muscle coordination?

Thanks guys.

ASpring, those would work even better, but only if you’re able to keep your pelvis neutral through the movement.

How would you decide on volume for these exercises?

That’s entirely dependent on the program they’re integrated into. I personally regulate volume the same way I do for all other work, by doing what I can, when I can and watching my system to see how it responds. If my abs and/or hip flexors are still sore too long after a session or if my performance has dropped and the above exercises can be identified as the culprit then I’ll reduce volume over the next session.

For everyone else, I’d recommend they do the same. A good starting point however, might be just reducing their low intensity ab volume a bit and throwing a few sets of weighted movements into their weight sessions. Adjust volume up or down as necessary. And as is the case, it’s always better to do too little than to do too much.

After your speed session or weights session?
Why do you need to lower the volume of low intensity abs? Isn’t that exactly the same as lowering the tempo volume in running in the hopes that you can then raise the speed volume?

After the speed session, during weights.

And I suggested lowering the volume of low intensity abs because I’m not sure that they don’t cause fatigue. I’m in the same boat regarding tempo.

I think that tempo does exact a toll on the body, but over time, its presence allows for a higher overall workload. Basically, tempo causes fatigue but it helps us to handle a higher load. Same goes for abs. Even low intensity abs require some regenerative resources, and when you add something to your program (like high intensity abs), volume from somewhere needs to be cut.

Great article, very interesting.

How do you decide between the isometric and the oscillatory variations of the ab bench exercises?

I also appreciate the article and I’m not trying to be a prick here (though I think I may be succeeding!). My point is, in a way, your point also. Something always has to go to make room for something else if you are already training maximally.
Where we differ is in where those cuts have to come from. You believe that you can cut from low intensity and add high intensity. I believe that any room for an additional element of high intensity must come from a cut in high intensity elsewhere, as these capacities are not interchangeable.

Ginroth, thank you. And the oscillatory version creates higher forces and results in more muscle fatigue. The isometric version is less stressful and helps teach the proper position. It would probably be wise to work from the isometric version to the oscillatory version.

Charlie, thank you, and I know you’re not trying to be a prick. I understand where you’re coming from. I suggested cutting the low intensity ab volume in order to prevent local muscle soreness. I know that you’ll need to cut high intensity volume when adding other kinds of high intensity volume, but the way I train kind of takes care of that. As such, it kind of slipped my mind to mention it.

My weights, and most of my other training, is done in a rotational format as no one component (sprinting aside) is more important than any other. So, one set of exercise A, followed by one set of exercise B, and so on.

When training like this, I can more easily assess fatigue (global and local) and therefore know when to call the workout quits. Also, my volume is regulated on a session to session basis, and the volume of each exercise is regulated relative to one another by assessing form, speed, ease of movement, and general rate of perceived exertion.

For someone who did not emply similar processes, then yes, adding in high intensity ab work would require they cut high intensity work from somewhere else.

So RJ it sounds like your system automatically adjusts the high intensity volume to accommodate the addition of the high intensity abdominal element.

Would this be correct?

That’s exactly correct. The system sorts itself out. Adding in one more element, such as ab work, will automatically reduce the volume of the other high intensity work by causing fatigue and form break down, signaling the end of the session.

One of the training mistakes I made - in a quest for mighty hip flexors, was to put my foot through the loop of a kettlebell. I would do 300 reps on each leg, each day, in a standing position. I usually did 15 reps per set. Another method was to flip a lorry tire, over and over again, using my foot under the tire.

The problem is thta both of those inovative training methods actually messed up my muscle lengths ofr sprinting and slightly slowed down my speed. You see; the support legs’ hams and glutes were tightening, and the calf was over-active. Not only that, but there was eventually; a cumulative fatigue, actually preventing me from getting enough knee lift.

More food for thought:

  1. We are told that the psoas is only active when the thigh is at least at a right angle to torso, and higher.
  2. We are told that the psoas muscle size is more important than the size of other hip flexors such as rectus femoris. (the Japanese study).
  3. Most ‘hip flexion’ exercises tend to do more for rectus femoris and sartorius than the psoas - therefor; not helping point 1 and point 2
  4. If we were to do gym exercise that work only in the physio and anatomists suggestion that psoas is only actyive in upper range - then we wouldn’t be getting full range of motion - would not be getting a dynamic exercise - and could actually get shortened and tightened psoas. From here - the psoas tends to have a mind of its own. Some profess that shortened and tightened psoas is in-active and non functional.
    Others prupose that tightened psoas results in anterior pelvic tilt (which they suggest is actually good for sprinting.) And every (and I mean every) world class sprinter - had anterior pelvic tilt. This suggests tight psoas, but you’d hardly suggest the elite sprinters had non-functional psoas.

So what we have is a bucket load of contradictions and a puzzle.

The question is:

How do you;
A) Significantly strengthen the psoas
b) making it over tight
yet having
c) anterior pelvic tilt (the sign of the great sprinter)
d) without loosing the functionality of the psoas
e) whilst still managing to train appropriate ranges of motion
f) without the exercise doing more for the rectus femoris and sartorius than the iliapsoas group.
(the Japanese study confirmed that it was the psoas size in relation to rectus femoris that had the strongest correlation to sprint speed, not the over all size per se. In other words, big psoas, average rectus femoris = high sprint speed. Or; big rectus femoris and gigantic psoas = great sprint speed. Or; small rectus femoris and medium size spoas = ok.

Nightmare. Lets have more discussion because it is important. I stopped doing incline sit uops a long time ago, as they seem to do more for the rectus femoris than the actual psoas major.

After all, in the incline bench, your feet are braced under pad, thus requiring rectus femoris contraction to anchor the legs.

The psoas, rectus and iliacus work together to hip flex if the rectus is recruited then so be it. Synergy not isolation is needed. The psoas will be recruited to stabilise the spine and assist in flexing the hip and thigh.

Goose, your problem didn’t stem from training the Psoas, but from doing it wrong in a number of ways. You were fed misinformation and/or interpreted a few things wrong as well. Not only were you training over the wrong ROM, but you added in the exercise without any idea of what it would do to you. As such, the volume burnt you out and the trained ROM increased reduced the flexibility of your psoas.

As for activation, Martn is right. The thigh does not need to be at a right angle to activate the psoas. In fact, training in this range will promote posas tightness. As I stated in the article, the best ROM over which to train the psoas is with the spine held neutral and the thigh in line with the body. The exercises I suggested and demonstrated do this.

Regarding activation, you can’t, nor do you want to isolate the psoas when training. It will always work together with the other hip flexors. And you misinterpreted that Japanese study. Psoas CSA compared to quadriceps femoris CSA. The rectus femoris is one of four quadricep muscles, and hypertrophy in it alone is very beneficial to sprinters for a number of reasons.

The rectus femoris activation you get from doing decline sit ups is just fine. Not only does the RF aid in hip flexion, but it also acts isometrically to transfer forces generated during through hip extension into knee extension. It’s a very useful muscle.

EDIT: Also, on the topic of anterior pelvic tilt, most sprinter display it while walking around, but once sprinting their pelvis is held neutral or even posteriorly rotated. There are very few situations in which I would actively try to have someone tighten their psoas.

Can you illustrate some of the exercises so there is no misunderstanding?

on the anterior pelvic tilt, i always thinked that it was bad for a sprinter because this don’t allow to use in the right form the ham and gluteus.
i tryed to reduce my anterior pelvic tilt (and now i have almost neutral …because anterior iliac spine is lower than the posterior one, so a little bit is normal)

Certainly, Charlie.

Here’s a video of the ab bench work (which I feel is the most directly beneficial):

I’ll get a video of split squats and hip flexion squats a bit later. I’m at school right now, but I’ll be heading home soon. After that, it’ll only take me a few minutes to film them.

Before I even get the videos up though, I’d just like to say that as long as the psoas are loaded when relatively lengthened (the thigh is in line with the body or close to it), you’ll be developing strength over the right part of the ROM and increasing or maintaining flexibility.

Okay, I just filmed an example of split squats and hip flexion squats (aka Bulgarian split squats).

And for those who managed to miss it, the ab bench variations again.