May
21

Which muscles are really used during the pedal stroke?

Your hamstrings are not made to produce power by curling at the knee and instead are made to produce power at the hips while helping to stabilize the knee joint.

 

One of the most persistent objections I hear from riders who have never tried flats is that without being attached to the pedals you can not use your hamstrings properly which forces you to rely too much on the quads the power the pedal stroke. By not being able to curl the knee joint during the upstroke of the pedal stroke you create muscular imbalances and tire out the quads faster, or at least that is what these riders say. However, this understanding of which muscles are used and how they are used during a pedal stroke is completely wrong and potentially dangerous over the long run.

When I ask why someone thinks that the muscles are used this way during the pedal stroke I am invariably led to some variation of this picture/ chart:

According to this theoretical model of muscles used during the pedal stroke the hamstrings are used maximally from 8 o’clock to 10 o’clock position while the glutes and quads are responsible for the downstroke part of the pedal stroke. This paints a completely false picture of the situation and leads a lot riders to assume that the hamstrings are only there to flex the knee joint on the upstroke, which would be impossible to do if you weren’t attached to the pedals. This, of course, would mean that it would be impossible to optimally pedal without clipless pedals, which is where the faulty logic stems from.

The problem with this whole notion is that this chart is completely theoretical and based on how the muscles work in isolation from each other. Unfortunately, the reality of how the muscles work together to create the actual pedal stroke movement is much different than the what this chart tells us. The model this chart is based on also assumes that all muscles that cross a joint are there primarily to flex that joint, as if the muscles on the front side mirror the actions of the muscles on the backside.

The human body is not set up so that the muscles are mirror images of each other – the hamstrings are not the “backside” quads. The hamstrings are made to powerfully extend the hips while less powerfully flexing the knee, the quads are made to powerfully extend the knee while less powerfully flexing the hip. Together they both work with and counteract each other to produce lower body locomotion. Train the hamstrings to flex the hips and stabilize the knee and the quads to flex the knee and help stabilize the hip joint – that is how those muscles function in real life and how we should train them, not based on the old model of training each muscle that crosses a joint to powerfully flex it.

In fact, trying to have a rider curl their hamstring to produce force on the upstroke is unnatural and asks the knee to produce force in an unstable position. Your hamstrings are not made to produce power by curling at the knee and instead are made to produce power at the hips while helping to stabilize the knee joint. The idea that you need to curl your leg through the bottom of a pedal stroke is simply wrong and based on old and faulty logic – you want to flex the hip to push the leg through the bottom of the pedal stroke, not flex the knee.

Just like when running you don’t want to produce power by flexing the knee, you simply use knee flexion to get the leg back into position for the next “push”. The human body is made to push, not to pull, and trying to apply pulling (curling the knee is a pull) to lower body locomotion isn’t the most effective thing to do.

You want to produce your power at the hips, not the knee joint. The reason that cyclists have the knee issues they do is because the knee joint lacks stability, not strength. This is why I am an advocate for standing up more to pedal because it forces the knee and hips joints to act and stabilize more naturally than seated pedaling does.

As an interesting side note, I came across this chart of a pedal stroke while researching this article. It looks like it was based on actual EMG readings, not a theoretical model.

As you can see the Biceps Femoris (fancy talk to hamstring) is most active on the downstroke and least active on the upstroke. In fact, where first chart shows the hamstring to be most active is actually the place it is least active according to the EMG in the second picture. In other words, the first chart is flat out wrong and in no represents what is actually happening during a pedal stroke.

Take another look at the second picture and you’ll see how the downstroke finds all of the muscle groups lighting up and the upstroke sees very little activity by comparison. This also underscores the findings in the Mornieux and Korff studies, which was that a powerful downstroke with the lead leg and a more passive return of the trail leg was the most powerful and efficient way to pedal. You shouldn’t be worrying about trying to create power on the upstroke, which means that you can create the most powerful and efficient pedal stroke without being attached to your pedals.

The idea that you can not optimally use your hamstrings during a pedal stroke without clipless pedals is based on faulty logic and theoretical models. Now that we have a more accurate insight into what is actually happening we see that models like the first picture/ chart need to stop being used as a way to think about pedaling our bikes. The hamstrings are one of the more important muscles used during the pedal stroke but it is how they work in concert with the other muscles of the lower body on the downstroke – not by themselves on the upstroke – that form the reality of pedaling your bike.

-James Wilson-

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  1. Blake says:

    While I have no doubt in that second chart, I’d love to see it overlayed on a crank based power meter’s output, just as a reference looking at the overall output.

    Reply • May 21 at 4:55 pm
  2. ED BIRCH says:

    I think the best way to ‘feel’ the way the muscles work in a natural movement is to walk up an incline and be conscious of exactly what your leg is doing – the hamstring is lifting the trailing legt and hip to a position where the hip/quad can power the forward[down] stroke/step
    i changed to flat pedals about 2 years ago [after reading the blog] and although it took a little time, i feel i am a lot stronger than i was after years with clips.Certainly a lot more confident in a tight spot!

    Reply • May 21 at 11:57 pm
  3. Ed Kihm says:

    Great article James and I really do appreciate all of your insight from all your articles and videos. Having said that I’ll have to say I still like my attack Z clipless pedals since I have the option of riding clipped or unclipped like a flat pedal. I find that I have more power on climbs when I can clip in and keep my legs spinning with even steady motion while sitting back in the seat to add traction to the rear tire.
    Also, in the article you wrote “The human body is made to push, not to pull”, well what am I doing when I do pull ups and chin ups? I would have to argue that the human body is made to do both. As I’m sitting in my chair I can lift my feet off of the floor, essentially pulling them up, what muscles are used for that? Those are the same ones I use with the clipless pedals.

    Reply • May 22 at 12:24 pm
    • bikejames bikejames says:

      I need to clarify that – the human body is made to optimally push, not pull. Yes, you can flex your joints in a away that results in pulling them into the body but you are typically much stronger when you are driving your limbs away from the body. For the most part, pulling seems to be mainly to get ready for the next push, not necessarily to be relied upon for force production.

      So yes, your body is made to both push and pull but in general it wants to move in a way that favors pushing and uses pulling simply to get reset for the next push. This is the point with the pedal stroke – just because you can flex the knee and pull up on the upstroke doesn’t mean you want to. This isn’t how the body was designed to lay down power and it isn’t a net gain in power or efficiency.

      Hope that makes more sense as you are are right about being able to pull, it is just a matter of if we want to emphasize it on the bike with the pedal stroke.

      Reply • May 22 at 2:34 pm
  4. chance says:

    I guess I see it as the body is better at pushing then pulling, think about pushing or pulling a car? whats easier? push up or pull up? what one can you do more of? especially the legs? do you think you could hand and pull up as much weight with your legs if it was attatched like hanging knees to chest or push that weight up like a squat?
    I don’t now I’m not an expert but that is how I see it and I know I can put way more power pushing down then pulling up on my pedals

    Reply • May 22 at 12:48 pm
  5. Luis says:

    I came from the off road motorcycling world and quickly started using clipless without much thought, simply because everyone in mountain biking used them. I was never convinced that they were better, but figured you just had to have them if you did XC. Your article in Dirt Rag made me go get platforms immediately and I’m not going back. Yes, I was laughed at on my Sunday morning ride with the boys, but I quickly showed everyone that I did not become any slower.
    I don’t care much about the theory and the charts, I can just say that I like them better. And that’s more than good enough for me.

    Reply • May 22 at 12:59 pm
  6. Jim says:

    Can talk all day about graphs and charts but in the field testing on your own is best in my opinion. I have been training the last couple of years for 12 hour rides so most of the week I use clipless. However this year, once a week I started using a fixed gear with no brakes and flats (in case I have to abandon ship quickly) to climb a single track hill with 5 step sections for power training. At first no luck clearing any of the 5 but last time over I have started to drive more from the glutes and pushing thru with the hips (a motion outlined in James’ ketttleball program) and feel I am generating more power. On my last ride with clipless I cleared a steep section on a different trail that I have never been able to clear. Was it as a result of using flats and finding the sweet spot with the glutes to generate power? Thru field testing I believe so… not a chart or graph! But also this winter I used James’ keetleball program with p90x plyometrics mixed in which I believed helped as well. I most likely will always use clipless but the flats definitely helped make that connection between power and glutes which helped when using clipless. So argue all you want both have a place in my program.

    Reply • May 22 at 3:15 pm
    • bikejames bikejames says:

      Wasn’t meant as “anti-clipless” as much as clearing up a myth about how they work that other riders have used as a reason to not try flats. Both can have a place on your riding.

      Reply • May 22 at 3:50 pm
  7. John Weirath says:

    Interesting.

    So what is the anterior tibialis (the muscle on the front of your shin that lifts the foot and bends the ankle) doing in that second chart from 270-360 degrees?

    That’s a lot of work it’s doing. So this EMG was done on flats, right? So the rider’s foot must have lifted off the pedal?

    No? They were clipped in? Well, the anterior tibialis shouldn’t be working that much on the bike because when we walk or run it only works to lower our toes to the ground — it shouldn’t be pulling that much — it’s not a prime mover.

    It helps to understand what an EMG shows — just because the orange line of the anterior tib is as tall as the red line of the biceps femoris, doesn’t mean they are working the same amount. These muscles are recorded on different channels. Likewise, just because the red line of the biceps femoris is less from 180-270 than it is from 0-180 doesn’t mean it’s not working back there, it just means it was working A LOT on the front end of the stroke, but no one is disputing that that is the case.

    So it would seem that the anterior tib and the biceps femoris are both doing work on the back side of the pedal stroke, much of which wouldn’t be possible with a flat pedal. So while I agree with the idea of pulling up on the back of the pedal stroke is not necessarily useful to add power to the stroke there is a distinct coordinating effect that this motion can have — and wouldn’t be possible without a clipless pedal — much as you mentioned how in running there is active knee flexion to set up, or coordinate, the next stride. We can have a discussion about the use of clipless pedals and not always refer to ADDING power but rather setting up or coordinating the pedal stroke. It’s why even the authors of the studies (Korff; Mornieux) you mentioned stated:

    “Although our results suggest that actively pulling on the pedal reduces gross efficiency during steady-state cycling, there may be situations during which an active pull is beneficial….A limitation of our study…is that it does not rule out the possibility that there may be a more efficient pedaling style if participants are given enough time to adapt to it. Longitudinal studies are needed to explore this possibility.”

    I still think flats have there place, and whoever wants to use them, should. No argument there.

    Glad to see that some discussion is moving the rhetoric from:

    “At the heart of this it (sic) my belief that clipless pedals hurt people.”

    to:

    “Wasn’t meant as “anti-clipless” as much as clearing up a myth about how they work that other riders have used as a reason to not try flats. Both can have a place on your riding.”

    Reply • May 22 at 6:42 pm
    • bikejames bikejames says:

      Thanks for the input. I’m pretty sure I didn’t say the hamstring wasn’t active on the upstroke and I’m not sure exactly what is going on with the tib but the take home message that the hamstrings contribute maximally to the pedal stroke on the downstroke and not the upstroke still holds true.

      And while I can appreciate the conservative conclusions of Mornieux and Korff, the fact still remains that according to what research we have the powerful downstroke and more passive return of the trail leg is what has been shown to work best. Coupled with my own experiences and anecdotal evidence I’ve seen, until someone produces a study showing something different I am going to go along with that notion, but everyone is free to wait and see.

      While my arguments for flats has become more refined since my first posts on this subject I still think that clipless pedals hurt people. I have heard from hundreds of riders and have come across injured riders on the trail who said they were hurt because they couldn’t get unclipped. I had a rider come up to me last night and say that he would be switching to flats as soon as his broken wrist healed – the broken wrist he suffered falling over from not being able to get out of his pedals.

      I have emails from dozens of riders thanking me for letting them know that it was alright to ride flats. Some of them disliked riding and were ready to give it up when switching to flats made them more confident and riding more fun. Whether some riders want to admit it or not, clipless pedals are pushed on new riders as “better” and there are a lot of riders suffering through them for no reason.

      I also believe strongly that there is a connection to clipless pedals and the type of pedal stroke it encourages/ allows and overuse injuries. Again, my own experience of hearing from dozens of riders – one of whom just wrote an article for Dirt Rag on how flats saved his riding career – who say that simply switching to flats cleared up knee, hip and low back pain tells me that, for some riders at least, clipless pedals are somehow causing overuse injuries.

      There are a lot of myths and half-truths about the advantages of clipless pedals and flats and riders deserve to know both before deciding.

      Reply • May 23 at 6:24 am
      • Vapor says:

        John you have so liitle faith in people’s ability to pedal. I am sure of my ability to make the same EMG graph on clips or flats. I do know what my anterior tibialis is up to. What is and is not possible for your body to do on the pedal upstroke, or better said what happens when people are pedaling in the best way, is not understood by you. Your argument about a coordinatIng effect is wrong.

        The clips are not required for any of the coordinating effect to happen or happen any more efficiently. I would argue that clips get in the way of learning to pedal in the most coordinated manner.

        There is the mass of the rider’s leg/foot/shoe to get out of the way on the upstroke. Do you mean to argue that a person cannot move it out of the way without pulling up on the pedal? Do you mean to say that a person can’t just lift their leg? Oh yeah, you are trying to get some of that torque on the upstroke via the foot being attached. Well sorry, as you agreed yourself, there really is no torque to be had. It is up to the rider to learn how to move their leg out of the way on the upstroke. Giving the foot something to pull on doesn’t make getting the leg out of the way easier. Don’t pretend in some coordinating effect, get coordinated and learn to pedal.

        There is truly a coordinating effect of clips. They keep your feet in place. Hey, especially at high rpm, it does take great coordination to keep your feet in the same place as the pedals are constantly moving and your feet are off at the ends of your large moving mass of legs. Add in your bike moving over the terrain and it gets difficult. Clips take care of this, but it’s a really good idea to learn to pedal just as well without them. It’s the way to own the coordination needed to really pedal well.

        Reply • May 31 at 12:27 am
  8. hendrick says:

    James, great article. I used to believe pedaling in a perfect 360 degree circle is the right way. but after reading all your posts in the last two years and tried pushing down the pedals I found I have more power especially during a climb.

    Reply • May 22 at 7:58 pm
  9. dblspeed says:

    It all makes perfect sense. When I am in my best form I feel\visualize my legs when extending not like pushing and pulling\lifting on the pedals, but more like snapping backwards, almost like trying to break them at the knee, clearly an exageration, but that’s the idea.

    Reply • May 23 at 8:20 am
  10. Srđan says:

    Thanks for the insightful and well researched article! Posting fact based articles like this and clarifying your standpoints in the comments is much appreciated.

    Reply • May 26 at 6:22 am
  11. jordan says:

    James,
    Appreciate this. As someone who works as a ghostwriter for medical researchers it is nice to see this presentation. I will look into my resources and see if I can find additional sources.

    With that said, I like clipless pedals for the downstroke and unlike many, they reduce my fear that my foot is going to slide off the pedal (particularly in sloppy situations). (I know some fear the opposite). It also forces me to take an optimal riding line since it is not as fast to pull my foot out and tends to set me up for the best maintenance of momentum. Just some thoughts.

    Reply • July 22 at 6:35 pm
  12. [...] 20.Which muscles are really used during the pedal stroke? | Mountain … Debunking one of the most popular charts used to explain how you power a pedal stroke. … i changed to flat pedals about 2 years ago [after reading the blog] and … about graphs and charts but in the field testing on your own is best in my opinion. … to the ground — it shouldn’t be pulling that much — it’s not a prime mover. http://www.bikejames.com/strength/which-muscles-are-used-during-the-pedal-stroke/ ch_client = "yexiran"; ch_width = 550; ch_height = 250; ch_type = "mpu"; ch_sid = "moversxia"; ch_backfill = 1; ch_color_site_link = "#0000CC"; ch_color_title = "#0000CC"; ch_color_border = "#FFFFFF"; ch_color_text = "#000000"; ch_color_bg = "#FFFFFF"; [...]

    Reply • September 24 at 4:01 pm
  13. Thaea says:

    So, I’d been training with people who insisted that when climbing hills, you *have* to focus primarily on the pull up part of the pedal stroke. I even worked with a coach who spent a lot of time making the push and pull parts of my pedal stroke “sound” the same and produce a similar amount of power. So in September this year while climbing a hill and focusing on “pulling” as I was told to do, the outside of my left knee started to hurt really badly. I ended up with an injury and ultimately tendonitis in the biceps femoris tendon, which was pulling the fibular head out of alignment. I wish I had had access to more info like your article sooner, so I wouldn’t still be nursing this injury halfway through December! :(

    Reply • December 16 at 3:25 pm
  14. […] the front of the upper leg (e.g. vastus lateralis, vastus medialis, etc.) in prior workouts. In an article by James Wilson, he references the following chart showing the muscles involved in the pedal stroke […]

    Reply • October 19 at 10:38 pm

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