One of the most persistent myths in the mountain biking world surrounds the pedal stroke and goes something like this – 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 most of us have been told. 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:

The myth we re told about what happens during the pedal strokeAccording 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 that tells rides that it is impossible to pedal optimally without them 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 and upstroke portion 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 a lot of riders have the knee issues is because the knee joint lacks stability, not strength. On a side note 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.

The reality of what muscles are used during a pedal stroke.

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 (et al. Int J Sports Med 2008; 29:817-822) and Korf (et al. Med Sci Sports Exerc 2007; 39:991-995) Cycling Efficiency Studies I have referenced in the Flat Pedal Revolution Manifesto.

In them you see 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.

So what does this mean for you?

1 – You can (and should) be able to pedal your bike very effectively with flat pedals. This myth is one of the most common ones I hear from riders as to why they don’t want to try flat pedals when in fact flat pedals will actually clean up and improve your pedal stroke. I have written extensively about this on my site and before you assume that I hate clipless pedals I suggest you read the article Just Because I am Pro-Flats Doesn’t Mean I am Anti-Clipless.

2 – You should train your legs to produce a powerful downstroke using the hips as the primary power source, not the knee joint. This means that leg curls and leg extensions are bad exercise choices since they reinforce this “knee powered” pedal stroke. Exercises like single leg deadlifts and single leg squats are much more effective since they train the legs to drive from the hips, not the knees.

3 – When riding don’t worry about “spinning circles” or “keeping equal pressure on the pedals”. Do not try to curl the hamstring through the return portion of the pedal stroke. While a good, efficient pedal stroke may feel like you are spinning circles the reality of what your muscles are doing to produce that feeling are much different. Your body has one way to optimally produce lower body locomotion and you simply want to apply it to the pedal stroke.

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.

7 thoughts on “Which Muscles are Really Used During the Pedal Stroke?

  1. GrafJ says:

    Been riding clipless for ages and thinking of goint to Flats – so came acrooss your articles. Thank you for explaining it all in such an informative and interesting way

  2. Peter says:

    A disclaimer: I am not familiar with the peer reviewed literature on this issue but suspect that not enough research has been done.That said, it seems things are a lot more complicated than presented above. It is very likely that the circle graph with the real world data will be unique to an individual subject. No two subjects will be the same. And there probability will be patterns to emerge based on personal anatomy and strength. And further patterns may be seen in uphill vs flat terrain pedaling and even at the beginning and end of rides as well as during sprints. It is very likely that the discussion above is representative of only one particular example of pedaling which may be more commonly seen. I suggest caution trying to change what feels natural and is pain free to YOU for some other way that claims correctness and efficiency. Using a power meter, a HR monitor, and slight pedaling variations maybe all that is needed to find the most efficient and healthy use of energy. Lastly, as a rider with decades of experience with professional and scientific medical background I believe there is a huge advantage for most to be had by using clipped pedals.

    • bikejames says:

      As you said, you are not familiar with the science. If you were you would see that while there is certainly room for questions and more answers, there is a strong trend towards what I present here and nothing at all to back up the other side. From a science based perspective you have to at least admit that your views go against the current literature but you hope that some day they will be proven correct. Until that other data comes out, though, I am going to go with what the science is currently telling us.

      BTW, I did a post on your response, which is what I call the “Baskin Robbins Argument”, which you can check out here. We can claim that everyone is different or we can go with what the science is telling us…again, the choice is yours but I’m going with the science.

  3. Daniel Edelstone says:

    I am not sure you still receive replies, but here goes. I notice that if I pull back with my hamstrings on the bottom of the cycle for a few cycles, I get an immediate increase in power and speed. But it hurts too much to maintain this action for more than 30 seconds. Is pulling back on the pedals OK for short bursts, say when you want to accelerate past your opponents in a race?

    • bikejames says:

      I’d recommend standing up and letting hips drive through that range of motion. Sitting and doing a leg curl action is really bad for your knees and isn’t as powerful. It is like using your lower back when lifting – sure, it can result in some extra strength but it isn’t good for you or necessary for max power. Standing pedaling is better for you knees and your most powerful pedaling position so use it when you need to accelerate past someone.

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