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When I first got my bike, I had the saddle too low and I experienced some pain in my right knee while riding. I seem to have "fixed" this problem by raising it some. However, that got me thinking... what would happen if I raised it even more so that my legs would be straight (not bent at the knee) when the pedal was at the bottom? Would this give me increased power? Have power tests been done to verify what level of leg extension produces the most power? Are there any problems allowing your leg to fully extend (straighten)? I may try this sometime but wanted to get some info here first. I asked someone at the local bikeshop and they told me there is a chance of hyperextending if I do that but I asked myself how if the position is fixed? I think the general rule is to have a little bit of knee flex while the pedal is at the bottom but maybe that is a guideline and not a "hard" rule.

I wanted to add that I don't use any fancy riding shoes or any clips. Just regular "street" shoes. Also, my typical longest ride in a single day is only about 10 miles max. That translates into about a little over 1 hour at an average speed of less than 10 MPH.

Also, I am not sure why some people might say it is "bad" to straighten your leg totally when riding cuz when we walk we have alternating straight legs so why not the same when we ride a bike? When we lift a heavy object off of the floor, the hardest part is when our legs are bent the most, indicating that is the most inefficient position. When our legs are nearly straight it is much easier for us to lift weight such as a heavy box that is already at waist height for us.

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    Raising the saddle that high will lead to your hips rocking from side to side as you pedal. This will cause back pain.
    – andy256
    Commented Mar 31, 2016 at 11:47
  • Should I try and confirm cuz not everyone has the same issues as they are "built" differently. I sleep on a couch so I am used to back pain.
    – David
    Commented Mar 31, 2016 at 11:49
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    1 hour vs.10 miles doesn't equate. That means that you are only travelling at 10 miles an hour. Unless you are doing technical mountain bike trails, then you should most likely be covering more than 10 miles in an hour. Adjust your bike position so that you are in the proper position and work on your fitness. I'm sure if there was something to be gained by putting your legs at full extension then we'd see track racers doing it, especially in the shorter distance track events, but since we don't see it, I'm going to say you should just follow the general body positioning advice.
    – Kibbee
    Commented Mar 31, 2016 at 12:31
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    You don't want them completely straight where your knee locks, you want the spot right before that. That is where you will see optimal muscle usage. Also don't take these guys bagging on your speed too hard, just keep on riding! As you do more i imagine you will see your average speed increase, unless you just like slow rolling and enjoying the weather!
    – Nate W
    Commented Mar 31, 2016 at 15:06
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    Just do it. The seat adjust is either a quick release, or a 5mm hex key, or at worst a 10mm nut. Put the seat where you want, ride it, and it its not right stop and ajust it then and there (take the tools with you of course.) What works for one person may not work for another, so Get On Your Bike And Ride!
    – Criggie ♦
    Commented Apr 1, 2016 at 3:02

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I seem to have "fixed" this problem by raising it some. However, that got me thinking... what would happen if I raised it even more so that my legs would be straight (not bent at the knee) when the pedal was at the bottom? Would this give me increased power? Would this give me increased power?

Saddle height is a well known as an important factor for power generation on the bike. There is however a sweet spot. Too low and you don't get to fully use the power range of your quadriceps. Too high and you will over extend and lose power (as you are heading outside the optimal functional range).

Your optimal saddle height is also affected by your flexibility and position on the bike. For example, if you are riding a road bike (that has a low slung cockpit position) hamstring flexibility becomes an important factor when determining your optimal saddle height.

Have power tests been done to verify what level of leg extension produces the most power?

Yes. This has been studied thoroughly. And while there are lots of general rules of thumb to get you into good starting place, the best possible saddle height is individual specific and depends on your own unique biomechanics (and can change over time). Saddle setback (front/back position) is another important factor for power generation.

Are there any problems allowing your leg to fully extend (straighten)?

Yes, this can lead to various repetitive stress injuries caused by how your body compensates for the saddle being too high. Different people may compensate in different ways and get different injuries as a result.

As a personal story, I was on recent short/fast/light tour when at in the final stretch I was getting some knee pains (outside, IT-band related) and I still had 120 km to finish the next day in order to catch a ferry and meet the kids in time for camping. After much consternation that evening, I tried lowering the saddle by 0.5-1.0 cm (as I was using a different shoe/pedal combination than normal). This completely alleviated the problem and I was able to ride the distance the next day and make the ferry sailing.

In the end the best advice is to make small changes and wait a bit to see the end effect. Record these changes in a notebook so you can look back and see the big picture. None of this is an exact science because each person has some aspect of their biomechanics that makes them unique.

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  • I agree even a slight change in saddle height can make knee pain go away. This was my experience too. When I first got my 26" MTB, I was just lazy and put the saddle is the lowest position but then noticed my right knee had a "twinge" every now and then. When I raised the saddle, not only did that pain go away, but the bike feels easier to pedal (like it is 1 gear lower in all gears). I am middle aged but have good range of motion (I play golf so that helps), so maybe for me nearly fully extended legs are optimal. I will try and report back.
    – David
    Commented Apr 1, 2016 at 12:16
  • It is well-known that having the seat too low places excessive stress on the knee joints and can cause knee injury. (And the "seat" is that thing on top of the "seat post".)
    – Daniel R Hicks
    Commented Apr 1, 2016 at 12:51
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    @DanielRHicks - even American companies who produce "seats" refer to them as "saddles." If you have an issue with terminology you have a lot of minds to change.
    – Rider_X
    Commented Apr 1, 2016 at 13:53

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