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  1. #1
    Senior Member metalheart44's Avatar
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    Knee Replacements and Forces on Knees While Cycling

    A knee replacement is in the near future for me and I have been having and ongoing discussion with my ortho doc(s) about the level of cycling I can do post replacement. I cycle about 150-200 a week now and usually do a couple climbing rides a week. The short version of the discussions with my doc(s) is that they suggest I will need to curtail my cycling post replacement in order to limit wear on the joint and possible premature failure.

    There are folks here and on other forums with knee replacements who cycle high miles at good speed and also climb a reasonable amount. This seems at odds with what the doc(s) are telling me. When I look at the TKR medical literature it seems there is not a large body of evidence about the medium to long term effects of athletic activity on knee protheses. There is some, but nothing that would be definitive either pro or con for higher levels of activity post replacement. And, yes, generally the literature suggests cycling post replacement is "good for the knees" but my reading of this is that by "cycling" the literature generally means "riding a bike" and not "cycling" as forum members would understand the term.

    So, I have an appointment soon with one of my ortho docs and I wan to discuss some of the literature I have found and forces on the knee from various kinds of physical activity, but especially cycling so I can understand their conservative approach about higher mileage cycling post replacement. I have found only a few articles about this and wonder if anyone here knows about the comparisons of forces on the knee from various types of physical activity. The one item I found seems encouraging:

    "We estimated the patellofemoral joint forces generated during pedaling on a bicycle ergometer. Our calculations were based on measurements from a force transducer mounted on the pedal, 16-mm cine-film sequences, and biomechanical models of the cycling motion and of the patellofemoral joint. Six healthy male subjects cycled at different work loads, pedaling rates, saddle heights, and pedal foot positions. The maximum patellofemoral compressive force was 905 N (1.3 times body weight [BW]) when cycling with an anterior foot position at 120 W, 60 rpm, and middle saddle height. The mean peak compressive force between the quadriceps tendon and the intercondylar groove was 295 N (0.4 BW), and the patellar-tendon and quadriceps-tendon strain forces were 661 N (0.9 BW) and 938 N (1.3 BW), respectively. The patellofemoral joint forces were increased with increased work load or decreased saddle height. Different pedaling rates or foot positions did not significantly change these forces."

    The other items I have found also suggest that relative to other activities, cycling does not generate significant forces on the knees, but these are generally studies that are using more of a "ride a bike" definition of cycling and not more intensive road biking. Anyone have some information that might help me in my discussions?

    Thanks

  2. #2
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    Looking at those observations, it doesn't seem like the cycling described in that study is any more strenuous than walking. I know that we easily do more than the 1.3x BW when walking up stairs; the other times when pedaling at (0.4 BW and 0.9 BW) constant effort, the force on the knee is less than that of a person standing idle (1 BW).

    Artifical joints however, don't have minions to self repair. I do not know much about them, but even if the wear rates were the same as a human cartlidge joint, the effect will be cumulative instead of an equilibrium scenario. Perhaps if you knew what kind (specific brand and model) of replacement you would be getting, you could look for studies on the mean lifetime of that product, with regards to different activity levels and diets.

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    Humvee of bikes =Worksman Nightshade's Avatar
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    Quote Originally Posted by metalheart44 View Post
    A knee replacement is in the near future for me and I have been having and ongoing discussion with my ortho doc(s) about the level of cycling I can do post replacement. I cycle about 150-200 a week now and usually do a couple climbing rides a week. The short version of the discussions with my doc(s) is that they suggest I will need to curtail my cycling post replacement in order to limit wear on the joint and possible premature failure.

    There are folks here and on other forums with knee replacements who cycle high miles at good speed and also climb a reasonable amount. This seems at odds with what the doc(s) are telling me. When I look at the TKR medical literature it seems there is not a large body of evidence about the medium to long term effects of athletic activity on knee protheses. There is some, but nothing that would be definitive either pro or con for higher levels of activity post replacement. And, yes, generally the literature suggests cycling post replacement is "good for the knees" but my reading of this is that by "cycling" the literature generally means "riding a bike" and not "cycling" as forum members would understand the term.

    So, I have an appointment soon with one of my ortho docs and I wan to discuss some of the literature I have found and forces on the knee from various kinds of physical activity, but especially cycling so I can understand their conservative approach about higher mileage cycling post replacement. I have found only a few articles about this and wonder if anyone here knows about the comparisons of forces on the knee from various types of physical activity. The one item I found seems encouraging:

    "We estimated the patellofemoral joint forces generated during pedaling on a bicycle ergometer. Our calculations were based on measurements from a force transducer mounted on the pedal, 16-mm cine-film sequences, and biomechanical models of the cycling motion and of the patellofemoral joint. Six healthy male subjects cycled at different work loads, pedaling rates, saddle heights, and pedal foot positions. The maximum patellofemoral compressive force was 905 N (1.3 times body weight [BW]) when cycling with an anterior foot position at 120 W, 60 rpm, and middle saddle height. The mean peak compressive force between the quadriceps tendon and the intercondylar groove was 295 N (0.4 BW), and the patellar-tendon and quadriceps-tendon strain forces were 661 N (0.9 BW) and 938 N (1.3 BW), respectively. The patellofemoral joint forces were increased with increased work load or decreased saddle height. Different pedaling rates or foot positions did not significantly change these forces."

    The other items I have found also suggest that relative to other activities, cycling does not generate significant forces on the knees, but these are generally studies that are using more of a "ride a bike" definition of cycling and not more intensive road biking. Anyone have some information that might help me in my discussions?

    Thanks
    I have had both knees replaced, one in 2003 and the other early 2004, so I have 10 years of VERY careful use of the knee implants.

    When first done my doctor told me two things.......keep your body weight low and don't stress the knee joint with heavy loads. There are two reasons for these instructions. The implant can loosen or the plastic wear "puck" can wear out too soon. When I pressed for what I can do cycling doctor told me that I can ride for fun and recreation but no more pounding the pedals for speed or standing up on the pedals. As long as my cycling is normal everyday riding I'm fine but not to press for speed,hills, or trail riding since they overload the implant.

    There is also one very important point for all who get joint replacement to remember.........Your body is your body and it will heal in it's own way so the surgery will vary from person to person WITH NO HARD AND FAST TEXT BOOK RESULTS GUARANTEED! It's important to listen to your body after you get the joint(s) replaced................
    My preferred bicycle brand is.......WORKSMAN CYCLES
    I dislike clipless pedals on any city bike since I feel they are unsafe.

    Originally Posted by krazygluon
    Steel: nearly a thousand years of metallurgical development
    Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?

  4. #4
    Senior Member metalheart44's Avatar
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    Nightshade, your comments are helpful and provide an important counterpoint to some information from another cyclist I know who is also ten years post TKR. His experience is that he now cycles about the same amount I do, he climbs, and he rides at a faster pace than I do (the only solace is he is 9 years younger than me). I don't think his ortho doc necessarily approves of his level of activity, but it is what he wants to do. So, your experience and his experience illustrates the dilemma: "recreational cycling" versus more aggressive cycling.

    In the absence of evidence about the medium to long term effects of more aggressive cycling with a TKR, I think one is left with the need to make very clear to the surgeon the desired level of post TKR activity and to work hard at the post TKR rehab stuff. And, then to ride and get feedback along the way. That is where I am. Recreational riding will just not do it for me. I want to ride more aggressively for all kinds of reasons and I plan to make that clear to my surgeon.

    What is clear is that some of the evidence suggests that the load on knees from stationary cycling (1.3 times body weight) is far lower than walking or walking up and down stairs. Even if the load from cycling is double the 1.3, it is not as much as stair walking. However, cycling has a lot more duration and revolutions so there are those factors to consider.

    As we age and want to continue to be active at an aggressive level, this issue will face more of us. I am trying to sort it out for myself, but what is clear is that while I can cycle at a level that works for me know, I have significant comprises in the rest of my life that makes a TKR desirable. It may be that I have to compromise cycling, but I hope not. Having some frank discussions with the surgeon about what I know, what the literature says, and his clinical experience may sort things out, but I doubt it. Only doing it and making the best of it will tell the story.

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    Metalheart, I am, 55 yoa, 10 years post TKR and looking at getting the left knee replaced in a couple months. I average about 1500 miles per year and I ride for a workout, not sight seeing. I also coach HS soccer and Track and Field, so I keep active. My oldest daughter is a Dr of Physical Therapy and would definitely let me know if I was doing something I shouldn't

    You might want to ask your doctor what type of knee he is wanting to put in as there are different types. Mine is a Depuy rotating platform knee. At my last checkup, I was told the knee looks real good for 10 years and I can keep doing what I am doing. The one thing I would impart to you and any others that ask me about getting their knee(s) replaced is to work hard and strengthen the surrounding muscles prior to your surgery. This helps with rehab after too.

    You might also ask your Ortho if he cuts your quad during the surgery to put in the new knee. My Doc had an assistant that would pull the quad to one side and then the other. This leads to quicker healing and not sure if it is a common practice or not. I know it wasn't 10 years ago.

    I would second what Nightshade said at the end of his entry. It is your body and only you know or will know how it responds post operation. I hope this helps and good luck.

  6. #6
    Senior Member Bill Kapaun's Avatar
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    Not sure how germane this is, but-

    A shorter crank may help since you don't have to bend the knee as much.
    I know nothing about replacement knees, but possibly if you avoid the extreme bend/angle it may last disproportionately longer???

  7. #7
    Humvee of bikes =Worksman Nightshade's Avatar
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    Quote Originally Posted by metalheart44 View Post
    In the absence of evidence about the medium to long term effects of more aggressive cycling with a TKR, I think one is left with the need to make very clear to the surgeon the desired level of post TKR activity and to work hard at the post TKR rehab stuff. And, then to ride and get feedback along the way. That is where I am. Recreational riding will just not do it for me. I want to ride more aggressively for all kinds of reasons and I plan to make that clear to my surgeon.
    From this statement I'm sure that you've not considered the failure of the joint AFTER surgery.

    Joint failure can be a very, very rough road for the patient indeed.........

    "Revision Total Knee Replacement is the replacement of the previous failed total knee prosthesis with a new prosthesis. It is a complex procedure that requires extensive preoperative planning, specialized implants and tools, prolonged operating times, and mastery of difficult surgical techniques to achieve a good result."

    Please!! Read the rest of this story........

    http://www.hss.edu/conditions_revisi...ent-faqs.asp#2
    My preferred bicycle brand is.......WORKSMAN CYCLES
    I dislike clipless pedals on any city bike since I feel they are unsafe.

    Originally Posted by krazygluon
    Steel: nearly a thousand years of metallurgical development
    Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?

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    I am 54 years old, 260 lbs. and have ridden 2000 miles with 90,000 feet of climbing with a 5 year old total knee replacement this year so far. The way I see it I was in pain for so long prior to replacement I am going to do what I want and not worry about it. I have lost almost 100 lbs cycling and if knee failed tomorrow it would have been worth it. I know that it will not last forever but revision procedures are getting better every year. I also think that my cycling has improved my other knee and kept me from having to have it replaced.

    I had my TKR to get my life back. Everyone has to do what they think is right.

  9. #9
    Senior Member metalheart44's Avatar
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    Quote Originally Posted by Nightshade View Post
    From this statement I'm sure that you've not considered the failure of the joint AFTER surgery.

    Joint failure can be a very, very rough road for the patient indeed.........

    "Revision Total Knee Replacement is the replacement of the previous failed total knee prosthesis with a new prosthesis. It is a complex procedure that requires extensive preoperative planning, specialized implants and tools, prolonged operating times, and mastery of difficult surgical techniques to achieve a good result."

    Please!! Read the rest of this story........

    http://www.hss.edu/conditions_revisi...ent-faqs.asp#2
    We all come at this with different experiences and needs. I have had two heart attacks and a host of other joint compromising injuries and subsequent surgeries. However, I am very happy with my current level of cycling and the health and psychological benefits I receive from cycling at a level that is satisfying to me. On the other hand, a host of daily life activities such as gardening, walking around the shopping mall, kneeling to repair my tractor, wading into a fast moving stream to fish, and other such activities are painful and debilitating. My wife is tired of my saying "ouch" at the least little movement. But, I can cycle 45 miles fives times a week at 18 mph and I love it. I experience some knee pain but when that happens, I back off. Sometimes I have to take a break for a few days, but I can get back to a level of cycling that is satisfying to me, but then it always happens again. It is a "cycle."

    I have had 4-5 intensive conversations with my surgeon who specializes in revisions. He has been explicit about what can go wrong and what his clinical experience tells him about the kind of activity I would like to have post-TKR. he is not encouraging about the level of activity I would like to have post-TKR and he encourages me to postpone the surgery until "the time is is right" I would like to have more mobility in the rest of my life without severely compromising cycling.

    At 69, maybe my prothesis will last 10 years, maybe my heart will last 5. I don't know. What I do know is that there does not seem to be enough medical evidence to suggest that more intensive cycling will lead to prothesis failure and the myriad of ugly consequences that my surgeon has described to me. He sees the worst of the worst when it comes to revisions and he is explicit about the severity of the adverse outcomes. I think I have my eyes open about that, but I also want to have informed discussion with him about the kinds of forces generated on knees during cycling and how that translates to what I can do after TKR. And, there just isn't much about intensive cycling as opposed to "recreational cycling."

    For example, a recent article reported on the results of 9 cyclists on stationary bikes riding at 40-60 rpm and 60-120 watts. The results showed that this level of cycling riders generate forces roughly equivalent to walking. http://www.ncbi.nlm.nih.gov/pubmed/23346556 When I look at my Strava data, I estimate that my average on a ride is 280+ watts with peak sin the high 400s. I do not know how that translates into forces on the knee, but that is what I am curious about so I can have discussion with my doc about the science and his clinical knowledge regarding the effects of those forces on prothesis wear.

    Risk is a variable and we all calculate it differently. I am just trying to get some variables in place to know if I should have a TKR in the near future or postpone it ........

    Thanks for your comments, they are helpful and thought provoking.

  10. #10
    Humvee of bikes =Worksman Nightshade's Avatar
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    Quote Originally Posted by metalheart44 View Post
    Risk is a variable and we all calculate it differently. I am just trying to get some variables in place to know if I should have a TKR in the near future or postpone it ........

    Thanks for your comments, they are helpful and thought provoking.
    Sounds like we may kindred souls in that we analyze everything to "know" what , and how, the topic at hand will affect us on a personal level. That said, it's always wise to postpone TKR until there is no other choice to ensure that the implant will last as long as possible due to the huge quantity of variables involved with mechanical joint therapy. I postponed my TKR until i got to the point of wheelchair or new knees.

    I've learned that ,in my case alone, I'm not able to do many things I used to do with my original knees. However, I had to learn what I could and could not do all over again as I healed so I was not able to predict anything about my new knees at all! Being a hard charging workaholic that revelation was most unwelcome but I still needed to come to terms and accept my new bodies limits. YOUR result will also vary causing you to adapt as every TKR recipient does. Good luck...........
    My preferred bicycle brand is.......WORKSMAN CYCLES
    I dislike clipless pedals on any city bike since I feel they are unsafe.

    Originally Posted by krazygluon
    Steel: nearly a thousand years of metallurgical development
    Aluminum: barely a hundred, which one would you rather have under your butt at 30mph?

  11. #11
    Senior Member Lacumo's Avatar
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    I'm a 67yo THR recipient, 10 months post-op. I've had a substantial amount of the wind taken out of my sails but I'm getting back. Can't yet quite do the distances and times I used to do a few years ago (before the hip started dragging me down), but I'm fairly close and getting closer. I have (>70yo) friends who've had TKRs done and had to discontinue their life-long competitive handball playing. We've all found that our new prostheses seem to determine our activity levels, set our tones and intensity levels and pretty much call the shots for us.

    You can push it as hard as you want to. As you determine how hard you want to push it, it'd be prudent to make your threshold of concern about possible prosthesis failure one of the considerations you base your decisions on. After any total joint replacement, your "new 100%" (when you finally get to that point) is never the equal of your old 100%. Good luck with it.

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    Elite Rider Hermes's Avatar
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    I do not have a knee replacement but here is a scatter chart of pedal force versus pedal velocity from yesterdays ride from my power meter. The colored bands are power zones. The ride was moderately hard using most cadences but not full power standing starts or accelerations out of the saddle uphill. There were standing on starts but not very hard.

    "Insanity: doing the same thing over and over again and expecting different results." Einstein

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    Elite Rider Hermes's Avatar
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    Are you using Stanford ortho docs?
    "Insanity: doing the same thing over and over again and expecting different results." Einstein

  14. #14
    astro
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    Quote Originally Posted by Hermes View Post
    I do not have a knee replacement but here is a scatter chart of pedal force versus pedal velocity from yesterdays ride from my power meter. The colored bands are power zones. The ride was moderately hard using most cadences but not full power standing starts or accelerations out of the saddle uphill. There were standing on starts but not very hard.

    Not sure what your mass is, mine is about 85 kilograms. So my weight is around 850 N. If I'm standing, 425 N on each foot. If your chart applied to me, it says almost always, the force is around a a quarter of the force from standing. Occasionally, it gets up to about 3/4 the force you would have from standing on one leg. Looks pretty benign to me.

    - Ed

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    astro
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    Quote Originally Posted by metalheart44 View Post
    A knee replacement is in the near future for me and I have been having and ongoing discussion with my ortho doc(s) about the level of cycling I can do post replacement. I cycle about 150-200 a week now and usually do a couple climbing rides a week. The short version of the discussions with my doc(s) is that they suggest I will need to curtail my cycling post replacement in order to limit wear on the joint and possible premature failure.

    ....


    Thanks
    I had a right TKR in January 2012. This year I'm up to 3700 miles and more than 150,000 ft of climb. My doc is not crazy about this.

    I'm pretty sure his success criteria are not the same as mine. Mine have to do with living the rest of my life at a fairly good quality of life. I think his may have to do with getting the maximum life out of the artificial knee.

    I already had to give up running (although every so often, I give it a shot - so far, don't want to start again). Working on an elliptical or a stationary bike in a gym is incredibly boring and doesn't motivate me enough to do it regularly.

    Also, if one does enough work on an elliptical or stationary bike to stay fit, that's probably almost as much work on the knee as one would get from cycling (but perhaps without the occasionally heavy loads from hills, etc.)

    According to the manufacturer's web site, my knee typically lasts at least 20 years. (Of course, this should probably be taken with a grain of salt.) Let's say with my cycling, it lasts 15 years. At that point I will be 81. My mother and father died at age 69 and 83, respectively. So that's pretty close to the end of life. If it lasts only 10 years, I will 76, so I might need a revision. But only one! In the mean time, I can do most of what I want or need to do: cycling, stand up for several hours in front of class, do maintenance around the house, etc.

    By the way, my knee doctor was reluctant to do the operation. My heart doctor said by all means, get the knee replaced so you can stay active.

    - Ed

  16. #16
    Senior Member metalheart44's Avatar
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    Hermes, thanks for that information. As I said before, generally the literature I am seeing reports on relatively low forces from cycling, but then those forces are from low power, low cadence stationary bikes. Here is one chart I found that shows relative forces:
    Activities of daily living


    Activity Peak Tibial Forces (×BW) Notes
    Walking [4851, 54] 2.5 – 2.8 Laboratory floor
    Treadmill Walking [51] 2.1 ± 0.2 1 to 3 miles per hour
    Power walking [51] 2.8 ± 0.4 4 miles per hour on treadmill
    Jogging [46] 3.1 – 3.6 Tumor replacement prosthesis
    Jogging [51] 4.2 ± 0.2 5 miles per hour on treadmill
    Stationary Bicycling [51] 1.0 – 1.5 Level 1–5; 60–90 rpm
    Golf (lead knee) [51] 4.4 ± 0.1 Left knee in a right handed golfer
    Golf (trailing knee) [51] 3.0 ± 0.2
    Tennis serve [51] 4.2 ± 0.1
    Tennis forehand [51] 4.3 ± 0.4
    Tennis backhand [51] 3.5 ± 0.6
    StairMaster Level 1 [51] 2.4 ± 0.1
    StairMaster Level 3[51] 3.3 ± 0.3
    Elliptical Level 1[51] 2.3 ± 0.2
    Elliptical Level 11[51] 2.2 ± 0.3
    Leg Press [51] 2.8 ± 0.1 Foot reaction force = 1 ×BW
    Knee Extension [51] 1.5 ± 0.0 Resistance = 0.2 ×BW
    Rowing machine [51] 0.9 ± 0.1

    It looks as if generating 500-600 watts results in what are relatively minor forces compared to other activities of daily living. Some of the newer literature using strain gage measurements in folks who have had TKR may someday generate some data about more intensive cycling.

    Ed ... my heart doc is all for my knee replacement, my ortho is cautious saying that there is likely to be too much wear from all of the rotations. My thinking is much like yours about the medium to long term consequences. At 69 I plan to keep going post TKR at whatever level my knees will allow. So it goes .......

    This has been extraordinarily helpful with all of you sharing your experiences and opinions.

    Thanks again!

    ps: Hermes -- not using Stanford ortho docs, mine are in the Sacramento area
    Last edited by metalheart44; 09-13-13 at 03:52 PM.

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    Elite Rider Hermes's Avatar
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    There is an ortho doc at Stanford that specializes in knee replacement and his research is in the area of replacement technology efficacy and etc. He is on the website and the only one that lists knee replacements. I am sure he has the skinny on the latest solutions and failure mode and effects. Considering how significant a TKR is, another opinion may not be a bad idea just to confirm the choice of replacement technology, procedure and its efficacy as you want to use it.

    I go to Stanford for the tougher issues and the docs are really good.
    "Insanity: doing the same thing over and over again and expecting different results." Einstein

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    I do not understand your comments about 500 to 600 watts generating minor forces. There are 746 watts per horsepower. So 600 watts is a small lawnmower engine and it is a lot of power with a lot of force. There is not 600 watts in my chart. The max that I hit yesterday was 347 watts. I weight 167 pounds.
    "Insanity: doing the same thing over and over again and expecting different results." Einstein

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    Senior Member metalheart44's Avatar
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    I think I am just having trouble actually seeing the values on the y axis, which I interpreted as watts and there is a data pot near 500 and I assumed that was watts. One of your previous posts indicated your mass is 85kg and I think you meant 75kg if your weight is 167, a number I have not seen since about 7th grade. Thanks for the pointer to the Stanford doc, I am going to look him up and see if I can get an appt.

  20. #20
    astro
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    Quote Originally Posted by metalheart44 View Post
    I think I am just having trouble actually seeing the values on the y axis, which I interpreted as watts and there is a data pot near 500 and I assumed that was watts. One of your previous posts indicated your mass is 85kg and I think you meant 75kg if your weight is 167, a number I have not seen since about 7th grade. Thanks for the pointer to the Stanford doc, I am going to look him up and see if I can get an appt.
    Sorry for muddying the waters. The 85 kg is my mass (weight 187 lbs). I wanted to interpret the force on the y axis in terms of body weight. Since I didn't know the poster's weight, I used mine. He later stated his mass was 75 kg, which is close enough to 85 kg that the conclusions hold - the forces are mostly a fraction of body weight and pedaling a bike seems fairly benign.

    - Ed

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    Elite Rider Hermes's Avatar
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    The y axis is Newtons (force) which is pedal force. The actual forces in the knee on the various surfaces of the bones may be different.
    "Insanity: doing the same thing over and over again and expecting different results." Einstein

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    metalheart44,

    Thank you for this thread.
    I went to see the orthopedist yesterday and I am scheduled for a TKR on my left knee.
    Thanks to all for the information.

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    Quote Originally Posted by metalheart44 View Post



    At 69, maybe my prothesis will last 10 years, maybe my heart will last 5. I don't know. What I do know is that there does not seem to be enough medical evidence to suggest that more intensive cycling will lead to prothesis failure and the myriad of ugly consequences that my surgeon has described to me. He sees the worst of the worst when it comes to revisions and he is explicit about the severity of the adverse outcomes. I think I have my eyes open about that, but I also want to have informed discussion with him about the kinds of forces generated on knees during cycling and how that translates to what I can do after TKR. And, there just isn't much about intensive cycling as opposed to "recreational cycling."


    You already know the answer you are looking for. More data is not going to change that. The data you wish for is not available anyway. Go for it.

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