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  1. #1
    Senior Member rdtompki's Avatar
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    % of Max HR at which glycogen being burned

    When I was a marathon runner 1/4 century ago I became very familiar with the rule of thumb - 2 hrs of glycogen. I could run 2 hours of 6 minute miles followed by 40+ minutes of 7 minute miles. You could set your watch by my demise.

    My current guesstimate of max HR at the advancing age of 67 is 165. I'm cruising at 120-130 and climb at 140 or so. On any reasonable downhill I'll just turn the pedals to keep things moving. 100K on the tandem take about 4.5 hours depending on climbing and while I'm working hard, I don't bonk. I may cramp, or feel the onset of cramps, but no feeling of hitting the wall.

    Is this simply a question of not having the aerobic capacity to burn glycogen at that 2 hour rate?
    Rick T
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  2. #2
    just another gosling Carbonfiberboy's Avatar
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    I'm about exactly the same as you. Maybe it's that we can eat so much more on the bike than a marathon runner can. I use a downloadable HR monitor and normally put in about 1.25 hours in Z4 on a hard training ride of up to, say 80 miles. Over that and it's less. But we definitely have a power drop off after that much time up there. We usually cap it at around 150 or so. LT is probably around 147. I think it hurts more now than it used to, so we have a tendency to stay away from the LT efforts, when it used to be normal to put in a 10 minute climb at over LT. I don't think I could do that now or maybe it's just that Stoker is not about to participate in such foolery. I find I can't go any harder than Stoker is willing to go. So there are many possibilities. Take your choice, or maybe it's all of the above plus some I haven't thought of.

  3. #3
    Senior Member mr_pedro's Avatar
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    Heart rate zone does not always give the same calorie expenditure, it depends on activity.
    Running 2 hours at a 6 min mile pace requires about 2200 Calories for a 155 lb person.
    The 100k in 4.5h, is that in km, amounts to about 14 mph. That will require about 850 Calories in the same 2 hours.

    Also, you mentioned using a tandem, these are much more efficient than the rugular bike figures above. There is twice the power with almost half the drag, meaning even less calories required on the tandem.

  4. #4
    Senior Member Speedskater's Avatar
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    Quote Originally Posted by rdtompki View Post
    When I was a marathon runner 1/4 century ago I became very familiar with the rule of thumb - 2 hrs of glycogen. I could run 2 hours of 6 minute miles followed by 40+ minutes of 7 minute miles. You could set your watch by my demise.

    **********
    That all adds up to a 2 hour and 43 minute marathon!
    That's some very fast marathon-ing.

  5. #5
    just another gosling Carbonfiberboy's Avatar
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    Quote Originally Posted by mr_pedro View Post
    Heart rate zone does not always give the same calorie expenditure, it depends on activity.
    Running 2 hours at a 6 min mile pace requires about 2200 Calories for a 155 lb person.
    The 100k in 4.5h, is that in km, amounts to about 14 mph. That will require about 850 Calories in the same 2 hours.

    Also, you mentioned using a tandem, these are much more efficient than the rugular bike figures above. There is twice the power with almost half the drag, meaning even less calories required on the tandem.
    Wrong.

  6. #6
    Senior Member rdtompki's Avatar
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    Quote Originally Posted by Carbonfiberboy View Post
    Wrong.
    +10
    Rick T
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  7. #7
    Senior Member rdtompki's Avatar
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    Quote Originally Posted by Speedskater View Post
    That all adds up to a 2 hour and 43 minute marathon!
    That's some very fast marathon-ing.
    We were fanatics. Best marathon was just under 2:43 at Napa although I ran a 2:47 climbing and descending over the Santa Cruz "hills". Those days are long gone.

    And from CFB: "Maybe it's that we can eat so much more on the bike than a marathon runner can."
    I agree with this. In the old days not only were our marathons sans nutrition, but we drank very little. If I knew then what I know now I might have been able to get under the magic 6 min/mile - would-a, could-a, should-a!
    Last edited by rdtompki; 09-17-12 at 08:50 AM.
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  8. #8
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    Quote Originally Posted by Carbonfiberboy View Post
    Wrong.
    Which part is wrong? The calorie figures for the running are accurate and the numbers for the bike look reasonable as well. The bottom line is running at a 6 min pace is far more intense than riding a bike at 14mph and will use far more calories.

    While running a marathon, most of the calories come from glycogen stores. On a bike riding for 4+ hrs close to 50% of the energy would come from fat rather than glycogen. If you're burning 500-600 Cals/hr on the bike and you eat 250-300 Cals/hr of carbs you won't be exhausting your body's glycogen stores, so you can ride forever. Perhaps not forever, as your ass and other bits might get sore, but bonking won't be the limiting factor.

  9. #9
    Senior Member rdtompki's Avatar
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    Quote Originally Posted by gregf83 View Post
    Which part is wrong? The calorie figures for the running are accurate and the numbers for the bike look reasonable as well. The bottom line is running at a 6 min pace is far more intense than riding a bike at 14mph and will use far more calories.

    While running a marathon, most of the calories come from glycogen stores. On a bike riding for 4+ hrs close to 50% of the energy would come from fat rather than glycogen. If you're burning 500-600 Cals/hr on the bike and you eat 250-300 Cals/hr of carbs you won't be exhausting your body's glycogen stores, so you can ride forever. Perhaps not forever, as your ass and other bits might get sore, but bonking won't be the limiting factor.
    Your observation about single versus tandem is generally inaccurate. Many (most?) captains find they are supplying the make-up power when climbing and accelerating. Pedal stoke to pedal stroke even in the flat I'm making up for the greater deceleration at the top and bottom extremes of each pedal stroke, effort that can't be supplied by my stoker. That zen-like feeling you have on a single when you're working hard, but it doesn't seem hard: "hard" to come by on a tandem.

    I don't know how quickly carbs can be convrted to glycogen and I'd agree that the effort riding a bike, taking downhill into account, is not as continuous as running, but it's certainly possible cycling to work at the same rate as when running, I'm just trying to either figure out how to get there or should I give up due to old age.

    Not much different on my single BTW, but I haven't tried an all-out effort much greater than two hours although that particular ride was going hard 100% of the time.
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  10. #10
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    Quote Originally Posted by rdtompki View Post
    Your observation about single versus tandem is generally inaccurate. Many (most?) captains find they are supplying the make-up power when climbing and accelerating. Pedal stoke to pedal stroke even in the flat I'm making up for the greater deceleration at the top and bottom extremes of each pedal stroke, effort that can't be supplied by my stoker. That zen-like feeling you have on a single when you're working hard, but it doesn't seem hard: "hard" to come by on a tandem.

    I don't know how quickly carbs can be convrted to glycogen and I'd agree that the effort riding a bike, taking downhill into account, is not as continuous as running, but it's certainly possible cycling to work at the same rate as when running, I'm just trying to either figure out how to get there or should I give up due to old age.

    Not much different on my single BTW, but I haven't tried an all-out effort much greater than two hours although that particular ride was going hard 100% of the time.
    I didn't comment on the effect of a tandem. It sounds like you might be 'fighting' your stoker.

    I didn't say it wasn't possible to burn as much energy as when running it's just that if you were to burn the 1100 Cals/hr you did when you were running 6min miles you'd be putting out a little over 300W. If you could do that for 2 hrs at 155lbs you'd be a very competitive Cat 3 racer. There are few 67 yr olds who can put out that much power.

  11. #11
    Senior Member mr_pedro's Avatar
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    So it is still not clear what you refer to with the +10 on the "wrong". Anyway, it is also a rather disrespectfull reaction to someone who takes the time to respond to your queries.

    Have a nice day
    Last edited by mr_pedro; 09-17-12 at 03:34 PM. Reason: Change of mind

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