TBrownRuns wrote:
twcronin wrote:
Running is relentless in punishing excess weight -- a rule of thumb is that you'll run about 2" slower per mile per pound of weight above your optimal running weight (which most of us - including myself at 180cm/73 kg - are). In metric units I guess that's about 3"/km slower per kg excess mass.
This is a terrible rule of thumb. I am 183cm and 83kg or 6Ā“0" 180-185lbs depending on how hydrated I am and I ran a 2:22:07 marathon last year. At the same weight now and feel pretty confident I can go under 2:20 this year without loosing any weight. If I apply this rule Kipchoge better watch out. If I loose some weight IĀ“m way better than him.
That being said, at risk of of being attacked like Alberto Salazar, yeah you need to stop lifting and loose weight immediately if you want to be fast. Light is fast. Some guys can go fast when they are heavy, like me, probably you, or Chris McCormick (the heaviest Ironman winner at 177lbs). You might try looking up his opinion on the topic. Even if you stop lifting all together and get a little faster I think you will still be able to enjoy your strength sports because it sounds like you have a pretty solid background. With any changes you want to make just go slow and try to find what exactly is right for you. I would say the following things about your points though.
1) Size of your heart and cardiac output is normally related to height (I'm 5'10") Sounds like bullshit. your heart, like any muscle, can get stronger when you exercise it 2) Running is about lifting/pushing your body through space and mass matters
Yeah mass definitely matters 3) Mass distribution is more important than total mass (i.e. heavy legs need to be driven back + forth, whereas a heavy waist line just sits there Total mass is what you should be concerned with
4) Fast twitch fibres are less efficient and tire quicker
whatĀ“s a fast twitch fiber? I donĀ“t think i have any of those. :) After my college running I took a year off and lifted a bunch of weight. I got to just over 200 pounds and my goal was to be able to back squat 500 and run a sub 5 minute mile the same day. Once I got to 425 on squat I realized that I could no longer run a sub 5 minute mile when only a year earlier it was no problem to knock out 6 mile repeats under 4:40. I went back to running because I realized I would never be a good power athlete but I was a decent runner. I say all this just to say, from my experience, your weight will play a significant roll in how fast you can run. but donĀ“t go too crazy with it. play around and try to find exactly what you want for a speed power combo.
I will maintain that it's not a terrible rule of thumb, and it is rooted in simple assumptions (see below!). That said, you're way out of my ability range to critique or give weight suggestions to! 2:22 is very impressive, good luck OTQ hunting in years to come.
Assumptions: You have body mass M [kg], a VO2 max of VDOT [ml O2/kg/min], and a specific oxygen requirement of RE [ml O2/kg/km] (inverse of running economy). This gives you a maximum aerobic speed of VDOT/RE (in km/min), or a "VO2max pace" of P=RE/VDOT (in min/km). For example, suppose you have VDOT=60 ml O2/kg/min and RE=180 ml O2/kg/km, that would mean P=3 min/km. If you lose 1 kg body mass, but maintain the same total aerobic capacity M*VDOT, and maintain running economy, then your VDOT goes up by a factor of (1+1/M) and your top-speed pace P goes down by a factor of (1+1/M), or changes by a fractional amount roughly -1/M.
If you are 80 kg and your top speed pace is 3:00/km, this would be a faster pace by about P/M=(180 s/km)/(80 kg) ~ 2.25 s/km per kg of body mass.
The same math of VO2max pace divided by body weight applies in english units too, which gives for a runner with a 5:00/mile VO2max pace and a bodyweight of 150 lb, the classic number of (300"/mile)/(150 lb) = 2"/mile/lb.
The heavier you are and faster you run, the smaller the pace gains per decrease in body mass. The lighter and slower you are, the bigger the gains in terms of pace.
At 185 lb and a VO2max speed of say 4:40/mile, I'd guess you are closer to 1.5"/mile/pound (and you are probably not much above optimal weight so your running economy and/or total O2 transport might suffer from dropping mass too).