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>At 01:13 PM 3/21/98 -0500, Dan Volker wrote: >>As a runner, the only way your legs should give out prior to you reaching a >>max HR, would be if your leg muscles were glycogen depleted, from either too >>long an event for your conditioning level, chronic overtraining, or >>insufficient nutrition since your last run. If your legs are fresh, and if >>you have the "heart" of an athlete---the will to take it to the max, you >>will hit a max HR in your time trial. > >I'm not talking about "giving out." I'm talking about not having that extra >strength required to push your heart all the way to the max. This is a >concept well understood by exercise physiologists who train runners. If you >like, I'd be happy to mail you a case study that deals with it. > >>Max HR's tend to stay the same, slightly declining with advancing >>years----what I'm trying to say is that they do not varry over a month or 6 >>months. > >You're right, but what will vary, depending on your training, is your >ability to push to that max HR. Your point seems to be that as long as >you're working as hard as you can, that you will get to max HR. This isn't >so. Reaching max HR requires two elements: a strenuous work load and a >sufficient period of time. As a runner, I choose the 5K for this because >the distance is short enough that I bust my buns, but long enough for my HR >to climb all the way to its max. In shorter distances, the exertion level >is greater but there isn't enough time; in longer distances, there's >certainly enough time but not enough exertion. Going back to your original >test idea, because I only cycle once a week, but have a pretty good aerobic >base from running, if I pedaled at a rate slow enough rate to prevent >shutdown, my heart would cruise along without having to work hard enough to >max out. If I pushed harder into the red zone, my HR would begin to climb >toward its max but not reach it because lactate build-up would prevent me >from staying at that load for a sufficient period of time. Shine, I'd first like to thank you for allowing me to stop arguing about why there is reason for a tech diver to be fit, as opposed to a HFS, and to get more into a discussion of exercise physiology, which I prefer. OK, here's the idea I haven't been properly conveying....Lets say I'm in a race, in a pace line with ten other riders. We are averaging 32 mph, each taking 8 second pulls at the front before rotating off. If I stay in my 52X12 ( this is the biggest, fastest gear) , my heart rate will slow down, but I will feel more lactate being produced in my leg muscles, and I will use up muscle glycogen at a much faster rate, than I would if I went to my 52X14 ( the rear cog goes 12,13, 14, 15, 16, 17, 18,19, ) ....by my using the 14 tooth gear, my pedaling cadence goes up to 120 rpm, and my heart rate goes from the comfortable 185 area, up to about 193, which is putting very close to the maximum aerobic out put I am cable of---but in doing so, I am allowing my aerobic system to provide power with less power demands to the leg muscles, and this will spare glycogen ( stored energy in the muscles) . If I can get away with riding in my 52X 14, because no one attacks hard enough to increase speed to more than 34mph, after 35 miles of this, as we approach the finish line, my legs will still have a large glycogen store, and I'll have a 42 mph sprint off of someone else's wheel to cross the line, hopefully first... If on the otherhand, someone starts attacking with 35 and 37 mph bursts, in the remaining 35 miles, I'll have to ride in my 13 or 12 tooth gear, or my cadence would go up to 135 or 140, which would cause my HR to go over 200, which would cause me to blow up. So by shifting to the 12 tooth gear, I can maintain 36-37 mph intervals, with a pedal cadence of 115 to 120 , which keeps my HR below the point at which I will "blow up", but this will be done at the expense of muscle glycogen in my legs...in this scenario, when we get to the last 200 yards of the finish line, when I stand up to go, I'll have nothing left to sprint with, and may even cramp up. What this long drawn out story is supposed to demonstrate, is that you can create more power by increasing heart rate and using a smaller gear, or by decreasing heart rate, and using a larger gear, provided your leg muscles are strong enough. Because of this effect, the ergometer type test for VO2 max is more reasonable than many others ( step tests, treadmill, ) for exactly the reasons you mentioned----muscle strength. The person who feels limited in the test due to large lactate build up, will have to spin faster, with less resistance--this will have the same effect as my example, in terms of wattage produced on the ergometer. I will agree with you that sedentary people should use the formula...., and,... also that this ergometer test will be less accurate on people who are not well trained on the bike---although the degree of this inaccuracy is far lower than the inaccuracy of the 220-your age formula, if applied to many of us. The VO2 max test will require an ergometer ( standing bike with wattage output meter) , since it is the most universally available tool to test VO2 max with, it more closely approximates the cardiovascular and muscular demands of swimming with fins on, and because if we want to do chamber simulations, the ergometer will be the easiest to use in the chamber . I think we will see that by training the cardiovascular and muscular system , as in competitive cycling training, you make several very important adaptations for decompression diving. Larger, highly vascularized muscle tissue will not "constrict" during the mild exertion of fin swimming on a 250 foot dive, whereas a sedentary diver, on the same dive, will work his muscles to a much greater percentage of maximal contraction for them, to reach the same speed----this will cause more constriction within the muscle......This physiological concept is best demonstrated by Olympic speed skaters...They engage in huge volume weight training ( Erich Heiden used to do 100 rep squats with 225 pounds , as just one of many very high rep, lactate producing workouts) ---the reason for this was not so much that they needed to be stronger to push their skates sideways as they sprinted down the ice, but rather, so that each muscle contraction was a very "minimal" contraction, and that by working the primary muscles at a low percentage of max contraction, circulation would stay at optimal levels. Those who had to work at much higher percentages of maximum contraction for the same "push", experienced reduced bloodflow in the primary leg and gluteal muscles, and high levels of lactic acid would "shut them down" long before the skater with ideal bloodflow, whose muscles were only requiring minimal contractions for the same "push". This relates well to decompression physiology, since none of us wants to really exert at depth, but those who have larger, more powerful leg muscles, and more developed vascularity in them, will be less likely to experience constriction from exertion, and its attendant predisposition to causing a bubble blockage, which will then kick off the whole DCS event. This would seem to be the underlying explanation for the experiment just mentioned involving two groups of pigs---one group aerobically trained, one group sedentary. The physiological testing for this type of fitness in humans, has historically been VO2max testing. >This is almost my point: factors having nothing to do with your HR prevented >you from reaching your max. Where I think we disagree is that, from my >experience and reading, the factors you listed can be enough to prevent you >from reaching max HR even if you don't start going bonkety-bonk -- and this >effect becomes more pronounced as you move away from your typical training >into something different. You can throw mental discipline into the equation >if you want, but, not only is it unquantifiable, it defeats your stated >purpose. Are you trying to measure max HR or discipline? OK, I see what you are getting at here. But I'm just trying to help predict max HR, for a VO2max test we will standardize on a bicycle ergometer. If you had a top trainer do a VO2 max test on you on a treadmill, you may score slightly better than you would on the bike ergometer, becuse you could generate more power at the higher heart rate you find you can sustain in running. But as a runner, you are going to show a relatively high VO2 max value, regardless of which testing measure used----as opposed to a sedentary obese diver, who will score low no matter what test is used. As an athlete, I appreciate your concern in not getting "cheated" out of the highest VO2max score you could possible get, but for the purposes of this decompression physiology issue, it will be better to just standardize the test, with the method that most closely approximates the muscle usage in fin swimming, in the most universally available test equipment. Besides, if you scored 58ml/kg on the ergometer, and on a treadmill test your run gave you a 60ml/kg VO2max, the difference here would not be significant in the prediction of DCS---we would expect DCS incidence to varry greatly between a person with 58ml/kg and one with 24ml/kg , i.e., the fit versus the unfit. Regards, Dan -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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