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120 bpm, largest heart volume and Z4 intervals
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pappatho
Nov 1, 09 16:34
Post #1 of 6 (209 views)
120 bpm, largest heart volume and Z4 intervals
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I listened to a talk by someone involved with CXC (feeder program for US Olympic cross country ski team). He made a statement that the recovery period for zone 4 intervals needs to bring the heart rate down to 120. He said it has been shown that almost universally the heart has the highest volume at 120 bpm. He also made a statement to the effect of not bringing heart rate down to 120 during these intervals can have long term negative effects on the heart. He defined zone 4 pace for these intervals as 5K pace. Is anyone aware of any studies that showed any of this?
craig taylor
Nov 1, 09 17:03
Post #2 of 6 (186 views)
Re: 120 bpm, largest heart volume and Z4 intervals [pappatho]
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1) I'd suggest asking the presenter to cite the studies - that's the best place to start.
2) Stroke volume (the volume of blood pumped per beat) and end-diastolic volume (the volume of blood in the heart immediately prior to contraction) both increase at exercise intensities well above 120 bpm in trained individuals. To say that cardiac volumes are maximized at 120bpm is incorrect. For example:
http://www3.interscience.wiley.com/...RETRY=1&SRETRY=0
3) Did the presenter explain what the volume of blood in the heart had to do with recovery? I haven't seen that one before. And which metric were they talking about? Stroke volume, End Diastolic Volume, End Systolic Volume?
4) What kind of long term cardiac effects result from incorrect recovery? And what's the proof?
5) Ignoring some of the challenges of using HR to prescribe training, people can have different definitions of zone 4, depending on how they arrive at that value. In this case, 5k pace was suggested - my experience is that 5k pace is 5-10% higher than what most coaches designate as the bottom or middle of zone4, but as long as the presenter and the audience have a common understanding of the pace/effort being discussed, it's not a big deal. Zones are a bit of an artificial construct anyways.
If you get any citations to support the presentation, please post the links.
thanks.
AndyPeterson
Nov 1, 09 17:09
Post #3 of 6 (182 views)
Re: 120 bpm, largest heart volume and Z4 intervals [pappatho]
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I can't believe this is a true statement.
While stroke volume plateaus pretty early with increasing exertion, it does still continue to increase a little bit as you get closer to max heart rate. Only someone with some diastolic dysfunction should have trouble keeping up with their preload as hear rate increases.
He may have meant that stroke volume plateaus at around 120bpm in a young elite athlete - that sounds about right.
Also, the point of coming back down between intervals is not cardiac, it has more to do with reloading ATP at the muscular level.
pappatho
Nov 1, 09 17:36
Post #4 of 6 (164 views)
Re: 120 bpm, largest heart volume and Z4 intervals [craig taylor]
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I think he had stated it can lead to arrhythmia (sp?). He said something like training where 120 bpm isn't obtained on recovery can can lead to thinner, leaner heart walls. When people stop doing these workouts they can then have heart problems. This is all a bit over my head, but sounded suspect.
My guess is he meant that stroke volume maximizes at 120 bpm, I could be wrong though.
craig taylor
Nov 1, 09 17:44
Post #5 of 6 (155 views)
Re: 120 bpm, largest heart volume and Z4 intervals [AndyPeterson]
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In Reply To:
While stroke volume plateaus pretty early with increasing exertion, it does still continue to increase a little bit as you get closer to max heart rate.
It seems to be an individual response - some athletes increase SV all the way to max, others don't. But even those who demonstrate a plateau typically do so at moderate intensities. Good debate here:
http://journals.lww.com/...upright_cycle.5.aspx
In Reply To:
He may have meant that stroke volume plateaus at around 120bpm in a young elite athlete - that sounds about right.
Children seem to demonstrate the same response as adults, scaled to their size (at least for males) - so the idea would still be questionable:
http://journals.lww.com/...upright_cycle.5.aspx
...but you may have different experience, given your background.
In Reply To:
Also, the point of coming back down between intervals is not cardiac, it has more to do with reloading ATP at the muscular level.
ATP is produced on demand, not stored, except for a small amount of ATP-CP. So, except in the case of very short maximal efforts, recovery is not about reloading ATP.
I think it's just a convenient number (120bpm) - I've certainly seen some coaches talk about the 'time to recover' down to a specific submaximal heart rate as an indicator of fitness after an effort or a test. Faster recovery is certainly an aspect of fitness, but I haven't seen anything indicating exactly what it means as an objective measure of fitness, or in terms of performance.
craig taylor
Nov 1, 09 17:54
Post #6 of 6 (145 views)
Re: 120 bpm, largest heart volume and Z4 intervals [pappatho]
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ask for the references - that's good advice for most presentations, etc. You don't have to be adversarial with the presenter, just ask for the proof, for your own education. If they produce the support, you've learned something. If they can't, you've learned something, too.
FWIW, part of my MSc thesis was on sudden cessation of exercise, after 3' of cycling work @ 80% VO2 power, versus an active 5' cool-down, in healthy untrained university aged males. We used contrast echo and 12-lead ECG. We didn't observe any ECG abnormalities, and pressures/volumes were normalized within the first ~60secs with abrupt cessation of exercise.
The body is built to work very well under a wide range of conditions.
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