I have read a few references to how the muscles in your legs during a long Ultra or Ironman effectively act as a pump cirulating blood back to your heart. In effect they work in unison and when the legs start failing the heart can no longer maintain a high heartrate (which is why your HR tails off late into an Ironman). I have noted that the moment I start walking, I have a really hard time getting my heartrate back up in Ironmans. Usually, I am never limited by aerobic distress during an ironman run. Its just that I cannot turn my legs over any more. My HR at this point is typically pretty low. At the 1995 Ironman Canada, I ran 4:05 and my HR never exceeded 110 bpm for the whole run, which was a full shuffle. As a point of reference, back then I would run an Olympic distance run, or even a full marathon pegged at 180 bpm.
Question 1: How true is this theory?
Question 2: Is this is why leg strength during an Ironman marathon is more important than pure all out leg speed?
Question 3: I was doing some reading on congestive heart failure etc etc and how the blood vessels through the body are all linked together etc etc so some of this would make sense. Can some of you docs elaborate on this ?
Question 4: Is this why weight training helps Ironman guys more than short course guys?
I’ve had similar sort of abstract thoughts along the lines of “my muscles are too weak/tired to fully stress my aerobic system.” It would seem reasonable to say that your heart muscle cannot “fatigue” during a race the same way that your legs can. So when you are running a 4:05 marathon, you are well within your aerobic limits, so why should your heart rate go up?
An interesting way to “test” this would be to see what happens if you swim for a really, really long time. I would guess if you did the swim equivalent of an IM-shuffle, your heart would also be low. That doesn’t necessarily refute this theory, but perhaps adds an interesting corrolary along the lines of “working muscles of any sort help to act as a pump.”
HR will depend upon three things. The demand for blood in the periphery, the state of hydration, and the fitness of the entire organism, including the heart, to the stress it is seeing.
If you can’t get your HR up during the “run” in an IM it is most likely due to the fact that your legs won’t work at a level to demand the blood necessary to bring the HR up. This is most likely due to local factors in the legs (the limiting muscle has run out of energy stores and can’t replenish it fast enough to sustain greater efforts, perhaps?)
Leg muscles do pump blood back to the heart during exercise is a manner of speaking but this would help to lower HR, not raise it, as it improves filling and CO is a combination of HR and stroke volume.
Leg endurance and muscle balance (not having one group of muscles fail before the others) is more important in an IM and pure leg speed.
Everything is linked together. There was a song about this once, something about the neck bone being connected to the head bone.
Weight training helps IM guys more than short course guys? I can’t imagine weight training being of much benefit to either but if there was an effect and I were to guess I would think it were the other way around. Where did this come from?
Your venous return system works by one way valves as opposed to the arterial system which is driven by the heart. Blood returns from the legs by muscular contraction driving the blood through the one way valves. I wouldn’t be surprised that the body adapts to extensive exertion by relying on this drive source in lieu of higher cardiac rate, when working at an aerobic rate.
Two anecdotes. 1) My fater-in-law was in the hospital a year ago with an infected cut on the bottom of his foot. He is a diabetic with poor circulation. They put a “sleeve” like device on his legs which rythmingly contracted to help return the blood to the heart. 2) I have a tape of the 2002 IMC race, in which the third place woman crossed the finish line tooling along just fine. After she stops, the wheels fall off, and the lights turned out. One of the commentators (Graham?) mentions that the legs are important in maintaining blood flow at the end of Ironmans, and shutting down to quick will result in such a collapse.
So, in fine Slowtwitch fashion, I have not answered not just one question, but all four questions with basically only anecdotal information and very little real information.
In essence the legs work with the heart as a “muscular pump” for returning blood to the heart. Veins in your legs have one way valves that prevent gravity from keeping blood from returning to the heart. When you contract the muscles in your legs, blood is forced superiorly in your veins to return to the heart. Those one way valves help to keep the blood flow moving back toward your heart. Less muscular contraction=less blood back to heart. Just my two cents.
“Less muscular contraction=less blood back to heart”
Is this also why people on long flight have issues with bloodflow going from legs back to heart cause when you are sitting down, there is no muscular contraction ?
So based on this theory, one might argue that taking walk breaks could actually be really negative if you are already on the brink of blowup.
"Is this also why people on long flight have issues with bloodflow going from legs back to heart cause when you are sitting down, there is no muscular contraction ? "
Bingo! No movement combined with being non-fit (for most of the general population) results in blood “pooling” in the legs, and the increased risk of blood clots forming and phlebitis.
If you lift your foot (dorsiflexion, toes up while heel on ground) while standing or sitting you will move approx 1 cup of blood back up towards your heart. This is what I was told by the doc in charge of a cardiac study with which I was involved earlier this year.
If you are stuck (i.e.: flight, standing on a train/in a queue) lift your toes towards your head, alternating feet. It does help alot. Back in the days when I used to swim in the morning then stand on the train to work, I would almost pass out after about 10minutes of standing still. Doing these little foot lifts stopped that from happening.
Rappstar and Dr. Day have it nailed. Something to consider, the azygous system runs right along the back side of your aorta, and it has one-way valves in it that help keep lymph fluid moving back toward the thoracic duct, where the lymph fluid is returned to the vascular circulation. Maybe from a theoretical point (don’t know about practical matter) a higher pulse rate in the aorta moves the lymph fluid more efficiently. So, if your pulse has dropped due to less workload by the legs due to decreased local energy useage, maybe this adds to the lower body edema that may be occuring. I know this azygous lymph flow really slows when we knock the pulsatile force out of the aorta during non-pulsatile cardiopulmonary bypass…whether it has any signifcant effect during an Ironman…I do not know.
Along those lines, remember when it was suggested bicylists wear some sort of support stockings to decrease edema during longer rides? What’s the current view of this?
“Less muscular contraction=less blood back to heart”
Is this also why people on long flight have issues with bloodflow going from legs back to heart cause when you are sitting down, there is no muscular contraction ?
So based on this theory, one might argue that taking walk breaks could actually be really negative if you are already on the brink of blowup.
It also explains why a lot of newbie military guys pass out after standing at attention for so long.
Forget about newbie Military guys. Even after 5 year of being on parade, standing at attention in scarlet uniforms in mid day sun for 2 hours, I’d still be on the verge of passing out and instinctively, start moving the toes in my boot back towards my head just to stay on my feet and not come thundering to the grouund.
In any event, what can one do in an Ironman itself to keep the blood pumping. Is this a case where “shuffle at all costs” really has some medical backing vs breaking into a walk ???
Hmm, I did a near face-plant once in formation after a long run, a quick shower and a hurried walk out to the flagpole. At the time I thought I was just bonking, but the sudden stop followed my not moving for a few minutes probably did me in. I had stood in formation for hours before without an issue and never had a problem, so I was surprised this happened after about five minutes.
As long as your legs are moving you should be ok at Ironman. If you were to stop, remain standing, and not move at all, then you would be in for some problems. Whether it is shuffling, walking or crawling, if you are moving you should be fine.
Yep I’ve had similar problems on long bike rides. After about maybe 80-120 miles if I do something like climb a hill and then coast down the other side I tend to get lightheaded for 10-20 seconds as my body attempts to re-regulate blood pressure and pull the blood from my legs. Moving my legs again fixes it immediately. This also is because I tend to clamp my legs together to stabilize the bike…thereby partially cutting flow through the major inner thigh arteries. I find myself doing that sometimes, and immediately stop it.