Physiology of efficiency of O2 use after endurance/intensity training

I have noticed that I breathe significantly more heavily for the same speed (and, I would assume, power output), after both endurance rides (e1/e2 - 3-5 hours) and interval training (e3+ 10-30 minutes of intensity, 2 hour ride). I was wondering if someone could help out with a physiological model to explain this, and if much research has been done in this area. What I am thinking is that a drop in the efficiency of processing oxygen occurs because of a combination of a breakdown in the bio-chemistry at a cellular level, combined with a drop in efficiency of capillaries which have been bombarded with blood for the whole session and therefore damaged.

If a breakdown in muscular bio-chemistry does occur, this would lead to hormone and other messenger releases, and a consequent rebuilding of muscles - recovery and training gain, no?

Its called EPOC, excess post exercise oxygen consumption

basically the body needs more oxygen post exercise to process wastes like latice acid that build up during exercise

its more pronounced in higher intensity exercise, a quick search for "epoc exercise" on google should give you heaps of info

OK, I like it. Thanks for the technical term - "EPOC" However, I'm talking not just about raised respiration at rest over a period up to 16 hours, but also under a training load in the next training session (say 24 or more hours later), while not feeling fully recovered. Admittedly, it would be unsurprising if these things were related.

Also: does the body really need more oxygen to process lactic acid and other waste after exercise?Is this what causes EPOC? I often hear cyclists talking about flushing lactic acid out on recovery rides, but I find this unconvincing. If this were the case, wouldn't we have lactic legburn off the bike? What actually happens is we experience lactic burn at a lower than usual power output - suggesting decreased efficiency of oxygen supply to muscles or of muscular use of oxygen, all leading to an anaerobic state.

Lactate removal is one factor in short term EPOC (along with replenishment of oxygen stores, adenosine triphosphate/creatine phosphate resynthesis, increased body temperature, circulation and ventilation). But "less is known about the mechanisms underlying the prolonged EPOC component". (Borsheim E, Bahr R., Effect of exercise intensity, duration and mode on post-exercise oxygen consumption., Sports Med. 2003;33(14):1037-60.)

This longer term EPOC effect seems to be what I'm trying to understand - and perhaps it would be a good area for further research, as it seems likely it would be linked to our recovery processes and thus training gains.

Your thoughts?

To explain further (as if you'd want me to - sorry I go on a bit), I'm suggesting that even after short term EPOC is over (times of 10-60 minutes seem common in most studies on pubmed), and lactic is gone, capillaries are knocked about from overuse, and muscles are less efficient because of bio-chemical changes. Then, (drumroll), we get long term EPOC, and a reduced power output for the same O2 intake. By my logic, either O2 is being used in some way to aid recovery and thus not to power the muscles (unlikely), or capillaries are stuffed and biochemistry is changed, leading to decreased aerobic efficiency and thus decreased aerobic power output. Or both are happening.

And, further, I think understanding what's going on at this level might be able to help us understand exactly how to improve endurance performance and what training stimuli produce the correct physiological response to get a training gain.

If any of this makes sense to you, let me know. I'm only a poor amateur sports scientist. Thanks very much for your help.

you are pretty much right, in the days after a hard ride the body has to rebuild any cells damaged by exerciseand this requires the input of energy

lactic acid doesn't hang around for more than an hour or two and recovery rides are more about pushing bood through the muscles to ensure that they get lots of nutrients and also to break up tiny adhesions that form when the muscle gets damaged

i'm a bit short on time now but i'll see if i can come up with a better explanantion tomorrow

until then perhaps ricstern or one of the other mods has got some info

Just to add to your comment about lactic acid. Once it's cleared out, the effects of that on the muscle can last for quite some time depending on the intensity and duration of training. Sometimes you might experience DOMS (Delayed Onset Muscle Soreness) from severe muscular breakdown. Like Duckwah said, the muscles have to rebuild after the damage is done, so it's those recovery rides that really come in handy to help in the recovery process.

Lactic acid is not the cause of DOMS, hydroxyproline is (well some people think so) DOMS is caused by the little tears that occur in muscles that have been worked hard

Did I say that lactic acid was the cause? If it came out that way, I didn't mean for it to. I just wanted to add another point about recovery after intense training. So it's not definitive that it's hydroxyproline is the cause?