By Team ICG® Master Trainers Joan Kent and Jim Karanas
The training adaptations that derive from indoor cycling are well documented and ubiquitous. Still, when we speak with new instructors, they seem to appreciate hearing the information. Also, everyone describes the benefits slightly differently, and a change can help students understand.
So even though this is review for most of you, we thought a list of aerobic training adaptations, as we describe them at ICG®, would be worth covering. Some are cardiopulmonary, some vascular, some muscle-specific, or other.
Increased Tidal Volume Improved aerobic conditioning moves more oxygen to the working muscles. The first adaptation is breathing capacity, called tidal volume. The volume of air the lungs can move with each breath increases with aerobic training due to improved diaphragm strength and breathing technique. Higher tidal volume has also been associated with longevity.
Increased Blood Volume Blood is actually an organ that responds to training by increasing in volume. With increased cardiovascular training, the body produces more red blood cells and blood to increase its oxygen-carrying capacity and oxygenate body tissues. Increased blood volume also increases the capacity to remove metabolic waste, improve recovery and sustain a greater muscle mass.
Increased Stroke Volume Stroke volume, the amount of blood ejected by the heart per beat, increases. This adaptation tends to occur at “slower” heart rates, or at least at rates less than 160 bpm. Increased stroke volume indicates improved heart function. When people talk about “strengthening” the heart, this comes the closest to being the underlying mechanism. In pumping more blood per beat, the heart moves a greater workload. The strength-training equivalent would be using a heavier weight and slow repetitions, versus pumping a lighter weight quickly.
Enhanced Capillary Network* Capillaries are blood vessels with walls only one cell thick. They surround the muscle cells and deliver oxygen and nutrients. The capillary network becomes denser with aerobic conditioning. This results in a greater available surface area for the transfer of oxygen to the mitochondria within the muscle cell.
Increased Mitochondrial Size and Density* Aerobic training results in an increase in both the size and density of mitochondria. Mitochondria are subcellular structures that convert fuel to energy aerobically. They are the receptor sites in muscle cells for the molecular oxygen needed to power the Krebs, or citric acid, cycle and produce ATP. Mitochondria are the only sites in the body that burn fat — with the exception of the heart, which can and will use whatever it gets, including lactate.
Increase in Type 1 Muscle Fibers* Aerobic conditioning also increases the sensitivity of working muscle to the effects of insulin, in part by promoting the development of Type 1 muscle fibers. Type 1 fibers are high-endurance fibers that respond well to insulin. (Type 2b are better for explosive power but less sensitive to insulin.) Everyone knows that cardio training can reduce the incidence of heart disease, hypertension, stroke, diabetes, cholesterol problems, and more. Improved insulin sensitivity is a significant mechanism in that, because insulin resistance underlies these conditions. (More about insulin resistance in a future post.)
Increase in Fat-Burning Enzymes This applies specifically to hormone-sensitive lipase (HSL), which moves fat from storage to bloodstream for utilization. HSL is activated when the body needs to mobilize energy stores, and responds positively to catecholamines and ACTH. It”™s inhibited by insulin and activated by the removal of insulin's inhibitory effects.
Items with an * are peripheral adaptations, specific to the working muscle. Thus, upper-body cardio training, such as arm cranking, will increase mitochondria, capillarization and development of type-1 fibers in the upper body in the same way that lower-body training affects the lower-body muscles involved.
Adaptations without an * are central adaptations that impact the entire body. Central adaptations permit a “transfer” effect, i.e., aerobic training with the upper body can improve aerobic performance using alternate muscles (in this case, the lower body). This was covered in Jim”™s post on “The Best Cross-Training for the Indoor Cyclist.”
It”™s important to address the impact of aerobic training adaptations on weight loss, because it”™s a primary goal of many who attend our classes. A distinction should be made between aerobic training and cardiovascular training generally.
In cardiovascular exercise, the heart, lungs and vessels of the body work at an accelerated rate to sustain exercise. It includes aerobic training. Aerobic training adaptations improve the body”™s ability to move oxygen to burn fuel for energy. Aerobic exercise has limited impact on weight loss because its built-in intensity ceiling becomes a limiting factor in several ways, the low calorie expenditure being only one. That”™s why anaerobic training is also necessary.
A major benefit of aerobic conditioning with respect to weight loss is that it supports the body”™s recovery from intense training. Trainers advocating only anaerobic work for weight loss often miss this point. Furthermore, as covered in many previous ICG® posts, training is about much more than weight loss.
Regardless, when it comes to the sheer pleasure of riding your bike, indoors or out, a well-developed aerobic system makes you feel fantastic.
Originally posted 2013-01-07 09:28:53.
Contact her at drjoan@foodaddictionsolutions.com
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10-4 Jim & Joan! Feeling fantastic is always the first take-away from every class. I’m trying to not forget reminding people how good they feel at the end of my classes.
Thanks for restating the point John. Feeling fantastic is the best benefit of aerobic fitness and is commonly overlooked in our results-driven industry.
Few thought:
-increase tidal volume, let is not forget that the best way to increase breathing capacity is by increasing the amplitude of it. The more you can relax or release or exhale the more you can take in. We train not just by strenghtening, training is strenghtening and “relaxing”, so better adaptation will be create if we work on both.
-blood volume thanks I learn something ! I am watching what is on the web about it, to try to understand the why of it … I see it more as an increase of volume to keep the blood elements concentration normal, as training will induce more red blood cell and other elements; those have to stay in some concentration to be really effective.
I try to find more scientifc datas. Do you have any research and information on the physiology of it.
-Stroke volume increase for 2 reasons, I think:
1st the heart adapt by increasing it is ability to release, the muscles is able to relax more increasing like that the volume.
2nd the blood return in the heart increase the volume by “stretching” the heart muscular cell; so short HIT interval training help too to increase heart volume, with the strong blood return create by the big variation of workload and contraction of the heart muscle.
Joan/Jim,
This post was great and my favorite topic.
No matter how many time and how many ways such adaptions are discussed I learn something. Cardiovascular training has been my passion for some time now.
Any time I begin a discussion of cardio training for my class I always pick one the adaptions mentioned here.
People get it. Thanks
Pascal and Chuck,
Thanks for reading our post and commenting. Sorry for the delayed reply; it’s a busy week.
Good point on tidal volume, Pascal. One thing I’d add about exhaling is that it’s not just a passive relaxation but can also be a very active release. In fact, the more air you can actively expel from the lungs, the greater the intake on the next inhale — seemingly without effort.
Our understanding is that aerobic training increases the RBCs, not just blood volume. The end result is an increase in blood viscosity, so concentrations do change. (Meanwhile, Jim is busy researching why athletes are dying on planes(!). It has to do with blood viscosity, low HRs and little movement. When he’s done, he’ll get back to you/us on it.)
Yes, stroke volume increases due to increased diastolic filling, which in turn increases blood ejection per beat. As you know, a pre-stretched muscle yields a greater force of contraction. As you mention, enhanced venous return definitely contributes to increased stroke volume, as well. That’s the reason that somewhat lower heart rates are more conducive to SV increase, making SV the primary determinant of cardiac output at those rates. Very high HRs reduce diastolic time and filling volume, making HR itself the primary determinant of output at high rates.
Chuck, I must take one of your classes sometime; you seem amazing.
Thanks,
Joan
Although training increases RBCs, it’s not to the extent to keep up with the increase plasma volume. A “normal” heamtocrit in a well trained athlete raises the index of suspicion for EPO use as it’s usually slightly reduced.
Vivienne
Vivienne:
Sorry for my tardiness in replying. Thanks for the new information. So, to your understanding, the number of RBC’s and plasma volume both increase with training. However, RBC concentration never increases. Thus, the cyclist would continue to have a normal hematocrit. An increase in RBC concentration indicates the use of EPO. This all makes good sense. The point that Joan was discussing with Chuck that I was researching was the incidence of cyclists dying on planes as a result of DVT – Deep Venous Thrombosis. The clots occur as a result of the slower blood flow in cyclists. This could be a result of a greater stroke volume and has also been linked to dehydration, which both make sense. I seem to remember that an increase in RBC concentration has also been suggested in the popular literature but your research is to the contrary.
We’re interested in your thoughts here. Thanks for posting.
Jim
No……the haematocrit usually drops a little with endurance training owing to the relative haemodilution of increased plasma volume. Same with pregnant women, come to that. Blood tests in the first trimester oftetimes show “anaemia” when, in fact, the plasma volume has increased with a bit of a lag in other cellular elements (RBC’s etc) THis is just basic cardiovascular physiology.
Don’t have much of an opinion on DVT’s on planes, etc. I doubt there’s that much of an epidemic outside of multiple reports on the internet and health scare stories in the popular press…….journalists do love the sensational. However, if just endurance training alone increased the RBC’s sufficiently to cause an increase in blood viscosity, there’ be no need for EPO. Maybe that’s one answer.
Vivienne
Jim, I had a bit of a wnader around the internet to see if I could get a reasonable explanation of this phenom without referring you to an ex. phys text and came across this http://www.sport-fitness-advisor.com/cardiovascular-system-and-exercise.html It’s a bit brief…..no explanations of mechanisms etc……but if you scroll right down to the last paragraph it mentions the disparity between increase in plasma volume and the cellular elements.
I’m sure I read somewhere that it might be an adaptation to allow for a reserve for sweating and temperature regulation. However, I asked my daughter (a veterinary cardiologist and endurance athlete herself) and she said that it’s a common finding across most animal species (not so sure about snakes or iguanas or black widow spiders etc…) even the ones that don’t sweat …..so there goes one theory. She reckons it’s probably an adaptation that provides for a greater increase in stroke volume so a lowered heart rate for the same cardiac output. Since you do get some increase in red cell volume, even with a reduced hematocrit etc. there’s more than enough O2 carrying capacity so there’s no need for the body to waste energy producing more red cells than it needs.
I always reckoned EPO was more of a risky placebo than a worthwhile PED.
Hope this helps.
Vivienne
Jim…..a follow up to my previous post (not sure if you can read it as I included a link and I’m getting the message that it’s awaiting moderation)….
Anyhoo…..we were out with a few of my husband’s cronies last night. All physicians from his dept. from professor down and certainly familiar with physiology and the pharmacology of these performance enhancing drugs and whatnot. We got to talking about the latest on Lance and the consensus was that, with EPO use, at least, the using might not be getting the benefits they expected. Even the testosterone/hGH use etc. might not be as “enhancing” as expected (one guy dabbled a bit a while back in *anti aging medications*)
Makes you ask if, come the passage of time, do you get your medals re-instated if the PED’s turned out to not “EP” as expected. (I’m picturing that old tyme poster of the cycling dudes puffing on cigarettes because they were thought to “open up the lungs”)
Vivienne