Exercise! - Science of Cardio question.

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08-18-2007, 06:00 PM
I have a question about cardio fitness. I understand it's sorta a in-depth question and I'm not execting anyone to have to give me science lesson so if you want to just point me into the right direction/URL where I might find the answer to this question that's fine by me. (Or if you want to explain that's cool too!)

Bare with me though as I'm not really quite sure how to phrase this question.

Everything I've found thus far just talks about the end effects of cardio training. I'm interested in finding out what changes are happening when you improve your cardio fitness. I understand some of the end effects of improvement (Increased Lung capacity, Lower Resting Heart Rate (which means more distance between resting and target therefore more blood/oxygen getting to the muscles when exercising) But I don't quite get How you get from Point A in your fitness level to Point C.... What is it that is happening to cause these improvements? How does working out at say 80% THR cause these improvements?

Did that make sense at all? heh, sorry sometimes the translation from head to text is a bit off. :)

08-18-2007, 08:07 PM
Aerobic exercise (cardio) is activity that your body does using oxygen as fuel. So as you condition yourself through cardio exercise, all the components that go into oxygen delivery and usage become more efficient.

Follow the path- your breathing becomes more regular and you can take in more air with each breath. Your lungs become more efficient at extracting the oxygen and injecting it into the blood stream.

Your heart becomes stronger in increasing its stroke volume and cardiac output. This means the fit heart pumps more blood per beat than the unfit heart, and so doesn’t have to work as hard.

The mitochondria in your muscles become more efficient at extracting and using the oxygen brought to it by the vascular system. During the aerobic process, glucose and fatty acids found in the blood stream are also used up as fuel. This means the carbs and fats that you have eaten, but have not yet been stored as fatty tissue, are used up.

The above is a very elementary explanation of what happens. It’s a process. An unfit person would start at maybe 15 minutes of cardio exercise, but eventually work up to 45 minutes. Each type of cardio exercise has its advantages. The low intensity, longer duration (walking) (40-60% of MHR) leads to increased blood flow and general health benefits. It begins the fat loss process.

Medium intensity and duration (around 70%) improves aerobic capacity and increases cardio and respiratory endurance.

High intensity with a shorter duration (80-85%) gives the biggest metabolism boost and the largest increase in cardio and respiratory endurance. If you can only do 10 seconds of sprints or running at first, you will eventually work up to minutes instead of seconds.

Higher than 85% and you get to the anaerobic threshold. This is when your body produces lactic acid and it learns to deal with this, thus increasing your endurance and efficiency. For the average person looking for general fitness and weight loss, this level is difficult to achieve and maintain. I did reach it and worked at it for about 10 months, but for the last year, I haven’t gone back to it.

The whole thing is a process. To get from point A to point C, you start where you are now. Work at different levels to take advantage of the different benefits. For medium intensity work, increase your speed and distance or time each week. For high intensity, increase your speed or number of intervals each week. Each person is different. When I do increase my high intensity work, I usually stay at that level for a week or two, because my body needs time to adapt. A younger person might not have to take that time.

This is a long answer, but I hope it makes it a little clearer for you. The aerobic system is the same whether you exercise or not. Exercise just makes it function more efficiently and stronger.

08-18-2007, 08:28 PM
Yes, that clears it up somewhat thanks! I see what you're saying about the stronger heart just being more efficent at it's job.

One last question about lungs/oxygen: So by using/stressing our lungs more are we just sorta opening up the air sacks (sorry don't know the technical term) wider therefore increasing capacity? If not how does the act of using them in cardio function make them function better?

I've noticed my resting heart rate go way down to the lower 60's and I'm breathing much deeper/slower which makes me feel more relaxed, and I can go much faster then I used to on my walks since I walk fairy briskly. Having enjoyed all these benefits and still improving weekly I just wanted to understand what was happening in my body. Thanks for taking the time to write all that all earlier... very much appricated!

08-19-2007, 05:42 AM

You can't change the SIZE of your lungs, but you can train them to be more efficient, to use more of the total lung volume to process air.

Whilst you do this you are also improving the blood's ability to transport oxygen around the body, and so improving energy supplies to working muscle sites! And lotsof other biological and physiological things too...

Here's one website that gets it said quite simply


And an academic powerpoint I direct my students to (I am a sports science lecturer - no really!)


I hope this helps, not bores:devil:

Stef :boxing:

08-19-2007, 02:25 PM
Hi Stef Thanks!

The website a bit too simple (but good for me to pass along to others) but the document is fabulous and pretty much exactly what I was asking! I only understand about 80-90 percent of the terms, but it gives me something to look up... and I sound a lot less like a dumb *** saying "HR decreases because of greater pulmonary efficiency" instead of my heart rate is lower. (grin) Thanks so much for sharing.

08-20-2007, 04:14 AM
No problems - I am just going back through my anatomy and physiology stuff ready for a new academic year! So all of this stuff is at my fingertips - and unfortunately running through my head - when I'd rather I was running through the countryside!!!

Ah well, at least I am moving on to my area of expertise next - exercise psychology - yippee!!

If you have any more queries shout out! Sometimes it is much easier to get on with stuff if you know WHY!!!!