I have been doing quite a bit of research on the net about forms of cardio and benefits/disadvantages of cardio etc... I have read many articles about the futlity of gym bunnies spending hour after hour on their cardio machines month in month out and how teh body adapts to steady state cardio after 8 weeks; However, I amnot sure I fully understand what this "adapts" means... I mean I know I burn less calories now running than I did two years ago because my body is a more efficent runner, but surely I am still burning calories?? (as it happens my running is quite varied)... I see a number of journals here where people do regular SS cardio for months simply to burn a few more calories to be able to eat more calories..

Can anyone enlighten me on what this "adapts" means exactly? and do we never adapt to HIIT? after all we adapt to weight routines?

With HIIT or weights you tend to increase the loads when things get easy. If on the other hand you do a 20 minute mile to start and never try to do better then it's not really the same thing is it?

I have been doing quite a bit of research on the net about forms of cardio and benefits/disadvantages of cardio etc... I have read many articles about the futlity of gym bunnies spending hour after hour on their cardio machines month in month out and how teh body adapts to steady state cardio after 8 weeks;

Can anyone enlighten me on what this "adapts" means exactly? and do we never adapt to HIIT? after all we adapt to weight routines?

The 8 week refers to the fact that if an untrained person does exercse that increases your VO2max and lactate threshold then their VO2max and lactate threshold will rapidly respond, and most of the gain comes in about two months.

BUT

Did you notice Lance Armstrong only doing 8 weeks of training and then knocking it off? Do elite rowers train for the Olympics for only 8 weeks?

If you want more than the weekend warrior level of cardiovascular fitness, it takes more than 8 weeks.

There is a whole range of adaptation to exercise that are interesting from the point of view of steady state exercise. However, most of them you can get more easily from a high intensity interval/circuit structured workout. The reason for this is that high intensity exercise forces the body to adapt the aerobic carbohydrate metabolism. And most of the machinery for the aerobic carbohydrate metabolism is shared with the aerobic fat metabolism - lungs, heart, blood vessels, etc. So you can increase your ability to burn fat by burning carbohydrates, and you can most quickly increase that ability with exercise intensities that you cannot sustain, which is why intervals/circuits are the weapon of choice. If you do tons of steady state work, you will still get these adaptations, but it takes a bigger investment in time, usually there is bigger risk of orthopedic injury, and it may take longer.

The one thing I know of that the fat metabolism doesn't really share with the aerobic carbohydrate metabolism is a big old overgrown mitochondrial capacity chock full of fat burning enzymes. If you never really go burn huge amounts of fat, then your body doesn't need to adapt. And if you work at high intensity, your body only has to burn carbohydrates under stress. So here steady state work at relatively low intensity is useful. Now for most people, they get all the benefit that they want from the circuit/interval stuff, so you get a lot of coaches saying nasty things about steady state. Well let's see how well those coaches do in endurance sports? Not so well. Most endurance sports involve some long easy work where you just put in hours.

Now as you suspect, people adapt to HIIT. And, as you might expect given that most of the metabolic equipment with HIIT is shared with LISS, the time it takes to mostly adapt to HIIT is a little less than eight weeks. (What a surprise! I told you that HIIT gets you there quicker....!) But do you hear the people who hate on LISS because of the 8 weeks mention this with HIIT? Oops.

The main reason to go with intense intervals/circuits is that the body adapts faster and to a slightly higher level for the same amount of exercise time. You can double up and use lifting - very few useful forms of lifting can be used for long steady state cardio.

Now in your particular case, you should be careful not to pay attention to much to beginner advice. You can tell untrained people all sorts of stuff and get good results, because there are lots of things they can stand to improve. The trouble with not being a beginner is then you start having to confront trade-offs. If you want more of X you might have to give up some Y unless you really get the training dialed in. Beginners don't have any Y worth worrying about, so they can make progress doing almost anything. The fastest progress for cardiovascular improvement for beginners, and most non-endurance athletes, is intervals/circuits.

The trouble is that you run marathons, and you didn't just start doing that. So if you want to improve beyond the easy improvements (which you probably already achieved) you have to think about what you are doing. I am just guessing, but since you put in mileage for training, then I would actually try and get you to focus most on intervals/circuits to get what the long runs haven't already got you. But still you want to put the long runs in to maintain your mitochondria. But you have to pay attention to your body. It's used to a certain style of work and your nutrition is probably adapted to that.

With HIIT or weights you tend to increase the loads when things get easy. If on the other hand you do a 20 minute mile to start and never try to do better then it's not really the same thing is it?

mmm:confused: well I have gotten faster over time running and I am thinking with HIIT there are also maximum time limits suggested for that to increase,though you can play around a lot with interval lengths of course. My point is partly surely say someone runs 4x10km a week, even if they don't speed up enormously and "adapt" surely there is still some benefit for them in the simple calories expended even if it does nothing much to improve their metabolism as HIIT or wts might? or do they "adapt" so much their metabolism actually slows down a little??