 One of the other really important findings that I came across was some of the molecular goings on at that level. Now, this is a really interesting and recently emerging area of research. In 2005, there was a study done which came up with an idea of what they call the AMPK PKB switch. I'll try and avoid using too much jargon, but essentially what they found out was there are two different metabolic pathways that stimulate either improvements in the physiology that underpins your cardiovascular fitness or the physiology that underpins your muscular strength and performance in that respect. This study was done on rats. It's great, we can extrapolate those findings to humans as we all love rat studies, especially in exercise and nutrition. But one of the problems was, again, it wasn't properly controlled. They used really poor representations of exercise. They didn't control for the intensity appropriately, and they compared what they noted was cardio exercise and resistance training exercise and suggested that there was under-resistance training exercise and increasing this pathway, they call the M-tor, that increases protein synthesis and increases the amount of muscle you have. In the cardio exercise, there was an increase in this AMPK activity, which is supposed to increase or adapt your physiology to be able to induce aerobic adaptations and improvements in cardiovascular fitness. This study was published in 2005. As most organizations and prominent researchers do, they jump on these new concepts and go, look, this proves our preconceived notions that resistance training and cardiovascular training are dichotomized, resistance training doesn't do anything for cardiovascular fitness. Predictably, loads of review papers came out and they said, oh, look, this fervour shows that you can't get the same adaptations from it. Had they waited a few more months, they would have realized that there was actually a paper done in humans that actually disproved that idea. And what they found was that by performing resistance training intensely to that point of failure, where we're maximally stimulating these metabolic processes, what happens is, is the body uses a molecule called adenosine triphosphate or ATP as its kind of universal currency for energy. So all the metabolic processes that go on are used to re-synthesize ATP so that we can then break it down and use it for muscular contraction and various other metabolic processes. So what happens when we start to work maximally is ATP starts to get broken down, used up quicker than we can produce it. And what the body does is it breaks it down from ATP to a molecule called ADP and then a molecule called AMP. And it's just tri-diam as it removes phosphate molecules. And what you get is if you work the muscle really intensely is the ratio of ATP to AMP starts to change. So what happens is the amount of AMP goes up significantly and the amount of ATP goes down considerably. So you get this change in this ratio. And this is what actually stimulates this AMPK pathway, which up until this point researchers have been saying it's only associated with cardio exercise and it's what produces cardiovascular adaptations. But what these researchers found was that as long as you perform intense resistance training AMPK is actually activated because what's happening is your AMP to ATP ratio is increasing significantly. So it's stimulating that metabolic pathway which is thought to actually lead to changes in the physiology that will improve cardiovascular fitness. Now what they also found was resistance training in the first two, three hours after intense resistance training, AMPK was up through the roof comparable to cardiovascular cardio exercise. I'll remember to keep using my quotation marks. It went through the roof. But then after about three hours it started to slowly come down and this mTOR pathway started to come up again. So we saw that after a period of time both pathways were being stimulated through intense resistance training, which would suggest that actually there is the potential if we assume that these molecular pathways are actually responsible for those adaptations for resistance training to produce cardiovascular fitness improvements and strength improvements as well. So that's kind of what goes on at the muscular level in terms of the responses. What happens at the cardiovascular level though is thinking on more of a gross scale. So it's what's happening in the in the vascular chair in the arteries and the veins and the capillaries and whatnot during exercise and what's actually happening in the heart. Now some of the research in this area in the vascular area, sorry, is limited. But what we do know is that kind of intuitively you would expect it anyway. The more intensely you start to work a muscle, the more progressively intensely you contract it, the more blood flow increases to that area, which seems reasonable because the body wants to get more oxygen there, wants to remove waste products and it wants to try and support that area that's being used intensely. So what you see is there's an increase in blood flow. Now what happens when we increase blood flow for a artery is that what we call the shear stress or the amount of stress that's been put on the walls of the artery increases significantly. We get a huge increase in peripheral blood pressure. So around the muscles that are being worked, blood pressure goes through the roof because the muscles are contracting, squeezing against the veins and arteries and what happens is you've got this huge peripheral stimulus to this huge stress to the peripheral vasculature. What actually happens though as the muscles start to contract intensely is although blood pressure significantly increases at the periphery, at the muscles being worked, we get an increase in what's called venous return. So your arteries take blood away from the heart and take it to the rest of the body and the veins return it back to the heart. And what happens is as the muscles intensely contract it kind of pumps and squeezes the veins and returns that blood to the heart a lot more efficiently. Now for years there's been a again another preconception that because of observational research where people have looked at bodybuilders and powerlifters and then looked at endurance athletes and found that there are differences in their heart physiology there's been the assumption that it's because of their training protocols as opposed to them selecting their sports because of their differences in physiology. So the idea has always been that resistance training increases the size of your heart it causes a kind of hypertrophy effect the same as it would do on your muscles to the actual heart muscle and the belief was because of the increased blood pressure that was shown during resistance training. Problem is usually when we measure blood pressure we measure it at the periphery so we'll measure it using a regular cuff on the arm in rare cases they'll measure it using a cuff on the leg but usually on the arm so it doesn't really give us a representation of what's actually going on in the heart during exercise. Now there have been studies done which have actually measured the pressure in the heart during intense resistance exercise and surprise surprise there's little to no change so the heart doesn't actually experience that much in the way of stress as compared to the peripheral vasculature during intense resistance training and partly that seems to be because of the improved return to the heart this improved venous return through that skeletal muscle pump and this shows up as there's no change in the vasculature myocardial pressure the left ventricle which pumps out blood because it gets more returned into it the heart can then more efficiently pump blood out so the heart's efficiency actually seems to increase the harder and harder we train using resistance exercise this doesn't seem to be the case in traditional cardio exercise though probably because there's a lack of this skeletal muscle pump action.