Exercise & Blood Pressure

hi everybody dr mike here in this video i want to talk to you about the role of exercise on the cardiovascular system and more specifically focus on blood pressure and talk about the fact that evidence is now coming out in the literature to highlight that certain modalities of exercise more specifically exercise like high intensity interval training training like crossfit tends to have the best effects in reducing blood pressure in hypertensive individuals so the first thing i want to talk about is what blood pressure is blood pressure is the amount of force that the blood puts on the walls of your arteries and if you go to the doctors they'll put a cuff around your arm they'll measure the pressure in your brachial artery and they usually give you two values these values usually are on average 120 over 80. and it's usually measured in something called millimeters of mercury which i'll talk about that in just one second now what this is representing is 120 is when your heart contracts so here's the left-hand side of your heart when that contracts to push blood out into your arteries these arteries are going to stretch now this stretch is the maximal stretch on the walls of the arteries from the contraction of the heart and that's what we call systole so the first value is known as the systolic value it's the maximum pressure in your arterial system the second value the bottom value is what we call the diastolic reading and what that's telling us is when your heart relaxes so when the heart relaxes remember there was a stretch in the arterial wall from systole when the heart relaxes the stretch recoils and snaps back to continue to push blood through so that's the lowest pressure and that's the diastolic reading now why do we use millimeters of mercury simply because in the early studies they connected our arteries up to a tube which went to a little cylinder and that cylinder had mercury in it and they went to see how much that mercury was displaced when the heart contracted and relaxed and it displaced 120 millimeters at the strongest contraction systole and 80 millimeters at diastole or relaxation so but you could use water or anything like that all right now because when the heart contracts it's going to contract relax contract relax the blood pressure is going to go up and down up and down and then when the arterial system branches the blood pressure is going to drop it's really hard to know what the average pressure is but we can calculate the average pressure known as the mean arterial pressure or the map and the mean arterial pressure is easy to calculate it is simply the diastolic pressure plus one third of the systolic pressure minus the diastolic pressure sounds complex but it's super easy diastolic pressure we know is 80 plus one third of 120 minus 80 which is 40. so one third of 40 is around about 13 80 plus 13 is going to give us 93 so the average is 93 millimeters of mercury that's the mean arterial pressure 93 millimeters of mercury so that means right here 93 millimeters of mercury the average pressure now the other thing is this the heart's going to contract and relax and push blood out now every minute the heart pumps out five liters of blood every minute we actually call that the cardiac output and as you can see i've got the equation for blood pressure here cardiac output is one of them i'll get to systemic vascular resistance in a sec so five liters a minute coming out of the heart now the blood vessels they branch and they're going to deliver they're going to basically say okay the heart you get this much of the five liters the brain you get this much gut you get this much how does it distribute it well basically the coronary vessels get around about five percent of that five liters the brain gets around about 15 the gut gets around about 25 the kidneys get around about 20 percent muscles get around about 20 and the skin gets around about 5 that's how it distributes it now we're talking about exercise muscles at rest get twenty percent of the five liters so that means one liter per minute at rest of blood is going to your muscles at rest what this ends up being is around about three mils of blood per minute per 100 grams of muscle tissue at rest now let's just say you're about to do some exercise you start to contract those muscles when you contract the muscles you start to use oxygen you start to use energy mainly in the form of glucose so that means the demand for those things go up now where do we get these things we get them from the blood so we now need to increase that one liter per minute up we need to increase the three meals per minute per 100 grams it needs to go up how do we do it there are little receptors at the muscle tissue that travel to the brain stimulate something called the sympathetic nervous system sympathetic nervous system which is known as our fight and flight system it gets activated in times of fear or stress to keep us alive in that moment and so this gets stimulated in the brain and it sends neurons down and these neurons are going to go to the blood vessels and what they do is they tell certain blood vessels to constrict and certain blood vessels to dilate this is what we call systemic vascular resistance think about all of this if you've got a tube of a particular diameter right so that's the diameter of the tube we've got blood going in there's going to be a certain amount of resistance that that blood is going to encounter because it's going to hit the walls of the vessel as it moves through all right now think about like this if i were to increase the diameter of that vessel relax it so now it's this big there's less resistance right more blood can move through without being impeded by the walls of the vessel so the resistance drops if the resistance drops drop resistance it's an equation for blood pressure if you drop one value blood pressure is going to drop if you constrict the blood vessel make it really narrow there's heaps of resistance the blood backs up backs up back up and the resistance goes up if the resistance goes up blood pressure goes up so what i'm saying is constrict the blood blood vessel blood pressure goes up all right keep that in mind so what's happening here sympathetic nervous system innervates certain blood vessels to constrict what it does is it tells the coronary arteries tells them to dilate we need more blood going to the heart so it relaxes the brain it relaxes the gut it constricts so we're stopping blood supply going to the gut that's 25 percent 25 percent of our cardiac output is no longer going to the gut anymore the kidneys it constricts a little bit the muscles dilate significantly the skin constricts significantly so we've got mainly from the gut from the skin 30 percent of our blood being redirected now mainly to the muscle tissue and this increases this one liter per minute to around about 20 liters per minute in intense exercise 20 liters of blood per minute just go into our muscles that in an athlete times 50 times 25 to 50 so you can actually get 200 ml per minute per 100 grams of muscle tissue of blood going to that area now what the sympathetic nervous system is doing it's telling those that are dilating like the muscle tissue right it's telling it to dilate and it's doing this by increasing the amount of adrenaline also known as epinephrine noradrenaline known as norepinephrine it's increasing the amount of nitric oxide in blood vessels this tells it to relax increases the amount of prostaglandins which is another chemical that tells blood vessels to relax as well really important and what happens is this the sympathetic nervous system also goes to the kid to the heart and it increases the contraction of the heart increases the heart rate of the heart so for some blood vessels you get an increase in systemic vascular resistance you get an increase in the heart rate an increase in the contractility which means more blood gets pumped out increases that cardiac output how much blood gets pumped out per minute significantly increasing blood pressure so during exercise your blood pressure goes up your mean arterial pressure of 93 millimeters of mercury will go up and up and up and up and in some cases it can go up to 117 millimeters of mercury that's the average that is extremely high now for people with hypertension you're probably thinking well hypertension is if you've got chronically elevated blood pressure so it's not at this at rest it can be something above this so it may be anywhere above 140 over 90 anywhere above that hypertension if taken over time so how can stimulating this increasing blood pressure during exercise be beneficial for people with hypertension well what happens is this once you finish exercise you get a reflexive drop in the sympathetic nervous system so you get a drop in adrenaline at rest you get a drop your noradrenaline at rest but you get a maintained increase in nitric oxide a maintain increase in prostaglandins and these two things together tell blood vessels to relax and dilate what that will do at rest is drop the systemic vascular resistance heart output will be normal contractility will be normal but blood vessel resistance is reduced so it's easier for blood to move through blood pressure is lower and this is how people with hypertension can benefit from increasing their blood pressure during exercise

Channel: Dr Matt & Dr Mike

Views: 148,159

Rating: 4.8983803 out of 5

Keywords: exercise, blood, presure, cardiac, output, movement, crossfit, hiit, high, intensity, interval, training, medicine, nursing, cardio, cardiovascular, hypertension, systole, diastole, flow, physiotherapy, physical, therapy, study, lecture, university, college, health, fitness

Id: 0k-YBNQwm7k

Length: 10min 16sec (616 seconds)

Published: Wed Sep 02 2020