So in this video we're going to examine the metabolic rate in an individual. So this is associated with heat production. So the total heat that we produce in our bodies remember how metabolic reactions are inefficient about 60% of that energy is lost as heat. So the total heat that we produce is really a sum total of the heat generated by the inefficiency of chemical reactions throughout the process and the mechanical work we do. So mechanical work, just imagine you're rubbing your hands, that's a mechanical work. Well, you're generating heat through friction. you're generating heat through the proteins that are found in muscles, actin and meosin moving against each other, right? So that produces heat as well as the 60% of energy loss when you break a chemical bond. Now this can be measured directly using a device called a calerimeter and it measures heat liberated from the body. However, we immerse the individual in a water chamber to more effectively measure that because we know that water temperature is going to be directly proportional to how much energy we invest into the system to warm it up. Much harder to measure it through air. It also can be indirectly measured using a device called a resperometer where we examine how much oxygen is being consumed by the individual. that relates directly to their metabolic rate since oxygen is the final electron acceptor at the end of the electron transport chain. So this is going to be directly proportional to the heat that that individual produces. Now the basil metabolic rate this reflects the energy the body needs to perform its most essential activities and it is always going to be measured in a post-absorptive state where the individual is completely mentally and physically relaxed preferably in a reclined position so there's not any undue strain on them and at room temperature so we're not dealing with uh shivering and all that. So this is going to be recorded in units of kilo calories per square meter of body surface per hour. And it can be influenced by a number of factors which we'll dive a little bit deeper into on the next slide including surface area, their age, their gender, their body temperature, stress and then thyroxine which is the hormone secreted by the thyroid gland. So when we look at surface area, in fact what we're looking at more so is body surface area to volume ratios. So when you have a high surface area and a minimum volume that increases the surface area to volume ratio. So if you look at somebody let's say who is thin that has a certain surface area and forgive the horrible drawing. All right. This person has a high surface area and a lower volume. Somebody who might have the same surface area, but let's say is obese, they're going to have a lower surface area to volume ratio. Now, what that means is somebody who's sort of a larger volume, they're able to retain that heat and they don't need to expend as much metabolic processes to retain the same body temperature. So somebody who's thinner that has a high surface area to volume ratio is going to have a higher metabolic rate, right? Burn more calories because they need to to maintain that body temperature. BMR also decreases with age and this is sort of tied into physical activity. As we get older, we become less physically active. So there's no longer as much energy demand than there was when we were younger. Males disproportionately have a higher basil metabolic rate. And this is usually associated with muscles, right? Males having testosterone, which is an anabolic hormone to build up muscle tissue. Males generally have more muscle, which means there's a greater demand for oxygen. there are increases with temperature or stress. So when you have a lower temperature, you're increasing the metabolic rate to generate more heat during periods of stress. For example, uh you need more energy to sort of get out of dodge, right? You're stressing out. The thyroid hormone thyroxine, this impacts oxygen consumption. So there's an increase in oxygen consumption. Uh and what's actually not even shown here is with this increase in oxygen consumption, you actually have have an effect on the heart as well. So it's going to increase the heart rate so that we're delivering more oxygen to the tissues so that we are more metabolically active. So it's going to promote higher levels of cellular respiration at individual cells. And by the way, every single cell in your body for the most part has receptors for the thyroxine hormone and this elevates the basil metabolic rate. Now physical training sort of uh is has very little effect on basil metabolic rate. It can increase your total metab metabolic rate but the minimum metabolic rate is not going to be influenced by physical activity. So the total metabolic rate is going to be the rate of kilo calorie consumption for all ongoing activity. So this is above and beyond includes above and beyond the necessities. So this can increase with skeletal muscle activity with physical exertion you know when we have hypertrophy when we build muscle for example uh that same individual will have a higher total metabolic rate. uh also food ingestion. This is what we call food induced thermogenesis. So individuals that consume higher levels of protein and alcohol will increase their metabolic rates.