The video discusses the significant benefits of high-intensity interval training (HIIT) on various aspects of health and fitness. This efficient exercise method involves short bursts of vigorous activity followed by periods of rest and has been shown to boost glucose homeostasis, improve insulin sensitivity, decrease fat mass, enhance mitochondrial function, and outperform moderate-intensity continuous exercise at reducing insulin resistance and improving cardiorespiratory fitness. The session delves into comprehensive research including meta-analyses, establishing HIIT as more effective than traditional exercise in improving a range of metabolic health measures.

The efficacy of HIIT is attributed to its impact on mitochondrial health and glucose utilization during intense activity. Lactate, often considered a byproduct of glycolysis, is highlighted as a crucial energy source and a signaling molecule reflective of muscle-communication with other organs. HIIT also optimally activates AMP kinase pathways which help improve mitochondrial function through processes such as mitophagy and mitochondrial biogenesis, contributing to increased energy efficiency and fitness outcomes.

Main takeaways from the video include:

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Key Vocabularies and Common Phrases:

1. homeostasis [ˌhoʊmiəˈsteɪsɪs] - (n.) - The tendency of a system, especially the physiological system of higher animals, to maintain internal stability. - Synonyms: (stability, equilibrium, balance)

High intensity abnormal training can improve glucose homeostasis, insulin sensitivity.

2. meta-analysis [ˈmɛtə-əˈnælɪsɪs] - (n.) - A statistical analysis that combines the results of multiple scientific studies. - Synonyms: (review, synthesis, overview)

A meta analysis of 50 different randomized controlled trials compared high intensity interval training to moderate intensity continuous exercise.

3. oxidative stress [ˈɑksəˌdeɪtɪv strɛs] - (n.) - A disturbance in the balance between the production of reactive oxygen species (free radicals) and antioxidant defenses. - Synonyms: (free radical damage, cellular stress, oxidation)

Improving HDL triglycerides and fasting glucose lowering oxidative stress, improving adiponectin and insulin sensitivity.

4. mitochondrial biogenesis [ˌmaɪtoʊˈkɒndrɪəl ˌbaɪoʊˈdʒɛnəsɪs] - (n.) - The process by which new mitochondria are formed in the cell. - Synonyms: (organogenesis, formation, development)

High intensity interval training is one of the most robust exercise modalities that can increase mitochondrial biogenesis.

5. systolic and diastolic blood pressure [sɪˈstɑːlɪk ənd daɪˈæstəlɪk blʌd ˈprɛʃər] - (n.) - The measurements of blood pressure during heartbeats and in between them. - Synonyms: (blood pressure measurements, cardiological metrics, heartbeat pressures)

Improving diastolic and systolic blood pressure, improving HDL triglycerides.

6. Glucose homeostasis [ˈɡluˌkoʊs ˌhoʊmiəˈsteɪsɪs] - (n.) - The balance of insulin and glucagon to maintain blood glucose. - Synonyms: (blood sugar stability, glucose regulation, sugar balance)

And that is why high intensity interval training is so potent and powerful at improving glucose homeostasis.

7. insulin sensitivity [ˈɪnsjɪlɪn ˈsɛnsɪˌtɪvɪti] - (n.) - How sensitive the body's cells are in response to insulin. - Synonyms: (insulin responsiveness, hormone sensitivity, cellular reaction)

And another systematic review of many different randomized controlled trials has found that again, high intensity interval training outperforms moderate intensity continuous exercise at improving cardiorespiratory fitness, improving diastolic and systolic blood pressure, improving HDL triglycerides and fasting glucose lowering oxidative stress, improving adiponectin and insulin sensitivity.

8. mitochondrial dysfunction [ˌmaɪtəˈkɑːndrɪəl dɪsˈfʌŋkʃən] - (n.) - A condition in which the mitochondria do not function correctly. - Synonyms: (mitochondrial failure, cell malfunction, energy production issue)

Subsequent studies have also identified structural defects in the mitochondria.

9. fasting glucose [ˈfæstɪŋ ˈgluˌkoʊs] - (n.) - The levels of glucose in the blood after fasting for at least 8 hours. - Synonyms: (blood sugar level, fasting sugar, glycated hemoglobin)

And another systematic review of many different randomized controlled trials has found that again, high intensity interval training outperforms moderate intensity continuous exercise at improving cardiorespiratory fitness, improving diastolic and systolic blood pressure, improving HDL triglycerides and fasting glucose lowering oxidative stress, improving adiponectin and insulin sensitivity, as well as beta cell function to produce insulin

10. adiponectin [ˌædɪpoʊˈnɛktɪn] - (n.) - A protein hormone produced and secreted by adipose cells that helps regulate glucose levels. - Synonyms: (protein hormone, metabolic regulator, adipose hormone)

Improving adiponectin and insulin sensitivity, as well as beta cell function to produce insulin.

This Type of Exercise Supercharges Metabolism, Optimizes Glucose Homeostasis, & Repairs Mitochondria

So let's start with high intensity interval training. So as I mentioned, this is a very time efficient way to get your heart rate up and exercise. So it involves very short bouts of intense exercise. One, we're talking about heart rate up at at least 75% max heart rate, followed by periods of recovery. There's a lot of different protocols we're going to discuss, but there have been lots of studies talking and showing that high intensity abnormal training can improve glucose homeostasis, insulin sensitivity. It also decreases fat mass, improves body composition and enhances mitochondrial function.

So a meta analysis of 50 different randomized controlled trials compared high intensity interval training to moderate intensity continuous exercise. So this would be exercise that's at a lower intensity, the kind of intensity where you can have a conversation but you're maybe still breathy, sometimes called Zone 2. And this is a longer duration type of exercise. So high intensity interval training outperforms moderate intensity continuous exercise at decreasing insulin resistance. It also improves HbA1C levels. So the long term biomarker for elevated blood glucose levels, it leads to a decrease in body weight and also significantly lowers fasting blood glucose levels. Again, this is 50 different randomized controlled trials.

And another systematic review of many different randomized controlled trials has found that again, high intensity interval training outperforms moderate intensity continuous exercise at improving cardiorespiratory fitness, improving diastolic and systolic blood pressure, improving HDL triglycerides and fasting glucose lowering oxidative stress, improving adiponectin and insulin sensitivity, as well as beta cell function to produce insulin. It increases PGC1 alpha, which is a biomarker for mitochondrial biogenesis, which we'll be discussing in a little bit. And it also improves cardiac function. And this is all better than moderate intensity continuous exercise. So it really provides a opportunity for people to have a time efficient way of improving metabolic health.

And part of that is because when you get your heart rate up high, when you are putting in the effort, you're putting a strong stress on your mitochondria and your muscle and your mitochondria are unable to produce energy quick enough to keep up with the demand. And so your muscle cells shift to using glucose as a source of energy through glycolysis, and that ends up producing lactate, which was thought to be a byproduct, a metabolic byproduct.

Well, decades, a couple of decades ago, Dr. George Brooks @ the University of California in Berkeley was one of the pioneers to find that lactate generated from exercise is anything but a byproduct. So steady state lactate levels are less than 1 millimolar. When you crank up the intensity of exercise, you can go anywhere up to 15, 17 millimolar. And that lactate gets in circulation and it's consumed by other organs. It goes into the brain, it goes into the heart, it goes back into the muscle, it goes to the kidneys, it goes to the liver. And it's serving a very utilizable source of energy.

So lactate can be used and converted into acetyl COA and used by energy by the mitochondria. But probably one of its most important roles is as a signaling molecule. It's a way for your muscle to connect, to communicate with other organs and other tissues. And one of its signaling roles is back in the muscle. It's increasing the translocation of glucose, four transporters to the cell surface of the muscle, glut four transporters. And so lactate gets back into the muscle. It's basically telling the muscle, hey, we're using a lot of glucose here for energy, so we need to bring more glucose in. And the way it does it is by increasing glute for transporters at the muscle.

And I mentioned lactate levels go up during this intense exercise. That's very transient. So after about 20 minutes, when exercise stops, your lactate levels go back to baseline because all these other organs, including the muscle, are consuming it so quickly. However, the increase in glucose for transporters stays elevated for up to 48 hours, with the first 24 hours being the most robust. So you're getting a long term effect from that signaling from lactate back to the muscle to increase GLUT4 transporters. And that is why high intensity interval training is so potent and powerful at improving glucose homeostasis.

So there was another Meta analysis of 36 randomized controlled trials that were looking at optimal conditions of high intensity interval training for improving body composition. And so it's been identified that the duration of the HIIT workout, high intensity interval training workout eight weeks, is optimal for improving body composition. The frequency is at least three sessions a week and the intervals are 60 seconds of 60 seconds or less of the robust intense interval followed by about 90 seconds of recovery. And this leads to improvements in reducing fat mass. Cycling and running was the best at doing that, also improving percent body fat. So body fat reduction. And that was the best with running and then increasing fat free mass, which includes muscle. And the best at that was actually cycling.

So these are some of the optimal conditions for improving body composition with respect to high intensity interval training. Protocols, we're going to talk about how high intensity minimal training can regulate mitochondrial function. But before we talk about that, I think it's important to recognize that people with metabolic syndrome, insulin resistance, obesity and type 2 diabetes have been identified to have pretty profound dysregulated mitochondria. So the mitochondria in skeletal muscle from people with type 2 diabetes and obesity have been found in multiple studies to respire about 40% less than skeletal muscle cells from people that do not have type 2 diabetes or people that are lean. So their mitochondria are dysfunctional. And subsequent studies have also identified structural defects in the mitochondria. So mitochondria from people with type 2 diabetes are fragmented.

So mitochondria are typically, they form a very connected network. This sort of look like vermicelli spaghetti. And that's a really beautiful network of mitochondria that are able to undergo respiration and do their functions quite robustly. When mitochondria become really fragmented, they are dysfunctional. They can't, you know, utilize or even produce energy very well. And they're on their way to basically dying and causing cells to die. So there's a very intricate connection between structure of mitochondria and the function of mitochondria. And that's important because vigorous exercise, high intensity exercise, has been shown to increase this repair process in mitochondria known as mitophagy. So when exercise is intense enough, it increases the nutrient sensing protein AMP kinase ampk, it activates it, and this causes the mitochondria to send the signal that they need to repair themselves.

And so mitochondria can be sort of dysfunctional or they can be really dysfunctional. So mitophagy can clear away an entire dysfunctional mitochondria to be used and recycled, or it can clear away pieces of a dysfunctional mitochondria. So when that, when you're doing that acute exercise, your mitochondria, if you have a dysfunctional one, the mitophagy pathway gets activated and the mitochondria fizzes off. It kind of goes through this mitochondrial fission process. And that damaged part of the mitochondria then goes and is recycled through the lysosome. And then what you have is a long term effect of after doing routine high intensity exercise, you then have more healthy functional mitochondria because you're just getting rid of the damaged part of the mitochondria. If the mitochondria is dysfunctional enough, you're going to get rid of the whole mitochondria.

And by the way, the AMP kinase pathway, many of you are probably thinking, oh well, that's a nutrient sensing pathway. It's activated during periods of fasting. And that is true. AMP kinase is activated during periods of fasting. And fasting is a powerful signal for inducing autophagy and mitophagy. However, in this particular study, people that did this high intensity, vigorous exercise for 30 minutes, it did not matter if they had fasted for 16 hours or not. There was no difference in the mitophagy. So in other words, the exercise itself was such a strong signal for activating mitophagy that it didn't matter if they had not fasted for 16 hours because it was so powerful on top of the repair process.

High intensity interval training is one of the most robust exercise modalities that can increase mitochondrial biogenesis. So the growth of new mitochondria, increasing mitochondrial volume. So you're having this double whammy effect where you're getting repairing of the mitochondria, getting rid of the unhealthy parts, and then you're increasing the growth of new mitochondria.

So one of the reasons high intensity interval training is very good at increasing mitochondrial biogenesis compared to, let's say, moderate continuous exercise is because lactate that's generated from that vigorous exercise is a signaling molecule to activate the protein that very much regulates mitochondrial biogenesis and skeletal muscle, PGC1alpha. So again, lactate is playing that signaling role. It's generated by the muscle, it's taken back up by the muscle, and then it's communicating with the muscle. It's saying, hey, we can't make energy fast enough because this exercise is so intense. We need more mitochondria to be able to do that. So it's an adaptation to the vigorous intensity exercise and that adaptation is making more mitochondria, which is obviously very beneficial for not only people with type 2 diabetes, metabolic syndrome, obesity, but also everybody. So mitochondrial biogenesis improves energy efficiency in mitochondria and also is associated with other benefits like decreased atrophy and improved exercise endurance as well. So there's a whole host of benefits with increasing mitochondrial biogenesis.

So a lot of the high intensity interval training protocols that were used in these systematic analysis and these meta analyses were evidence based HIIT protocols. So Tabata is one that's used, that's a 20 second on, 10 second off interval, 20 seconds at the highest intensity you can do, you're going all out and then you're resting for 10 seconds and that's repeated eight times for a total of a four minute workout. In some cases, the Tabata protocol was repeated twice.

The Wingate HIIT protocol is another very commonly used one. And that is a 30 second all out sprint followed by four minutes of active recovery where you're low intensity. And then you do that four to six times. That's about a 20 minute or so workout. And then there's the conventional workout, it's the one minute on, one minute off. So you're going as intense as you can for one minute and then you have one minute of very light active recovery and then you repeat that 10 times. That's a 20 minute workout.

It is hard, but it's very, very effective at improving a variety of metabolic parameters. And then there's the clinical workout, also known as the Norwegian 4x4, which I like to call it because the Norwegian ski team often uses this HIIT protocol for their training. It's a four minute interval where you're going as intense as you can for four minutes and then you have light recovery for three minutes. So you're going very, very light, getting your heart rate down. And that's repeated four times. So it's about a 25 minute workout.

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