FoundMyFitness

#082 The Science of Vigorous Exercise — Should We Train Hard or Train Long? | Martin Gibala, Ph.D.

Tue Sep 19 2023

High Intensity Interval TrainingVO2 MaxMitochondriaLactateInterval Training

Description

High Intensity Interval Training (HIIT) offers a time-efficient way to improve cardiovascular health and fitness. It involves alternating between short bursts of high-intensity exercise and periods of rest. HIIT has been shown to elevate VO2 max, enhance metabolic adaptations, and optimize time spent exercising. Additionally, HIIT has unique effects on brain health and cancer metastasis resistance. Measuring VO2 max and heart rate accurately is important for optimizing training intensity. Mitochondria play a crucial role in fat oxidation during exercise, and high-intensity interval training can stimulate mitochondrial biogenesis. Lactate produced during high-intensity exercise has potential benefits for brain health. Interval training has been shown to provide greater improvements in cardiovascular health compared to continuous training. However, there is ongoing debate about the level of evidence required to recommend interval training. It is important to consider individual risk factors and consult with a healthcare professional before engaging in vigorous intensity exercise.

Insights

HIIT offers a time-efficient way to improve cardiovascular health and fitness

High Intensity Interval Training (HIIT) involves alternating between short bursts of high-intensity exercise and periods of rest. It has been shown to elevate VO2 max, enhance metabolic adaptations, and optimize time spent exercising.

Measuring VO2 max and heart rate accurately is important for optimizing training intensity

Calculating maximum heart rate using the equation 220 minus age may underestimate or overestimate intensity. Measuring maximum heart rate directly on oneself or through a stress test in a lab can provide more accurate results. The World Fitness Level calculator is a valid tool for estimating VO2 max.

Mitochondria play a crucial role in fat oxidation during exercise

High-intensity interval training can stimulate mitochondrial biogenesis, which enhances the capacity to burn fat. Increasing levels of Carnitine Palmitoyltransferase (CPT), an enzyme inside mitochondria, is important for increasing fatty acid oxidation.

Lactate produced during high-intensity exercise has potential benefits for brain health

While lactate has traditionally been considered a waste product, it can be a valuable fuel for various organs including the brain. High-intensity exercise has unique effects on the brain compared to continuous, moderate exercise.

Interval training provides greater improvements in cardiovascular health compared to continuous training

Interval training has been shown to provide greater improvements in cardiovascular health, body composition, and blood sugar levels compared to continuous training. However, there is ongoing debate about the level of evidence required to recommend interval training.

Summary

Transcript

High Intensity Interval Training (HIIT)

00:00 - 08:10

HIIT offers the option to be healthy even on busy days
HIIT allows you to achieve more by doing less, but with greater intensity
There is a debate between zone 2 training and high intensity interval training for cardio-respiratory benefits
40% of people may not see improvements in their VO2 max without high intensity training
HIIT creates more physiological stress in a short period of time, yielding exponential benefits
Incorporating HIIT into routines optimizes time and enhances metabolic adaptations and cardiovascular health
HIIT can elevate VO2 max, which is a strong predictor of longevity
Achieving significant health benefits in shorter durations is essential as our lifestyles have become increasingly sedentary
Misconceptions about HIIT include its impact on fat oxidation and whether it is better than fasting for autophagy
Vigorous exercise has unique effects on the brain and cancer metastasis resistance
Pushing past the lactate threshold through vigorous exercise may offer cognitive enhancement
Exercise intensity affects blood flow, sheer force, and may reduce the risk of cancer metastasis

VO2 Max and Cardiorespiratory Fitness

15:05 - 22:15

VO2 max is the best objective measure of cardiospiritory fitness
Higher cardiosphericity fitness is associated with a reduction in all-cause mortality and chronic diseases
Observational studies show an inverse relationship between VO2 max and all-cause mortality with no apparent upper limit
Engaging in physical activity for general health is different from how elite endurance athletes train
Elite athletes engage in 80% low to moderate intensity training and 20% high intensity training
For individuals with limited time, engaging in more vigorous intensity exercise may potentiate gains in fitness
The greatest gains in VO2 max are achieved by moving out of the low range, but there are diminishing returns at higher levels of fitness

Measuring VO2 Max and Heart Rate

22:00 - 29:01

Calculating maximum heart rate using the equation 220 minus age may underestimate or overestimate intensity
Measuring maximum heart rate directly on oneself is a better approach
A stress test in a lab can accurately measure maximum heart rate, but it can also be done cheaply at home with a reasonably accurate device
The World Fitness Level calculator is a valid tool for estimating VO2 max based on research conducted in Norway
While the calculator provides an estimate, it allows tracking changes over time and assessing the effectiveness of training programs
Submaximal exercise tests are another option for estimating VO2 max

Mitochondria and Fat Oxidation

35:16 - 43:05

High-intensity interval training is a potent stimulus for mitochondrial biogenesis, or the generation of new mitochondria
Mitochondria are a network of organelles that can change in size and capacity
Exercise, regardless of type, is a stress that triggers changes in muscle compounds associated with the growth of new mitochondria
High-intensity interval training may result in a more rapid or larger increase in mitochondrial content compared to continuous exercise over the short term
Mitochondrial content largely determines fat oxidation during exercise, and increasing mitochondrial content can enhance fat oxidation capacity
Increasing levels of Carnitine Palmitoyltransferase (CPT), an enzyme inside mitochondria, is important for increasing fatty acid oxidation
There is debate about the best way to increase mitochondrial content and maximize fat oxidation capacity in athletes

Lactate and Brain Health

42:41 - 49:59

During high intensity interval training, when going above 80% max heart rate, the lactate threshold is reached and fat burning may decrease temporarily
However, high intensity exercise increases mitochondrial biogenesis, which enhances the capacity to burn fat later on
Epinephrine and norepinephrine released during higher intensity exercise stimulate lipolysis, the breakdown of triglycerides into fatty acids
Increasing lipolysis alone does not necessarily increase fatty acid oxidation; the limit for fat oxidation resides in the muscle at the level of CPT enzyme
Mitochondrial biogenesis can be increased through high intensity exercise, promoting skeletal muscle health and turnover of mitochondria
Exercise is a stress that temporarily disrupts cellular processes, but recovery leads to improved cellular function over time
Vigorous exercise can temporarily impair mitochondrial capacity immediately post-exercise or in the short term before recovery occurs
There is nuance in the effects of different types of exercise on mitochondrial health and recovery time

Insights on Interval Training

1:58:32 - 2:05:48

Interval training can provide greater improvements in cardiovascular health, body composition, and blood sugar levels compared to continuous training
Many people with cardiometabolic diseases can benefit from interval training
There is ongoing debate among experts about the level of evidence required to recommend interval training
Vigorous intensity exercise can transiently increase the risk of an event during exercise, especially in de-conditioned individuals with underlying risk factors
The absolute risk of events during exercise remains relatively low, but there is a statistically significant increase in risk with vigorous exercise
Engaging in any form of exercise, including moderate intensity, is better for health than remaining sedentary
Individuals with certain conditions like atrial fibrillation or unstable angina should avoid engaging in vigorous intensity exercise