#082 The Science of Vigorous Exercise — Should We Train Hard or Train Long? | Martin Gibala, Ph.D.
Dr. Martin Gibala, a muscle physiologist and HIIT pioneer, discusses how high-intensity interval training (HIIT) can rival or surpass moderate exercise benefits for VO2 max, brain health, and longevity, even in short durations. He also covers various protocols, muscle adaptations, and the unique advantages of vigorous exercise.
Deep Dive Analysis
23 Topic Outline
Introduction to HIIT vs. Zone 2 Training Debate
Defining High-Intensity and Interval Training
HIIT vs. Zone 2 for VO2 Max Improvement
Understanding VO2 Max and its Importance for Longevity
Training Intensity Distribution for Athletes vs. Exercisers
Measuring Maximal Heart Rate and Estimating VO2 Max
Cardiovascular Adaptations to High-Intensity Interval Training
Skeletal Muscle and Mitochondrial Adaptations from HIIT
Fat Oxidation and Mitochondrial Biogenesis
Autophagy and Exercise Intensity
Exercise Snacks and VILPA (Vigorous Intermittent Lifestyle Physical Activity)
Muscle Fiber Types and Age-Related Changes
Metabolic Effects of HIIT: Afterburn and Body Composition
Unique Brain Benefits of Vigorous Exercise (Lactate & Sheer Force)
Anti-Metastatic Effects of Vigorous Exercise
HIIT Protocols: Tabata, Wingate, Re-HIT, and Longer Intervals
Perceived Exertion vs. Objective Intensity
Interval Walking for Health Benefits
Contraindications and Risks of High-Intensity Training
Resistance Training as Aerobic Exercise and Interference Effect
Guidelines for High-Intensity Training and Sex Differences
Bone Density, Joint Issues, and Hypoxic Training
Future of HIIT Research and Training Methodologies
12 Key Concepts
High-Intensity Training (HIT)
HIT generally refers to exercise performed at a relative heart rate of about 80% of your maximum, where you are working hard but not at an all-out sprint.
High-Intensity Interval Training (HIIT)
HIIT is a type of interval training that involves alternating periods of relatively hard effort (e.g., 80% max heart rate or higher) with periods of backing off for recovery, and repeating this pattern multiple times. It's designed to create significant physiological stress in a short duration.
VO2 Max
VO2 max is the maximum rate at which the body can take up and utilize oxygen during incremental exercise. It reflects the peak integrated capacity of the cardiovascular, respiratory, blood, and skeletal muscle systems, serving as the best objective measure of cardiorespiratory fitness and a strong predictor of longevity.
Cardiac Output
Cardiac output is the maximum rate of blood and, in turn, oxygen that is pumped out of the heart every minute. It is the primary factor determining an individual's VO2 max and is influenced by both maximal heart rate and stroke volume (the amount of blood squeezed out with each beat).
Mitochondrial Biogenesis
Mitochondrial biogenesis is the process of generating new mitochondria within cells. Exercise acts as a stressor, leading to acute changes in ATP demand, calcium levels, and other compounds that signal pathways associated with the growth of new mitochondria, enhancing the muscle's energy production capacity.
Lactate Shuttle Theory
This concept describes lactate not merely as a metabolic waste product, but as a valuable fuel and signaling molecule. Lactate produced in active skeletal muscle can be released into the bloodstream and circulated to other tissues, including the heart, liver, and brain, where it can be converted back to glucose and utilized for energy.
Vigorous Intermittent Lifestyle Physical Activity (VILPA)
VILPA refers to unstructured, brief bursts of vigorous effort embedded into daily activities, such as taking the stairs quickly or walking rapidly for a short distance. Research suggests that even accumulating a few minutes of VILPA daily can lead to substantial reductions in all-cause mortality risk.
Exercise Snacks
Exercise snacks are defined as brief bouts (less than or equal to one minute) of vigorous intensity exercise that are spread throughout the day. These can be structured (e.g., jumping on a stationary bike) or incorporated into daily routines, aiming to break up sedentary periods and improve health markers.
Reduced Exertion High-Intensity Training (Re-HIT)
Re-HIT is a specific protocol of high-intensity interval training that typically involves one to two 10-20 second all-out efforts within a 10-minute total workout. The 'reduced exertion' refers to the lower perceived discomfort compared to longer sprint efforts, while still eliciting significant physiological adaptations.
Size Principle (Muscle Fiber Recruitment)
The size principle describes the progressive recruitment of muscle fibers based on intensity. Slower, smaller Type I (slow-twitch) muscle fibers are recruited first for low to moderate intensity activities, while faster, larger Type II (fast-twitch) muscle fibers are engaged for more powerful, high-intensity movements when greater force is required.
Afterburn Effect (EPOC)
The afterburn effect, or Excess Post-exercise Oxygen Consumption (EPOC), refers to a heightened rate of metabolism and calorie burning during the recovery period after exercise. While HIIT can cause a greater afterburn effect than moderate exercise, the magnitude of this difference is relatively small and dissipates quickly.
Non-Response to Exercise
Non-response to exercise occurs when individuals engage in training but do not see measurable improvements in specific metrics, such as VO2 max. For instance, approximately 40% of people may not improve their VO2 max even when meeting guidelines for moderate intensity exercise, but this can change with more vigorous activity.
15 Questions Answered
HIT generally refers to working at a relative heart rate of about 80% of maximum. HIIT adds the 'interval' component, meaning these hard efforts are interspersed with periods of backing off and repeating the pattern.
Both can improve VO2 max, but vigorous intensity exercise (like HIIT) can lead to similar or even greater improvements in VO2 max in shorter durations, and may eliminate 'non-response' seen in some individuals with moderate intensity exercise.
VO2 max is the best objective measure of cardiorespiratory fitness, and a higher fitness level is strongly associated with a reduction in all-cause mortality and the development of chronic diseases like cardiovascular disease and type 2 diabetes.
Instead of using the 220 minus age formula (which has high variability), a better way is to measure it directly by performing an all-out sprint (e.g., 400m run) or incrementally increasing intensity on a stationary bike until exhaustion, measuring heart rate at the end.
Yes, by increasing mitochondrial content and the activity of enzymes like carnitine palmatil transferase (CPT) within muscle cells, which are crucial for getting fatty acids into mitochondria to be burned.
High-intensity exercise has been shown to be a potent stimulus for autophagy in human skeletal muscle, potentially more so than an overnight fast, even without being in a fasted state during exercise.
Exercise snacks are brief (≤1 minute) vigorous exercise bouts spread throughout the day. VILPA (Vigorous Intermittent Lifestyle Physical Activity) involves embedding vigorous effort into daily activities (e.g., taking stairs quickly). Both can significantly reduce mortality risk and break up sedentary behavior.
Yes, vigorous exercise can increase lactate levels, which acts as a fuel and signaling molecule for the brain, potentially increasing BDNF and improving executive function. Increased blood flow and sheer force during intense exercise also contribute to brain health.
Vigorous exercise introduces mechanical stress (turbulence in bloodstream) that can reduce the viability of circulating tumor cells, potentially lowering the risk of cancer metastasis, with more intense exercise possibly amplifying this effect.
For very short, very hard intermittent efforts, perceived exertion scales may not accurately reflect the objective intensity, as people often rate these efforts as less unpleasant than they are physiologically demanding.
Yes, interval training comes in many forms. Even slight variations in pace during walking (interval walking) can provide greater benefits than continuous steady-state walking for older or deconditioned individuals, including those with type 2 diabetes.
While generally safe and beneficial for many, individuals with certain conditions like unstable angina or atrial fibrillation should avoid vigorous intensity exercise. Consulting a doctor for clearance is always recommended, especially for those with underlying health issues.
High-intensity resistance training (e.g., bodyweight circuits, CrossFit style) can provide both strength gains and some aerobic conditioning. While a slight 'interference effect' (blunting gains) might occur if cardio and strength are done very close together, it's generally small and negligible for most people; separating sessions by a few hours can mitigate this.
Current evidence suggests that sex-based differences in response to HIIT are likely subtle. For post-menopausal women, HIIT is generally beneficial, and concerns about chronically elevated cortisol levels are largely unfounded, as basal cortisol levels may even decrease.
High-impact activities (like running) are generally better for bone density. For individuals with joint issues like osteoarthritis, non-weight-bearing activities like vigorous interval cycling are excellent for maintaining activity and fitness without exacerbating joint pain.
52 Actionable Insights
1. Avoid Sedentary Lifestyle
Prioritize physical activity and actively avoid a sedentary lifestyle, as remaining sedentary poses the greatest risk to your health.
2. Escape Low Fitness Range
To achieve the most significant health benefits, focus on elevating your physical activity or VO2 max level out of the low fitness range.
3. Integrate Vigorous Daily Activity (VILPA)
Embed short bursts of vigorous effort (e.g., taking stairs quickly, walking briskly) into your daily routine and activities, known as Vigorous Intermittent Lifestyle Physical Activity (VILPA).
4. Daily VILPA for Longevity
Aim for at least three to four minutes of VILPA daily, as it’s associated with substantial reductions (25-30%) in all-cause mortality risks.
5. VILPA Benefits Everyone
Engage in VILPA-like activities regardless of your current exercise habits, as it provides protective health benefits for both non-exercisers and committed exercisers.
6. Break Sedentary Time with VILPA
Use VILPA or exercise snacks to simultaneously break up prolonged periods of sedentary behavior, offering a double benefit for health.
7. Exercise Based on Enjoyment
Select an exercise type you genuinely enjoy, whether vigorous intermittent or continuous moderate, as personal preference is crucial for consistent adherence.
8. Prioritize Intensity for Efficiency
To be healthy even on busy days and achieve more with less time, focus on greater intensity in your workouts, making every minute count.
9. Maximize Benefits with HIIT
Incorporate High-Intensity Interval Training (HIIT) into routines to create more physiological stress in a short period, yielding nearly exponential benefits for the time invested.
10. Short Vigorous Workouts for VO2 Max
Engage in more vigorous or high-intensity exercise for shorter periods to achieve similar improvements in VO2 max, especially if time-pressed.
11. Vigorous Exercise for VO2 Max Responders
If moderate-intensity exercise isn’t improving your VO2 max, consider engaging in more vigorous exercise, as it can eliminate non-response in some individuals.
12. Boost Cardiorespiratory Fitness
Strive for higher cardiorespiratory fitness, as elite levels are associated with a nearly 80% lower risk of mortality compared to less-fit peers.
13. Intense Exercise Boosts Fat Oxidation
Engage in high-intensity exercise, even above traditional ‘fat-burning zones,’ to improve your overall ability to oxidize fat in the long term.
14. Exercise for Mitochondrial Health
Engage in regular exercise to support the routine maintenance and turnover of cellular processes, promoting overall mitochondrial health and capacity.
15. Boost Mitochondria for Fuel Oxidation
Focus on increasing mitochondrial content in your muscles, which enhances both fat and carbohydrate oxidation capacity, achievable through various methods including short, intensive exercise.
16. Exercise Lowers Blood Sugar
Engage in exercise to increase glucose transport capacity on muscle cell membranes, which helps move more glucose into muscles, lowering chronically high blood sugar levels.
17. Exercise Reduces Diabetic Medication
If you have diabetes, starting an exercise program can improve muscle fitness and glucose transport, potentially allowing for a reduction in diabetic medication.
18. Vigorous Exercise for Insulin Sensitivity
Consider incorporating vigorous, high-intensity exercise, as some evidence suggests it can lead to greater improvements in markers of insulin sensitivity.
19. Venture Beyond Comfort Zone
Engage in vigorous exercise and push past your comfort zone to unlock unique and perhaps unrecognized benefits that are otherwise elusive.
20. Vigorous Exercise for Cognition
Engage in vigorous exercise that pushes past the lactate threshold to potentially achieve unique cognitive enhancement.
21. Elevate Lactate for Brain Health
During high-intensity workouts, aim to increase your lactate levels, as this is correlated with improved executive function and may offer benefits for neurodegenerative disease prevention.
22. Intense Exercise for Blood Flow
Engage in more intense exercise to increase blood flow and sheer force, which offers dose-dependent benefits for brain health and may disrupt circulating tumor cells.
23. Vigorous Exercise & Cancer Risk
Incorporate vigorous exercise into your routine, as it may reduce the risk of cancer metastasis by introducing mechanical stress to cancer cells.
24. Strength Train for Fast-Twitch Fibers
Engage in strength training to maintain the viability of fast-twitch muscle fibers, which are progressively lost with age and are important for power and preventing falls.
25. HIIT for Body Composition
Incorporate High-Intensity Interval Training (HIIT) to support weight management and improve body composition, potentially leading to a slight loss of fat mass and an increase in lean mass.
26. Utilize HIIT’s Afterburn Effect
Leverage the ‘afterburn effect’ (heightened metabolism post-HIIT) to burn more calories in recovery, as these small differences can accumulate over time.
27. Daily Exercise Snacks
Engage in ’exercise snacks’ – less than or equal to one minute of vigorous intensity exercise (e.g., jumping on a stationary bike, air squats) – at least four or five times a day.
28. Target 80% Max Heart Rate
For high-intensity exercise, aim for a relative heart rate of about 80% of your maximum heart rate.
29. Measure Max Heart Rate Directly
To accurately determine your maximal heart rate, either run a 400-meter loop as hard as possible or progressively increase intensity on a stationary bike until exhaustion, measuring your heart rate directly.
30. Estimate VO2 Max with Calculator
Utilize the ‘World Fitness Calculator’ online to get a reasonable estimate of your VO2 max and track changes over time, even if the precise number isn’t 100% accurate.
31. Submaximal Tests for VO2 Max
For a more personalized VO2 max estimate than an online questionnaire, perform submaximal exercise tests like a shuttle run or beep test, which provide direct data on your physical capacity.
32. Beginner Interval Walking
If new to exercise, start interval training by walking fast for a few light posts, then backing off, and repeating this pattern without worrying about specific heart rate percentages.
33. Vary Walking Pace with Intervals
Enhance the benefits of walking by adding gentle intervals, slightly varying your pace to create hills and valleys of effort, even if not full sprint training.
34. Start Intervals Beyond Comfort Zone
Begin interval training by pushing slightly beyond your comfort zone for a short period (e.g., walking faster for two light posts), then recovering, and repeating.
35. Vary Your Exercise Regimen
Adopt a varied training approach, similar to diversifying investments, by incorporating different types of exercise, including short, sharp, and hard efforts, for overall fitness.
36. Add Longer Intervals for VO2 Max
If primarily doing short sprint-style intervals (like Tabata), consider incorporating longer intervals (3-5 minutes) at the highest sustainable intensity to maximize VO2 max gains.
37. Maximize VO2 Max with 3-5 Min Intervals
To maximize gains in VO2 max, perform three to five minute repeats at the highest sustainable intensity.
38. 1-Minute On/Off Intervals for VO2 Max
Incorporate 1-minute on, 1-minute off intervals, repeated 5 to 10 times, for significant improvements in VO2 max, with 5 repeats offering substantial benefits.
39. Vary Interval & Recovery Periods
To optimize training and challenge your body in different ways, vary the duration of your high-intensity intervals and recovery periods.
40. Perform the ‘One Minute Workout’
Engage in the ‘One Minute Workout’ protocol: three 20-second vigorous intervals with recovery in between, plus a 5-minute total warm-up and cool-down, for a 10-minute total workout.
41. Try Reduced Exertion HIIT (re-HIT)
Engage in re-HIT, a 10-minute workout involving one to two 10-20 second very high-power efforts, which feels less uncomfortable than longer sprints due to shorter duration.
42. 4-Second All-Out Sprints
Engage in 4-second all-out efforts followed by 12 seconds of recovery, repeated multiple times, as even deconditioned individuals can achieve high power outputs with this method.
43. High-Intensity Bodyweight Training
Incorporate high-intensity bodyweight exercises (e.g., calisthenics, air squats, burpees) as a form of interval resistance training to gain both strength and aerobic conditioning efficiently.
44. Combine Functional & Aerobic Training
For a balanced approach, combine high-intensity functional or bodyweight training with aerobic interval training (e.g., on a bike or elliptical) across your weekly sessions.
45. Separate Training for Maximal Gains
To maximize gains from both aerobic and resistance training, ideally separate these sessions by a few hours rather than performing them back-to-back.
46. Interval Training for Chronic Conditions
Consider interval training even if you have cardiometabolic diseases, heart disease, type 2 diabetes, or are older, as many individuals can safely perform and benefit from it.
47. HIIT over Inactivity, Moderate First
If the choice is between HIIT and no exercise, choose HIIT; if deconditioned or older, start with moderate exercise as preconditioning before moving to more intense interval training.
48. Avoid Vigorous Exercise with Angina
Do not engage in vigorous intensity exercise if you have certain conditions like unstable angina or atrial fibrillation; consult a doctor for clearance.
49. Low-Impact Exercise for Joint Issues
If you have joint injuries or osteoarthritis, remain active by choosing less weight-bearing activities like cycling, which allows for vigorous exercise without damaging the joints.
50. HIIT Doesn’t Cause Chronic High Cortisol
Do not worry about high-intensity interval training causing chronically elevated cortisol levels, as evidence suggests basal cortisol levels may even stay lower in those who practice it.
51. Be Mindful of Extreme Exercise Risk
If you are an extreme exerciser (very high intensity, very high volume over a lifetime), be mindful that this may carry some increased cardiovascular risk.
52. Explore Blood Flow Restriction Training
Consider exploring blood flow restricted training, as there is interesting ongoing work suggesting potential benefits, especially for those with joint issues.
9 Key Quotes
High-intensity interval training, in many ways, is about doing more with less.
Host
Some studies show that there is no upper limit to the benefit of cardiorespiratory fitness on mortality.
Host
The greatest gains are with the smaller changes in fitness, right? So we talk, we look at, you know, people who are, have low, moderate and high physical activity levels or low, moderate and high VO2 max levels, the greatest bang for your buck is just getting out of that low range.
Dr. Martin Gibala
The longest 30 seconds of your life.
Dr. Martin Gibala
We like to think of exercise as this panacea and it's, it's not, it's not a vaccine against, uh, ill health outcomes.
Dr. Martin Gibala
The greatest risk to your health is just remain sedentary is absolutely true.
Dr. Martin Gibala
If your choice is between doing hit and doing nothing, do hit.
Dr. Paul Thompson (quoted by Dr. Martin Gibala)
All interval training is not created equal.
Dr. Martin Gibala
The poison is in the dose.
Dr. Martin Gibala
8 Protocols
Direct Maximal Heart Rate Measurement
Dr. Martin Gibala- Go to a local high school or running track and run a 400-meter or 400-yard loop one time around as hard as you can.
- Alternatively, on a stationary ergometer (bike), ride at incrementally higher intensities, increasing the wattage by 10 or 20 watts every minute until you can no longer continue.
- Measure your heart rate at the end of the all-out effort using palpation, a chest strap, or a monitor.
VO2 Max Estimation (World Fitness Calculator)
Dr. Martin Gibala- Access the World Fitness Calculator online (e.g., from Norwegian Technological University).
- Answer a few questions about your age, sex, typical activity levels, resting heart rate, maximal heart rate, BMI, and waist circumference.
- The calculator will provide a reasonable estimate of your VO2 max.
- Use this estimate as a baseline to track changes over time after engaging in a training program.
General Interval Training (Beginner)
Dr. Martin Gibala- Choose an activity like walking around the block.
- For a short period (e.g., the next two light posts), pick up your pace to feel a bit more out of breath and unable to talk comfortably.
- Back off to a comfortable pace.
- Repeat this alternating pattern a few times.
One-Minute Workout Protocol (Sprint Interval Training)
Dr. Martin Gibala- Perform a 5-minute warm-up.
- Engage in three 20-second all-out sprint intervals.
- Include recovery periods between the intervals.
- Finish with a cool-down, making the total workout duration 10 minutes.
VO2 Max Optimization (Longer Intervals)
Dr. Martin Gibala- Perform 3-5 minute intervals at the highest sustainable intensity you can maintain for that duration.
- Repeat these longer intervals 4 times within a workout session.
- Include appropriate warm-up, cool-down, and recovery periods between intervals.
Minute On/Minute Off Interval Protocol
Dr. Martin Gibala- Perform 1-minute all-out efforts.
- Follow each 1-minute effort with 1 minute of recovery.
- Repeat this sequence 5 to 10 times.
Exercise Snacks Protocol
Dr. Martin Gibala- Engage in brief bouts of vigorous intensity exercise (e.g., jumping on a stationary bike, performing air squats or burpees).
- Ensure each bout lasts less than or equal to one minute.
- Spread these bouts throughout the day, aiming for at least 4-5 times daily.
Interval Walking
Dr. Martin Gibala- Alternate periods of walking at a faster, more vigorous pace (e.g., up a gentle hill or just picking up speed).
- Follow the vigorous periods with periods of slower, recovery walking.
- This approach can be beneficial even for individuals with lower fitness levels or type 2 diabetes.