Vigorous Exercise: Longvity and Brain Benefits

Today we’re diving deep into the science and practicality of incorporating vigorous intensity exercise into our lives. It’s not just about living longer; it’s about enriching the quality of life at essentially every stage and also influencing brain function.

During vigorous exercise, our muscles essentially become mini biochemical labs synthesizing compounds like lactate and myokines. These aren’t just muscle-bound; they get into circulation, travel to far-off tissues, and signal to them, providing a variety of benefits including the synthesis of elements like brain-derived neurotrophic factor (BDNF), crucial for brain health and neuronal health. They also potentially initiate anti-cancer mechanisms.

Not only are muscles little chemical producing factories, but they also act like sponges to soak up compounds that can be harmful to the brain, improving mental health and reducing neurodegenerative disease risk.

We’re going to dive deep into the realm of VO2max optimization. VO2max is not just a measure of cardiorespiratory fitness; it’s directly linked to longevity. Essentially, the higher your VO2max, the longer you’re likely to live, and there doesn’t seem to be an upper limit to the life-extending benefits of enhanced cardiorespiratory fitness, at least within your genetic potential.

We’ll discuss how to calibrate high-intensity efforts with zone 2 training methodologies for improving VO2max, with a focus on the Norwegian 4×4 protocol. We’ll even touch on straightforward tactics like assessing VO2max with the 12-minute run test.

Equally important, we’ll explore the processes of mitophagy and mitochondrial biogenesis – cornerstones for cellular rejuvenation, essentially reversing the aging process on a cellular level.

There are a lot of questions to answer: What is vigorous exercise? What is high intensity exercise? What about zone 2 training? Let’s start by covering what vigorous exercise is and isn’t.

Zone 2 training is also sometimes known as aerobic base training. It primarily targets aerobic energy systems and can be sustained for longer durations – we’re talking an hour or more. Some experts define this type of training to be around 70-80% of maximum heart rate, possibly lower for less fit people. It’s also defined by the “talk test” – you should be able to talk comfortably but not sing.

Zone two training involves exercising at a moderate intensity. It’s a steady-state type of lactate threshold training. Lactate threshold refers to the point at which the body begins to produce lactate faster than it can clear it away. Keep in mind there’s individual variation in determining lactate threshold because people can have different baseline lactate levels and rates of lactate production and clearance, even at the same relative exercise intensity. For example, trained athletes might have a higher lactate threshold in terms of both exercise intensity and lactate concentration compared to untrained individuals. Genetics also play a role.

Now let’s talk about vigorous exercise. Generally speaking, vigorous exercise represents a level of exertion where exercise goes beyond the lactate threshold, which means lactate begins to accumulate in the muscles more rapidly.

There are various intensities within vigorous exercise. A level of intensity referred to as the maximal steady state threshold, sometimes called zone 3, is above the lactate threshold. It’s challenging to hold a conversation and it’s difficult to maintain this level of exercise for longer than 20-30 minutes. This level of intensity is somewhere between 80-85% max heart rate.

However, vigorous exercise also includes exercising at intensities higher than this, so higher intensity training where there’s significant lactate accumulation and you’re close to your anaerobic threshold. This is a level of intensity around 85-95% max heart rate and it’s difficult to maintain for longer than a few minutes. Sometimes this type of training intensity is called zone four training.

Then there’s the all-out, near maximal intensity. This is sometimes called zone five training. These are shorter intervals, generally hard to maintain for longer than 1 minute.

So when we’re talking about high intensity interval training (HIIT), it involves alternating between periods of high-intensity vigorous exercise and periods of lower intensity rest, depending on the HIIT protocol. These can include intervals ranging from zone three to zone five, followed by recovery periods.

The idea that HIIT is only anaerobic is a misconception. While high intensity interval training exercise does rely more heavily on anaerobic energy systems, it still requires significant aerobic metabolism, so HIIT can improve both aerobic and anaerobic fitness. In my opinion, getting your heart rate up to at least 80% max, so that’s at least 80%, is a really good place to be if you are targeting brain benefits, and we’ll dive more into that soon.

I want to start by talking about cardiorespiratory fitness, healthspan, and longevity. VO2max is a measure of maximal oxygen uptake which reflects an individual’s ability to utilize oxygen during exercise. It’s considered one of the best indicators of cardiorespiratory fitness, and it’s associated with improved healthspan and increased lifespan.

Higher cardiorespiratory levels as measured by VO2max have been consistently linked to a reduced risk of mortality and longer lifespan. In one study involving only men, for every 10 unit increase in VO2max (10 ml/kg/min), there was a 70-77% lower risk of death from cancer and an 11% lower all-cause mortality (dying from non-accidental causes).

Another study published in JAMA in 2018 found that there was no apparent upper limit to the benefit of cardiorespiratory fitness on mortality within normal ranges of human life expectancy. In fact, the study reported that elite performers (the top 2.3% on the fitness test) had an 80% reduction in mortality risk compared to the lowest performers (bottom 25% on the fitness test). When comparing the elite performers to the high performers (between the top 25% and top 2.3%), the elite performers had a 20% mortality risk decline.

But going back to what I said earlier about moving out of the low fitness group, that alone gives huge advantages for life expectancy. People in the low fitness group had a five-fold higher risk of death than the elite performers. But what is also interesting is that the risk of dying due to low fitness was similar or even bigger than risks associated with having heart disease, smoking, or diabetes. So being more fit is really good for your health at every level, and there’s always room for improvement.

The question is, well how can we improve our VO2max? Lots of different training protocols like zone 2 training and high intensity interval training improve cardiorespiratory fitness and can increase VO2max.

HIIT has been shown to significantly improve VO2max even with shorter training durations because HIIT recruits both aerobic and anaerobic energy systems, increasing workout intensity and cardiovascular stress, leading to greater adaptations. But this is important – there are individuals who engage in steady state zone 2 training that do not experience significant improvements in VO2max. In fact, research has shown that approximately 40% of people do not see measurable VO2max increase even after engaging in moderate intensity exercise for several months. But when these “non-responders” incorporated more vigorous intensity exercise like HIIT, they started to see improvements in VO2max.

This suggests that adding higher intensity exercise to an exercise routine can eliminate non-response and lead to greater cardiorespiratory fitness benefits. The reason for non-response to moderate intensity exercise is not completely understood, but the addition of vigorous intensity exercise provides a stronger stimulus for adaptations leading to increased cardiorespiratory fitness. So I think these findings highlight the importance of incorporating vigorous intensity exercise, like HIIT, for improvements in VO2max.

For individuals pressed for time who can’t dedicate hours per week to steady state training, shorter HIIT sessions can still drive significant fitness gains. As you think about how much time to dedicate to each type of exercise for VO2max and other benefits, the answer depends on individual goals, enjoyment, commitment level, etc.

For endurance athletes, it’s easy – they already dedicate hours per week to zone 2 training, with about 20% going to shorter vigorous sessions, commonly known as the 80/20 rule. But it’s wrong to apply this rule to casual exercisers doing under 10 hours per week. For committed exercisers (3-5 days a week of training), I’d say half that time should be vigorous intensity for VO2max and brain benefits. Casual exercisers (2-3 days a week) should spend over half their sessions doing vigorous training for rapid fitness gains.

There are variety of VO2max training protocols. Key principles include longer intervals like 2-5 minutes at max sustainable intensity with rest/recovery between, such as:

3-5 minute repeats at highest intensity you can maintain
Popular 4 x 4 minute Norwegian protocol: 4 minutes at 85-95% max HR, with 3 minutes light active recovery between intervals, repeated 4 times
1 minute on/1 minute off intervals for 10-25 minutes at max 1-minute effort

To measure VO2max improvements without specialized lab equipment, validated tests like the 12-minute run/walk Cooper test can be used. Using total distance covered, VO2max can be estimated with formulas. Some wearables also estimate VO2max during exercise using heart rate and motion data. The 12-minute test is useful for assessing training program efficacy over time.

I want to shift gears for a minute and talk about unique longevity benefits of vigorous exercise related to changes in heart structure. As we age, the heart undergoes inevitable changes – it gets smaller, stiffer, impacting efficiency and exercise capacity while elevating cardiac risk. But consistent vigorous aerobic exercise can combat these effects.

A landmark study showed that two years of vigorous exercise in 50-year-olds reversed aging of their hearts by ~20 years, making them look more like a 30-year-old! By the end of the 2-year training protocol, participants were exercising 5-6 hours per week with a large portion being vigorous intensity. They also did the Norwegian 4×4 VO2max interval training once weekly. Reversing heart aging by 20 years with exercise training is astonishing.

Let’s shift gears again and talk about metabolic adaptations where vigorous exercise really shines. HIIT more efficiently and potently improves glucose control and insulin sensitivity than moderate continuous workouts. Both can enhance muscle adaptations and glucose regulation, but HIIT has more robust, rapid effects without demanding longer durations.

Research has found HIIT enhances muscle’s ability to take up glucose and improves glucose transport capacity. During HIIT, the rapid energy demand relies on both aerobic and anaerobic metabolism. The anaerobic pathway and lactate production stimulates glucose transporter expression and activity on muscle cells, allowing more efficient glucose uptake. This is likely due to intense metabolic stress of HIIT.

Several studies show HIIT improves glucose uptake, insulin sensitivity, and type 2 diabetes risk reduction compared to moderate continuous exercise which also improves glucose transport, just less robustly and requiring longer durations.

Other metabolic adaptations relate to mitochondria, which produce energy as ATP, vital for muscles and organs like the brain and heart. As we age, mitochondria become less efficient at producing energy, but increasing mitochondrial volume/density – known as mitochondrial biogenesis – helps overcome this. Exercise, especially vigorous, powerfully stimulates mitochondrial biogenesis due to metabolic stress and lactate production.

Lactate acts as a signaling molecule to increase PGC-1α, a major regulator of mitochondrial biogenesis. During vigorous exercise, accumulating lactate in muscles gets shuttled into mitochondria to produce energy. Exercise increases mitochondrial numbers per cell, allowing more lactate usage. Both HIIT and zone 2 training increase mitochondrial content and fat oxidation capacity by increasing activity of enzymes involved in fat metabolism like CPT.

Another way exercise improves mitochondrial health is via mitophagy – the selective removal of damaged, dysfunctional mitochondria for quality control and cellular health. When you stress mitochondria via exercise, the body triggers elimination of damaged ones and replacement with new, healthy mitochondria (biogenesis). Limited human research suggests vigorous aerobic exercise in particular enhances mitophagy. It’s likely both HIIT and moderate exercise stimulate this process to varying degrees.

For skeletal muscle adaptations like mitochondrial biogenesis and fat oxidation, the choice between HIIT and zone 2 depends on goals, time availability and personal preferences. HIIT offers time efficiency and rapid improvements with shorter durations. Zone 2 can yield similar mitochondrial and performance benefits with greater training volume/duration. Incorporating both is ideal for a balanced approach.

For committed exercisers doing 2-5 hours of weekly training, I suggest half being vigorous intensity not just for VO2max but brain benefits as well. Let’s discuss why high intensity exercise uniquely benefits brain health.

Animal studies show HIIT’s neuroprotective and cognitive benefits stem largely from lactate production and related metabolic stress. During intense exercise, lactate shuttles from muscle into circulation, crosses the blood-brain barrier, and acts as a signaling molecule, triggering adaptations.

Neurons use lactate as a preferred energy source since less energy is required compared to glucose. In fact, support cells in the brain called astrocytes constantly produce lactate through glycolysis for neuronal use. Studies reveal lactate generated during exercise directly fuels and enhances brain activity.

Using lactate spares glucose for other processes like glutathione production – a powerful brain antioxidant. This holds relevance for brain aging, traumatic brain injury recovery, and more.

Further, lactate signals increases in plasticity factors like BDNF and new blood vessel growth factor VEGF at the blood-brain barrier, protecting its integrity. Breakdown of the blood-brain barrier increasingly appears to be an early sign of dementia. Through lactate signaling, vigorous exercise uniquely supports multiple aspects of brain health.

Beyond lactate, exercise intensity also impacts muscle release of compounds called myokines that signal the body’s physically active state. Released myokines have anti-inflammatory, anti-cancer, metabolism, and brain benefits dependent on intensity and duration. The greater the exercise intensity and duration, the greater the myokine release.

Also, muscles act as sponges to remove compounds like kynurenine to protect the brain. Physical activity regulates levels of enzymes on muscle cells that soak up harmful metabolites like this for conversion to innocuous byproducts instead of neurotoxic compounds. Here too, intensity and duration impact efficacy.

I want to shift gears and talk about short bursts of HIIT called “exercise snacks” incorporated throughout the day for metabolism and health benefits. Research shows timing these vigorous bursts shortly before/after meals offers blood sugar regulating effects by rapidly increasing glucose transporters on muscle to enhance uptake. This also lowers post-meal blood glucose excursions and reduces insulin demand. Exercise snacks can benefit diabetes management.

Beyond direct metabolic impacts, exercise snacks combat prolonged sedentary time. Too much sitting elevates risk of premature death and certain cancers, even among active people. By breaking up sedentary periods, exercise snacks mitigate these risks as well.

Cognitive benefits also arise from exercise snacks acutely increasing blood flow to the brain and enhancing motivation/mood. While limited evidence exists currently, initial findings indicate cognitive improvements, making them enticing for desk workers and students.

As a final note, incorporating similar concepts of vigilant lifestyle physical activity (VILPA) – like sprinting up stairs – into daily routines for just minutes per day substantially reduces early mortality and conditions like cardiovascular disease and cancer for all groups studied, including non-exercisers. This re-emphasizes the potent benefits of accumulating small vigorous activity bursts through the day.

In summary, vigorous exercise uniquely optimizes cardiorespiratory fitness, metabolism, muscular health, and brain function through signaling molecules like lactate and myokines. It opportunistically stresses physiology to adapt. HIIT elicits rapid, robust effects, while steady zone 2 training accrues comparable benefits with greater duration. Incorporating vigorous efforts via structured HIIT or lifestyle physical activity snacks/VILPA provides efficient anti-aging effects.

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