Latest / Hardiness with Dr Paul Taylor / Science just decided the best type of exercise training - and it's compelling: Wisdom Wednesdays

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Science just decided the best type of exercise training - and it's compelling: Wisdom Wednesdays · Hardiness with Dr Paul Taylor

• 0:05
  Speaker 1: Hey everybody, welcome to another edition of Wisdom Wednesdays. Now
• 0:09
  Speaker 1: imagine I offered you an exercise choice. One option is
• 0:13
  Speaker 1: 90 minutes on an exercise bike at a pace that
• 0:16
  Speaker 1: you can comfortably chat to the person next to you.
• 0:19
  Speaker 1: Option two is about 20 minutes on the same bike
• 0:22
  Speaker 1: of which only three minutes would be real exercise, the
• 0:27
  Speaker 1: kind of unpleasant stuff where you briefly question your choices
• 0:31
  Speaker 1: in life. Now, if I told you that the 20
• 0:35
  Speaker 1: minute option would build about the same amount of new
• 0:38
  Speaker 1: mitochondria in your muscles as the 90 minute one, and
• 0:42
  Speaker 1: would send you a far bigger chemical message around your body,
• 0:46
  Speaker 1: I suspect that most of you would take the short,
• 0:49
  Speaker 1: uncomfortable option, particularly if you've got a job, a family,
• 0:52
  Speaker 1: a commute, and a busy calendar. This is the result
• 0:57
  Speaker 1: of one of the largest analyses of exercise adaptation ever
• 1:01
  Speaker 1: carried out.
• 1:02
  Speaker 2: It's a brilliant paper.
• 1:03
  Speaker 1: That looked at almost everything you'd wanna know about what
• 1:08
  Speaker 1: happens inside your muscles when you train. So we're going
• 1:12
  Speaker 1: to do a deep dive into it because some of
• 1:15
  Speaker 1: the findings beyond the headlines are every bit as interesting.
• 1:20
  Speaker 1: So you may remember from school, or if you've listened
• 1:23
  Speaker 1: to this podcast, that the mitochondria are the powerhouses of
• 1:27
  Speaker 1: the cells, amongst other things. They're where most of your
• 1:31
  Speaker 1: energy in the form of ATP gets made. And how
• 1:34
  Speaker 1: much mitochondria you carry in your muscles is tied not
• 1:38
  Speaker 1: just to your fitness, but to how well you handle
• 1:41
  Speaker 1: blood sugar, how well you age, and your risk of
• 1:44
  Speaker 1: a long list of chronic diseases. Now, another thing that's
• 1:48
  Speaker 1: important in exercise adaptation are your capillaries, the tiny blood
• 1:52
  Speaker 1: vessels that deliver oxygen and fuel to your mitochondria, because
• 1:57
  Speaker 1: there's not much point in having a big engine if
• 1:59
  Speaker 1: the fuel line is pretty crappy. Now, for years, exercise
• 2:04
  Speaker 1: scientists have been debating what grows mitochondria best.
• 2:08
  Speaker 2: One camp says it's volume.
• 2:10
  Speaker 1: Of exercise, meaning the more hours you put in, the
• 2:12
  Speaker 1: more you get out of it in terms of mitochondria.
• 2:15
  Speaker 1: The other says it's intensity, that they say how hard
• 2:20
  Speaker 1: you go matters more than how long. And it's even
• 2:23
  Speaker 1: got a name in the Journal of Physiology. It's called
• 2:25
  Speaker 1: the mitochondrial content contest. So let's dig into this study.
• 2:31
  Speaker 1: A team from Norway and Denmark recently published a systematic review.
• 2:35
  Speaker 2: And meta-analysis in the journal Sports Medicine.
• 2:38
  Speaker 1: They pulled together around 50 years of research. 353 studies
• 2:44
  Speaker 1: on mitochondria and another 131 on capillaries covering close to
• 2:49
  Speaker 1: 6,000 people of all ages, fitness levels and health conditions.
• 2:54
  Speaker 1: And every one of those studies involved taking muscle biopsies
• 2:59
  Speaker 1: before and after a training program. So this is a very,
• 3:03
  Speaker 1: very interesting and comprehensive study. And they sorted the training
• 3:07
  Speaker 1: into three different buckets. Endurance training is a classic steady
• 3:12
  Speaker 1: state cardio jog or ride where you can hold a conversation.
• 3:15
  Speaker 1: High intensity training is harder intervals or hard continuous work
• 3:20
  Speaker 1: above a lactate threshold. And then there's sprint interval training
• 3:24
  Speaker 1: or SIT, which is repeated all out or near all
• 3:28
  Speaker 1: out efforts. Lasting of between kind of 5 and 30
• 3:35
  Speaker 1: plus seconds, but typically around 20 to 30, with plenty
• 3:39
  Speaker 1: of recovery, low level in between them, right? They then
• 3:43
  Speaker 1: measured a ton of stuff. They looked at five different
• 3:47
  Speaker 1: markers of mitochondrial content, including the volume of muscle fiber
• 3:52
  Speaker 1: taken up by mitochondria under an electron microscope, and.
• 3:55
  Speaker 2: The activity of four key enzymes.
• 3:58
  Speaker 1: They also looked at capillaries in two ways, the number
• 4:01
  Speaker 1: per muscle fiber and the number per square millimeter of muscle.
• 4:06
  Speaker 1: They looked at muscle fiber size, the proportion of slow
• 4:10
  Speaker 1: twitch and fast twitch fibers, and whole body aerobic fitness
• 4:14
  Speaker 1: measured at VO2 max. And they also checked whether age, sex, menopause, disease,
• 4:21
  Speaker 1: how often people trained, how long the program ran, how
• 4:25
  Speaker 1: fit they were to start with, and even how much
• 4:28
  Speaker 1: muscle was involved and whether that changed any of the answers.
• 4:33
  Speaker 1: So this has got to be one of, if not
• 4:36
  Speaker 1: the most comprehensive.
• 4:38
  Speaker 2: Exercise papers ever published.
• 4:41
  Speaker 1: Firstly, let's discuss what they found about the changes in
• 4:44
  Speaker 1: the mitochondria. When they adjusted for things like the number
• 4:48
  Speaker 1: of sessions and starting fitness, all three of the different
• 4:52
  Speaker 1: exercise approaches grew mitochondria by roughly the same amount. It
• 4:56
  Speaker 1: was about 23% increase for endurance training, 27% for both
• 5:01
  Speaker 1: high intensity and the sprint interval training.
• 5:04
  Speaker 2: And statistically, there was no clear winner.
• 5:06
  Speaker 1: So if you love your long, slow Sunday ride, then
• 5:09
  Speaker 1: keep it because it is effective. But here's the part
• 5:12
  Speaker 1: that matters if you're a busy person. Across those studies,
• 5:16
  Speaker 1: the endurance groups put in an average of about 39
• 5:20
  Speaker 1: hours of training. The high intensity groups around 23 hours
• 5:26
  Speaker 1: and the sprint groups around eight hours. And it's actually
• 5:30
  Speaker 1: a bit harsh on the sprint crowd. Because the researchers
• 5:34
  Speaker 1: actually counted their warm-ups, their cool-downs and recovery periods as
• 5:39
  Speaker 1: training times for the sprinters. And anybody who's done sprint
• 5:42
  Speaker 1: interval training knows it's not really training whenever you're doing
• 5:45
  Speaker 1: those parts of it.
• 5:47
  Speaker 2: Now, when you work it out per hour, sprint.
• 5:50
  Speaker 1: Intervals were around 2.3 times more efficient than high-intensity training
• 5:55
  Speaker 1: and nearly four times more efficient than steady endurance training
• 5:59
  Speaker 1: at building mitochondria. High intensity training in turn was about
• 6:04
  Speaker 1: 1.7 times more efficient than steady endurance work. So there's
• 6:09
  Speaker 1: a clear staircase where the harder you go, the more
• 6:14
  Speaker 1: bang for your buck you get for every minute of effort. Now,
• 6:18
  Speaker 1: the timing was actually revealing too. Sprint training got off
• 6:21
  Speaker 1: the mark fastest. with mitochondrial content already up by about 20%
• 6:28
  Speaker 1: after just two weeks, compared to about 14% for endurance training. However,
• 6:34
  Speaker 1: the sprint groups they intended to level off, whereas endurance
• 6:38
  Speaker 1: and high intensity training kept climbing steadily between six and
• 6:42
  Speaker 1: 10 weeks and beyond. Now, the author's summary is that
• 6:45
  Speaker 1: high intensity can make up for low volume in the
• 6:48
  Speaker 1: short term, But if you want your gains to keep
• 6:51
  Speaker 1: coming over months, then you need to add a bit
• 6:54
  Speaker 1: of volume or keep progressing. Now, frequency mattered as well,
• 6:58
  Speaker 1: with six sessions a week beating four and four beating two.
• 7:02
  Speaker 1: And starting fitness actually made a big difference. People who
• 7:06
  Speaker 1: started untrained gained the most, which is not surprising because
• 7:10
  Speaker 1: the window of adaptation is much bigger. and well-trained people
• 7:14
  Speaker 1: gained only about 7%. But here's a really important part
• 7:19
  Speaker 1: of it. When you looked at the gains per hour,
• 7:22
  Speaker 1: well-trained people saw no measurable improvement from either endurance or
• 7:27
  Speaker 1: high-intensity training, and sprint intervals were the only thing that
• 7:31
  Speaker 1: moved the needle for them. So if you're already fit
• 7:34
  Speaker 1: and short on time, definitely prioritize the sprint interval training. Now,
• 7:39
  Speaker 1: the researchers also compared exercises that use a lot of muscle,
• 7:43
  Speaker 1: like cycling or running, with exercise that isolates a small amount,
• 7:48
  Speaker 1: like one-legged cycling or knee extensions that they often do
• 7:52
  Speaker 1: to just dive in pretty deeply into muscle changes. Now,
• 7:56
  Speaker 1: mitochondrial growth was the same in both. That tells us
• 8:00
  Speaker 1: that the main trigger for is the metabolic stress inside
• 8:05
  Speaker 1: the working muscle itself, rather than how hard your heart
• 8:09
  Speaker 1: and lungs are working, which is a nice clue as
• 8:13
  Speaker 1: to why the short, brutal efforts work so well. Now,
• 8:17
  Speaker 1: when we talk about capillaries, that was a slightly different story.
• 8:21
  Speaker 1: Capillaries per muscle fiber increased about 15% with endurance training, 13%
• 8:27
  Speaker 1: with high intensity, and 10% with sprints. And those differences
• 8:32
  Speaker 1: weren't statistically significant. So no meaningful difference there. Capillary density,
• 8:37
  Speaker 1: which is the number per square millimeter of muscle, did
• 8:41
  Speaker 1: favor endurance training at 13% versus 7% for high-intensity work,
• 8:46
  Speaker 1: with sprint training not producing any clear change in that.
• 8:50
  Speaker 2: But that's largely.
• 8:52
  Speaker 1: an artifact of the measurement because harder training grows the
• 8:57
  Speaker 1: muscle fibers more. So the same number of new capillaries
• 9:00
  Speaker 1: just got spread over a bigger area. Now, what actually
• 9:04
  Speaker 1: surprised me was how quickly it all happened. Most of
• 9:07
  Speaker 1: the capillary growth came in the first four weeks and
• 9:11
  Speaker 1: then it tended to stall. And it only showed up
• 9:14
  Speaker 1: in people who were untrained or moderately trained. Now, the
• 9:18
  Speaker 1: authors think that the new capillaries that are created, they
• 9:22
  Speaker 1: intend to reduce the stress on the vessel walls, which
• 9:27
  Speaker 1: actually removes the very signal that tells the body to
• 9:30
  Speaker 1: grow them in the first place, right? So there's a
• 9:33
  Speaker 1: stressor effect that then tends to settle down. Now, let's
• 9:37
  Speaker 1: talk about muscle size and fiber type. Now, you don't
• 9:41
  Speaker 1: normally think of cardio as something that builds muscle, but
• 9:44
  Speaker 1: it does at least at the level of individual fibers.
• 9:48
  Speaker 1: They found that fiber size grew by about 6.5% with
• 9:52
  Speaker 1: endurance training, 9% with high intensity training, and 12% with sprints. Now,
• 9:58
  Speaker 1: the sprint figure was a statistically significant difference because there
• 10:02
  Speaker 1: was only a handful of studies. It wasn't powered properly,
• 10:05
  Speaker 1: as we say, but the direction is what you'd expect
• 10:08
  Speaker 1: since sprinting recruits your big, fast-twitch fibers.
• 10:12
  Speaker 2: And again, most of.
• 10:13
  Speaker 1: The growth came within the first four to eight weeks.
• 10:16
  Speaker 1: And it was seen in untrained and moderately trained people,
• 10:20
  Speaker 1: but not in well-trained, which is not a surprise, really. Now,
• 10:24
  Speaker 1: the fiber type results are where it gets interesting for
• 10:28
  Speaker 1: an old debate. Now, overall, training didn't significantly change.
• 10:34
  Speaker 2: The proportion of slow twitch or type 1 fibers.
• 10:37
  Speaker 1: But endurance and sprint training pulled in opposite directions, with
• 10:41
  Speaker 1: endurance training nudging people slightly towards more slow twitch fibers,
• 10:47
  Speaker 1: and sprint training nudging them towards fast twitch. And that
• 10:51
  Speaker 1: difference between the two was statistically significant, right? So fast
• 10:54
  Speaker 1: twitch fibers, they're the ones we tend to lose first
• 10:58
  Speaker 1: as we age, and they're the ones that save you
• 11:02
  Speaker 1: when you trip on the stairs and you can recover
• 11:05
  Speaker 1: your feet quickly. So for those of us north of 50,
• 11:08
  Speaker 1: a training style that keeps them in play is definitely
• 11:12
  Speaker 1: a good thing. And we know from other studies that
• 11:15
  Speaker 1: muscular power, which is about fast twitch fibers, is more
• 11:19
  Speaker 1: important than muscular strength or endurance when it comes to longevity.
• 11:24
  Speaker 2: Now on to VO2 max.
• 11:26
  Speaker 1: So VO2 max, which is your maximum capacity to use
• 11:29
  Speaker 1: oxygen and is one of the strongest predictors of how
• 11:32
  Speaker 1: long you'll live, that.
• 11:34
  Speaker 2: Improved with everything.
• 11:35
  Speaker 1: By about 10% with endurance training, 12% with high-intensity training,
• 11:40
  Speaker 1: and 9% with sprints. And actually, research from all their
• 11:44
  Speaker 1: stuff shows that some people don't really improve their VO2
• 11:47
  Speaker 1: max with low-intensity endurance training, but almost everybody does with
• 11:51
  Speaker 1: high-intensity and sprints, right? And here, the high-intensity intervals showed
• 11:55
  Speaker 1: a slight edge. but it was just short of statistical significance. Now,
• 12:00
  Speaker 1: per hour of training though, sprints were about 2.9 times
• 12:05
  Speaker 1: more efficient than high intensity training and almost five times
• 12:10
  Speaker 1: more efficient than endurance training. And after just two weeks,
• 12:15
  Speaker 1: sprint training had already lifted VO2 max by about 8%,
• 12:19
  Speaker 1: which is really significant. And that was compared with under 4%
• 12:22
  Speaker 1: for endurance training. And the same patterns showed up again
• 12:27
  Speaker 1: with more sessions per week producing bigger gains and the
• 12:31
  Speaker 1: least fit improving the most, which is really, really important
• 12:35
  Speaker 1: because Improving your VO2 max is so important, particularly if you.
• 12:40
  Speaker 2: Are the least fit.
• 12:41
  Speaker 1: If you can move from the lowest 25% of the
• 12:45
  Speaker 1: population turned to your VO2 max to below average, you
• 12:48
  Speaker 1: reduce your risk of all-cause mortality almost in half, right?
• 12:54
  Speaker 2: Which is frigging massive.
• 12:56
  Speaker 1: And they found that women showed larger percentage gains than men,
• 13:01
  Speaker 1: although in absolute terms, the improvement was much the same.
• 13:06
  Speaker 1: So that's partly because women typically start from a lower
• 13:09
  Speaker 1: baseline of VO2 max. Now, people under 35 tended to
• 13:13
  Speaker 1: improve a little bit more than older participants, probably just
• 13:17
  Speaker 1: because their bodies are more adaptable when they're younger. Now,
• 13:21
  Speaker 1: there was one sobering note for the well-trained, though. When
• 13:25
  Speaker 1: gains were expressed per hour, their VO2 max didn't measurably
• 13:29
  Speaker 1: improve with any of those approaches whatsoever. which is kind
• 13:32
  Speaker 1: of what you expect once you've done a lot of
• 13:35
  Speaker 1: the hard work. Now, there was an interesting nuance that
• 13:38
  Speaker 1: I found in the paper in that the mitochondria increased
• 13:42
  Speaker 1: by about two to three times as much as VO2 max.
• 13:46
  Speaker 1: So for endurance and high intensity training, the ratio was
• 13:48
  Speaker 1: about 2.2, but for sprints, it was 3.0. In other words,
• 13:53
  Speaker 1: sprints seem to do more of their work in the muscles,
• 13:57
  Speaker 1: whereas longer training also leans a little bit harder on
• 14:00
  Speaker 1: the heart and the circulation, right? And the link between
• 14:03
  Speaker 1: the two was real but modest. And the changes in
• 14:07
  Speaker 1: mitochondria and capillaries were only moderately correlated.
• 14:11
  Speaker 2: With changes in VO2 max.
• 14:12
  Speaker 1: So your VO2 max number doesn't tell you the whole
• 14:15
  Speaker 1: story of what's happening inside your muscles. Now, let's have
• 14:20
  Speaker 1: a quick chat about age, sex, and disease. This might
• 14:23
  Speaker 1: be my favorite part of the paper. The mitochondrial gains
• 14:27
  Speaker 1: were not affected by age, sex, menopause, or disease. People
• 14:33
  Speaker 1: with type 2 diabetes, obesity, heart disease, And chronic obstructive
• 14:37
  Speaker 1: pulmonary disease adapted just as well as healthy people of
• 14:42
  Speaker 1: similar fitness and healthy people over 35 improved.
• 14:47
  Speaker 2: As much as those under 35.
• 14:50
  Speaker 1: Now, the author's conclusion is that the ability to adapt
• 14:53
  Speaker 1: to training is maintained throughout life. which, if you're in
• 14:56
  Speaker 1: my age bracket, is probably the best news that this
• 14:59
  Speaker 1: meta-analysis can give you. Now, they didn't look at people
• 15:02
  Speaker 1: who were severely old, who were very old. And we
• 15:07
  Speaker 1: know that kind of when you get into your 60s
• 15:11
  Speaker 1: and your 70s, those adaptations drop off a little bit, right? Now,
• 15:16
  Speaker 1: this all links really nicely to a study that I
• 15:20
  Speaker 1: recently talked about in another podcast episode, where researchers at
• 15:24
  Speaker 1: Rockefeller University in New York, working with Victoria University here
• 15:28
  Speaker 1: in Melbourne, compared a single session of 90 minutes of
• 15:33
  Speaker 1: moderate cycling with six 30-second all-out sprints, each separated.
• 15:37
  Speaker 2: By about four minutes of easy recovery.
• 15:41
  Speaker 1: And so that's three minutes of actual hard work versus
• 15:43
  Speaker 1: 90 minutes of moderate work. They then measured nearly 3000
• 15:47
  Speaker 1: proteins in the blood. And immediately after the moderate ride,
• 15:52
  Speaker 1: about seven proteins had changed. Immediately after the sprints, 714
• 15:56
  Speaker 1: had changed, which was almost a quarter of everything they measured.
• 16:02
  Speaker 1: And this wasn't just a shock of something new because
• 16:04
  Speaker 1: the same pattern held after the participants had trained three
• 16:08
  Speaker 1: or four times a week for eight weeks. Now, when
• 16:12
  Speaker 1: they checked those proteins against health data from more than
• 16:15
  Speaker 1: 53,000 people in the UK biobank, they found 33 proteins
• 16:22
  Speaker 1: linked to a lower risk of obesity, type 2 diabetes
• 16:26
  Speaker 1: and metabolic disease. Sprinting moved 32 out of 33, while
• 16:31
  Speaker 1: 90 minutes of moderate cycling moved 3 out of 33.
• 16:36
  Speaker 1: So when we put these two studies together, One tells
• 16:39
  Speaker 1: you that sprinting builds mitochondria and fitness at least as well,
• 16:43
  Speaker 1: and actually probably slightly better than long sessions in a
• 16:46
  Speaker 1: fraction of the time. And the other paper gives us
• 16:49
  Speaker 1: a glimpse of why. because a short, brutal effort sets
• 16:53
  Speaker 1: off a body-wide response with muscle, fat, liver, blood vessels,
• 16:58
  Speaker 1: and even the brain all getting a nudge to adapt.
• 17:02
  Speaker 1: So the quick question is, why would the body work
• 17:05
  Speaker 1: like this, right? And so I've got an idea on this.
• 17:08
  Speaker 1: It's just my idea. I think there's a good evolutionary
• 17:11
  Speaker 1: story here. For most of human history, Daily life involved
• 17:16
  Speaker 1: a lot of low-level movement, right? Hunter-gatherers and groups like
• 17:20
  Speaker 1: the Hadza in Tanzania still clock up way more moderate
• 17:25
  Speaker 1: activity in a day than most of us manage in
• 17:27
  Speaker 1: a week. That steady walking, digging, carrying, and simply, it's
• 17:32
  Speaker 1: just business as usual, right?
• 17:34
  Speaker 2: With the background hum of being human, right?
• 17:37
  Speaker 1: What was rarer were the short, all-out movements, such as
• 17:42
  Speaker 1: chasing down an animal, sprinting away from something that wanted
• 17:44
  Speaker 1: to eat you, scrambling up a tree, or fighting.
• 17:47
  Speaker 2: Those were brief, but they were.
• 17:49
  Speaker 1: Also moments with the highest stakes, often life-or-death moments. So
• 17:54
  Speaker 1: it makes a lot of sense to me that a
• 17:56
  Speaker 1: body that's shaped by those pressures would treat a maximal
• 18:01
  Speaker 1: effort as a priority signal. Something along the lines of, Jesus,
• 18:05
  Speaker 1: that was close. We must be better prepared for that
• 18:09
  Speaker 1: the next time. And then send that message to every
• 18:12
  Speaker 1: system that could possibly help. So steady, moderate effort is
• 18:16
  Speaker 1: what the body was built to do all day. So
• 18:19
  Speaker 1: it's no surprise that that it doesn't trigger the same
• 18:22
  Speaker 1: alarm bells and same adaptations as the intense stuff. And
• 18:26
  Speaker 1: remember that the paper that we're discussing here found that
• 18:29
  Speaker 1: the mitochondria respond to the stress inside the muscle rather
• 18:34
  Speaker 1: than the strain on the heart or cardiovascular system, which
• 18:37
  Speaker 1: fits neatly with the idea that it's the local emergency
• 18:42
  Speaker 1: that drives the systemic upgrade. This is hormesis in action.
• 18:47
  Speaker 1: It's the same principle I talk about a lot on
• 18:50
  Speaker 1: this podcast, that short, sharp doses of stress make us stronger, right?
• 18:57
  Speaker 1: It's the long, continuous stress that kills us. Now, the
• 19:02
  Speaker 1: irony of modern life is that most of us get
• 19:05
  Speaker 1: neither the all-day background movement nor the occasional flat-out burst
• 19:10
  Speaker 1: of and our mitochondria actually pay the price because they do.
• 19:14
  Speaker 2: Not adapt, right?
• 19:16
  Speaker 1: So there's a couple of things to keep in perspective
• 19:19
  Speaker 1: from this podcast. Sprint gains tend to level off after
• 19:24
  Speaker 1: a number of weeks. Inturance training is better for capillary density,
• 19:28
  Speaker 1: and high-intensity intervals had a slight edge on total VO2
• 19:32
  Speaker 1: max gains. So the best long-term program isn't sprints alone.
• 19:36
  Speaker 1: It's probably a combination. So my take is that sprints
• 19:40
  Speaker 1: should be your foundation if time is tight, but keep
• 19:43
  Speaker 1: doing walking and maybe the occasional zone two session and
• 19:47
  Speaker 1: progress your sessions over time and throw in a bit
• 19:49
  Speaker 1: of heat. if you want the most comprehensive adaptations and
• 19:53
  Speaker 1: if you've got heart disease or significant risk factors clearly
• 19:56
  Speaker 1: you need to get an all clear from your doctor
• 19:59
  Speaker 1: before you start doing any of the really intense stuff
• 20:02
  Speaker 1: so here's the takeaway for me a really simple way
• 20:05
  Speaker 1: to start Pick something that's low impact, like a stationary
• 20:09
  Speaker 1: bike or a rower or go and find a hill,
• 20:13
  Speaker 1: which is much kinder to your hamstrings and Achilles than
• 20:15
  Speaker 1: running on flat ground. And particularly for those of us
• 20:19
  Speaker 1: who are north of 50, warm up for a few minutes,
• 20:22
  Speaker 1: get some blood flow and circulation going on.
• 20:24
  Speaker 2: And then do.
• 20:25
  Speaker 1: Four to six all-out efforts of 20 to 30 seconds
• 20:30
  Speaker 1: with two to four minutes of very easy.
• 20:33
  Speaker 2: Movement in between. And then finish with a few minutes
• 20:36
  Speaker 2: of cool down.
• 20:37
  Speaker 1: That whole thing takes you less than 20 minutes, but
• 20:40
  Speaker 1: it's only about three minutes of work, right? And two
• 20:44
  Speaker 1: or three of those sessions a week is plenty to
• 20:47
  Speaker 1: stimulate really significant.
• 20:49
  Speaker 2: Adaptations, right?
• 20:51
  Speaker 1: And then throw in your longer study state cardio, maybe
• 20:55
  Speaker 1: a HIIT study, right? One well-known Canadian study, which was
• 20:59
  Speaker 1: included in this review, had people do just three 20-second
• 21:03
  Speaker 1: sprints inside a 10-minute session, three times a week. And
• 21:07
  Speaker 1: after 12 weeks, they got similar improvements in fitness and
• 21:10
  Speaker 1: insulin sensitivity as people doing 50 minutes of moderate exercise
• 21:15
  Speaker 1: despite a five-fold lower time commitment. Now that is buying
• 21:21
  Speaker 1: for your buck. So you know I'm a fan of
• 21:23
  Speaker 1: the Stoics, and Seneca has written that it's not that
• 21:27
  Speaker 1: we have a short time to live, but that we
• 21:30
  Speaker 1: waste a lot of it. And when it comes to exercise,
• 21:34
  Speaker 1: I don't have time. has always been the most popular excuse.
• 21:39
  Speaker 1: But the science is making this harder and harder to justify.
• 21:42
  Speaker 1: And it actually reminds me of a cartoon that I
• 21:47
  Speaker 1: actually saw or actually used in a recent presentation. Or
• 21:51
  Speaker 1: it's a doctor talking to a patient who's clearly not
• 21:54
  Speaker 1: in good shape. And he says, what fits better into
• 21:57
  Speaker 1: your busy schedule? Exercising one hour a day or being
• 22:02
  Speaker 1: dead 24 hours a day?