Tag: cardio

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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Which is more important: feeling healthy, or being fit? That’s the question addressed by a new British Journal of Sports Medicine study from Steven Blair’s group at the University of South Carolina. Blair is best known for pioneering the research that suggests that fitness is more important than fatness as a predictor of health outcomes. In this case, he and his colleagues take a look at “self-rated health” (SRH), which has been touted lately as a valuable health-assessment tool.

SRH is assessed by simply asking:

How would you rate your overall health?

The answers are poor, fair, good or excellent. The researchers compared the predictive values of SRH to aerobic fitness, assessed using a maximal treadmill test (with the modified Balke protocol, which is apparently highly correlated to VO2max). The study followed 18,488 men who were tested between 1987 and 2003, 262 of whom died during the 17-year follow-up period. They controlled for age, BMI, physical activity, smoking, alcohol, heart disease, diabetes, cancer, and several other confounders.

Not surprisingly, being fit and having a high SRH reduced your chance of death dramatically. The real question is what happens when you separate the two factors. Aerobic fitness was strongly protective against mortality even when all other factors were controlled. SRH and mortality were were still inversely correlated, but the association was “only marginally significant (p=0.09)” once aerobic fitness was controlled for.

Given the previous research topics of this group, I suspect they set out to show that all the apparent predictive power of SRH is just a byproduct of aerobic fitness. It seems safe to conclude that fitness is indeed the more important of the two, but it’s interesting that SRH retained some predictive power. Their thoughts on why this might be:

One plausible explanation is the afferent information that conveys messages from the organism to the brain. These messages are usually not brought to consciousness because they function at lower levels of the central nervous system. However, this afferent information is perceived by the individual as sensations, feelings and emotion and is the sense that reflects the physiological condition of the entire body. Another theory explaining a person’s perceptions of their health involves a family of proteins called cytokines. Cytokines are involved in inflammation processes and play a major role in infectious conditions and also the pathogenesis of many chronic diseases. Research is beginning to show that the inflammatory process and certain cytokines are associated with tiredness, impaired sleep, depressive mood and poor appetite.

On one level, this seems a bit needlessly complicated. After all, most of us can probably make a reasonable assessment of how healthy we are without relying on unconscious afferent feedback and cytokines! Still, the idea that our “sensations, feelings and emotion” can reflect our underlying health status is also interesting — and inarguable. After a few late nights, skipped workouts and junk-food binges, we tend to feel like crap. This isn’t just guilt and fatigue: it’s the body sending a distress signal.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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What exactly is the purpose of a warm-up before exercise? According to a new study in the Journal of Strength and Conditioning Research, it’s:

to enhance physical performance, to reduce muscle soreness, and to prevent sports-related injuries by increasing the body temperature.

But if the main mechanism of the warm-up is literally to warm the body, could we accomplish the same thing by, say, sitting in warm water? That’s what this study tested: three different cycling tests (six minutes at 80% VO2max) after (1) no warm-up, (2) an “active” warm-up of 20 minutes easy cycling, or (3) a “passive” warm-up of soaking the legs in 39-C water for 20 minutes. The result: the active warm-up allowed subjects to use more oxygen (measured VO2) with less effort (lower HR), and possibly lower lactate accumulation (though the latter wasn’t statistically significant).

So what does this mean? It suggests that the benefits of a proper warm-up aren’t just the result of raising your temperature. Higher temperature does confer some benefits: for example, your muscles and tendons become more elastic, reducing the risk of injury. Nerve signals from brain to muscle are transmitted more quickly. The rate of metabolic reactions inside your cells speeds up by 13% for each degree C that the temperature increase.

But there are other benefits beyond temperature. Crucially, the active warm-up causes your blood vessels to dilate to speed the flow of oxygen to working muscles. When you start the main workout or race, the sudden increase in demand puts you into temporary oxygen debt, because your heart, lungs and muscle metabolism can’t respond instantly to the higher demand. If you’re properly warmed up, your systems are already partly ready for the increased demand (blood vessels dilated from the warm-up, heart rate already elevated, etc.), so they can deliver more oxygen than if they were starting cold. That means the short period of initial oxygen debt doesn’t last as long — and since aerobic metabolism is more efficient that anaerobic metabolism, it means that you’re more efficient overall.

The practical take-away: well, we all know that warm-ups (as opposed to sitting in a luke-warm bath) are important, so this doesn’t change anything. But there’s still lots of debate about exactly what a warm-up is supposed to do, and what the best way to do it is — hence all the posts about dynamic versus static stretching, for example. In the long run, figuring which parts of a warm-up really do boost performance will help us design better warm-up routines.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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The debate about whether “extreme” exertions like running a marathon can damage your heart continues to simmer. The latest addition is a paper published online last week in Medicine & Science in Sports & Exercise by a group from TU Munich. One of the co-authors is Stefan Moehlenkamp, whose recent studies of fibrosis in the hearts of veteran marathon runners have stirred up controversy.

In this study, they took blood tests (and various other measurements) from 102 participants in the Munich Marathon, before, immediately after, 24 hours, and 72 hours after the race. They were looking at the rise and fall of various “cardiac biomarkers” that signal possible heart damage, in particular and newly developed test for cardiac troponins that is much more sensitive than previous tests.

We already know that troponin levels rise after a marathon — but we don’t whether that’s a signal that heart muscle cells are dying, or whether it just signals some temporary damage, in the same way that your leg muscles are temporarily “damaged” by a marathon but quickly recover. When heart muscle cells actually die, as in a heart attack, levels of troponin stay elevated for four to seven days, as troponin continues to leak from the dead cells. In contrast, temporary damage causes a sharp peak in troponin that returns to normal after a few days. Here are the results:

Combining this sharp peak and quick decline with the other measurements in the study, the researchers conclude that “cardiac necrosis [i.e. cell death] during marathon running seems very unlikely.” Instead, the evidence points to temporary damage to cell membranes, possibly caused by decreased availability of oxygen or ATP during the race.

Referring to the earlier study that found fibrosis in veteran marathon runners, the researchers write:

Findings of myocardial injury, as seen in older marathon runners (5) are probably independent of marathon running but rather related to cardiovascular disease or risk factors, particularly smoking.

Does this mean the controversy is over? Far from it. For one thing, this study was written before more recent results showed possible heart damage in elite athletes who weren’t former smokers. More research, as always, is needed. But the results are encouraging — I remain pretty firmly convinced that the cardiac benefits of training for and competing in marathons dramatically outweigh the putative risks.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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“High-intensity interval training” (HIT) has been a big buzzword for the past few years, with plenty of studies showing that short, intense bursts of exercise can produce many of the same results as long, steady cardio sessions. Martin Gibala’s group at McMaster just published a new study in Medicine & Science in Sports & Exercise with a couple of points worth noting:

• You don’t have go “all out”: Many of the early studies used 30-second Wingate tests at 100% exertion, which is pretty challenging for inexperienced or unfit exercisers. The more moderate protocol Gibala has been studying is cycling 10 x 60s hard with 60s recovery. The hard sections were done at 60% peak power (80-95% of heart rate reserve) — so hard, but not fall-off-the-bike hard.
• Anyone can do it: Instead of using relatively fit subjects, this study used older (average age 45) subjects who were sedentary (no regular exercise program for at least a year).

The most interesting result for me: subjects improved their insulin sensitivity by 35% on average after just two weeks, three sessions a week. Lots of other parameters also improved, but insulin sensitivity is something that we know is crucially important in avoiding and managing metabolic syndrome. And the whole workout, including the three-minute warm-up and five-minute warm-down, takes less than half an hour.

By no means am I suggesting that interval training is the One True Answer to fitness (and neither are Gibala et al.). There are good arguments for varying what type of workout you do. But in terms of bang for buck, it’s hard to compete with HIT.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

***

Interesting riddle posed by a case report in the European Journal of Applied Physiology (third post from that journal this week — I need to check it more often!): who is the mystery cross-country skier who appear to have one of the highest VO2max readings ever recorded, at 90.6 ml/min/kg?

Here are the clues:

• The test was performed at the University of Innsbruck in Austria.
• The subject was “a young elite cross country skier,” male, 22 years old.
• The test took place 4 years before the skier won an Olympic gold medal.

Austria didn’t have any gold medalists in XC skiing in 2010 (and none of the winners are the right age anyway). Same with 2006. They had a gold medalist in 2002 (Christian Hoffmann), but he’s two years too old. They did win the 2006 men’s team event in Nordic combined, and one of the team members — Michael Gruber — would have been 22 years old in 2002, four years earlier. But come on… are you telling me that the man with one of the highest VO2max readings in history was a part-time ski-jumper?! If so, that’s a pretty good reminder that VO2max isn’t everything…

So what is the ultimate highest value? The paper notes an “anecdotal report” in a 2003 textbook by Astrand of someone testing 94 ml/min/kg (anyone know who that was?). They also discuss some measurements on cyclists in the 1990s by Randy Wilber (who is a co-author of this paper) at the US Olympic Training Center. The 1997 paper they cite is a comparison of 10 mountain bikers with 10 members of the US Cycling Federation National Road Team, but they also cite some unpublished data on “American elite male road cyclists who had won individual stages (and the General Classification) of the Tour de France.” There aren’t many of the latter around, are there? Anyway, a few of these cyclists tested at over 80 ml/kg/min at 1860 metres, which they argue equates to 85-86 at sea level, and roughly comparable to about 90-91 if they were doing arm-and-leg exercise (like skiing) rather than just leg exercise (cycling).

But that’s a lot of approximations. I’ve never seen a peer-reviewed report over 90 until this one. Anyone else?