Paleo, the pace of evolution, and chronic stress

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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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My Jockology column in today’s Globe and Mail takes a look at the paleo diet — or rather, the paleo “lifestyle.” The column is actually in the form of an infographic in the paper, beautifully illustrated as “cave art” by Trish McAlaster. Unfortunately, the online version so far just lifts the text, without any of the data and graphics that accompany it. Nonetheless, it’s hopefully worth a read!

As a teaser, here’s an excerpt from a section on how the pace of evolution has changed over the past few thousand years, and what that means for the quest for the perfect “ancestral” diet:

The paleo diet depends on the assumption that our genes haven’t had time to adapt to the “modern” diet. Since evolution depends on random mutations, larger populations evolve more quickly because there’s a greater chance that a particularly favourable mutation will occur. As a result, our genome is now changing roughly 100 times faster than it was during the Paleolithic era, meaning that we have had time to at least partly adapt to an agricultural diet.

The classic example: the ability to digest milk, which developed only in populations that domesticated dairy animals. More than 90 per cent of Swedes, for example, carry this mutation. Finnish reindeer herders, in contrast, acquired genes that allow them to digest meat more efficiently, while other populations can better digest alcohol or grains. The “ideal” ancestral diet is most likely different for everyone. [READ THE WHOLE ARTICLE]

And, as another teaser, here’s a section of Trish’s infographic illustrating the difference between the acute stress of the paleo lifestyle compared to the chronic stress of modern life:

Ice baths: “lab fatigue” vs. “real fatigue”

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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Ice baths after a hard workout are very popular, but the evidence for them has always been a little shaky. A group of British researchers (including a pair from the English Institute of Sport) have just published a major meta-analysis in the British Journal of Sports Medicine that adds a couple of interesting insights. The analysis covers 14 different studies with a total of 239 athletes.

What I found most interesting is the following distinction they decided to make:

For the purpose of this review, exercise will be subdivided into two categories: ‘eccentric exercise’ that refers to the stress caused from exercise incorporating high mechanical stress (eg, eccentric contractions) and ‘high-intensity exercise’ that refers to stress caused from exercise with a high metabolic cost as well as some elements of eccentric muscle contractions (eg, repeat sprint sports).

It’s well known that the best way to induce muscle soreness is with eccentric muscle contractions, particularly unfamiliar ones. So most lab experiments on muscle soreness involve simple things like lowering a dumbbell or stepping off a box over and over — it may not be exhausting, but it sure leaves you sore. The problem is, this isn’t the kind of damage that most athletes are interested in recovering from — they’re interested in recovering from training sessions that feature familiar but intense exercise.

So is there a difference between the two? Yes: the meta-analysis found dramatically stronger effect on recovery from “high intensity exercise” than from “eccentric exercise.” It’s worth noting that only two studies looked at the former, while 12 looked at the latter. Still, it offers a possible explanation for why so many athletes believe ice baths help them in training, while lab studies of eccentric exercise continue to find ambiguous results.

Speaking of results, what were the overall conclusions? I quite like the use of forest plots to give a quick visual sense of the overall data. Here are the results for perceived recovery from muscle soreness, with each dot representing a study result (some studies appear more than once for results at 24, 48, and 72 hours after exercise, which is why there are more than 14 dots). Dots to the right of the thick line mean that the ice bath group recovered more quickly; dots to the left of the line indicate that the control group recovered more quickly:

Looks pretty convincing, eh? Unfortunately, the picture is a bit muddier if you look at an objective measure like creatine kinase in the blood (a marker of muscle damage), though there’s still a statistically significant effect in favour of ice baths:

Same goes for recovery of strength:

In the end, we’re still plagued by the fact that it’s impossible to placebo-control an ice bath study. The perceived soreness results do look encouraging, but it’s hard to rule out the effects of the fact that most of the subjects probably expected to feel better when they had the ice bath. By no means is the science settled here yet.

Which brings us to another point that’s currently being hotly debated in scientific and athlete circles (as commenter Rich pointed out last time I blogged about ice baths): If inflammation is part of the body’s adaption response to stress, and ice baths reduce inflammation, does that mean ice baths reduce your adaption to hard training? Interestingly, the lead author of the current study, Jonathan Leeder of the English Institute of Sport, commented on this question in an EIS press release last year:

“There’s evidence to suggest that if you constantly decrease the stress in training that the body won’t adapt, so long term use of a recovery technique, such as an ice bath, should be reviewed to avoid any detrimental effects on performance and to ensure that these techniques have their biggest impact when needed during competition” [Leeder] adds.

But is there really evidence to back this hypothesis up? Here’s what Leeder and his co-authors say in the peer-reviewed BJSM:

It has, however, been suggested that the inflammatory response is critical for optimal repair of damaged tissue. Although the mechanisms of training adaptation are not fully understood, it may be detrimental to reduce the commonly accepted damage-repair-adaptation model by diminishing the inflammatory response; however, there is a lack of evidence to support this. This raises the question of whether frequent or habitual use of strategies designed to reduce inflammatory responses can be detrimental for elite athlete adaptation to training.

So that’s where we’re at: no one really knows whether repeated ice baths have a practically significant effect on reducing adaption to training. From what I understand, the English Institute of Sport has been advising its athletes to avoid ice baths after routine sessions during heavy training phases, but to incorporate them during tapering and competition. In other words, periodize your recovery protocols so that you maximize adaption during training periods and maximize recovery during competition periods. Does this work? Maybe we’ll find out at next year’s Olympics!

 

Sports medicine: evidence-based or sales-based?

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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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Great article by Gina Kolata in the New York Times on the challenges facing sports medicine doctors, and lack of evidence-based medicine that sometimes results:

[…] Patients “see a high-profile athlete and say, ‘I want you to do it exactly the same way their doctor did it,’ ” said Dr. Edward McDevitt, an orthopedist in Arnold, Md., who specializes in sports medicine.

The result is therapies that are unproven, possibly worthless or even harmful. There is surgery, like a popular operation that shaves the hip bone to prevent arthritis, that may not work. There are treatments, like steroid injections for injured tendons or taping a sprained ankle, that can slow the healing process. And there are fads, like one of Ms. Basle’s treatments, P.R.P., that soar in popularity while experts debate whether they help.

All this leads Dr. Andrew Green, a shoulder orthopedist at Brown University, to ask, “Is sports medicine a science, something that really pays attention to evidence? Or is it a boutique industry where you have a product and sell it?”

“For a lot of people it is a boutique business,” he said. “But are you still a doctor if you do that?”

The article focuses on platelet-rich plasma (PRP) therapy, since it’s a perfect example of the hype-before-evidence phenomenon that’s so common in sports medicine. Kolata discusses the mishmash of conflicting evidence, and the reasons the treatment seems plausible. But she also points out the inevitable conflicts of interest from some of the scientists whose evidence is used to support PRP:

They included Dr. Allan Mishra, an orthopedist in private practice in Menlo Park, Calif., who is supported by and gets royalties from one of the P.R.P. equipment makers, Biomet, and is on the board of directors and owns stock in another company, BioParadox, which is exploring the treatment for cardiovascular disease.

Dr. Mishra says more research is needed but offers the treatment for a variety of injuries. His Web page includes a TV news video that claims P.R.P. cured a Stanford football player, James McGillicuddy, with a torn knee tendon. On the program, Dr. Mishra says that, in general, 90 percent of the patients he treats “get better and stay better” after the treatment.

Wow, 90 percent success rate! Too bad he didn’t publish those results, because that’s not what any of the studies say. It sounds more like he “has a product and is selling it” — and unfortunately, that’s all too common with “breakthroughs” in sports medicine and physiotherapy.

How long does jetlag affect physical performance?

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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Athletes have to fly to competitions — it’s an inevitable part of international sport. But flying long distances can hurt performance. There are lots of “rules of thumb” that people use to plan travel and competition (e.g. allow one day of recovery for each time zone crossed), but not a lot of hard evidence. Australian researchers have just published a neat study in the European Journal of Applied Physiology that sheds a little light on this question.

The study looked at five members of the Australian skeleton team before and after a flight to a training camp in Canada that took 24 hours and involved four different flights (so a pretty brutal travel schedule, but not that rare for athletes). Two days before they left, they did a bunch of power tests: box drop jumps, squat jumps, and countermovement jumps. Once they arrived in Canada, they repeated these measurements daily for 11 days. Some Canadian skeleton athletes (who didn’t have to fly) also did some of the tests as a control.

The data, frankly, is pretty messy. Performance clearly drops after the flight, but the various measurements aren’t perfectly consistent about when the biggest drops come and how quickly performance returns. Here’s a bit of sample data, showing the squat jump height. The two squares (instead of circles) are the Canadian controls — they basically just show that there’s not much day-to-day variation in the measurements for non-jetlagged athletes:

So what’s going on? The researchers believe that it’s not just being cooped up in a plane for a day that causes the problems:

We would contend that a symptom of jet lag is circadian misalignment and as such the performance declines that we are reporting are the result of circadian misalignment due to trans-meridian flight.

Seems fairly reasonable. The solution:

This research highlights that where possible, athletes performing explosive short duration efforts as part of a competitive environment should time their arrival in the destination country following long haul travel at least five days prior to the competition.

This I’m a little more skeptical about. Looking at the data, it’s hard to see any particular break point after five days. That being said, in the balance between leaving too little time to recover versus arriving too early and being out of your element for too long, five days does seem like pretty good common sense.

Cryosaunas, frostbite and Justin Gatlin

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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Just last week, I posted about the first serious study on the use of “cryosaunas” for post-workout recovery. Now I have an important update for athletes considering using a cryosauna: make sure to take off any sweaty clothes before you enter the sauna! According to AP, Justin Gatlin, the 2004 Olympic champion sprinter (and convicted doper), has arrived in South Korea for the World Championships sporting a serious case of frostbite caused by wearing sweaty socks into a cryosauna:

“You wake up at 9 o’clock in the morning in Orlando and it’s already 90 degrees,” said the 29-year-old Gatlin, who lives and trains in Florida. “So we’re already hot, drenched with sweat. Get in the booth, socks were wet, socks froze to me instantly.”

[…] Gatlin said the pain from the frostbite had subsided and the injury hadn’t affected his stride. But it is still bothersome because the wounds on his heels are near the level where his socks sit and where the back of his running spikes touch.

“It’s better than it was. It was all pussed up and blistered. It bubbled up and it stayed bubbled up for a good four or five days,” Gatlin said, lifting up his sweat pants to reveal the scabby scars that resemble big blisters.

So there you go: using liquid nitrogen for post-workout recovery has some downsides. Who knew?