How salty is your sweat? A home test kit

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)

***

I just noticed, a little belatedly, that an article I wrote for the March issue of Canadian Running magazine is now available online. It describes my experiences with a home sweat analysis kit from Medion Corporation, and compares the results to a laboratory sweat test I did with Lawrence Spriet of the University of Guelph and the Gatorade Sports Science Institute.

In the name of science, I dabbed some shaving cream on the back of my leg and scraped clear a fist-sized area of bare skin. I was about to undertake a new home sweat test to find out exactly how much salt my sweat contains, and I needed to make sure the absorbent patches would stay glued to my skin once the fluid started to flow…

It was an interesting experience, and the home test kit was pretty neat (though a little pricey at $250). It measured a lower sodium concentration than I got in the lab test, something that I think may be due to the fact that I was dehydrated before the lab test (I cycled for 40 minutes in hot sun just to get to the lab).

Overall, I’m not sure what to make of this information. I’ve just been reading The Runner’s Body, the book by the Science of Sport bloggers, and they argue that the theory linking electrolyte loss to muscle cramps is mistaken (a topic I’m looking forward to digging into a little more deeply). Personally, I’ve generally focused on (relatively) shorter distances, so my training runs don’t tend to be multi-hour affairs — which means I’ve never really worried about electrolytes. But for marathoners and triathletes out there, is knowing how salty your sweat is a piece of information that would help you plan your hydration strategy?

Kevin Sullivan’s training: seven years of detailed analysis

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)

***

I don’t know how I missed this, but there was a paper in the December issue of the Journal of Strength and Conditioning Research that is pure track-geek heaven. It’s called “Performance Modeling in an Olympic 1500-m Finalist: A Practical Approach,” and in it, researchers from Eastern Michigan University take seven years of Canadian miler Kevin Sullivan’s logs (from 2000 to 2006) and subject them to detailed analysis.

The goal of the research is to see if they can use basic “impulse-response” training theory to predict upward and downward trends in Sullivan’s race performances. To put it simply, they assume that:

Performance = Fitness – Fatigue

Makes sense so far. Every time time you train, you create some fatigue… and then a little while later, your body compensates by increasing your fitness a bit. So at any given moment, your performance ability can be estimated by adding up the contributions of every training session you’ve done toward your fitness and fatigue. Yesterday’s training session will have a big impact on your fatigue, but none on your performance. A session from three weeks ago, on the other hand, will have a performance impact but not much of a fatigue impact.

So how do you model the impact? Without getting too far into the nitty-gritty, the researchers add up every bit of running Sullivan does and calculate its pace as a fraction of the pace he could maintain all-out for an hour (akin to what runners would think of as threshold pace). A day in which he ran all-out for an hour would get a score of 100. As it turns out, over the course of a full year, he tends to average between 50 and 55 of these “points” per day. During base training, he averages over 60, with individual days sometimes exceeding 100.

So they plug this training data into the “impulse-response” formulas to see if there’s any correlation with performance. Previous studies in other sports have found good predictions averaged over whole teams, but it’s trickier with an individual athlete. They’re not trying to predict exactly how fast he’ll run in a given race — rather, it’s a question of looking for trends, to see whether his “performance score” is getting higher or lower. That way, coaches can react by taking extra rest, training harder, or whatever.

sullivan2

As an example, I’ve included one of the figures here. It shows (A) his 2000 season, when he came fifth at the Olympics, and (B) his 2004 season. The dotted line shows his “training score” — basically how hard he’s training — and the solid line shows his predicted performance. The triangles show his race performances, converted to Mercier points. The circled ones are at the Olympics. In their discussion section, they suggest that maybe he peaked a little too early in 2000 — but it seems to be they’re using their 20-20 hindsight vision to make that call, because that’s not what their model predicts. On the contrary, the solid line is highest right after the Olympics, so maybe he peaked a little late… or maybe he peaked just right. There are many debates that track geeks could have about this data — which is why it’s so much fun!

The original reference: J Strength Cond Res. 2009 Dec; 23(9): 2515-23.

Stretching is still bad even if you follow it with more warm-up

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)

***

I’m a little more than a year late in reporting on this paper, but I just stumbled across it while researching another story, and thought it was interesting. As I discussed in a recent post, there’s a
lot of evidence emerging these days that stretching has some acute negative effects. When I wrote about this topic in the Globe back in 2008, one of the researchers I spoke to basically said (and I paraphrase): “The studies all show that pre-game stretching makes you weaker and slower, but athletes don’t really care. So the best thing you can do is encourage them to stretch early in their warm-up, and then do some more dynamic activity afterwards to help ‘shake out’ the negative effects of stretching before game time.”

So the paper I just found, from the January 2009 issue of the European Journal of Applied Physiology, tackles this very question:

Recently, it has been suggested that the published research, testing after an acute bout of stretching, does not reflect current practice where individuals follow up a bout of stretching with further activity. Therefore, the aim of this study was to investigate the use of stretching followed by a secondary bout of movement.

Basically, the subjects did a five-minute warm-up on the treadmill; then did a vertical jump test; then either did nothing, static stretching, or dynamic exercises; then did another jump test; then they all did another set of warm-up exercises (i.e. high knees, skip-steps, side-stepping, cross-overs and zig-zag running); then did another series of jump tests after 10, 20 and 30 minutes.

The results: after the first stage, the static stretching group jumped lower, while the dynamic exercise group jumped higher. After the second part of the warm-up, the static stretchers still jumped significantly lower than both the dynamic group and the controls. So you can’t just “shake out” the negative effects of stretching (at least with this particular protocol): once you’ve done it, you’re stuck with the effects for an hour or two.

UPDATE (a few minutes later): Okay, as I dig more, I find more studies on this topic. For example, this November 2009 study, titled “Negative effect of static stretching restored when combined with a sport specific warm-up component,” which reaches the opposite conclusion. Clearly, this debate is far from settled.

More back-pain breakthroughs: the role of the La-Z-Boy

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)

***

In the wake of last week’s article on strength training and back pain, I got an e-mail letting me know about another important aspect of back pain recovery that I’d neglected to mention:

While there’s plenty of advice out there about how to exercise correctly, there’s not much out there about how to relax – which should be part of any exercise regimen – particularly for people experiencing back pain.

Fortunately, my correspondent had the answer:

To that end, did you know – and this is something both physicians and chiropractors apparently agree on (see below) – there’s now a recent, and valid, medical argument that time spent in your La-Z-Boy, might actually be good for your lower back?

Gadzooks, what wonderful news!

Okay, okay, you’ve now figured out that my new friend is a PR guy for La-Z-Boy. But I thought the e-mail was pretty funny — and, unlike many of the unintentionally hilarious PR pitches I receive, he thought so too:

I hope you’ll receive this email in the spirit its intended, 50% in all seriousness, 50% tongue planted firmly in cheek.

I have to admit, he had my hopes up. I was looking forward to reading about clinical trials where people watched TV from La-Z-Boys versus flimsy folding chairs or something. In the end, the “medical evidence” was a survey of doctors and an endorsement from the American Chiropractic Association. Their doctor-spokesperson recommends “relaxing in reclining furniture that offers total body and lumbar support as well as varying degrees of reclining, since every person has unique support needs.”

So take it for what it’s worth (i.e. it’s common sense, but it’s not evidence). And lobby your local La-Z-Boy dealer to sponsor an actual clinical trial, so I can really write about this!

Can strength training combat chronic back pain?

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)

***

This week’s Jockology column takes a look at some rather surprising research from the University of Alberta on back pain and lifting weights:

The question

My lower back is killing me. What can I do about it at the gym?

The answer

It’s the classic moving-day injury: You’re hoisting a dresser or grabbing one end of a sofa, then – bam! – you throw out your back.

So it may come as a surprise to hear that a promising solution for chronic lower-back pain, according to a series of recent studies from the University of Alberta, is lifting weights. A whole-body strengthening program dramatically outperforms aerobic exercise for those whose nagging back pain lingers for many months, the researchers say. And the more you lift, the better. [read on…]

There’s always a risk in reporting on research like this that it will get taken out of context. I should emphasize here this research applies to chronic (i.e. not immediately after you throw your back out) and non-specific (i.e. not related to a specific disc or muscle problem) back pain. And it’s not advocated strengthening the lower back itself — it’s strengthening other areas of the body, like the arms and legs, to take some load off the back.

For that matter, even that diagnosis remains controversial:

This one-size-fits-all approach has limitations, though, according to Stuart McGill, a professor of spine biomechanics at the University of Waterloo .

“There’s actually no such thing as non-specific back pain,” he says. “It just means you haven’t had an adequate assessment.”

Still, the results of the studies are interesting — and very much worth thinking about, in my opinion. They’re just not for everybody with back pain.