Tag: running

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Interesting new study in the September issue of Journal of Sports Sciences that Amby Burfoot recently tweeted about, which appears to show that running on grass causes more hemolysis — the rupture of red blood cells — than running on asphalt.

It’s been known for a long time that prolonged running causes hemolysis. In fact, most forms of prolonged exercise can cause some hemolysis, simply because blood is being pumped around so vigorously and exposed to high oxygen fluxes. But running is particularly susceptible because of the footstrike: the cells get squashed as they pass through the capillaries of the foot at the moment of impact. Is this a problem? Well, excessive hemolysis can play a role in iron insufficiency — but this is generally only a problem if there are other exacerbating factors like overtraining. In this case, hemolysis is mainly interesting not because it’s a serious problem, but because it can tell us something about how different surfaces affect footstrike impacts.

The new study, by researchers in India, is very simple. Ten runners ran for an hour at 60-70% max heart rate on grass, while another 10 did the same on asphalt. Blood samples were taken before and after. The researchers expected to find more hemolysis from the harder asphalt surface, but they instead found the opposite. So what’s going on? Although the grass was superficially smooth and even, they speculate that its underlying unevenness affected the runners’ strides:

Running on uneven and inconsistent surfaces like the beach or grass can cause more injuries because each step creates varying pressures and forces in the feet, ankles, knees and hips as runners most constantly adjust to the surface. These natural surfaces also tend to slope and create a dangerous off-centre force on the ankles and feet while running. Even though the grass surface appeared to deform relatively more than asphalt, it was assumed that the uneven nature could have led to inappropriate pressure distribution and impact forces on the foot, which could have resulted in an increased haemolysis in these runners.

As Burfoot points out, this is reminiscent of Benno Nigg’s ideas: whether a surface is hard or soft, your leg automatically adjusts to cushion the impact. But on surfaces where you’re unable to correctly predict exactly how your foot will land — i.e. grass — that automatic adjustment can’t take place, and that’s when strong uncompensated forces shoot up your legs.

So it all fits together, right? Well, I have one caveat. Here’s the data from the new study for the two key measures of hemolysis (unconjugated bilirubin and lactate dehydrogenase, for those keeping score at home):

As you can see, the pre-run differences between the two groups (which were assigned randomly) are greater than the change from pre- to post-run! So statistical analysis may suggest that the two groups responded differently, but for now I’d treat this finding very cautiously. This study really should have been conducted as a randomized crossover trial, so that each runner was measured under both conditions. Bottom line: great idea for an interesting study, but until the results are replicated somewhere else I’d take the conclusions with a grain of salt.

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Instead of a Jockology column this week, my editors at the Globe and Mail asked me to write about the phenomenon of recreational runners hiring elite distance runners to coach them. I spoke to a bunch of runners ranging from beginners to veterans road warriors, working with coaches like Marilyn Arsenault, Jerry Ziak and Brandon Laan, to find out why they decided to get coaching and what they’re learning from it:

As she recovered from a hysterectomy last year, Dee Ogden was eager to resume running but nervous about the post-surgical impact on her running form. So she did something that surprisingly few runners do: She hired a coach.

“When you learn tennis, you learn about your stroke and form,” says Ms. Ogden, 44, a registered nurse in Victoria. “Why wouldn’t you do that with running?” [READ ON…]

 

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Do you ever find that your breathing locks into sync with your stride when you’re out running? Or with your pedal cadence when you’re cycling? (No points if it happens when you’re swimming.) It happens to most people, but it comes and goes, so there’s been decades of debate about whether it’s a “good” thing, and whether we should try to synchronize breathing with stride. I go into this topic (plug alert) in my new book (pp. 83-85, for the record), but I just noticed a new study in the European Journal of Applied Physiology which adds some interesting insight. It’s a little bit involved, but it’s pretty interesting — so bear with me!

First things first: this was a study (by researchers at UMass-Amherst) of walking, not running — but it’s likely that the same basic processes are at work. Essentially, there are two cyclic systems at work: the “locomotory” system (your legs) and the respiratory system (your lungs). Both are fulfilling separate goals (to keep you moving as efficiently as possible, and to keep your muscles supplied with oxygen), but they also interact with each other — e.g. changing stride can drive greater demand for oxygen. So you’ve got what physicists call a “coupled oscillators” system. The question is: when the two systems are in sync, do they function more efficiently? Do you burn less oxygen at a given pace if your breathing matches your pace?

Here’s what the study did: it had volunteers walk at a natural pace at whatever stride frequency felt natural. Then, keeping the same pace, it had them increase or decrease stride frequency by 10% and 20%, while doing sophisticated monitoring of how closely the breathing rate matched the stride rate, and also monitoring oxygen consumption (a measure of efficiency).

First finding: forcing stride frequency away from its preferred “natural” value made the walkers less efficient. They consumed more oxygen when they either increased or decreased their stride. This is exactly as expected, and has been observed in many previous experiments.

Second finding: changing stride frequency had no effect on how often breathing rates locked in with stride rates — it stayed pretty much the same. Since efficiency changed and synchronization didn’t, this suggests that synchronization doesn’t help (or hurt) your efficiency. Previous studies have found conflicting results for this question, so this is an interesting observation.

But here’s the key finding. The number of different synchronization patterns was greatest at the naturally chosen stride rate. At the lower and higher frequencies, subjects were more likely to lock into their favourite pattern, which was two strides per breath. At the preferred stride frequency — where they were most efficient — they spent a greater proportion of time jumping to different patterns, like 3:1, 4:1, 2.5:1, 4.5:1 and even 7:1. Here’s the data:

So what does this mean?

This would indicate that the greatest variation in the dominant coupling strategy used allowed the participant to explore coupling strategies with the goal of minimizing oxygen consumption.

In other words, we’re efficient at our “natural” stride frequency not because we can breathe in sync with our strides, but (in part) because we don’t let ourselves get locked into one breathing pattern. Instead, we’re unconsciously trying different breathing patterns constantly, finding the one that’s most efficient at that moment and then re-optimizing a  moment later. The moral: don’t try to consciously lock your breathing into a prescribed pattern.

(This doesn’t mean you should never pay any attention to your breathing. It may be, for example, that in stressful race situations you have a habit of breathing shallowly because of nerves. Trying to look out for this and correct it is different from, say, trying to exhale on every second left footstrike.)

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

I blogged a few weeks ago about a study on strength training and cycling efficiency, and a commenter asked why so many of these studies are done on cyclists rather than runners. In response… here’s a interesting running study, just posted online at the Journal of Strength and Conditioning Research, that looks at muscular endurance and running economy.

The question they set out to ask was: does having better muscular endurance allow you to maintain better running economy (i.e. burn less energy while running at a given pace) as you get tired? To test it, they asked 10 well-trained runners to do two 30-minute runs at a moderate pace. In the middle of one of the runs, the runners had to speed up to VO2max pace for four minutes, then slow back down — enough to tire them out a bit without exhausting them. As expected, their running economy got worse after the four-minute surge by 3.0%. This is typical: as runners get tired, their running economy gets worse.

What remains hotly debated is why, exactly, running economy gets worse with fatigue. I’m not going to delve into the details of all the various mechanisms that have been proposed to explain this — it’s almost certainly caused by a mix of many different factors. One possibility relates to your knee flexors (a.k.a. hamstrings and surrounding muscles on the back of your leg above the knee) [UPDATED 6/27: had mistakenly written knee extensors], which contract eccentrically to act as a “brake” during each stride. There’s some evidence that eccentric contractions decline more quickly than concentric contractions during exercise — so as that braking action gets less effective as you fatigue, your stride gets less efficient.

Okay, now we finally get to the point. The researchers also tested the eccentric muscle endurance of the knee and hip flexors and extensors of all their subjects, then looked for correlations with the running economy results. Sure enough, they found that eccentric knee flexor endurance was “strongly related” to how much running economy worsened after the fast section of the run. Bingo!

So what does it mean? Well, there’s a big chasm between saying “hamstring quad endurance and running economy changes are linked” and concluding “therefore, you should do X, Y and Z in training.” However, it’s not crazy to see this as a good argument for some lower-body strength training and plyometrics. Here’s what the authors conclude:

Our results suggest that coaches and athletes could effectively implement conditioning strategies that challenge eccentric muscle actions. These strategies include plyometrics, resistance training with an emphasis on eccentric portion of repetitions, down-hill running and over-speed training.