Physiology Friday #255: Strength Training for Endurance, Optimal HIIT Protocols, Omega-3s + a Big Announcement!
The latest scientific insights from the world of endurance.
Greetings!
Welcome to the Physiology Friday newsletter.
Details about the sponsors of this newsletter including FSTFUEL electrolytes, Examine.com, and my book “VO2 Max Essentials” can be found at the end of the post. You can find more products I’m affiliated with on my website.
Beginning next week, I have the extreme privilege of taking over the Run Long, Run Healthy newsletter—currently authored by the 1968 Boston Marathon champion and running legend Amby Burfoot (formerly of Runner’s World).
Earlier this year, Amby and his colleague Thomas Watson of Marathon Handbook approached me with the offer. Amby had decided to move on to the next chapter of his career and didn’t want his thriving newsletter to fizzle out. As a subscriber to Physiologically Speaking, he thought I’d make a capable predecessor and invited me to continue sharing the latest advice on how runners of all levels can improve their performance using science.
Physiologically Speaking will stay the same, of course! No worries there. If you have no interest in yet another newsletter, that’s fine by me.
But if you’re a runner (or not) and want to also receive the Run Long, Run Healthy newsletter, you can do so by subscribing here. The format is a bit different from my usual in-depth study breakdowns and a tad less “sciencey” (but no less informative!) The biggest difference—it is much more specific to running. Every week you’ll get 6 short(ish) study breakdowns, 3 short interesting findings from the world of running, and 1 great quote.
To give you a taste of what the RLRH newsletter has to offer, I’ve used the latest edition (written by Amby) for today’s post. I hope you enjoy it, and as always, thanks for reading.
See you next Friday.
~Brady~
Friends: This is my last week producing the RLRH newsletter, but don’t worry--You’ll keep receiving it in the weeks to come. I’m voluntarily retiring, and turning the reins over to Brady Holmer, writer, exercise physiologist, and 2:26 marathon runner. He was my first pick for the job.
You don’t have to do anything to your current subscription. RLRH will keep reaching your email in-box through the same channels as now.
I’m proud of the authoritative, specialized running newsletter that I began in the early Covid days, and have been gratified by your support and readership. Thanks so much. Stick around to continue receiving the best and most evidence-based news about running stronger, faster, and healthier.
I won’t be far away. I plan to contribute articles and more to Marathon Handbook on a regular basis. You’ll be alerted to these, and lots of helpful running content, if you subscribe here to the free MH newsletter.
Stay well. Amby
The Impressive Power Of Progression Runs
During his best running years, Tom McGlynn qualified for 3 Olympic Marathon Trials. Then he switched focus to his online coaching business at RunCoach.
Now, a dozen-plus years later, the Penn State grad with a 2:20 marathon best has less time for training. He’s down to 4 runs a week. This has made him recognize the power of progression runs.
He’s seen it in his own running, and also among RunCoach users. “Many of our runners perform better with this negative-splits approach to their training runs,” he says.
The benefits derived from progression runs is also the topic of this article by Matt Fitzgerald, another training expert. He and McGlynn define progression runs as workouts where you finish faster than you start.
Usually progression runs are done by road runners on the road, rather than the interval sessions on the track that are favored by elite stars aiming for the Olympics. Fitzgerald writes: “As a broad guideline, I recommend that all runners include at least one progression run per week in their training.” These sessions are perhaps best suited to low- and modest-mileage runners.
I started doing them myself for the first time last summer. In the heat and humidity, I didn’t want to slog through long runs.
Instead, I ran several 6-milers each week with the last 2 miles at half-marathon or marathon pace. When I began doing these workouts, I thought I would dread them.
I didn’t. In fact, I always looked forward to the last 2 miles. For some reason, concentrated running is often easier than mindless running even when the mindless stuff is slower.
Besides, half marathon pace and marathon pace aren’t truly hard--not when you only do them for 2 miles. They simply require a little more … well, a little more focus. And a slightly quicker stride turnover.
Psychologically, they’re easier than those slow, earlier miles due to a well-known phenomenon that Fitzgerald refers to as “smelling the barn.” I think he meant “smelling the hay in the barn,” but it’s all basically the same. More at Outside Online, including Fitzgerald’s descriptions of 3 different types of progression runs.
Stop Making This Mistake Now: Your #1 Injury Prevention Tip
If you’ve followed RLRH for a while, you know how much I like military studies of performance and injury-prevention. The Army has the absolute best volunteer subjects … because they’re not volunteers at all. They’re conscripts, and they have to follow orders.
Also, the Army and other military branches have high motivation to perform and analyze such studies. The injuries during inductee training, and sometimes the outright loss of new soldiers, has a high, measurable cost that the services would like to reduce. Improved training techniques can likewise lower costs.
Here an Army research team followed a large number (827) of incoming cadets at the U.S Military Academy. Before and after 9 weeks of training, the researchers measured a range of “running spatiotemportal parameters” like stride length, stride cadence, and the contact time of each footfall.
The goal? To see what stride characteristics were linked to running injuries.
Result: About 18 percent of trainees lost more than 3 days of training due to injuries. Surprisingly, those with the shortest strides were more likely to register injuries than those with the longest strides. However, this association disappeared after multivariate regression analysis that included previous injury history, and fitness level before the onset of training.
One major factor was left.
Conclusion: “Study participants running with the longest ground contact times were 2.15 times more likely” to incur an injury than those with the shortest contact times.
Long contact times are often caused by overstriding, extending the lead foot in front of your center of gravity, and wearing soft, high-heeled shoes. Try to avoid these. Also, though not often noted, soft surfaces like grass, sand (beaches), and some trails tend to increase contact times. Be cautious on these surfaces. More at Orthopedic J of Sports Medicine with free full text.
How Strength Training Improves Your Biomechanics & Endurance
The farther you run, the more tired you get, and the slower you go. There’s not much debate about that. The world record in the mile is 3:43.13, held by Hicham El Guerrouj.
By comparison, the record pace in a marathon is 4:36 per mile (Kelvin Kiptum). The current world-record for the 24-hour run required a 7:15 pace. That was achieved by Aleksandr Sorokin in 2022 when he covered 198.599 miles. (Hmmm, makes me think someone should establish a big-money 200 Mile Challenge for the first runner to surge past that barrier in 24 hours. But that’s not what I came here to discuss.)
Rather, we wonder how our running biomechanics change with longer distances and slowing paces. And what we might be able to do to reduce this slow-down effect. That’s the subject of a recent systematic review titled “Influence of Fatigue on the Modification of Biomechanical Parameters in Endurance Running.”
Here’s a quick look at what the authors found: 1--Stride frequency doesn’t drop much with longer, slower running. Rather, we use a mostly-maintained stride frequency to fight other changes.
2--Stride length plunges with distance. As your muscles get more fatigued, you can’t retain that long, smooth stride you started with.
3--Vertical oscillation (“bounce”) drops in the first 30 minutes of running, and then somehow holds steady.
4--Ground contact time increases with longer distances. This happens because your legs muscles are too fatigued to produce a quick “pop” of energy return when you hit the road. They need to stay on the ground longer to produce the energy you need.
These reductions occur first because of neuromuscular fatigue--brain, and legs. Second, from cardiovascular fatigue. And third from “cardiac cost,” often called “cardiac drift.” The longer you hold onto a given pace, the higher your heart rate goes. The heart effort climbs.
Of course, trained runners differ from the untrained. The better your preparation for a long race, the better you can deal with the growing fatigue. The authors note that well-trained runners “optimize their running biomechanics in response to their physiological state.”
These results--particularly the shortening stride length, and increasing contact time--reinforce that strength training can improve endurance running performance. More at International J of Exercise Science with free full text.
Make Sure Your Strength Training Is “Functional”
This seems an excellent time to talk about “functional” strength training. We all know we should include more strength work in our training programs. But we don’t always focus enough on functional strength training.
What’s the difference between functional and traditional strength training? The latter aims to build muscle size and definition across all parts of your body. Among other things, it produces an Instagram-worthy “look.”
Functional strength training, on the other hand, doesn’t care about your whole-body. This sounds limited, sure. A bit distorted. But wait a minute.
Functional strength training simply wants to strengthen the muscles that will help you perform better in a given event (like running), and/or help you recover from injury. Marathon runners don’t need bulging biceps. But more powerful calf muscles would be nice.
Here researchers performed a randomized, controlled trial on young adults with knee pain. All subjects trained with an experienced physiotherapist 3 times a week for 6 weeks. Half did functional strength training aimed at improving “hip and knee muscle control” during “daily movement patterns.”
In other words, all exercise was weight-bearing. Running is an intense, weight-bearing activity.
The other half did traditional training that included “non weight-bearing exercises.” Picture someone sitting on an exercise bench--or reclining on one--while performing strength routines.
Result: Subjects doing the functional strength training enjoyed greater improvements in both “pain reduction and function” than the traditional training group.
Conclusion: Among individuals with knee pain, functional training “may result in greater improvements in pain and knee function” than training that is not insistently weight-bearing. The study didn’t include any measures of endurance running. But these would benefit more from a functional approach than a traditional approach. More at J of Orthopedic Surgery & Research with free full text.
Is There A “Sweet Spot” For Interval Training Distances?
A group of top running experts and statisticians recently performed several meta analyses investigating high intensity interval training for runners. They sought to find out things like: How does high intensity training (HIT, or HIIT) affect physiological variables such as vo2 max and running economy? How does it affect actual time trials?
Also, if the physiological variable improves, will the time trial results necessarily get faster? These are key questions. Because too often you get one, but not the other.
For example, you might be interested in how your max heart rate changes after several months of training a certain way. We’re all interested to some degree in heart-rate. But what you REALLY WANT TO KNOW is: Did I get any faster after this training period?
Here’s what the researchers found: You gotta do time trials. They wrote: “Time trials should be included when assessing effects of HIIT on endurance performance.”
Why? Because other measures are all up-and-down. For example, training that boosts vo2 max tends to diminish running economy, and vice versa.
That means you can’t accurately evaluate a training program by measuring the physiological “pieces”--they simply don’t provide a complete picture. Stated another way: “The whole is greater than the sum of the parts.”
Conclusion: The meta analyses did “provide evidence of substantial improvements” in highly trained endurance athletes. In other words, HIT training can be very effective.
Of course, there are many kinds of HIT training. Some focus on short repeats--10 to 30 seconds. And some last quite a bit longer--4 to 10 minutes.
It appears that “combining aerobic and anaerobic types of HIIT may be more effective” than just concentrating on one type vs the other. As is often true, all training is good. You just have to get the mix of ingredients right. More at Frontiers in Physiology with free full text.
How Omega-3 Fatty Acids Affect Exercise Performance/Recovery
The editors of a sports nutrition journal recently requested that a panel of experts perform a “critical examination” of how omega-3 fatty acids affect “exercise performance, recovery, and brain health.” That’s a big ask, also an important one, as omega 3s (ω-3 PUFAs) are a popular consumer supplement.
The panel returned with a largely positive report intended to “provide a scientific foundation for athletes, dietitians, trainers, and other practitioners” in “healthy and athletic populations.” The full report is available for free at the link below. Here’s a quick summary covering just a handful of the panel’s conclusions.
1--Athletes might be “at a higher risk” of w-3 PUFA problems than non athletes.
2--ω-3 PUFA “has been shown to enhance endurance capacity.”
3--ω-3 PUFA supplementation “may decrease subjective measures of muscle soreness following intense exercise.”
4--ω-3 PUFA supplementation “can positively affect various immune cell responses in athletic populations.”
5--ω-3 PUFA supplementation “is associated with improved sleep quality.”
Panel members noted that athletes can obtain omega-3 fatty acids through diet or supplements. Top dietary sources: Cold-water fatty fish like mackerel, sardines, salmon, trout, and herring.
Supplements: A daily intake of 1-3 grams of EPA and DHA combined “is often recommended.” EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are two of the most important types of omega-3 fatty acids. They are considered “very long-chain fatty acids” due to their chemical makeup. More at J of the International Society of Sports Nutritionwith free full text.
What!!?? A Shirt That Helps You Run Faster?
Yes, that was the conclusion reached by a sports science team that tested a high-compression polyester-and-spandex torso shirt. And they reported no funding from the company that makes the shirt.
In their trial, the researchers enlisted 30 veteran male marathoners for a 4-week test period. During that time, half the runners wore a “Mr. Poly” shirt in training, while the other half continued wearing their normal apparel. The Mr. Poly shirt was claimed to have a “high stretch and ergonomic design to support the body’s natural movements” and “minimize fatigue.”
The researchers did not monitor anyone’s training during the 4-week period. But after 4 weeks, those who had been wearing their Mr. Poly shirts showed “significant improvements” in their static balance, cervical lordosis angle, and vo2 max.
Conclusion: The garment “enhances balance, posture, and aerobic capacity in male amateur runners, offering potential benefits for performance and injury prevention.”
But here’s what I keep wondering. How the heck do you get out of a shirt like this once you manage to squeeze into it?
More at Annals of Applied Sports Science with free full text. Here what the shirt looks like, front (A) and back.
When Processed Foods Might Be Good For You
Something new is happening in the world of ultra processed food: Knowledgeable experts are beginning to defend some processed foods.
That’s a big change. In the last decade, we’ve all read 100s of articles about processed foods, and how they are contributing to obesity and illness rates.
The most demonized foods are those containing added sugars, salt, and saturated fats. Also: additives, emulsifiers, colorings, and other unpronounceable and never-seen-in-real-life ingredients.
I’ve just finished reading a half-dozen recent articles on processed foods. None propose that pre packaged strawberry yogurt is better than plain yogurt with fresh strawberries. They simply note that there are some really bad processed foods (chips, sugar-sweetened sodas, processed deli meats) and others that are often good food choices (pre-packaged, fruit-flavored yogurt, for example).
In a NY Times column, a diet researcher wrote that definitions of what is/is not a processed food are so vague as to “border on useless.” A nutritionist wrote at Slate that she ate 80 percent processed foods for a month. “At the end of my experiment, I actually felt better than I had before.”
How about this recent headline from Vox? “You’re being lied to about ultra-processed foods.” Meaning: Most articles are “wildly misleading.”
In the New Yorker, physician Dhruv Khullar goes deep into the subject, interviewing many top-rank experts. In particular, he describes the work of my favorite nutrition researcher, Kevin Hall. Hall performs strictly-controlled obesity research at the National Institutes of Health.
Several of his recent studies have basically refuted his working hypothesis that ultra-processed foods would automatically lead to weight gain. They did when the foods contained lots of fats, sugar, and salt. But they didn’t if they were processed with minimal fats, sugar, and salt.
The latter might include packaged apple-cinnamon oatmeal. Or, again, flavored yogurt.
Near the end of his article, Khullar tours a New York supermarket with Marion Nestle, one of the country’s veteran, highly regarded nutrition experts. (And, no, she’s not a member of the Nestle big-foods company known for its KitKats and hot-chocolate powder.)
Walking along the breakfast-cereals aisle, she can barely contain her disgust. She picks up a box of Apple Jacks, and says: “This is where it starts. ‘Hydrogenated coconut, modified food starch, degerminated yellow corn flour, yellow six, red forty, blue one. Yuck, yuck, yuck!’ ”
Next she eyes a box of Shredded Wheat, apparently her personal breakfast favorite. Shredded Wheat is obviously a highly processed food. You don’t find perfectly bite-sized wheat bundles in any farmer’s field. But Nestle nods approvingly, since the only ingredients are wheat and wheat bran.
Then she confesses her dirty little secret. Every morning, she sprinkles a little sugar on her Shredded Wheat. I do the same, with brown sugar, on my oatmeal. Now I don’t feel so guilty.
I think the message here is pretty clear: Eat the processed foods you enjoy that don’t include an excess of fat, sugar, salt, and weird chemicals. Increase the fiber in your diet whenever possible.
Doritos? I don’t think so … except maybe once a year on Super Bowl Sunday. More at The New Yorker.
SHORT STUFF You Don’t Want To Miss
GREAT QUOTES Make Great Training Partners
“Discipline is choosing between what you want now and what you want most.”
– Abraham Lincoln
That’s all for now. Thanks for reading. This is my last edition of RLRH, but you’ll keep receiving the same great content next week from Brady Holmer. Keep reading to stay up-to-date on the best, most evidence-based news about running stronger, faster, and healthier. I’ll be following along with you. Amby
The VO2 Max Essentials eBook is your comprehensive guide to aerobic fitness, how to improve it, and its importance for health, performance, and longevity. Get your copy today and use code SUBSTACK20 at checkout for a 20% discount. You can also grab the Kindle eBook, paperback, or hardcover version on Amazon.
Examine.com: Examine is the largest database of nutrition and supplement information on the internet.
FSTFUEL combines electrolytes with amino acids to help your body maintain hydration and optimal functioning during exercise or intermittent fasting, so you don't have to choose between fasting and fitness. If you want to try some, the guys at FSTFUEL have agreed to give my audience a 30% discount on their orders. Just use the coupon code BRADY30 at checkout.