The Wellness Brew - Issue 27

Somewhere between a third and half of runners get hurt in a given year, and most of the advice meant to prevent it hasn't held up well under testing. The 10% rule in particular, which is built into training plans and running watches, turns out to predict almost nothing. This week: what the largest study ever done on running injuries actually found, and the handful of things that genuinely lower your risk.

But first, we filtered the noise — here's what's worth knowing this week.

Xylitol shows up in sugar-free gum, mints, protein bars, baked goods, and most "natural" toothpastes. Data presented at the European Society of Cardiology Congress in Munich last month looked at 17,710 people across a Canadian and a British cohort and found those with the highest blood xylitol levels had a 57% higher rate of heart attack, stroke, or cardiovascular death over six years than those with the lowest. The British cohort, followed longer, showed an 18% increase. Two caveats matter a lot here. This is observational and hasn't been peer-reviewed or published yet, so it's early. And it measured xylitol in blood rather than what people ate, which isn't the same thing, since your body makes small amounts of xylitol on its own during normal glucose metabolism. It does line up with a 2024 Cleveland Clinic study that found similar associations. Consider this seriously if you’re regularly consuming “sugar-free” foods that contain xylitol instead. — European Society of Cardiology, August 2026.

A big swing at Lp(a) misses

Lipoprotein(a) is a blood marker that's roughly 90% genetically determined, barely responds to diet or exercise, and shows up elevated in about one in five people. It's been one of the more promising targets in cardiology for a decade. Last week Novartis announced that its Phase III trial of pelacarsen, the furthest-along drug designed to Lp(a), failed to hit its primary endpoint. Across 8,323 patients with elevated Lp(a) and existing cardiovascular disease, the drug lowered Lp(a) substantially but didn't reduce heart attacks, strokes, cardiovascular deaths, or urgent procedures compared to placebo. Everyone in the trial already had established heart disease and was on well-controlled standard care, with average LDL around 66. So what this study leaves open is whether lowering Lp(a) earlier, before disease develops, would change anything. — Novartis, September 2026.

Two kinds of sugar beat one at breakfast

Here's a small, practical finding for anyone doing long endurance sessions. Researchers gave eight trained male cyclists a carbohydrate-heavy breakfast in two versions: one where the carbohydrates were all glucose, and one where ⅓ of the carbs were fructose. Same calories, same total carbohydrate. The cyclists who got the fructose version lasted meaningfully longer in a later endurance test that day. The reason has to do with where each sugar goes. Glucose gets distributed throughout the body, while fructose is processed mainly in the liver. After an overnight fast, liver glycogen is what's depleted while muscle glycogen stays intact. Eight participants, all male, so this is a small study rather than a settled one. But the practical version is easy: if you're training long in the morning, a breakfast that includes fruit alongside your usual carbohydrates may be doing more than the same calories from oats or toast alone. — Podlogar et al., International Journal of Sport Nutrition and Exercise Metabolism, 2022.

About a month into training for a full Ironman last year, I pulled my soleus. That's the deeper of the two calf muscles, the one that does most of the work when you run.

It wasn't dramatic. Just a tightness I initially thought was cramping until it didn't go away, and then a few weeks of rest followed by months of delicate running, backing off, feeling fine, pushing again, and feeling it again. Anyone who has dealt with a lingering soft tissue injury knows the pattern. It's less an event than a negotiation.

I still feel little pulls in it now and then, and I still do accessory work for it every week. This weekend I'm running The Rut 50k in Big Sky, Montana, which means I've spent most of this year building volume on the road and trails. So far (knock on wood), no issues.

Running injuries are common. In the largest study ever done on this, 35% of runners got hurt over an 18-month period. [2] This week, we tackle what you can and what you can’t do in order to avoid common running injuries. 

Every runner knows the 10% rule. Don't increase weekly mileage by more than 10% over the week before. It's in training plans, coaching apps, and the algorithms inside running watches.

It has never had much behind it. The origin isn't a study, it's coaching intuition that got written into running books in the 1980s and stuck because it was easy to remember.

When researchers finally tested it, it didn't hold up. A randomized trial assigned 532 novice runners either to a 13-week program built explicitly on the 10% rule or to a standard 8-week program with much steeper progression. There was no significant difference in injury rates between them. [1]

Then last year, something more useful landed. Researchers at Aarhus University tracked 5,205 runners across 87 countries through their Garmin data for 18 months, covering 588,071 running sessions. A total of 1,820 of them got injured. The team tested three different ways of measuring training load to see which actually predicted getting hurt.

Week-to-week mileage change, the thing the 10% rule tracks, didn't predict injury. Neither did the acute-to-chronic workload ratio, another metric built into a lot of training software. [2]

What did predict it was the length of a single run relative to your recent longest one.

Runners who pushed a single session more than 10% beyond their longest run of the previous 30 days had a 64% higher risk of overuse injury. Push it 30 to 100% beyond, and risk rose 52%. Double it, and the risk more than doubled. [2]

Read those numbers again, because the first one is the surprise and it’s a meaningful reframe. Injuries didn't come from a slow accumulation of too many miles. They came from one overly ambitious run.

It’s worth being precise here. Researchers linked each reported injury to the runner's most recent session, and in practice most injuries were reported either on the same day as the long run or within a day or two of running. 

What to do with that: stop worrying so much about your weekly total and start paying attention to your long run. Build it in steps against your recent longest effort, not against last week's total mileage. Additionally, be careful with your first run following the long run as your injury risk is elevated at that moment. If your longest run in the past month was 10 miles, then 11 is already in the elevated-risk band and 14 is well into it. 

Different names, largely overlapping causes.

Runner's knee (patellofemoral pain). Pain around or behind the kneecap, worse on stairs and downhills. Usually a load tolerance problem at the knee driven by weakness further up the chain, at the hips and glutes.

Shin splints (medial tibial stress syndrome). Diffuse ache along the inside of the shin. Often a volume or surface change. The important thing to know is that shin pain that becomes sharp, localized to one spot, and hurts when you press on it is a different problem, and that one needs imaging rather than patience.

Achilles tendinopathy. Stiffness and pain at the back of the heel, worst in the first steps of the morning. Tendons adapt more slowly than muscles do, so they tend to be what fails when training ramps faster than tissue can keep up.

Plantar fasciitis. Sharp heel pain on the first steps out of bed. Related to calf and foot strength, and to sudden increases in time on feet.

Calf strains. My particular friend. Often the soleus, which handles enormous load during running and gets almost no direct training in most people's routines.

Much of this list runs through the same areas: calves, feet, hips, glutes. Which is why the fixes also overlap.

Of everything studied for running injury prevention, resistance training has the strongest support.

A meta-analysis of 25 randomized controlled trials covering 26,610 participants found that strength training reduced sports injuries to less than a third of the rate seen without it, and cut overuse injuries roughly in half. [3]

Stretching, in the same analysis, showed no significant benefit at all.

The reasoning holds up. Loading tendons increases their tensile strength. Loading bone increases density. Strengthening hips and glutes changes how the knee and ankle absorb force on every footstrike, and there are a lot of footstrikes.

What to actually do, and it’s not complicated:

On stretching: static stretching before running doesn't reduce injury risk and can slightly reduce power output. A dynamic warm-up is the better use of those minutes.

Here's where most running injury advice stops, and where I think the more interesting material lives. Your tissue's ability to tolerate load isn't only a function of how you train.

Underfueling.

Chronic underfueling raises injury risk and it's well established. When energy intake doesn't cover both training and basic physiological function for long enough, bone metabolism changes, hormone production drops, and tissue repair slows. It happens faster than you'd think. In a controlled study, five days of low energy availability was enough to shift bone turnover toward breakdown rather than building in trained men. [4] 

Two things make this sneaky.

The first is that underfueling is easy to do without meaning to. As training volume goes up, appetite doesn't always follow. You may not feel underfueled. Instead, you feel tired, or like your legs are heavy, or you assume you need more sleep.

The second is that plenty of runners are underfueling on purpose. Cutting weight while building volume is common, and there's a logic to it, since running is a weight-bearing sport. But doing it during a heavy training block is a genuinely risky trade, and stress fractures are the way that bill comes due.

The takeaway isn't a number. It's to have a rough sense of what your training actually costs you and make sure you're covering it. If you're adding hours to your week, food has to be part of the plan, not an afterthought.

Vitamin D.

A study of 802 NCAA Division I athletes tracked over six years found that those who stayed below 40 ng/mL had a 12% higher rate of stress fractures than those who reached or maintained that level. [7]

The threshold is the interesting part. The Endocrine Society considers anything above 30 ng/mL sufficient, so an athlete can be technically fine by clinical standards and still sit in the higher-risk group here.

Context that makes this matter more: most people aren't anywhere near that number. Analysis of national survey data found only about 23% of Americans reach 30 ng/mL, meaning roughly three in four fall short of even the conservative clinical threshold. [11] 

This is a blood test, not a guess. Ask for 25(OH)D at your next physical and find out where you actually are.

Sleep.

A prospective study of adolescent athletes found that those sleeping fewer than 8 hours a night were 1.7 times more likely to be injured than those getting 8 or more. [8]

That study was in adolescents, so don't transfer the exact number to a 42-year-old. But broader reviews report similar associations in adult athletes. Sleep loss slows tissue repair, blunts growth hormone release, elevates cortisol, and degrades coordination and reaction time. Every one of those makes an injury more likely.

If you're adding training volume and holding sleep constant, you're widening a gap.

Alcohol.

This one has a cleaner number than I expected. Researchers gave trained subjects a hard training session followed by alcohol, and measured muscle protein synthesis, which is how muscle repairs itself after work.

Alcohol reduced it by 37% when consumed without protein. [9] When subjects drank alcohol and consumed an optimal dose of protein, muscle protein synthesis was still 24% lower than with protein alone. Eating well afterward helps, but it doesn't undo it.

To each their own on this. But a few drinks the night after a long run is a real cost to recovery, not a neutral one, and during a hard training block those costs stack.

Running injuries aren't mostly a story about weekly mileage. The research makes that fairly clear: the metric everyone tracks, and the one built into most watches, didn't predict who got hurt. The single ambitious session did.

But load is only half of it. The other half is what your tissue can tolerate when that session arrives, and that's built out of things that happen away from running — what you lift, what you eat, how you sleep, what you drink. A runner who's underfueled and sleeping six hours has less margin for the same 14-miler than one who isn't.

That's the frustrating part and also the encouraging part. There's no single lever. But there are five or six, most of them unglamorous, and you can control all of them.

Five things you can do this week:

1. Track your long run, not your weekly total.
Look at your longest run in the past 30 days. Going more than 10% beyond it is where risk climbs, and it climbs steeply past that. Weekly volume can move around more than you've been told, as long as no single session takes a big jump.

2. Lift twice a week, and start with calves.
Bent-knee calf raises for the soleus first, since it's the muscle doing the most work and getting the least attention. Then single-leg work and hips. Heavy and brief beats high-rep circuits. If you're going to skip the rest of this list, don't skip this one.

3. Eat for the training you're actually doing.
If your volume is going up, your intake has to go with it. Cutting weight during a heavy block is the trade that ends in stress fractures.

4. Get your vitamin D tested.
Ask to test your 25(OH)D at your next physical. Most people fall short of even the conservative threshold. Aim for levels above 40 ng/mL.

5. Protect sleep during heavy weeks, and know what a few drinks costs.
Both affect how well your body repairs the work you just did. 

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Wellness, filtered.

Anthony - The Wellness Brew

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Disclaimer: The Wellness Brew is for informational purposes only and does not constitute medical advice. The content published here is not intended to diagnose, treat, cure, or prevent any disease or health condition. Always consult a qualified healthcare professional before making any changes to your diet, supplement routine, or lifestyle.