​The Science of Post-Run Nutrition: Explaining the 4Rs Framework​​

In today’s episode, Brady and Thomas do a deep dive on post-run nutrition, exploring the 4Rs framework and how they (and their audience) can apply it to their running routines.

Listen and subscribe to the show wherever you get your podcasts:

How Race-Day Heat Affects Your Marathon Time (and Who It Hits the Hardest)

When temperatures rise, running becomes more challenging. An unseasonably warm day can turn even the most well-laid marathon race strategy into a fight for survival. Sometimes, hydration just doesn’t cut it. So if you’ve ever wondered, “Is this heat ruining my race?”, science now has an answer for you. A new study took a deep dive into how air temperature affects marathon finishing times—not just for elites, but for the average runner, too.

The researchers analyzed historical temperature and race data from six major marathons: Boston, Berlin, Chicago, New York City, Lincoln (Nebraska), and Grandma’s (Minnesota). They tracked finishing times for three groups: The top 10 men, the top 10 women, and the median overall finisher.

They had two main goals. First, to see if these races are getting hotter over time. Second, to determine how air temperature on race day impacts finishing time for elites vs. the average runner.

Their key metric? How closely race-day temperature correlated with finishing times over decades.

Average runners are the most heat-sensitive. In five of the six marathons, higher temperatures significantly correlated with slower finishing times for median finishers. This was true even after controlling for field size. Elite men were somewhat affected. Their times slowed with heat in four of the six races. Elite women, on the other hand, were surprisingly resilient. Only one race (Lincoln) showed any significant heat impact on the top 10 women. This continues a curious trend seen in other studies: elite female marathoners may be more heat-tolerant than their male peers.

In terms of race-day temperature trends, only Berlin is clearly heating up. Among the six marathons, Berlin was the only one with a statistically significant rise in temperature over time. Chicago came close, but didn’t quite hit significance.

What’s the “optimal” marathon temperature? It might be even lower than we thought. Previous research suggested 10–12°C (50–54°F) was best for performance. But this study suggests average runners may perform best in temperatures closer to 5–10°C (41–50°F).

What this means for runners

If you're not finishing in the top 1% of the field (and even if you are), air temperature on race day should absolutely factor into your race planning—average runners are more vulnerable to heat-related slowdowns than elites. That means choosing cooler-weather races—or at least being ready with heat-specific prep—is smart and strategic. And while you can't control the weather, you can train for it: heat acclimation, hydration, and cooling strategies matter more than ever. For race organizers, the takeaway is equally important—those aiming to support the masses, not just elites, should rethink start times and race dates when possible.

RELATED ARTICLE: Heat Training for Runners: How To Prepare For Hot Races​

Should You Skip Stretching Before a Run?

Let’s talk about one of the most polarizing warm-up debates in running: stretching. I’ve lost count of how many runners have told me they stopped stretching before runs because it “kills running economy,” or that static stretching makes them feel sluggish. Admittedly, I rarely stretch for longer than a minute or two before heading out the door. But others swear by a few minutes of dynamic mobility to get things firing. So who’s right?

​A new systematic review and meta-analysis dives into the question of whether stretching actually impacts running economy.

The researchers sifted through over 7,700 studies and narrowed it down to 17 eligible trials. These included a total of 181 participants for acute effects (think: pre-run stretching) and 57 participants for chronic effects (long-term stretching protocols over weeks).

They looked at all types of stretching: static, dynamic, and proprioceptive neuromuscular facilitation (PNF), analyzing each for its effect on running economy—measured mostly via oxygen utilization at various intensities (think: how much energy you use to run at race pace).

The quality of evidence was mixed at best. Most studies were small, lacked blinding, and used varied protocols. Even so, a pooled meta-analysis was performed to try to quantify the overall effect.

Across all 15 acute studies, stretching had no statistically significant effect on running economy. Neither static nor dynamic nor PNF stretching reliably improved—or worsened—economy.

As for long-term effects? There were only two studies, both from over 20 years ago, and both also found no significant impact on running economy from chronic stretching protocols.

Interestingly, even the assumed mechanism—that stretching reduces muscle-tendon stiffness, and that reduced stiffness impairs running economy—remains unproven. Despite this being the basis of most anti-stretching arguments, none of the included studies actually measured changes in tendon stiffness.

What this means for runners

If you enjoy stretching before your runs—keep doing it. This review found no consistent evidence that it hurts performance. But don’t expect it to boost your running economy either. The takeaway here isn’t that stretching is bad; it’s that it's probably neutral, at least when done in reasonable doses. The exaggerated fear of “stretching kills performance” doesn’t hold up under scrutiny. Just avoid excessive or prolonged stretches right before hard efforts, and keep your routine consistent with what feels good for your body. And if you’re stretching to prevent injury or improve flexibility? That’s a different conversation—but one worth having.

RELATED ARTICLE: The 15 Best Dynamic Stretches For Runners​

Can Super Shoes Reduce Injury Risk?

There’s been no shortage of hype around so-called “super shoes” in recent years—those high-stack, carbon-plated, springy-soled trainers that have redefined marathon racing and rewritten record books. But beneath all the talk about performance gains, a quieter (and arguably more important) question has been lingering: What do these shoes do to our bodies biomechanically? Do they increase injury risk, help us avoid it, or arse they just “shifting the stress” somewhere else?

​A new study used musculoskeletal modeling to compare technologically advanced running shoes (“super shoes”) with both minimalist shoes and conventional cushioned trainers to answer this question once and for all.

Fifteen recreational male runners ran on a treadmill wearing three types of shoes: super shoes (the Nike AlphaFly Next%), ultralight, low-drop shoes, and your typical neutral trainer (the Adidas Ultraboost 20). The researchers collected detailed biomechanical data, including joint angles, ground reaction forces, and internal muscle and joint reaction forces.

Super shoes showed a clear shift in foot strike pattern, nudging runners toward a forefoot or midfoot strike (foot strike angle decreased by over 4° compared to the daily trainers). They also reduced ankle joint reaction forces and muscle forces in key stabilizers like the soleus (part of the calf muscle) and peroneus longus (part of the shin). Meanwhile, minimalist shoes increased loading on the ankle and calf muscles by several multiples of body weight, even while reducing peak vertical ground reaction force. Importantly, super shoes managed to alter strike patterns and reduce internal loading, without increasing mechanical demand on the knee or hip.

What this means for runners

These findings challenge the long-standing suspicion that super shoes might trade injury risk for performance. In fact, this study suggests the opposite—they may promote a more efficient strike pattern while reducing key internal loads associated with Achilles tendon and ankle injuries. For runners prone to calf and lower-leg issues, this could be a biomechanical win. That said, not every runner will respond the same way: those who already forefoot strike may see the most significant benefit, and long-term effects still need investigation. However, the right super shoe, matched to your gait, could help you run longer and healthier (see what I did there?)

RELATED ARTICLE: Puma Claims It’s Built the Fastest Super Shoe of All Time. But Will Anyone Run in It?​

Here’s what paying subscribers received this week in addition to the studies you just read. If you’d like access to the full RLRH newsletter, consider becoming a paid subscriber!

- The BEST protocol for acclimating to the heat

- Do compression shorts reduce muscle damage?

- Why you might need more carbs during hot-weather runs

- The best protocols for finding maximal heart rate

That’s all for now. Thanks for reading. As always—Run Long, Run Healthy.

~Brady~