Your Strength Training Is Protecting Something You've Never Thought to Measure

You already know strength training improves how efficiently you run. We covered that in Issue 001. The research on that is clear and consistent.

But here is the question nobody was asking until recently: does strength training keep your efficiency from falling apart when you get tired?

Because that is when it matters most. Not mile one. Mile eighteen. The back nine of your ultra. The final kilometer when the race actually gets decided.

A 2025 randomized controlled trial published in Medicine and Science in Sports and Exercise set out to answer exactly that question. And the finding that stood out most was not the running economy result. It was a 35% improvement in what happens when runners are already exhausted.

The Research

Citation: Zanini M, Folland JP, Wu H, Blagrove RC. Strength Training Improves Running Economy Durability and Fatigued High-Intensity Performance in Well-Trained Male Runners: A Randomized Control Trial. Med Sci Sports Exerc. 2025;57(7):1546-1558. doi: 10.1249/MSS.0000000000003685. PMID: 40016936.

Researchers took 28 well-trained male runners, averaging a 39-minute 10k, VO2max of 58.6, and split them into two performance-matched groups for 10 weeks. One group continued their normal running training unchanged. The other added maximal strength and plyometric training twice per week on top of their running. Both groups maintained their existing running without modification.

Two things were measured. First, running economy at every 15-minute checkpoint across a full 90-minute run at marathon-effort intensity, somewhere between aerobic and anaerobic threshold, a sustained but not all-out effort. Second, immediately after that 90-minute run, a time to exhaustion test at 95% of VO2max. That is a very hard effort, designed to simulate the final push of a race when the legs are already loaded with 90 minutes of fatigue.

What They Found

Running economy held up better in the strength group. As fatigue accumulated across the 90-minute run, the strength training group maintained their efficiency better than the running-only group. Their economy degraded less as time went on.

The headline finding: a 35% improvement in time to exhaustion. After 90 minutes of running, the strength group could sustain high-intensity effort at 95% of VO2max significantly longer than before the 10-week program. The running-only group did not see the same improvement.

Think about what that means in practice. After 90 minutes of running, the strength group had more left. They lasted 35% longer at a very high intensity. Their legs had not given up.

The running-only control group maintained their fitness but did not see the same durability or fatigued performance gains.

What This Means for Your Training

Most races are decided in the final miles. A kick. A push. Whoever falls apart less. This study is about exactly that.

The concept the researchers were testing is called running economy durability: not just how efficient you are when fresh, but how well that efficiency holds up under fatigue. It is a more race-relevant outcome than any lab test done on fresh legs, and until recently almost nobody had measured it.

Here is how I think about this practically for different race distances:

Half marathon and marathon runners: the 90-minute run at threshold effort is essentially your race. The durability finding is directly applicable. Holding your economy together across that duration is exactly what separates a strong finish from a painful fade.

Ultra runners: the carryover is slightly less direct because ultras are not run at 95% of VO2max. But being more efficient throughout a long effort, and having more reserve when you need to push, still matters. The durability piece translates. The high-intensity finish piece is more about shorter-distance racing.

Recreational runners: the less trained you are, the more potential gain you have from strength work, which is consistent with what the fueling research showed as well. The 39-minute 10k population in this study is genuinely fast. If the effect holds at that training level, it likely holds or improves for runners earlier in their development.

The Protocol They Used

This is the part I appreciate most about this study: they gave us the actual protocol. Twice per week, approximately 45 minutes per session, progressing over 10 weeks. Here is exactly what they did:

A few things worth noting about this protocol structure:

The load progresses meaningfully. It starts at 65 to 80% of 1RM in weeks one through three and builds to 85 to 90% by weeks eight through ten. That is heavy. The plyometrics also progress in demand, from pogo jumps and hop-and-stick early on to drop jumps and bounds for distance later.

This is the same combination principle covered in Issue 001, and the same progressive structure built into Phase 3 and 4 of the 12-Week Runner Strength Foundation Program. Heavy load plus plyometrics, progressed deliberately over time.

The seated isometric calf raises are worth highlighting specifically. Loading the calf at 80 to 100% of maximal voluntary force directly connects to the soleus work covered in Issue 002: that the soleus is the most undertrained muscle in most runners' programs, and that it responds to heavy load, not bodyweight endurance work.

How To Apply It

Two sessions per week on top of your normal running. Not instead of running. On top of it. The study kept both groups running normally and added the strength work as an additional stimulus.

Start light in weeks one through three. The 65 to 80% of 1RM range in the early weeks is not arbitrary. Your body needs to build the movement patterns and baseline coordination before the heavy loading in weeks eight through ten becomes productive. Skipping to heavy weight immediately is how people get hurt and stall out.

The plyometrics matter as much as the strength work. Pogo jumps and hop-and-stick in the early weeks build the reactive strength and tendon stiffness that makes the bounds and drop jumps in later weeks transferable to running. Do not drop the plyometric component to save time.

The calf work is non-negotiable. Both the back squat and single leg press are included, which cover the hip and quad patterns, but the seated isometric calf raises at maximum voluntary force are targeting the soleus specifically. Nearly 8 times body weight per step. Train it accordingly.

Give it 10 weeks before judging results. The study ran 10 weeks for a reason. Neuromuscular adaptations that improve durability and fatigued performance take longer to develop than basic strength gains. Two weeks of this protocol will not show you what 10 weeks shows.

If you do not have a barbell for back squats: a heavy goblet squat or loaded split squat covers the same stimulus. Single leg press can be replaced with a Bulgarian split squat or a weighted step-up. The specific equipment matters less than the load and the progressive overload structure over time.

The Bigger Picture

This study completes a picture that has been building across the last several issues.

Strength training makes you more efficient when fresh. Fueling protects your performance when fatigued. And now, strength training also keeps your efficiency from degrading under fatigue and improves what you can do at the end of a long effort.

Three separate research questions. Three consistent answers all pointing at the same conclusion. The runners who are training smart are doing both the strength work and the fueling. Not one or the other.

The back half of your race is where everything you have built either holds or falls apart. The research is getting increasingly clear on what helps it hold.

Hit reply and tell me: do you notice your form or pace falling apart in the final miles of your longer efforts? I read every reply and the answers shape what I cover next.

Keep running happy, healthy, and strong, Spencer

Related Articles

• Does Strength Training Improve Running Economy? (Issue 001)
• What Dr. Google Gets Wrong About Your Calf Muscle (Issue 002)
• Can Hill Work Replace Your Gym Time? I Ran the Study on Myself to Find Out (Issue 003)
• Carbohydrate Fueling for Endurance Runners (Issue 004)