Why runners need a barbell: strength protects economy in the final kilometers

A familiar scene: the first kilometers feel easy, your form is tight, your breathing is even. But closer to the finish your body seems to fill with lead, your stride falls apart, and holding the same pace suddenly costs noticeably more. This is not only about fuel and dehydration. It is about running economy — how much oxygen you spend per kilometer. And as a recent study shows, what helps you protect it under fatigue is not yet another tempo interval, but a barbell.

What was studied

The team of Zanini and colleagues (Medicine & Science in Sports & Exercise, 2025) took 28 well-trained male runners — average VO₂max around 58.6 ml/kg/min, a 10K of 39:02. They were randomly split into two groups: one kept its usual running volume, while the other added strength and plyometric training twice a week for 10 weeks on top of the same running.

The testing was clever. Instead of a short economy measurement while fresh, the runners performed a 90-minute run in a hard zone (about 79.7% VO₂max, pace around 13 km/h), and the oxygen cost per kilometer was recorded every 15 minutes. Immediately afterward came a run to exhaustion at 95% VO₂max (about 16 km/h), simulating a finishing surge on tired legs. The whole sequence was repeated after 10 weeks.

The key finding: economy under fatigue

Here is what matters to grasp. At minute 15, while the legs were fresh, there was no difference between the groups. Strength work did not make the runners radically more economical in a rested state — and that is an honest result, not a disappointing one.

The difference showed up toward the end. By minute 90, economy in the strength group had even improved by 2.1%, whereas in the control group it worsened by 0.6%. Looking at the "drop-off" relative to the start of the run, the worsening of economy by minute 90 shrank from 4.7% to 2.1% in the strength group. Put simply, the barbell did not so much raise average VO₂ as slow the breakdown of technique and efficiency under fatigue — what scientists call durability, or "resilience."

Performance under fatigue rose even more strikingly: time to exhaustion after the 90-minute effort gained 35% in the strength group versus an 8% drop in the control group. In parallel, leg press rose by 22%, and jump height by nearly 6%. And, dispelling the main fear, body mass did not increase: fat mass even fell (about −11.5%), and the gain came from minimal muscle.

Why does it work this way? Strength and jumps make tendons stiffer — they store and return elastic energy better with each step. Plus neuromuscular efficiency: muscles engage more precisely and tire less, so running mechanics stay tight for longer. For context: a meta-analysis in Sports Medicine long ago showed that strength work improves running economy overall; this study adds a key stroke — the effect is especially valuable precisely when you are tired.

How to fit in strength work

Practical advice for the amateur:

Frequency. Two strength sessions a week. That is exactly how the participants trained, and it is enough.
What to do. The foundation is heavy multi-joint movements: squats, deadlifts, leg press. Plus 1–2 plyometric exercises (jump squats, jumps, bounds) — short and crisp, for explosive stiffness, not "to the burn."
How much. Aim for 3–5 sets of 3–6 reps with a heavy load (on the order of 80–90% of max). Few reps, heavy weight.
Hard, but not to failure. In the study the barbell was moved with maximal intent, but sets were not taken to full failure. Leave 1–2 reps in reserve: the goal is strength and the nervous system, not muscle destruction.
When to schedule it. Not right up against your key running work. Separate heavy strength and a quality interval/tempo onto different days, or at least by several hours, so one does not eat into the other.
The mass myth. "I'll bulk up and get heavier and slower" — in this study mass did not grow. Heavy low-rep sets deliver strength and stiffness, not size.
Bonus — injury prevention. Stronger muscles, tendons, and ligaments better tolerate the impact load of running. Fewer missed sessions — more consistent weeks.

Limitations

Do not transfer the numbers literally to yourself. The sample was only 28 well-trained men, just 14 per group, and only 10 weeks. How women, beginners, or masters veterans would respond, the study does not directly answer, though the direction of the effect is probably similar. The intensity of the 90-minute test is hard, but it is not an exact copy of your race pace. And the gain in "average" economy was modest: the whole value lies in durability and finishing performance, not in an instant jump in speed.

The bottom line

Strength and plyometrics twice a week for 10 weeks barely changed running economy while "fresh," but preserved it through the end of a 90-minute effort (−2.1% versus +0.6% in the control group).
Time to exhaustion after a long run rose by 35% — right where a race's final kilometers are decided.
Mechanisms: tendon stiffness and neuromuscular efficiency, resistant to fatigue.
Format: heavy squats/deadlifts/leg press + plyometrics, 3–6 reps with a heavy load, hard but not to failure, separate from key running.
Body mass did not grow — the myth that "the barbell will hinder running" was not confirmed. As a bonus — injury prevention.

Source: 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. Medicine & Science in Sports & Exercise, 2025;57(7):1546–1558. https://doi.org/10.1249/MSS.0000000000003685