The Only Running Performance Factor You Can Improve in the Gym

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Most runners think of strength training as optional. Something you do if you have extra time, or maybe to prevent injuries. The idea that lifting weights could directly make you faster at running feels counterintuitive. Running makes you faster at running. That's the logic.

But a growing body of research says otherwise. And a 2024 meta-analysis pulled all the evidence together into one clear picture.

What Are the Three Factors That Determine Running Performance?

Exercise scientists have long identified three physiological factors that determine how fast you can run a distance race:

1. VO2max — the maximum amount of oxygen your body can use during exercise. Think of this as your engine size.
2. Lactate threshold — the intensity at which lactate builds up faster than your body can clear it. This determines how long you can sustain a hard effort before your legs start to burn.
3. Running economy — how much oxygen you need at a given pace. Two runners with the same VO2max can have very different race times based on how efficiently they use that oxygen.

Running itself improves all three. But here's the critical insight: VO2max and lactate threshold respond primarily to running. Strength training doesn't meaningfully move the needle on either one. Running economy, however, is a different story.

What Is Running Economy and Why Should You Care?

Running economy is essentially your fuel efficiency. It measures how much oxygen you burn at a specific pace. A runner with good economy uses less oxygen at 8:00/mile pace than a runner with poor economy at the same speed. Less oxygen demand means less effort, which means you can sustain that pace longer or run faster at the same effort.

Here's why this matters so much: for trained runners, VO2max plateaus relatively quickly. After a year or two of consistent training, your engine size is close to its genetic ceiling. Lactate threshold improves with well-structured intensity distribution, but it too has limits.

Running economy, though, can keep improving for years. Elite runners often have nearly identical VO2max values. The difference between them on race day comes down to economy. The runner who wastes less energy per stride wins.

Does Strength Training Actually Improve Running Economy?

Yes. And the evidence is now strong enough to call it settled science.

A 2024 systematic review with meta-analysis published in Sports Medicine examined the effect of different strength training methods on running economy across multiple running speeds. The researchers pooled data from controlled trials of middle- and long-distance runners who added strength training to their programs.

The findings were clear: runners who added strength training used less oxygen at the same speeds compared to runners who only ran. The improvements were consistent across studies and meaningful enough to affect race performance.

An earlier meta-analysis by Balsalobre-Fernandez et al. (2016) in the Journal of Strength and Conditioning Research found similar results in highly trained runners, confirming that the benefits aren't limited to beginners. Even experienced runners with years of training saw economy improvements from adding strength work.

Why Do Heavy Lifts Work Better Than Light Weights?

This is where the research gets specific and practical. Not all strength training is equal when it comes to improving running economy.

The 2024 meta-analysis found that heavy resistance training (think squats and deadlifts at 3-5 reps with heavy load) and plyometric training (box jumps, bounding, depth jumps) produced the biggest improvements. Light weights with high repetitions did not produce the same benefits.

Why the difference? It comes down to neuromuscular adaptations, not muscle size. Heavy lifting and plyometrics train your nervous system to produce force more quickly and efficiently. Specifically, they improve:

• Rate of force development — how fast your muscles can generate force during the brief ground contact time of each stride
• Tendon stiffness — stiffer tendons store and return more elastic energy with each step, like a firmer spring
• Motor unit recruitment — your brain gets better at activating muscle fibers in the right sequence and timing

These adaptations mean each stride costs less energy. You push off the ground more efficiently, waste less force in unwanted directions, and recapture more energy from the impact of landing. None of this requires bigger muscles. In fact, the research consistently shows that runners who add heavy strength training do not gain significant body mass.

Does Running Speed Change How Much Strength Training Helps?

Yes, and this is one of the more interesting findings from the 2024 meta-analysis. The benefits of strength training for running economy are more pronounced at faster speeds.

This makes physiological sense. At faster paces, ground contact time gets shorter. Each stride demands more force in less time. The neuromuscular improvements from heavy lifting and plyometrics become more valuable precisely when the demands are highest.

A 2022 systematic review in Sports Medicine - Open by Blagrove et al. directly compared heavy resistance training to plyometric training. They found that heavy resistance training had a slightly larger effect on both running economy and time trial performance, though both methods were effective. The takeaway: if you only have time for one approach, heavy lifting edges out plyometrics. If you can do both, that's the ideal combination.

A 2024 study in the European Journal of Sport Science by Eihara et al. tested plyometric versus resistance training in recreational runners and found that both approaches improved running economy, though neither improved 5K time on its own over a short training block. The running economy gains need time to translate into race performance.

How Should Runners Structure Strength Training?

Based on the pooled research, here are the practical guidelines:

1. Frequency: 2-3 sessions per week. This is the range most studies used. More than 3 sessions risks interfering with running recovery. Fewer than 2 may not provide enough stimulus.
2. Duration: at least 8-12 weeks. The meta-analysis found that programs lasting 10 weeks or longer produced better results. This isn't a quick fix. The neuromuscular adaptations take time to develop.
3. Exercise selection: compound movements. Squats, deadlifts, lunges, step-ups, and calf raises should form the core. These mirror the movement patterns and muscle groups used in running.
4. Loading: heavy, with low reps. Aim for 3-5 sets of 3-6 reps at 75-85% of your one-rep max. This is different from what most runners do in the gym. Circuit training with light dumbbells doesn't produce the same adaptations.
5. Plyometrics: add them in. Box jumps, single-leg hops, bounding, and depth jumps develop the elastic properties of tendons. Start with low volume (2-3 sets of 5-8 reps) and build gradually to avoid injury.
6. Timing: separate from hard running days when possible. Ideally, do strength work on easy run days or with several hours between sessions. Doing heavy squats the morning before an interval workout will compromise both sessions.

What About the "Won't Heavy Lifting Make Me Bulky?" Concern?

This is the most common objection runners raise, and the research addresses it directly. Heavy lifting with low reps builds neural strength, not muscle mass. The adaptations are in how your brain talks to your muscles, not in the size of the muscles themselves.

Runners who add heavy strength training in the studies consistently did not gain significant body weight. The concurrent endurance training (all the running you're already doing) acts as a brake on muscle hypertrophy. Your body simply doesn't have the recovery resources to build large muscles while also running 30-60 miles per week.

In fact, the high-rep, lighter weight approach that many runners default to is actually more likely to cause some hypertrophy than the heavy, low-rep approach. That's one more reason the research favors heavy lifting for runners.

How Does This Fit Into a Complete Training Plan?

Strength training doesn't replace running. It supplements it. The research is clear that the running economy improvements come on top of your existing run training, not instead of it.

The key is periodization. In a well-structured training plan, strength work is heaviest during base-building phases and tapers down as race-specific work increases. During peak mileage weeks, strength sessions might drop to maintenance levels (1-2 sessions with reduced volume). During a polarized training block, strength work fits naturally on the easy days that make up 80% of your training.

This is also where strength training connects to injury prevention. While the primary performance benefit is improved economy, stronger muscles and tendons are more resilient to the repetitive impact of running. You get a two-for-one: better performance and lower injury risk.

References

• Vikmoen, O. et al. (2024). "Effect of Strength Training Programs in Middle- and Long-Distance Runners' Economy at Different Running Speeds: A Systematic Review with Meta-analysis." Sports Medicine. PMC 11052887.
• Balsalobre-Fernandez, C. et al. (2016). "The Effects of Strength Training on Running Economy in Highly Trained Runners: A Systematic Review with Meta-Analysis of Controlled Trials." Journal of Strength and Conditioning Research. PubMed.
• Blagrove, R.C. et al. (2022). "Heavy Resistance Training Versus Plyometric Training for Improving Running Economy and Running Time Trial Performance: A Systematic Review and Meta-analysis." Sports Medicine - Open. PMC 9653533.
• Eihara, Y. et al. (2024). "The effects of plyometric versus resistance training on running economy and 5-km running time in middle-aged recreational runners." European Journal of Sport Science. Wiley.
• Lum, D. & Barbosa, T.M. (2019). "Brief Review: Effects of Isometric Strength Training on Strength and Dynamic Performance." International Journal of Sports Medicine. Reference for isometric vs. heavy resistance comparison.