Here is an amazing systematic review and meta-analysis that looks at how different types of strength training affect running economy. While running economy is measured by how much oxygen we consume at a certain pace, we rarely see strength exercises as a tool to improve economy.
Researchers analyzed 31 studies with 652 runners who were performing strength training in different ways. They compared heavy strength training (80–90% of 1RM), submaximal loads (a wide range of light weights, 40–80% of 1RM), plyometrics (mostly jumps), isometrics (exercises without movement), and mixed strength training. After the training, improvements in running economy were analyzed at different speeds.
Strength training can improve running economy, but not all types work the same way:
1️⃣ Heavy strength training showed the most consistent improvements, especially at higher running speeds and in better-trained runners.
2️⃣ Plyometric training also showed positive effects, mainly at slower paces (around 5 min/km).
3️⃣ Submaximal loads (light weights) and isometric training showed little or no clear improvement in running economy.
→ The main conclusion: strength training can help runners become more efficient, but the method matters.
The exact strength loads most likely depend on the target race distance. The shorter the race, the more involvement from fast type II muscle fibers, so heavier gym work makes more sense. The authors also point in this direction, but for now there is still not enough research to be very specific.
The fact that isometrics and light weights don’t improve running economy doesn’t mean we shouldn’t use them. They have other important benefits at the right training stage for the right people.