The Effect of Strength Training on Endurance Performance Determinants in Middle- and Long-Distance Endurance Athletes: An Umbrella Review of Systematic Reviews and Meta-Analysis.

This umbrella review asked whether strength training helps middle- and long-distance endurance athletes, by pooling together 17 systematic reviews (12 of them including meta-analyses) that examined effects on things like VO2max, running economy, endurance performance, and lactate thresholds. Strength programs were grouped into maximal-strength, explosive-strength, and reactive/plyometric training. Across these reviews, running economy (how efficiently the body uses oxygen at a given pace) showed moderate to large improvements consistently. Four meta-analyses looked at VO2max and none found significant changes, suggesting strength training helps maintain rather than boost this measure.

For endurance performance itself, three studies on plyometric training found small effects, with one exception showing a large effect versus a control group. The authors flagged that most included reviews had low or critically low confidence ratings, due to incomplete literature searches and unclear handling of publication bias, which limits how strongly these findings can be trusted.

This research summary looked at whether adding strength training to running programs helps endurance athletes perform better. Researchers combined findings from 17 existing systematic reviews (12 with meta-analyses, meaning they statistically pooled results from multiple studies) covering athletes who compete in middle- and long-distance running. The clearest result was that strength training was linked to improvements in running economy, meaning athletes used oxygen more efficiently while running at a given speed.

However, when it came to VO2max, the maximum amount of oxygen the body can use during exercise, four separate analyses found no significant change, suggesting strength training may help maintain this fitness marker rather than improve it. Effects on overall endurance performance were mostly small, with one study finding a larger benefit compared to a group that did not strength train. Importantly, the researchers found that most of the underlying reviews had low or very low confidence ratings, due to incomplete searches and unclear reporting practices.

This means the overall picture, while suggesting some benefit, comes from evidence that has real limitations in reliability.

This is a summary of research, not medical advice. Talk to your own healthcare provider about anything affecting your care.

This umbrella review synthesized 17 systematic reviews (12 with meta-analyses) examining strength training effects on endurance performance determinants in trained middle- and long-distance athletes, categorizing interventions as maximal-strength (>80% 1RM), explosive-strength (<80% 1RM), and reactive/plyometric training. Running economy showed the most consistent signal, with moderate to large effects reported across studies. VO2max showed no significant change across four meta-analyses, consistent with strength training supporting maintenance rather than enhancement of aerobic capacity in already-trained athletes.

Endurance performance findings were more mixed: three studies on plyometric training found small effects, with one notable exception showing a large effect versus control. A key caveat is the risk-of-bias assessment, which found most included reviews had low or critically low confidence, stemming from incomplete literature searches, unclear exclusion criteria, and inadequate handling of publication bias. This substantially tempers how the pooled conclusions should be interpreted, since combining multiple lower-confidence reviews does not automatically produce high-certainty evidence.

The heterogeneity in training protocols and outcome measures across the primary literature likely also contributes to the inconsistent findings on performance outcomes.