Research Review: When More Strength Won’t Make You Faster

BLUF (Bottom Line Up Front)

In trained male soccer players, two tests—isometric mid-thigh pull (IMTP) peak force relative to bodyweight and standing broad-jump (SBJ) impulse—best predicted 20 m and 40 m sprint times. Speed improved as those metrics rose until about IMTP ≈ 2.0 × bodyweight and SBJ impulse ≈ 0.29 m/s; beyond those levels, added strength or impulse showed little additional benefit for sprint time in this cohort. Countermovement-jump height and Nordic hamstring strength contributed much less. Findings are associational (not cause-and-effect).

Purpose

Identify which common strength/power tests predict 20 m and 40 m sprint times in soccer, and pinpoint the “strong enough” levels where more gains stop meaningfully improving sprint speed. 

Test Subjects

60 male outfield soccer players (Western Australia National Premier League), ages 16–26 years; average height ~1.77 m; average body mass ~71 kg

Methods

• Sprint testing: Three 40 m sprints on an indoor track with electronic timing gates at 0 m, 20 m, 40 m; ~60 s rest between trials. Best 20 m and 40 m times analyzed. General warm-up (~15 min) preceded testing.
• Jump tests:
  • Countermovement jump (hands on hips) and standing broad jump (with arm swing) on dual in-ground force plates (sampling 1000 Hz).
  • SBJ impulse expressed relative to body mass (reported as change in velocity, m/s).
  • Three trials each, ~60 s rest; best trial analyzed.
• Strength tests:
  • IMTP on a force plate (600 Hz), bar fixed at mid-thigh; two practice pulls, then three maximal 5-s efforts, ~60 s rest; peak force normalized to bodyweight.
  • Nordic hamstring (NordBord, 50 Hz), three maximal bilateral reps; peak force normalized to bodyweight (left/right).
• Modeling: Random-forest regression with 5-fold cross-validation predicted 20 m and 40 m times from the test metrics. Feature importance ranked test usefulness; partial-dependence plots identified level-off (“saturation”) points. Predictions matched actual sprint times closely (typical errors ~0.04 s for 20 m and ~0.07 s for 40 m). 

Findings

What best predicted sprint time?

• The two best predictors for both 20 m and 40 m: IMTP peak force (relative to bodyweight) and SBJ impulse. Countermovement-jump height and Nordic hamstring strength contributed far less in this sample. 

Where sprint-speed gains level off (“saturation” points)

• IMTP peak force: Benefits accrued up to ~2.0 × bodyweight; above that, greater IMTP was not linked to meaningfully faster 20 m or 40 m times. 
• SBJ impulse: Benefits accrued up to ~0.29 m/s; above that, higher impulse added little to sprint-time prediction. 

How accurate were the predictions?

• The models tracked sprint time closely, with typical errors ~0.04 s (20 m) and ~0.07 s (40 m). 

What the level-off means in practice

• Sprinting speed depends not only on how much force you can produce, but how you apply it within very short ground contacts. Once athletes reach ~2.0 × BW (IMTP) and ~0.29 m/s (SBJ impulse), more general strength/impulse shows limited sprint-time payoff in this group; shifting training time toward sprint-specific mechanics and coordination becomes more relevant.

Practical Applications

• Below the thresholds? Prioritize raising IMTP toward ~2.0 × bodyweight and SBJ impulse toward ~0.29 m/s; improvements here are associated with faster 20 m/40 m sprint times. 
• At or above the thresholds? Maintain strength/power, and shift more emphasis to sprint-specific work(technique, rhythm, ground-contact timing) rather than chasing ever-higher IMTP/SBJ numbers.
• Monitoring: Track IMTP PF and SBJ impulse as primary checkpoints to guide when to emphasize strength/power vs. sprint skill. 

Limitations

• Cross-sectional design: associations, not cause-and-effect.
• Model interpretability: Random forests capture complex patterns but can be harder to interpret; plots assist but do not expose every interaction.
• Generalizability: Thresholds reflect this cohort of trained male soccer players; validate before applying elsewhere.
• Skill not fully captured: Lab tests don’t encompass sprint skill/coordination, which also drive speed. 

Conclusion

For trained male soccer players, strength and horizontal jump impulse matter most up to clear benchmarks—about IMTP ~2.0 × bodyweight and SBJ impulse ~0.29 m/s. Beyond those points, extra gains show diminishing returns for sprint time in this study, so program to reach those levels, then allocate more time to sprint-specific mechanics and coordination to translate existing strength into speed. 

Bibliography

Vial, S., Scanlan, M., Beranek, P., Kadlec, D., Barley, O. R., & Cochrane Wilkie, J. (2025). How strong is strong enough? Assessing when physical performance tests cease to be predictive of sprint performance in trained football players. Journal of Strength and Conditioning Research, 39(10), e1195–e1201.