What changes

Caffeine dosing is commonly associated with a 2–4% relative improvement in endurance time-trial performance in meta-analyses.

When this tends to work

• Conditions similar to: Cycling and running time trials, trained amateurs, WADA-legal dosing
• You can measure Time trial completion time reliably
• The intervention is implemented consistently, not half-measured

When to be careful

• Your audience or product differs materially from the cited context
• Compliance costs or second-order effects outweigh the lift
• Evidence label is meta_analysis—treat wide ranges as planning bands, not promises

Practical takeaway

Use the cited range for prioritization and test design. Verify against your own data before scaling.