Effort percentage represents the intensity at which you're running relative to your maximum ability. 100% effort means running at your current fitness capacity for that distance. Training at various effort levels (70%, 80%, 90%) helps develop different energy systems and prevents overtraining.

Common training zones based on effort: Easy runs (65-75%), Tempo runs (85-90%), Threshold workouts (90-95%), Race pace (95-100%), and Intervals (100-110% of race pace). Use your recent race performance as a 100% reference, then scale down for training paces.

Yes, for shorter distances. If you use your 5K time as a reference, your 1500m pace would be faster (around 105-110% effort relative to 5K). Similarly, interval training often targets paces faster than race pace for the training distance.

Heat, humidity, wind, and hills all increase perceived effort. Running in hot conditions might feel like 90% effort even at a pace that normally feels like 80%. This calculator helps you adjust target times when conditions make running harder or easier.

Effort percentage is based on pace, while heart rate zones measure physiological response. Both are useful but can differ - your heart rate might be elevated on a hot day even at an easy pace. Using both metrics together provides the most complete picture of training intensity.