## TL;DR

Running is one of the most accessible and effective forms of cardiovascular exercise. Training principles: build gradually (10% rule: don't increase weekly mileage by >10%), polarized training (80% easy, 20% hard), recovery weeks (every 3-4 weeks reduce mileage). Proper running form: midfoot strike, cadence 170-180 steps/min.

## Core Explanation

Couch to 5K (C25K): 9-week beginner program. Easy runs: conversational pace (Zone 2) — builds aerobic base. Tempo runs: comfortably hard — raises lactate threshold. Intervals: hard efforts with recovery — improves VO2max. Long run: weekly, 20-30% of weekly mileage. Injuries: shin splints, runner's knee, plantar fasciitis — most from too much, too soon. Shoes: replace every 500-800km.

## Further Reading

- [Daniels' Running Formula (Jack Daniels, 4th Ed)](https://www.humankinetics.com/products/daniels-running-formula-4th-edition)