Sappijuoksun

Sappijuoksun is a term used in Finnish endurance running to describe a form of high-intensity running aimed at rapidly increasing metabolic stress in working muscles, commonly through elevated lactate production. The term is used primarily in Finnish coaching and athletic communities and lacks a single standardized definition in scientific literature.

Typical training characteristics include short, intense efforts followed by recovery, such as intervals or tempo efforts performed at or near maximal sustainable pace. Sessions are designed to improve peak speed, lactate tolerance, and running economy, and are often integrated into a broader training plan that builds a base before introducing high-intensity work.

Origins and usage vary; the phrase is mostly encountered in colloquial coaching discussions and training programs in Finland rather than in formal sport science where equivalent concepts are described with more precise terminology (for example, lactate threshold and high-intensity interval training). Athletes and coaches emphasize progressive loading and attention to recovery to mitigate injury risk.

See also: high-intensity interval training, lactate threshold training, tempo run, interval training.