Fartlekharjoittelut

Fartlekharjoittelut, a Finnish term for fartlek training, is a flexible form of interval or speed training that blends continuous running with unstructured bursts of varied intensity. The concept was introduced in the 1930s by Swedish athlete Sonja Edström, who sought a training method that combined the benefits of steady‑state endurance and lactic threshold work without the rigid structure of traditional interval sessions.

In a typical fartlekharjoittelut session, the athlete jogs for a base period, then accelerates for a predetermined distance or time, often guided by natural landmarks, music, or a partner’s whistle. The intervals may last from a few seconds to several minutes and can be repeated with or without rest periods. Because the tempo changes are self‑determined, the training can be adapted on the fly to match the runner’s current fitness level, terrain, and environmental conditions.

The physiological benefits of fartlekharjoittelut include improved cardiovascular capacity, enhanced lactate clearance, and increased muscular endurance. It also encourages mental flexibility, as athletes learn to regulate effort without external pacing cues. Coaches and recreational runners frequently use the method in cross‑country, road, or track training plans to break monotony and promote holistic fitness gains.

Fartlekharjoittelut is popular in Nordic countries, where ski and track athletes incorporate its principles into off‑season conditioning. Although the approach is informal, several scientific studies have confirmed its efficacy in boosting VO₂ max and anaerobic power when conducted at least 2–3 times per week. The technique remains a staple in endurance training literature and is widely taught in Finnish sports schools and community running clubs.