Fartlek

Fartlek, Swedish for « speed play », is a continuous run mixing faster and slower stretches by feel, without stopping.

• A classic one: 15 minutes easy, then 6 to 10 surges of 1 to 3 minutes at a hard but controlled effort, each followed by an easy jog of about the same length.
• Or use landmarks: speed up to the next lamppost or the top of a hill, then jog until recovered.
• The fast parts are around 10 km race effort, not a sprint: you should finish the last surge in control.
• Once a week is enough, in place of an interval session, with an easy day after.

It is the gentlest way to bring speed into your running, ideal before structured intervals.