Fartlek Run Session: Speed Play for Triathlon

Session Overview

Fartlek — Swedish for “speed play” — is one of the most effective and enjoyable run sessions you can do. This 45-minute outdoor session blends easy running with surges of effort using natural landmarks rather than strict intervals. It builds speed, improves your ability to change pace mid-run, and breaks the monotony of steady-state training.

What You’ll Need

• Running shoes suitable for road or light trail
• GPS watch (optional — this session is deliberately unstructured)
• Water bottle for warm days

Warm-Up (10 minutes)

10 minutes of easy jogging at conversational pace (RPE 3-4). Include 4 x 20-second gentle strides in the last 2 minutes — relaxed accelerations to 5K pace, not sprinting. Let your breathing settle fully before starting fartlek efforts.

Main Set

Use landmarks around you — lamp posts, trees, corners, junctions — to guide your surges. Alternate hard efforts with easy jog recoveries. There’s no precise structure; the goal is to feel free and responsive. Aim for 25 minutes of fartlek play within the main set.

• Sprint hard (RPE 8) to the next lamp post or tree — then jog easy (RPE 3) until you feel recovered
• Run at 10K pace (RPE 7) for 60 seconds — recover for 60-90 seconds easy jog
• Pick up to 5K pace (RPE 8) between two corners — recover at easy jog
• Repeat surge-recovery pattern for 25 minutes, varying effort lengths between 20 seconds and 2 minutes

Cool-Down (5 minutes)

5 minutes of very easy jogging back to your starting point, letting your heart rate drop below 130 bpm. Follow with 3-4 minutes of light stretching: calves, hip flexors, and hamstrings.

Coaching Notes

• Resist the urge to use a watch for every surge — the joy of fartlek is instinctive speed play
• Common mistake: making every effort a sprint. Vary the intensity from tempo to near-sprint
• Scaling down: keep surges at 10K effort only; limit to 15 minutes of fartlek in the middle
• Scaling up: extend main set to 30 minutes and include some 2-3 minute sustained tempo surges
• Target overall RPE average: 6 out of 10 — hard efforts balanced by easy recovery jogging