Categories / Running & athletics
Interval Running (Fartlek)
Unstructured speed bursts during a run.
How to start
During an easy run, pick a landmark ahead (a lamp post or a tree) and run faster to it, then jog until you feel recovered. Start with four to six bursts of 20 to 30 seconds.
How to progress
Add a burst or lengthen each one a little every week or two. Keep one fartlek session a week and make the other runs easy.
What the evidence says
Evidence: moderate
Fartlek is an informal kind of interval training. A 2024 meta-analysis of 34 studies of highly trained endurance athletes found that adding high-intensity interval training to normal training improved most performance measures, by between about 1% and 2%. Most studies were in trained athletes, so results for beginners may differ, and fartlek itself, with its unstructured bursts, was not tested separately.
Take care: Hard efforts raise injury and strain risk. Warm up for at least 10 minutes and build your easy running first. Check with a GP if you have a heart condition.
Sources
12-week starter plan
You should already run 30 minutes comfortably. Do one fartlek session a week and one easy run. Bursts are hard but not an all-out sprint.
Tick each week as you finish it; your ticks are saved on this device only. Repeat a week if it felt hard. Weeks 4, 8 and 12 hold steady so you can settle. This is a general plan, not medical advice.
Add reminders to your calendar
Pick your days and time. You will download a calendar file that adds 12 weeks of reminders to Google, Apple or Outlook calendar.
Calories and weekly minutes
Enter your details for a rough estimate. Based on about 10 METs (Running with hard bursts (estimated)). Real figures vary by 20% or more between people.
Tips and common mistakes
Tips
- Warm up with 10 minutes of easy running first.
- Pick landmarks as you go: it keeps it playful.
- Recover fully by jogging until your breathing settles.
Common mistakes
- Making every burst a flat-out sprint.
- Skipping the warm-up.
- Doing fartlek on consecutive days.
Kit and cost
Low cost Approximate UK prices.
- Running shoes (about £60 to £130)
- Optional: a running watch with interval alerts
- Light layers
Frequently asked questions
What does fartlek mean?
It is Swedish for "speed play". You mix faster and slower running in an unplanned way.
Is fartlek better than steady running?
It trains your speed and raises your fitness quickly, and it breaks up the run. A mix of easy and harder days is best.
How hard should the bursts be?
Comfortably hard: you cannot talk but you could keep it up a little longer. Not a sprint.
How often should I do fartlek?
Once or twice a week at most, with easy days between.
Good for: Heart & fitness Power & speed Endurance
Compare with similar options
| Interval Running (Fartlek) | Trail Running | Cross Country Running | Half Marathon Training | |
|---|---|---|---|---|
| Typical session | 40 min × 2/wk | 60 min × 2/wk | 45 min × 2/wk | 60 min × 4/wk |
| Effort | ●●●●○ | ●●●●○ | ●●●●○ | ●●●●○ |
| Cost | Low cost | Low cost | Free | Low cost |
| Equipment | No equipment | Basic kit | Basic kit | No equipment |
| Impact | High impact | Medium impact | Medium impact | High impact |
| Fitness needed | Moderate fitness | Moderate fitness | Moderate fitness | Moderate fitness |
| Evidence | moderate | limited | limited | limited |