Spark Plugs
75 min · 50-60 TSS · IF 0.67 · 65-75% FTP · Zone 2
What this workout does
A Zone 2 ride with a mid-ride cluster of 20-second brisk efforts. The sparks recruit fast-twitch fibers and keep your legs honest without meaningfully raising the day's stress.
Zone 2 riding provides the aerobic base stimulus while the 20-second efforts at 90-100% FTP briefly recruit fast-twitch fibers, keeping them responsive through low-intensity blocks. The efforts are too short to generate meaningful fatigue. Useful deep in base season, or as a leg-opener two days before racing.
How to ride it
Indoor / trainer
Ride steadily at 65-75% FTP. Mid-ride, do 6x20 seconds at 90-100% FTP - brisk and seated, not sprints - with about 2.5 minutes of easy spinning between. Then settle back into Zone 2.
Outside
Any road with a clear, safe stretch for the efforts. Keep the ride at 65-75% FTP, then for each 20-second spark lift to 90-100% FTP with quick cadence - a strong acceleration, not an all-out lunge.
Workout structure (75 min)
- Warm-up 10m 58% - Steady 20m 70% 6x - Opener 20s 95% 100rpm - 2m 40s 63% - Steady 20m 70% - Cool-down 5m 53%
Targets are a percentage of FTP. This is the same shorthand the free workout builder understands — paste it there to edit any step, or download the workout for Zwift, Garmin or any smart trainer.
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