Sweet Spot Turbo: 2×20-Minute Power Blocks Session

Session Overview

This structured 60-minute turbo session builds functional threshold power through two extended sweet spot blocks — efforts held just below your lactate threshold that generate high aerobic stimulus without the recovery cost of true threshold work. Performing this session weekly during base and build phases is one of the most time-efficient ways to raise FTP and improve your triathlon bike split over a full training season. It suits intermediate triathletes who can hold a demanding but controlled effort for 20 minutes at a time.

What You’ll Need

• Turbo trainer or smart trainer
• Power meter (strongly recommended — sweet spot is defined by power, not feel alone)
• Heart rate monitor (useful for tracking drift across both blocks)
• Fan, water bottle, and towel

Warm-Up (10 minutes)

Begin with 5 minutes of easy spinning at 90–95 rpm at 50–55% of FTP. Then complete 3 x 1-minute progressive efforts: minute 1 at 65% FTP, minute 2 at 75% FTP, minute 3 at 85% FTP. Take 1 minute easy between each. Finish with 1 minute easy before the first main block. By the end of the warm-up, your legs should feel warm and ready but not pre-fatigued.

Main Set

Sweet spot intensity is defined as 88–93% of FTP. On a heart rate monitor, this corresponds to roughly zone 4 (85–90% of max HR). It should feel hard but controlled — you can still speak in short phrases, but you wouldn’t want to have a conversation. Maintain 85–90 rpm cadence throughout both blocks.

• Block 1: 20 minutes at 88–93% FTP. Stay smooth, keep cadence consistent, resist the urge to go harder in the first 5 minutes when it feels manageable.
• Rest: 5 minutes easy spinning at 50–55% FTP. Use this to eat and drink if needed. Mentally prepare for the second block.
• Block 2: 20 minutes at 88–93% FTP. This block will feel harder than the first from minute 10 onwards — that’s normal. Aim to match or come within 3–5% of your Block 1 average power.

Cool-Down (5 minutes)

Spin easy at 90+ rpm at 45–50% FTP for 5 minutes to clear lactate and bring heart rate down. Stretch your hip flexors, quads, and lower back after dismounting — these are the primary muscles taxed by an extended aero position on the turbo.

Coaching Notes

• If you don’t have a power meter, use RPE: sweet spot should feel like a 7/10 — uncomfortably hard but sustainable. Breathing is deep and rhythmic, not gasping.
• Progression: once you can complete both 20-minute blocks consistently, extend each block by 2–3 minutes per week until you reach 2 x 30 minutes — at which point you’ve moved into true threshold territory.
• If you blow up in Block 2 (power drops more than 10% below Block 1), your FTP estimate may be slightly high — reduce by 3–5% and try again next week.
• Aim to do this session once per week during a 12-week build block for significant FTP gains. Avoid doing it within 48 hours of a long ride or race simulation.