Muscular Endurance Turbo Ride: 3×15-Minute Sub-Threshold Blocks

Session Overview

This 60-minute muscular endurance turbo session uses three 15-minute blocks just below your functional threshold power (FTP) to build the aerobic strength needed for long bike legs in triathlon. Ideal for intermediate cyclists targeting 70.3 or Olympic distance, it develops the ability to sustain strong power without burning matches early in a race.

What You’ll Need

  • Turbo trainer or smart trainer with ERG mode
  • Cycling computer or training app (Zwift, TrainerRoad, Wahoo)
  • Knowledge of your FTP — do a ramp test first if unsure
  • Cycling shoes, chamois pad, and a fan for ventilation
  • Water bottle — at least 750ml

Warm-Up (10 minutes)

5 minutes easy spinning at 85-90 RPM in Zone 1 (50-60% FTP). Then 3 × 1 minute building: first minute 60% FTP, second minute 70% FTP, third minute 80% FTP. Follow with 2 minutes easy before the main set.

Main Set

Three 15-minute blocks at 88-92% of FTP, with 3 minutes of easy recovery spinning at 55-60% FTP between each. Keep cadence at 85-95 RPM throughout — resist the urge to mash a big gear. If you can’t hold pace in the final block, reduce to 85% FTP next time.

  • 15 min @ 88-92% FTP — smooth 90 RPM cadence, controlled effort
  • 3 min easy recovery — 55% FTP, stay loose
  • 15 min @ 88-92% FTP — focus on consistent power output
  • 3 min easy recovery — spin the legs out
  • 15 min @ 88-92% FTP — finish strong, hold form through the last 5 minutes

Cool-Down (7 minutes)

7 minutes spinning at very easy effort (Zone 1, under 55% FTP) at 90+ RPM. Focus on flushing the legs and letting your heart rate return towards normal before stepping off the bike.

Coaching Notes

  • Sub-threshold work (88-92% FTP) is more specific to long-course triathlon than pure threshold — you’ll rarely race above FTP for extended periods in a 70.3 or Ironman.
  • Avoid starting too hard — power should feel moderate-hard by block 3, not all-out from minute one.
  • Scale down: reduce to 85% FTP with 5-minute rest intervals. Scale up: shorten rest to 2 minutes or extend blocks to 20 minutes.
  • RPE should be around 7/10. Zone 3-4 heart rate is the target; if HR climbs above Zone 4 in block 1, reduce the power target.

Training at your own risk. The information provided is for general guidance only and is not a substitute for professional medical advice. Please consult a doctor before starting any new exercise programme, especially if you have any pre-existing health conditions.