10 Indoor Cycling Workouts for Triathletes (Sprint to Ironman)

Your week should include three workout types:

1. Sweet spot (88–94% FTP) — the biggest fitness-per-hour return. Do 2× per week. 2. VO2 max intervals (110–120% FTP) — the missing piece for most triathletes. Do 1× per week. 3. Endurance (60–75% FTP) — easy zone 2 to build aerobic base. Do 1× per week.

For 4–6 hours per week of bike training, that's 3–4 sessions. Always do hard sessions on the same day as easy runs, never with hard runs. Test your FTP every 6–8 weeks — see our FTP test explained guide first.

1. Sweet Spot 3×12 (60 min total) — Warm-up 15 min, then 3×12 min @ 88–92% FTP with 4 min easy between. Cool-down 5 min. The best 'first hard ride' workout.

2. Sweet Spot Pyramid (75 min) — 8-10-12-10-8 min @ 90% FTP, 4 min easy between. Great mental progression.

3. VO2 Max 5×4 (60 min) — Warm-up 15 min, then 5×4 min @ 110–115% FTP with 4 min easy between. The classic VO2 builder. Brutal but effective.

4. VO2 Max 8×3 (55 min) — 8×3 min @ 115–120% FTP with 3 min easy. Slightly less total work, higher intensity per interval.

5. Threshold 2×20 (75 min) — 2×20 min @ 95–100% FTP with 10 min easy between. The 'race the watch' classic for 70.3/Ironman pacing.

6. Over-Unders 3×10 (60 min) — 3 sets of 10 min alternating 1 min @ 105% / 1 min @ 95% FTP, 5 min easy between sets. Builds lactate tolerance.

7. Endurance Z2 (90 min) — Steady 60–70% FTP, focus on cadence (90–95 rpm). Watch a movie. Do this weekly.

8. Race-Pace Brick Prep (75 min) — Warm-up 15 min, then 45 min @ planned race watts (typically 70–80% FTP for 70.3, 65–75% for Ironman). Immediately followed by 15 min easy run. The single best 70.3/IM workout.

9. Short-Power Sprints (45 min) — Warm-up 15 min, then 10×30 sec all-out / 4 min easy. Builds top-end and bike handling. Good in off-season.

10. Cadence Drills (60 min) — Warm-up 10 min, then 5×5 min @ 100–110 rpm @ 70% FTP / 5 min @ 70 rpm @ 70% FTP. Builds neuromuscular efficiency — see our triathlon cadence explained article.

Aim for 3–4 sessions per week. Always have at least one full day off the bike.

Week	Mon	Wed	Fri	Sun
1	Endurance Z2 (90 min)	Sweet Spot 3×12	Off	Brick Prep (75 min + 15 run)
2	Endurance Z2	VO2 5×4	Off	Sweet Spot Pyramid
3	Endurance Z2	Over-Unders 3×10	Off	Threshold 2×20
4 (recovery)	Endurance Z2 (60 min)	Sweet Spot 2×10	Off	Endurance Z2 (75 min)

Week 4 cuts volume by 30%. Then re-test FTP and start the next block.

If you ride outdoors on weekends, swap the Sunday session for a long outdoor ride and move Brick Prep to Wednesday.

ERG mode — Your smart trainer holds the target watts no matter what cadence you spin. Use for:

• All structured intervals (sweet spot, VO2, threshold)
• Recovery rides where you want zero brain effort
• Anyone learning to pace

Slope mode (or 'level') — Resistance increases with simulated gradient. You control watts via gear and cadence. Use for:

• Race-pace simulation (your bike outside doesn't have ERG)
• Sprints (ERG mode lags on 30-sec efforts)
• Long endurance rides where you want to feel terrain changes

For a full breakdown see our cycling apps and ERG mode guide.

Rule of thumb: ERG for intervals, slope for race-pace and sprints. Switching between them mid-session is fine.

The hardest part of triathlon training isn't doing the sessions — it's ordering them so you arrive fresh.

Same day, OK:

• Hard bike + easy 20–30 min run (brick)
• Easy bike + hard swim
• Easy bike + easy run

Same day, avoid:

• Hard bike + hard run (injury risk, neither session is high-quality)
• Hard bike + long swim (form breaks down)

Order matters:

• Bike → run on brick days, always
• Swim → bike if same day (swim is least taxing on legs)
• Run → never followed by hard bike

If you only have 3 days per week, do bike/run as bricks and put swim on a separate day. See our brick workouts guide for full session structures.

Most triathletes quit the trainer in week 3 because the setup is miserable. Fix four things:

1. Cooling — A 20-inch box fan minimum. A second fan on your back if your pain cave is over 22°C. Indoor sweat rates are 2–3× outdoor.

2. Hydration — Two bottles within reach: water on the trainer, electrolyte mix on a side table. You'll lose 1–1.5 L/hour indoors.

3. Towel — Drape over the bars. Sweat in your headset = $200 repair.

4. Entertainment — Zwift or TrainerRoad for intervals, Netflix for endurance. Music alone makes 90 min feel like 4 hours.

For a full home setup see our smart bike trainers complete guide.

Mistake 1: Riding too hard, too often. 80% of your indoor time should be easy or moderate. Two hard sessions per week is the maximum for most.

Mistake 2: Skipping the warm-up. Cold-starting a 110% FTP interval is how you spike heart rate, blow the session, and demoralize yourself. Always 15 min easy first.

Mistake 3: Holding your aero position the whole time. Sitting up costs nothing indoors and saves your lower back. Save aero for race-pace blocks only.

Mistake 4: Ignoring cadence. Locking in at 75 rpm indoors trains a habit you'll regret on race day. Spin 88–95 rpm for most sessions.

Mistake 5: No outdoor riding. Indoor is efficient but doesn't teach bike handling, cornering, or open-road pacing. Get outside at least once every 2 weeks if possible.