Free Tool

INTERVAL SESSION BUILDER

Enter your FTP, pick a training goal and available time. Get a complete structured interval session with power targets, cadence ranges, and estimated TSS. Every session backed by sports science.

YOUR FTP (WATTS)

Don't know your FTP? Use your best 20-minute power and multiply by 0.95. Or try the FTP Test Calculator.

AVAILABLE TIME

TRAINING GOAL

EXPERIENCE LEVEL

THE SCIENCE BEHIND INTERVAL PRESCRIPTION

Why intervals work. Interval training allows you to accumulate more total time at a target intensity than continuous exercise at the same power. A rider who can hold 300W for 20 minutes continuously might accumulate 40 minutes at 300W in a session of 5x8-minute intervals. That extra time at the target intensity is what drives specific adaptation - whether that is increased VO2max, raised lactate threshold, or improved fat oxidation at tempo pace.

Work-to-rest ratios matter. The recovery duration between intervals is not arbitrary. For VO2max work, Seiler's research shows that 1:1 work-to-rest ratios (e.g. 4 minutes on, 4 minutes off) maximise time at peak VO2 because the recovery is short enough that oxygen uptake does not fully drop between efforts. For sprint work, longer rest (1:5 or more) allows phosphocreatine resynthesis so each effort can be fully maximal. For threshold and sweet spot, shorter recoveries maintain the metabolic environment that drives adaptation.

Cadence prescription. Higher cadences (95-110 rpm) during VO2max and sprint intervals reduce the muscular force per pedal stroke, shifting more stress toward the cardiovascular system. Lower cadences (85-95 rpm) during threshold and sweet spot work increase muscular tension, which can drive peripheral adaptations like improved lactate clearance within the working muscles. Both have their place - the cadence targets in each session are prescribed to match the intended physiological stimulus.

TSS as a load metric. Training Stress Score (Coggan, 2003) estimates the total physiological cost of a session. An hour at FTP = 100 TSS. The estimates here use a time-weighted average of each interval's midpoint power as a proxy for Normalised Power. Actual TSS from your power file will vary depending on how closely you hit the targets and how variable your power is within each interval.

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Quick answer

Enter your FTP in watts, choose a training goal (VO2max, threshold, sweet spot, tempo, sprint, or endurance), set your available time, and the builder returns a complete session structure — warm-up through cool-down — with wattage targets, cadence ranges, RPE, estimated TSS, and recovery guidance. Twenty sessions across six training goals, matched to your time and experience level.

WHAT IT DOES

This tool prescribes a complete structured interval session based on your FTP, training goal, available time, and experience level. You get a visual session timeline, a block-by-block breakdown with power in watts and percentage of FTP, cadence targets, RPE, and an estimated Training Stress Score. Each session includes a physiological explanation of what the workout targets and when to schedule your next hard session.

WHO IT'S FOR

→Cyclists who know their FTP and want a structured session without a full coaching plan
→Self-coached riders looking for session variety across different training goals
→Time-crunched athletes who need a workout that fits a specific time window
→Riders preparing for a specific event and choosing between VO2max, threshold, or sweet spot work
→Anyone who trains on a smart trainer and wants targets to load into ERG mode

HOW IT WORKS

The session library contains twenty prescriptions across six training goals, built from established protocols: Seiler's polarised VO2max blocks, Ronnestad's 30/15s protocol, Coggan's threshold model, and Overton's sweet spot framework. The builder filters sessions by your training goal, experience level, and available time, then expands the selected session into a timed segment list. TSS is estimated from the time-weighted average intensity factor across all segments.

01
Enter your FTP
Type your Functional Threshold Power in watts. If you do not know it, use your best 20-minute power multiplied by 0.95 or use the FTP Test Calculator.
02
Select your available time
Choose how long you have to train: 30, 45, 60, 75, or 90 minutes. The builder matches sessions that fit your window.
03
Pick a training goal
Choose from VO2max, threshold, sweet spot, tempo, sprint power, or endurance. Each goal prescribes sessions targeting a different physiological adaptation.
04
Set your experience level
Beginner, intermediate, or advanced. Some protocols (Ronnestad 30/15s, Tabata, progressive sweet spot) require intermediate or advanced experience.
05
Review and copy the session
Read the session timeline, interval breakdown, TSS estimate, and recovery guidance. Copy the session to paste into your training log or head unit.

EXAMPLE CALCULATIONS

Time-crunched amateur, 250W FTP, 60 minutes available, threshold goal

· FTP: 250W
· Time: 60 min
· Goal: Threshold
· Level: Intermediate

Classic 2x20 at 238-263W (95-105% FTP). Warm-up 10 min, 2x20 min work with 5 min recovery, 5 min cool-down. Cadence 85-95rpm. Est. TSS: 72. Next hard session in 48-72 hours.

Advanced rider, 300W FTP, 75 minutes, VO2max goal

· FTP: 300W
· Time: 75 min
· Goal: VO2max
· Level: Advanced

Classic 5x4 at 318-360W (106-120% FTP) with 4 min recovery at 150-180W. Warm-up 10 min, 5x4 min work, cool-down 5 min. Cadence 95-105rpm. Est. TSS: 85. 48-72 hours before next intensity.

LIMITATIONS

TSS estimates use a time-weighted average of target power as a proxy for Normalised Power. Actual TSS from your power file will differ depending on how closely you hit the targets and how variable your power is within each interval. Power targets assume your FTP is current and accurate. The session library covers the most common and well-researched protocols but does not replace a coach who can sequence sessions across a training block and adjust for individual response.

When to see a coach

If you are doing the right sessions but not adapting — FTP flat for 8+ weeks despite consistent training — the issue is usually how sessions are sequenced across the week, recovery between hard days, or fuelling. A coach can audit your training load distribution, spot overreaching before it becomes overtraining, and adjust the plan based on your individual response.

FREQUENTLY ASKED QUESTIONS

How do I choose between VO2max, threshold, and sweet spot sessions?+

It depends on your training phase and goals. Sweet spot (88-94% FTP) is the best return-on-investment for time-crunched riders in the build phase. Threshold (95-105% FTP) directly raises your FTP ceiling and belongs in the final 6-8 weeks before a target event. VO2max (106-120%+ FTP) improves your aerobic ceiling and is most effective in the speciality phase or when your FTP has plateaued despite consistent threshold work. Endurance and tempo sessions build your aerobic base.

How many interval sessions should I do per week?+

Most amateur cyclists benefit from 2-3 structured interval sessions per week, with the remaining volume at endurance pace (Zone 2). A typical build-phase week might include one sweet spot session, one threshold or VO2max session, and the rest at Z2. During race-specific preparation, shift toward more threshold and VO2max work. Never stack hard sessions on consecutive days without recovery between.

What is the Ronnestad 30/15 protocol?+

Developed by Norwegian researcher Bent Ronnestad, the 30/15 protocol alternates 30 seconds at 130% FTP with 15 seconds at 50% FTP, repeated 13 times per set across 3 sets. Research shows this format produces more time at VO2max than traditional long intervals because the brief recovery periods prevent complete metabolic recovery while the high power demands force rapid re-recruitment of muscle fibres. It is marked as advanced-only due to the extreme metabolic stress.

How accurate is the TSS estimate?+

The TSS estimate uses a time-weighted average of each interval's midpoint power as a proxy for Normalised Power. It will be close to your actual TSS if you hit the power targets consistently. Variable power within intervals (surging above target, dipping below) will typically produce a higher actual TSS than the estimate. Treat it as a planning guide, not a definitive number.

Should I use ERG mode or resistance mode for intervals?+

ERG mode works well for steady-state intervals like sweet spot and threshold blocks, where holding a consistent power is the goal. For VO2max and sprint sessions, resistance mode is often better because it lets you respond to fatigue naturally and adjust your effort within the target range. Over-unders specifically benefit from resistance mode so you can feel the transitions between the under and over segments.

What cadence should I target during intervals?+

Higher cadences (95-110 rpm) during VO2max and sprint intervals reduce muscular force per pedal stroke, shifting stress toward the cardiovascular system. Lower cadences (85-95 rpm) during threshold and sweet spot work increase muscular tension, which drives peripheral adaptations in the working muscles. The cadence targets in each session are prescribed to match the intended physiological stimulus. If a specific cadence feels unnatural, prioritise hitting the power target over the cadence target.