# Fartlek & Interval Workout Builder

Builds a ready-to-run interval or fartlek session card from one anchor number: warm-up + reps × work + recoveries + cool-down with per-segment pace, power or split targets (Daniels zones from a 5K time, Coggan %FTP zones, or erg splits from a 2K time), work:rest ratio, CR-10 RPE distribution, and a polarized-training intensity-mix check.

> Canonical page: https://elysiatools.com/en/tools/fartlek-interval-workout-builder

- **Category:** Fitness

- **Keywords:** fartlek, interval workout builder, interval training, reps and sets, speed play, vo2max intervals, threshold cruise intervals, tempo run, running pace zones, daniels running formula, coggan power zones, ftp intervals, erg training zones, rowing workout, work rest ratio, rpe distribution, training session planner

## Overview

Pick your sport (run / ride / row) and session focus (fartlek speed play, VO2max intervals, threshold cruise intervals, tempo steady, aerobic). Give one anchor — recent 5K time, cycling FTP, or 2K erg time — plus a total duration (or hard-distance) target. The tool fills interval length, reps and recoveries from published conventions (Daniels I bouts 3-5 min with ~equal jog recovery; cruise intervals ~10 min with 2 min floats; a fixed 14-min speed-play pattern for fartlek), renders a printable session card with pace / watts / split targets and RPE per segment, and shows the easy/moderate/hard time split against the ~80/20 polarized reference. Leave work, reps and recovery at 0 for the auto structure or override them individually.

## Inputs

- **Sport** (select)
- **Session focus** (select)
- **Target type** (select)
- **Target value** (number): Duration mode: total minutes, e.g. 50. Distance mode: hard km, e.g. 5
- **Anchor: 5K time (min) / FTP (W) / 2K time (min)** (number): Run: 5K PB in minutes (e.g. 25). Bike: FTP watts (e.g. 250). Row: 2K time in minutes (e.g. 8)
- **Warm-up (minutes)** (number): e.g. 10
- **Cool-down (minutes)** (number): e.g. 10
- **Work interval length (minutes, 0 = auto)** (number): 0 = use the zone convention (4 min VO2max / 10 min cruise); steady & fartlek use fixed structure
- **Reps (0 = auto)** (number): 0 = fit as many reps as the target allows; not applicable to steady/fartlek sessions
- **Recovery between reps (minutes, 0 = auto)** (number): 0 = zone convention (equal jog for VO2max / 2 min float for cruise)

## When to use

- Planning high-intensity VO2max or threshold cruise interval workouts with target paces, power zones, or split times.
- Designing unstructured or speed-play fartlek sessions that follow recognized physiological conventions.
- Evaluating workout design to ensure segment work-to-rest ratios and overall intensity distributions match polarized training targets.

## How it works

- Select your discipline (running, cycling, or rowing) and workout focus, such as VO2max, threshold cruise intervals, tempo, aerobic, or fartlek.
- Enter an anchor performance metric (5K running time, cycling FTP in watts, or 2K erg split time) along with your target workout duration or hard distance.
- Optionally customize warm-up, cool-down, interval duration, reps, or recovery minutes, or leave them at zero to apply standard physiological conventions.
- Generate a workout card featuring segment-by-segment targets, CR-10 RPE scores, work-to-rest ratios, and a polarized training intensity breakdown.

## Use cases

- Distance runners calculating Daniels 'I' and 'T' pace splits for track or road interval sessions.
- Cyclists programming structured turbo trainer or road threshold blocks based on percentage of FTP.
- Rowers structuring ergometer interval pieces with target split times and stroke-rate guidance.

## Frequently asked questions

### How are pacing and power zones calculated?

Pacing uses Jack Daniels running formulas anchored to your 5K time, cycling targets derive from Coggan %FTP power zones, and rowing splits scale from your 2K ergometer benchmark.

### What happens if I leave work duration, reps, and recovery set to 0?

The builder automatically assigns standard defaults, such as 4-minute VO2max bouts with equal recovery or 10-minute threshold intervals with 2-minute floats, scaled to your target time.

### Can I plan workouts by hard distance instead of total time?

Yes. Switch the target type to hard distance and input your target kilometers to structure reps and recoveries around a specific work volume.

### What is the intensity distribution check?

It categorizes the workout time into easy, moderate, and hard zones to help you compare the session structure against the classic 80/20 polarized training model.

### How does the tool handle surplus session time?

Any leftover duration not filled by whole interval-recovery cycles is automatically absorbed into an extended cool-down segment.

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