BUILT BY A SUB-1:50 FINISHER

Train by effort.
Not by feel.

5 training zones using Karvonen or Fox formula. Free, no signup.

Age
Resting HR
Choose formula

Your zones

Max HR · bpm

Real experience

How I used HR zones for sub 1:50.

The mistake that kept me plateauing at sub 1:55.

Zone 3

Every session "moderate".

I started training for my sub-1:50 running every session at "moderate effort" (around Zone 3). I improved slowly for months.

70/30

Breakthrough split.

Once I learned to actually run at the correct zones, training became purposeful. Easy runs became truly easy (Zone 2). Hard intervals hit right intensity (Zone 4-5). Recovery happened.

Karvonen

Why Karvonen over Fox.

Karvonen uses your resting heart rate for more accurate zones. For someone age 22 with resting HR of 60, the formulas give similar results. For older runners or those with low resting HR, Karvonen is significantly more accurate.

The toolkit

Pair this with race-day planning.

  1. 01

    Pace Calculator

    Calculate your exact splits per km / mile.

    Calculate →
  2. 02

    Training Plan

    12-week fragmented-time plan for busy runners.

    Build plan →
  3. 03

    Gel Timing

    Plan your race-day fueling based on finish time.

    Plan gels →
  4. 04

    Treadmill Converter

    Convert outdoor pace to treadmill speed + incline.

    Convert pace →