Your average HR during the last 20 minutes is your estimated LTHR (Lactate Threshold Heart Rate). This value alone produces Joe Friel's published running HR bands, including the open lowest and highest zones.
Threshold Pace
4:37
min/km
Speed
13.0
km/h
30min Distance
6.50
km
LTHR
—
bpm
| Zone | Pace (min/km) | % Threshold |
|---|---|---|
Zone 1 | Slower than 5:57 | Slower than 129% |
Zone 2 | 5:16 - 5:57 | 114-129% |
Zone 3 | 4:54 - 5:13 | 106-113% |
Zone 4 | 4:34 - 4:51 | 99-105% |
Zone 5a | 4:29 - 4:37 | 97-100% |
Zone 5b | 4:09 - 4:26 | 90-96% |
Zone 5c | Faster than 4:09 | Faster than 90% |
Estimate running threshold pace from a 30-minute solo time trial. Shows Joe Friel's seven published pace bands and, from final-20-minute LTHR, seven running heart-rate bands.
A 30-minute solo time trial gives you a practical field estimate of threshold pace. It is most useful when the course, weather, footwear, and fatigue are similar each time you repeat the test.
Warm up thoroughly, then run for 30 minutes at the hardest even effort you can sustain without fading. Enter either the distance covered or the average pace. If you record heart rate, use the average from the final 20 minutes as the LTHR field estimate.
The threshold pace is the average pace entered for the whole 30-minute effort. The seven pace rows reproduce Joe Friel's published running percentage bands, including their open faster/slower boundaries; they are not laboratory measurements or promises about race pace.
Heart-rate zones appear when you provide a valid final-20-minute average. Whole-bpm boundaries use the published running percentages: below 85%, 85–89%, 90–94%, 95–99%, 100–102%, 103–106%, and above 106% of LTHR. The lowest and highest bands are open rather than capped by maximum heart rate. Heat, dehydration, altitude, accumulated fatigue, medication, and sensor error can all move heart rate independently of fitness.
Choose one zone convention and use it consistently rather than mixing boundaries from different platforms. Retest after a meaningful training block, not after every good workout, and compare both pace and perceived effort before changing targets.
Not necessarily. They can be close for some runners, but race ability, course conditions, and the time required to complete a 10K vary. Use the field test result as its own estimate.
Heart rate rises during the opening minutes. Averaging the final 20 minutes reduces the influence of that early response and better reflects the sustained part of the test.
Joe Friel's published guidance suggests every four to six weeks during relevant training periods. Keep the route and conditions comparable, and avoid treating normal day-to-day variation as a fitness change.