CORE Heat

CORE Heat

Heat training data fields for the Hammerhead Karoo, driven by a CORE body temperature sensor.

Core and skin temperature, the Heat Strain Index read straight from the sensor, CORE’s heat zones, today’s heat training load and your heat adaptation score — drawn large in DIN 1451 Mittelschrift, so the number fills the field, and colored in CORE’s own zone colors.

Download core-release.apk How to install

Always the latest release. Every field needs a CORE sensor paired to the Karoo. Free and open source, under the Apache-2.0 license.

A 38.6 °C core on 35.1 °C skin: Heat Strain Index 4.1, heat zone 3.

Nine fields

All fields appear in the Karoo’s field picker under CORE Heat. The Karoo passes on the CORE’s core and skin temperature; everything else is worked out by CORE Heat, following CORE’s own definitions.

Heat colors
Karoo theme
Units

Heat colors and raised decimals are CORE Heat’s two settings, in its app on the Karoo’s main menu; the theme and units follow the Karoo. Every field on this page is drawn in your browser by a port of the extension’s own renderer, at a Karoo 2’s pixel sizes.

Heat - Core Temp

Core body temperature, colored by the current heat zone.

Heat - Skin Temp

Skin temperature, colored by the current heat zone.

Heat - Strain Index

The Heat Strain Index, 0–10, read from the sensor itself.

Heat - Zone

CORE’s heat zone, 1–4, cut from the index.

Heat - Training Load

Today’s heat training load, 0–10.

Heat - Adaptation

The Heat Adaptation Score, 0–100 %, colored by level.

HUD

The three HUD fields are one tile each: core and skin temperature side by side, each centred in its half and colored by the heat zone, with a hairline between them. Across the top, CORE and SKIN sit over their numbers, and between them a pill shows the metric the HUD is named for.

Heat - HUD Zone

One square per zone, lit up to the current one, beside the Heat Strain Index.

Heat - HUD Training Load

A square past each of 2, 4, 6 and 8, so the first comes on when the day starts counting toward adaptation.

Heat - HUD Adaptation

One square per adaptation level, lit up to the current one, beside the score.

On a half-width tile

There is no room for the labels beside the pill, so the pill takes the top row alone. CORE is still on the left and SKIN on the right.

Heat zones

CORE’s four zones on the Heat Strain Index: 1 (0–0.9), 2 (1.0–2.9), 3 (3.0–6.9, the one to train in) and 4 (7.0+). The CORE broadcasts the index, but the Karoo does not pass it on, so CORE Heat connects to the sensor over Bluetooth to read it. Until that connection is up, or without it, the index is estimated from core and skin temperature using the zone chart CORE publishes.

The estimate, over core and skin

Drag the point, or use the sliders. On cool skin the core can run well past 38 °C before anything registers; on hot skin the whole scale compresses.

  • Zone 1 HSI 0–0.9, no heat strain
  • Zone 2 1.0–2.9, moderate
  • Zone 3 3.0–6.9, high: train here
  • Zone 4 7.0 and up, extremely high
CORE’s four heat zones over skin temperature from 28 to 38 °C and core temperature from 36.5 to 40.5 °C. Each zone boundary falls as skin temperature rises. The table view below lists the boundaries.
Table view
Core temperature at which the index reaches each zone, by skin temperature (°C)
SkinZone 2 (HSI 1.0)Zone 3 (HSI 3.0)Zone 4 (HSI 7.0)
2838.8039.6240.00
2938.6739.5640.00
3038.5439.4339.99
3138.4139.2539.95
3238.2639.0239.90
3338.1038.7739.82
3437.9238.5139.72
3537.7038.2439.58
3637.4637.9839.41
3737.1937.7239.21
3836.8837.4938.98

Estimated HSI 4.1

Zone 3 high heat strain, the zone to train in

38.6 °C
35.1 °C

Training load and adaptation

Today’s heat training load is built up from time spent at an elevated index, and the days’ loads build your heat adaptation score.

Heat training load

Today’s total, 0–10, built up from time spent at an elevated HSI. Like CORE, it only counts while a ride is recording with a heart rate coming in.

CORE gives the load no colors, so the HUD’s pill takes a violet of its own, deeper with each step. The load’s own field stays uncolored.

  1. 2.0 or less not counting toward adaptation yet
  2. Above 2 the day counts toward adaptation
  3. Above 4
  4. Above 6
  5. Above 8

Heat adaptation score

0–100 %, raised by days with a load above 2 and decaying after two days without one. It is colored by CORE’s four levels.

  1. Thermal Rookie from 0
  2. Heat Accustomed from 25
  3. Heat Adapted from 50
  4. Heat Champion from 90

Reading the index from the sensor

Grant Bluetooth permission in the CORE sensor card of the CORE Heat app (main menu → CORE Heat). The same card shows whether the index on screen is the sensor’s or the estimate.

  • Firmware 0.8.7 or later

    The sensor only sends its index from CORE firmware 0.8.7 on. Update it in the CORE app.

  • Only your sensor

    CORE Heat only uses a sensor once its core and skin temperatures match the Karoo’s own reading, so on a group ride it will not latch onto a riding partner’s CORE.

  • One connection to spare

    A CORE accepts up to three Bluetooth connections. If the Karoo, your phone and a watch already hold them, pair the CORE to the Karoo over ANT+ to leave one free.

In your FIT file

The Karoo records a CORE’s core and skin temperature in the ride’s FIT file itself. CORE Heat adds the heat data it cannot record, as developer fields. A ride without a CORE gets none of these.

Every second

heat_strain_index
The index when it comes from the sensor — the field name CORE asks recording devices to use.
estimated_heat_strain_index
The index when it is the estimate, so no analysis tool mistakes one for the other.
heat_zone
The heat zone, 1–4.

In the ride summary

heat_training_load
This ride’s share of the day’s load.
heat_adaptation_score
The heat adaptation score.
avg_heat_strain_index max_heat_strain_index
The ride’s average and highest index.
time_in_heat_zone_1 to _4
Time in each heat zone, in seconds.

Install

CORE Heat is installed from its latest release on GitHub.

Karoo 3

With the Hammerhead Companion app

  1. Open the latest release in your phone’s browser.
  2. Long-press the core-release.apk link and share it with the Hammerhead Companion app.
  3. Your Karoo shows an install prompt — press Install.

Karoo 2

By manual sideload

  1. Download core-release.apk from the latest release.
  2. Set up your Karoo for sideloading — DC Rainmaker has a step-by-step guide.
  3. adb install core-release.apk

Adding fields to a ride profile

  1. Settings
  2. Profiles
  3. your profile
  4. Data Pages
  5. pick a page
  6. Add Field
  7. CORE Heat
  8. choose a field

To update later, long-tap the CORE Heat icon on the main menu and select Update.