Description
TSS is a running data field that shows a live, continuously accumulating Training Stress Score for the activity in progress, instead of only a number after the workout ends.
Made by Runima - https://runima.fit
Each second the field estimates an intensity factor from pace or heart rate and folds it into the running total using the standard formula: TSS equals duration in hours, times intensity factor squared, times 100. Pace based intensity uses a grade adjusted, normalized graded pace, similar in spirit to Normalized Power for running: altitude and distance samples are smoothed with a rolling regression, and the Minetti running cost model converts the resulting grade into an equivalent flat ground pace. Heart rate based intensity uses percent heart rate reserve relative to lactate threshold heart rate, so resting heart rate differences between athletes are accounted for.
Auto mode prefers pace and automatically falls back to heart rate whenever pace is not usable, for example indoors, on a treadmill, or with poor GPS reception. Pace only and heart rate only modes are also available.
GPS on a wrist worn device is not a perfectly steady signal. TSS Field measures real elapsed time on every tick rather than assuming a fixed interval, treats an unusually long gap as a signal dropout rather than real data, resets its pace smoothing and falls back to heart rate for that tick, caps implausible speed readings, and caps how much any single tick can contribute to the total, so one bad reading cannot produce a large, incorrect jump in the score.
The live TSS number and intensity factor are written to the FIT file every second, so after syncing to Garmin Connect the activity page shows a Training Stress Score chart and an Intensity Factor chart, plus a Total TSS summary stat. The field displays as a plain label and value, styled the same way as Garmin's own built in metrics.
FEATURES
Live, continuously accumulating Training Stress Score, styled like a built in Garmin metric.
Automatic switching between pace based and heart rate based intensity, with manual pace only or heart rate only modes.
Grade adjusted, normalized graded pace using a rolling altitude and distance regression and the Minetti running cost model.
Heart rate based intensity using percent heart rate reserve relative to lactate threshold heart rate.
Hardened against unstable GPS: real per tick elapsed time, automatic recovery from signal gaps, capped per tick contribution.
Training Stress Score and Intensity Factor charts, plus a Total TSS summary stat, on Garmin Connect after syncing.
Optional debug data logging to the FIT file for reviewing a specific run.
What is new
Fixed the timing, grade precision, dropout recovery, validation, settings caching, stale FIT values, and session-reset issues. Removed 15 unsupported manifest targets.
Screenshots
Supported language (1)
Compatible devices (159)
Approach® S50
Approach® S70 (42mm)
Approach® S70 (47mm)
Captain Marvel
Captain Marvel
D2™ Air
D2™ Air X10
D2™ Air X15
D2™ Mach 1
D2™ Mach 1 Pro
D2™ Mach 2
D2™ Mach 2 Pro
Darth Vader™
Darth Vader™
Descent™ G2
Descent™ MK2
Descent™ MK2
Descent™ Mk2S
Descent™ Mk2S
Descent™ MK3 - 43mm
Descent™ MK3i - 51mm
Enduro™
Enduro™
Enduro™ 2
Enduro™ 3
epix™ (Gen 2)
epix™ (Gen 2)
epix™ Pro (42mm)
epix™ Pro (47mm)
epix™ Pro (51mm)
fēnix® 5 Plus
fēnix® 5 Plus
fēnix® 5S Plus
fēnix® 5S Plus
fēnix® 5X Plus
fēnix® 5X Plus
fēnix® 6
fēnix® 6
fēnix® 6 Dual Power
fēnix® 6 Pro
fēnix® 6 Pro
fēnix® 6 Pro Dual Power
fēnix® 6 Pro Solar
fēnix® 6 Solar
fēnix® 6S
fēnix® 6S
fēnix® 6S Dual Power
fēnix® 6S Pro
fēnix® 6S Pro
fēnix® 6S Pro Dual Power
fēnix® 6S Pro Solar
fēnix® 6S Solar
fēnix® 6X Pro
fēnix® 6X Pro
fēnix® 7
fēnix® 7
fēnix® 7 Pro
fēnix® 7 Pro – Solar Edition (No Wi-Fi®)
fēnix® 7S
fēnix® 7S
fēnix® 7S Pro
fēnix® 7X
fēnix® 7X
fēnix® 7X Pro
fēnix® 7X Pro No Wi-Fi
fēnix® 8 AMOLED (43mm)
fēnix® 8 AMOLED (47mm/51mm)
fēnix® 8 Pro
fēnix® 8 Solar (47mm)
fēnix® 8 Solar (51mm)
fēnix® E
First Avenger
First Avenger
ForeAthlete 245
ForeAthlete 245 Music
ForeAthlete 645 Music
ForeAthlete 745
Forerunner® 165
Forerunner® 165 Music
Forerunner® 170
Forerunner® 170 Music
Forerunner® 245
Forerunner® 245
Forerunner® 245 Music
Forerunner® 245 Music
Forerunner® 255
Forerunner® 255 Music
Forerunner® 255S
Forerunner® 255S Music
Forerunner® 265
Forerunner® 265S
Forerunner® 570 - 42mm
Forerunner® 570 - 47mm
Forerunner® 645 Music
Forerunner® 70
Forerunner® 70
Forerunner® 745
Forerunner® 945
Forerunner® 945
Forerunner® 945 LTE
Forerunner® 955 Dual Power
Forerunner® 965
Forerunner® 970
Instinct® 3 – 45 mm, AMOLED
Instinct® 3 – 50 mm, AMOLED
Instinct® Crossover AMOLED
MARQ® (Gen 2)
MARQ® Commander (Gen 2) – Carbon Edition
MARQ™ Adventurer
MARQ™ Adventurer
MARQ™ Athlete
MARQ™ Athlete
MARQ™ Aviator
MARQ™ Aviator
MARQ™ Aviator (Gen 2)
MARQ™ Captain
MARQ™ Captain
MARQ™ Commander
MARQ™ Commander
MARQ™ Driver
MARQ™ Driver
MARQ™ Expedition
MARQ™ Expedition
MARQ™ Golfer
MARQ™ Golfer
Mercedes-Benz Venu®
Mercedes-Benz Venu®
Mercedes-Benz Venu® 2
Mercedes-Benz Venu® 2
Mercedes-Benz Venu® 2S
Mercedes-Benz Venu® 2S
quatix® 6
quatix® 6X
Rey™
Rey™
tactix® 7
tactix® 7 – AMOLED Edition
tactix® 8 – 47 mm, AMOLED
tactix® 8 – 51 mm, Solar
Venu®
Venu®
Venu® 2
Venu® 2
Venu® 2 Plus
Venu® 2 Plus
Venu® 2S
Venu® 2S
Venu® 3
Venu® 3S
Venu® 4 – 41 mm
Venu® 4 – 45 mm
vívoactive® 3 Music
vívoactive® 3 Music
vívoactive® 4
vívoactive® 4
vívoactive® 4S
vívoactive® 4S
vívoactive® 5
vívoactive® 6
Recent metric trend
Rating
Reviews
Snapshot dates
2026-10-27 → 2026-10-31