Training Metrics
How Smagpie measures your training
It’s Tuesday morning. You check your athlete’s Form: −22 Fatigued. The threshold workout you planned for Wednesday becomes easy aerobic. That decision took three seconds — because the math was already done.
Every number below exists to help you make a better coaching decision.
Similar Science, Our Own Names
Smagpie’s metrics are built on the same published exercise science used across the endurance coaching industry — Coggan, Banister, Minetti. We use our own names to stay clear of trademarks and to evolve our calculations as the science improves.
| Smagpie | ≈ You May Know As |
|---|---|
| Training Load Score (TLS) | TSS |
| Smoothed Power (SP) | NP |
| Effort Index (EI) | IF |
| Fitness / Fatigue / Form | CTL / ATL / TSB |
Training Load Score (TLS)
How hard was that session? TLS puts a single number on every workout — endurance or strength — so you can compare sessions, track weekly volume, and spot when load is climbing too fast.
Benchmark: 100 TLS ≈ one hour at your threshold. An easy 45-minute jog might be 35. A hard 90-minute interval session might be 150.
Calculation Pipeline
Power Data → Smoothed Power (SP) → Effort Index (EI) → TLS
Smoothed Power
When your bike has a power meter, Smagpie computes Smoothed Power — a 30-second rolling average raised to the 4th power, then root-averaged. This emphasizes hard surges and intervals, reflecting the real physiological cost of variable riding.
Grade-adjusted speed uses cycling physics: total power P = (Fgravity + Frolling + Faero) × v, solved for the flat-ground speed requiring equal power. Default parameters: 80 kg total mass, Crr = 0.004, CdA = 0.32 m².
Show the math
SP = (mean(rolling_avg_30s4))0.25
EI = SP ÷ FTP
TLS = duration_hours × EI2 × 100
Fallback
HR-Based (TRIMP)
No power meter? Smagpie falls back to heart rate using the Banister TRIMPexp model — an exponential weighting that accounts for the disproportionate cost of high heart rate zones. Uses your resting HR, max HR, threshold HR, and a gender-based weighting constant. When speed and GPS grade data are present but no power meter, Smagpie also computes Grade-Adjusted Speed using a cycling aerodynamic model — not the running formula — giving a more accurate effort estimate on hilly rides.
Show the math
TRIMPexp = ∑(duration × HRreserve × 0.64 × ek × HRreserve)
TLS = (TRIMPexp ÷ TRIMP1hr@threshold) × 100
Threshold Setting
Functional Threshold Power (FTP) in watts
TLS Type Badge
Shows “Power” or “HR (TRIMP)” badge on workout detail
Effort Index (EI)
How intense was that session relative to your threshold? An EI of 100 means you were at threshold the entire time. A recovery jog might be 60. A VO2max interval session might average 110.
EI uses sport-specific calculation: Smoothed Power divided by FTP for cycling, normalized GAP divided by threshold pace for running, and swim pace divided by Critical Swim Speed for swimming.
Typical EI Ranges
Fitness, Fatigue & Form
The big picture. These three numbers turn weeks of individual workouts into a trend you can act on — when to push, when to back off, and when your athlete is ready to race.
Fitness
Your training bank account. A 42-day rolling trend of daily TLS. Slow to build, slow to fade. Represents the accumulated training your body has absorbed.
Rises with consistent training. Falls during rest weeks and off-season.
Fatigue
The recent withdrawal. A 7-day rolling trend — fast-moving, responsive to the last few days of training. Spikes after hard blocks, drops quickly with rest.
High Fatigue after a build week is expected and productive.
Form
Are they ready? Form = Fitness minus Fatigue. Positive means rested and ready. Negative means absorbing load. The sweet spot for racing is slightly positive.
Optimal race readiness: typically +5 to +15.
Form Readiness Labels
Smagpie translates the raw Form number into coaching-friendly labels. A club rider sees “Fresh” and knows they’re good to go. A triathlete sees “Fatigued” at −18 and knows it’s a planned build block, not a problem.
Detrained or extended taper — fitness is declining
Peaked, race-ready, good to push
Normal training — manageable load
Absorbing training load — planned build block
Injury/illness risk — recovery needed
Start-of-day convention
Today’s Fitness, Fatigue, and Form values reflect all workouts through yesterday. When your athlete checks readiness at 6am before training, they see pre-workout Form — it won’t shift mid-day after they upload.
Efficiency Score & Aerobic Decoupling
Is the engine improving? These two metrics track aerobic development over time — the kind of progress that doesn’t show up in a single workout but transforms an athlete over months.
Efficiency Score (ES)
How much speed are you getting per heartbeat? ES divides average speed by average heart rate, scaled per sport. A rising ES at the same intensity over weeks means the aerobic engine is improving.
ES = (Avg Speed ÷ Avg HR) × sport constant
The trend is the signal. A single ES value means little — compare the same type of workout across weeks or months to see real aerobic development.
Aerobic Decoupling %
Can your athlete hold pace without their heart rate drifting? Smagpie splits steady-state sessions at the midpoint and compares efficiency in each half. Heart rate rising for the same pace means the aerobic system is working harder to maintain output.
≤ 5%
Strong base
> 5%
Still building
Only calculated for steady-state sessions longer than 20 minutes with low variability. Intervals and races produce unreliable decoupling values — Smagpie filters them out automatically.
Perceived Exertion & Workout Feel
The athlete’s voice. Objective load (TLS) plus subjective experience (RPE and Feel) gives you the full picture. A TLS of 80 that “felt like a 9” is a very different signal than a TLS of 80 that “felt like a 5.”
RPE — Perceived Exertion
The standard Borg CR-10 scale: how hard did the session feel on a scale of 0–10? Coaches worldwide already speak this language. Combined with TLS, RPE reveals when an athlete is handling load well — or struggling.
Workout Feel
How did you feel overall? A 5-point scale from terrible to amazing. Trending Feel over time reveals early fatigue signals — declining feel at constant load is a warning sign before anything shows up in the numbers.
Terrible
Poor
OK
Good
Amazing
Where RPE & Feel come from
Garmin watches
Automatically imported from Garmin Connect when athletes rate their activity after upload.
Session Tracker app
Athletes rate RPE and Feel on the session complete screen — works for any workout type including strength.
What you need to set up
Smagpie provides sensible defaults, but your metrics are only as good as your thresholds. Set these in each athlete’s benchmark settings for accurate calculations.
Cycling
- • Functional Threshold Power (FTP)
- • Threshold HR (for HR fallback)
Running
- • Threshold running pace
- • Threshold HR (for HR fallback)
Swimming
- • Critical Swim Speed (CSS)
HR-Based Calculations
- • Resting heart rate
- • Max heart rate
- • Gender (affects HR weighting)
Strength
- • No thresholds needed
- • Volume calculated from logged sets
RPE & Feel
- • No setup needed
- • Athletes rate after each session
Numbers that help you coach better
Free to start. Every metric above is included — no premium tier, no add-ons. Connect a watch or log a session and the numbers start working.