endurance-coach/reference/zones.md

Training Zones & Field Testing

Professional coaching requires accurate training zones derived from field tests, not arbitrary percentages of max HR.

Lactate Threshold Heart Rate (LTHR) Zones

LTHR is the heart rate at lactate threshold—the intensity you could sustain for approximately 60 minutes in a race. It's more accurate than max HR for prescribing training.

Running LTHR Zones (Friel 7-Zone System)

Zone	Name	% of LTHR	Purpose	Feel
1	Recovery	< 81%	Active recovery, warm-up/cool-down	Very easy, could talk indefinitely
2	Aerobic	81-89%	Aerobic base building, fat oxidation	Easy, full conversations
3	Tempo	90-93%	Muscular endurance, aerobic capacity	Moderate, sentences only
4	Sub-threshold	94-99%	Lactate tolerance, threshold extension	Hard, few words at a time
5a	Threshold	100-102%	Lactate threshold improvement	Very hard, race effort for 60min
5b	VO2max	103-106%	VO2max development	Extremely hard, 3-8min max
5c	Anaerobic	> 106%	Neuromuscular power, speed	Max effort, < 3min

Cycling LTHR/Power Zones

Zone	Name	% of LTHR	% of FTP	Purpose
1	Recovery	< 81%	< 55%	Active recovery
2	Aerobic	81-89%	56-75%	Endurance base
3	Tempo	90-93%	76-90%	Muscular endurance
4	Sub-threshold	94-99%	91-99%	Threshold extension
5a	Threshold	100-102%	100-105%	FTP improvement
5b	VO2max	103-106%	106-120%	VO2max intervals
5c	Anaerobic	> 106%	> 120%	Neuromuscular power

Swimming Zones (CSS-based)

Zone	Name	Pace Relative to CSS	Purpose
1	Recovery	CSS + 15-20 sec/100m	Warm-up, cool-down
2	Aerobic	CSS + 8-12 sec/100m	Aerobic endurance
3	Tempo	CSS + 3-6 sec/100m	Lactate tolerance
4	Threshold	CSS pace	Threshold development
5	VO2max	CSS - 3-5 sec/100m	VO2max intervals

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Field Testing Protocols

Run: 30-Minute Threshold Test

1. Warm up 15 minutes easy (Zone 1-2)
2. Run 30 minutes at the hardest sustainable pace (simulate race effort)
3. Record average HR for the entire 30 minutes = LTHR
4. Cool down 10 minutes easy
5. Average pace = approximate lactate threshold pace

Note: Some coaches use final 20 minutes of a 30-min test to exclude early pacing errors.

Bike: 20-Minute FTP Test

1. Warm up 20 minutes including 3x1min high-cadence spin-ups
2. Ride 20 minutes at maximum sustainable power
3. Average power × 0.95 = FTP
4. Average HR = approximate cycling LTHR
5. Cool down 10-15 minutes

Alternative: 2x8 minute test with 10min recovery; average power × 0.90 = FTP

Swim: Critical Swim Speed (CSS) Test

1. Warm up 400m easy with drills
2. Swim 400m time trial (all-out, record time)
3. Rest 10 minutes (active recovery)
4. Swim 200m time trial (all-out, record time)
5. CSS = (400m distance - 200m distance) / (400m time - 200m time)

Example: 400m in 6:40 (400 sec), 200m in 3:00 (180 sec) CSS = 200m / 220 sec = 0.909 m/sec = 1:50/100m

When to Retest

• Every 6-8 weeks during base/build phases
• After recovery weeks (when fresh)
• If perceived effort no longer matches prescribed zones

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Running Pace Zones (VDOT / Jack Daniels)

For athletes with known race times:

Zone	Name	Description	How to Determine
E	Easy	Daily running, long runs	59-74% VO2max; 1:00-1:30/km slower than threshold
M	Marathon	Marathon race pace	75-84% VO2max; sustainable for 2-4 hours
T	Threshold	Tempo runs, cruise intervals	83-88% VO2max; ~60min race pace
I	Interval	VO2max development	95-100% VO2max; 3-5min repeats
R	Repetition	Speed, neuromuscular	> 100% VO2max; short reps with full recovery

Pace Estimation from Threshold:

• Easy pace: Threshold + 50-70 sec/km
• Marathon pace: Threshold + 15-25 sec/km
• Interval pace: Threshold - 15-20 sec/km
• Repetition pace: Threshold - 25-35 sec/km

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Power-Based Training (Cycling)

When power data is available, use power zones exclusively—they're more accurate than HR which lags and drifts.

Workout Type	Zone	Duration	Recovery	Weekly Frequency
Endurance	2	1-5 hours	N/A	2-4x
Tempo	3	20-60 min continuous	N/A	1-2x
Sweet Spot	3-4 (88-93% FTP)	2x20-30 min	5-10 min	1-2x
Threshold	5a	2-4 x 8-15 min	5-8 min	1x
VO2max	5b	4-6 x 3-5 min	3-5 min	1x
Anaerobic	5c	6-10 x 30sec-2min	2-4 min	0-1x

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Auto-Calculation in Compact Plans (v2.0)

In the v2.0 compact plan format, you only need to specify threshold values. The plan expander automatically calculates all zone ranges using the standard percentages documented above.

Specifying Zones

# In your compact plan YAML
athlete:
  zones:
    hr:
      lthr: 165 # Auto-calculates HR zones
    power:
      ftp: 250 # Auto-calculates power zones
    swim:
      css: "1:45" # Auto-calculates swim zones

What Gets Calculated

From LTHR (165 bpm example):

• Zone 1 (Recovery): < 134 bpm (< 81%)
• Zone 2 (Aerobic): 134-147 bpm (81-89%)
• Zone 3 (Tempo): 148-154 bpm (90-93%)
• Zone 4 (Sub-threshold): 155-163 bpm (94-99%)
• Zone 5a (Threshold): 165-168 bpm (100-102%)
• Zone 5b (VO2max): 170-175 bpm (103-106%)
• Zone 5c (Anaerobic): > 175 bpm (> 106%)

From FTP (250W example):

• Zone 1: < 138W (< 55%)
• Zone 2: 140-188W (56-75%)
• Zone 3: 190-225W (76-90%)
• Zone 4: 228-248W (91-99%)
• Zone 5a: 250-263W (100-105%)
• Zone 5b: 265-300W (106-120%)
• Zone 5c: > 300W (> 120%)

From CSS (1:45/100m example):

• Zone 1: 2:00-2:05/100m (CSS + 15-20s)
• Zone 2: 1:53-1:57/100m (CSS + 8-12s)
• Zone 3: 1:48-1:51/100m (CSS + 3-6s)
• Zone 4: 1:45/100m (CSS)
• Zone 5: 1:40-1:42/100m (CSS - 3-5s)

Field Testing Still Required

Auto-calculation does NOT replace field testing. The calculated zones are only as accurate as the threshold values you provide.

Athletes should perform field tests (see protocols above) to establish accurate LTHR, FTP, and CSS values. Include validation workouts in the first 1-2 weeks of any plan when working with estimated or manual data.

Expanding to See Calculated Zones

To see the expanded zones, use:

npx endurance-coach expand plan.yaml --verbose

This shows the full expanded plan including all calculated zone ranges