Lactate Threshold Training: How to Find and Train at Your LT

If you could improve only one physiological variable to become a faster endurance athlete, lactate threshold would be it. More than VO2max, more than raw aerobic capacity, your ability to sustain high power or pace without accumulating lactate determines how fast you can race. Yet most athletes either ignore it or train it wrong.

What Is Lactate Threshold?

Lactate is a byproduct of carbohydrate metabolism. At low intensities, your body produces and clears it at roughly equal rates. As intensity rises, production outpaces clearance. Lactate threshold is the inflection point where accumulation begins to accelerate meaningfully.

Sports scientists identify two distinct thresholds:

• LT1 (First Lactate Threshold / Aerobic Threshold): The point where lactate first rises above baseline — roughly 2 mmol/L. Below LT1 you are in purely aerobic territory. This corresponds to a comfortable, conversational pace.
• LT2 (Second Lactate Threshold / Anaerobic Threshold): The intensity at which lactate accumulation becomes rapid and unsustainable — around 4 mmol/L. This is the ceiling of what you can sustain for 40–60 minutes in a race, and closely corresponds to FTP in cycling.

Raising both thresholds means you go faster at every intensity level.

Why Lactate Threshold Matters More Than VO2max

Two athletes can have identical VO2max values but wildly different race results. The differentiator is almost always threshold. An athlete who sustains 85% of VO2max at threshold will consistently beat someone who can only hold 70% — even with the same aerobic ceiling.

For cyclists, LT2 performance correlates directly with time trial and climbing results. For runners and triathletes, LT2 pace tracks marathon and half-iron race pace. Improving your threshold pace by 10–15 seconds per kilometre translates to significant time savings at goal events.

How to Find Your Lactate Threshold Without a Lab

The 20-Minute FTP Test (Cycling)

Ride as hard as you can sustain for 20 minutes on a flat course or trainer. Take 95% of your average power — this closely approximates your Functional Threshold Power (FTP), which tracks LT2. Garmin Edge devices with a power meter can run this test automatically.

The Talk Test (LT1)

LT1 corresponds roughly to the highest intensity at which you can speak in full, comfortable sentences. Increase intensity in small increments every 3–4 minutes. The moment speaking becomes noticeably laboured, you have crossed LT1.

Garmin Lactate Threshold Detection

Garmin devices with FirstBeat Analytics — Edge 530, Edge 830, Edge 1040, Forerunner 955/965, Fenix 7 series — can estimate lactate threshold automatically from a guided workout. It uses HRV and performance data to calculate your LT heart rate and corresponding pace or power. Accurate enough for training purposes and more accessible than lab testing.

How to Train Your Lactate Threshold

Building LT1: High Volume at Low Intensity

LT1 responds to volume. Long, easy Zone 2 aerobic work gradually shifts LT1 upward — you produce more power or pace before lactate starts rising. The key is staying below LT1. Most athletes train too hard on easy days, spending time in the grey zone between LT1 and LT2 that is hard enough to fatigue but not hard enough to drive adaptation.

• Keep easy rides at or below your LT1 heart rate (typically 65–75% max HR)
• Aim for 3–5 hours per week minimum in Zone 2 during base building
• Adaptation is measured in weeks and months, not days

Building LT2: Threshold Intervals

LT2 requires sustained efforts at or just below threshold. Effective formats include:

• 2 × 20 minutes at FTP: The workhorse threshold session. Two efforts with 5 minutes recovery between. Hard but manageable.
• 3 × 10 minutes slightly above FTP: Higher intensity, shorter efforts. Useful for pushing LT2 upward.
• Sweet spot (88–93% FTP): Sub-threshold intensity allowing more total time near threshold with less fatigue. Practical for time-crunched athletes.

One to two threshold sessions per week is sufficient for most athletes. More than that and fatigue accumulates faster than adaptation.

Tracking Progress on Garmin

The clearest sign threshold training is working: your LT2 power or pace rises while your LT2 heart rate stays the same or drops. You are doing more work for the same physiological stress. Track this using Garmin’s Lactate Threshold HR and Pace/Power readouts, updated automatically after guided tests. Retest every 4–6 weeks during a structured block.

Common Mistakes

• Training in the grey zone: Too hard on easy days, not hard enough on threshold days. You get fatigued without the corresponding adaptation.
• No aerobic base: LT2 intervals on a weak aerobic foundation yield poor results. Build LT1 first.
• Testing too frequently: Threshold tests are a training stress. Test every 4–6 weeks, not every week.

The Bottom Line

Lactate threshold training is not glamorous but it is the highest-leverage physiological variable most amateur endurance athletes can improve. Build your aerobic base to raise LT1, add structured threshold intervals to raise LT2, and retest every 4–6 weeks to confirm progress. Consistent, disciplined threshold work is what unlocks performance breakthroughs at every level.