Anaerobic Threshold
The anaerobic threshold is the exercise intensity at which lactate accumulates faster than the body can clear it, marking the upper limit of sustainable effort. For HYROX athletes, it defines race pace and determines how quickly you recover between stations.
Definition
The anaerobic threshold (AnT) is the exercise intensity at which anaerobic energy production begins to significantly supplement aerobic metabolism, causing lactate to accumulate in the blood faster than it can be cleared. Also called the onset of blood lactate accumulation (OBLA), it is typically identified at a blood lactate concentration of approximately 4 mmol/L. For HYROX® athletes, the anaerobic threshold represents the red line - the intensity above which fatigue escalates rapidly and pacing falls apart.
The Science
At rest and low intensities, muscles produce energy almost entirely through aerobic pathways. As intensity rises, the demand for ATP outpaces aerobic supply, and anaerobic glycolysis ramps up. This produces lactate and hydrogen ions as by-products. Below the anaerobic threshold, the body clears lactate as fast as it is produced. Above it, lactate accumulates exponentially, pH drops, and muscular fatigue accelerates.
The anaerobic threshold typically occurs at 80-90 % of max heart rate in trained athletes and at 75-85 % of VO2 max. It is closely related to - but distinct from - the lactate threshold (LT1, ~2 mmol/L) and the ventilatory threshold.
Why It Matters for HYROX®
HYROX® demands repeated surges above and below the anaerobic threshold:
- Running segments are ideally paced just below AnT to preserve capacity for stations.
- High-output stations (Sled Push, Wall Balls, SkiErg) push athletes above AnT, flooding muscles with lactate.
- Recovery ability between stations depends on how quickly lactate can be cleared - a function of how well-trained the AnT is.
Raising the anaerobic threshold lets you run faster, push harder at stations, and recover more quickly in transition.
How to Measure It
| Method | Details |
|---|---|
| Lab lactate test | Blood draws at incremental intensities; AnT at ~4 mmol/L |
| Field lactate test | Portable Lactate Pro 2 device during step test |
| Talk test | Intensity where continuous speech becomes impossible |
| Heart rate deflection | HR drift analysis during graded treadmill test |
| 30-min time trial | Average pace/HR over a maximal 30-min run approximates AnT |
How to Improve It
- Tempo runs - 20-40 min at AnT pace (comfortably hard). 1-2 sessions per week.
- Cruise intervals - 3-4 x 10 min at threshold with 2-min jog recovery.
- HYROX® simulations - race-pace sessions where running segments are held at 85-90 % max HR.
- Zone 2 base work - builds the aerobic engine that supports a higher AnT.[1]
- Lactate shuttle training - alternate between supra-threshold station work and sub-threshold running to train lactate clearance.[2]
HYROX® Benchmarks
| Level | AnT Running Pace (min/km) Men | AnT Running Pace (min/km) Women |
|---|---|---|
| Beginner | 5:30-6:00 | 6:00-6:30 |
| Intermediate | 4:45-5:30 | 5:15-6:00 |
| Competitive | 4:15-4:45 | 4:45-5:15 |
| Elite / Pro | Sub-4:15 | Sub-4:45 |
FAQ
What is the difference between anaerobic threshold and lactate threshold? The lactate threshold (LT1) is the first rise in lactate above baseline (~2 mmol/L). The anaerobic threshold (LT2/OBLA) is the higher intensity at ~4 mmol/L where lactate accumulation accelerates. Both matter, but AnT is the more race-relevant marker for HYROX® pacing.
Should I train above or below my anaerobic threshold? Both. The majority of volume (80 %) should sit below AnT to build your aerobic base. The remaining 20 % should include work at and above AnT to push the threshold higher.
Can station work improve my anaerobic threshold? Yes. High-rep, moderate-load station simulations (Wall Balls, SkiErg intervals) performed at threshold intensity are an effective way to raise AnT in a HYROX®-specific context.
Dial in your threshold pacing with ROXBASE - data-driven training for HYROX® athletes.
Sources
Wang Z, Wang J (2024). The effects of high-intensity interval training versus moderate-intensity continuous training on athletes' aerobic endurance performance parameters. European journal of applied physiology. https://doi.org/10.1007/s00421-024-05532-0 ↩
Pereira PE, Esteves G, Carvas N (2024). Effects of high-intensity interval and moderate-intensity continuous training on the anaerobic threshold of highly trained athletes in endurance sports: a systematic review with meta-analysis. The Journal of sports medicine and physical fitness. https://doi.org/10.23736/S0022-4707.24.15855-0 ↩
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