Your watch gives you a threshold pace. Your lab test gives you a threshold heart rate. Both suggest a precise line. In reality, threshold is an estimated zone, and treating it as a single number leads to some of the most common training mistakes.
What threshold actually is
Threshold describes a balance: the point where your aerobic system can still keep up with the lactate you produce. Lactate itself is not the villain. It is a fuel and a signal, not the direct cause of fatigue.
Threshold values vary widely by person, testing method, conditions, and training history. The number on your watch is an estimate, not a boundary.
How to judge threshold without false precision
Use several signals together:
- Effort: hard but controlled
- Breathing: labored but rhythmic
- Sustainable duration: you could hold it considerably longer than the session asks
- Splits: consistent from first rep to last
How to build threshold
- Build the aerobic base first. Aerobic volume develops the clearance and transport foundation threshold depends on.
- Start below the line. Accumulate time just under threshold and extend total time gradually.
- Split the work when it helps. Shorter reps with short rests often improve control and repeatability.
- Progress carefully. Move from steady running to sub-threshold time, then to threshold-plus work, hills, surges, a faster final rep, or alternations.
- Keep it repeatable. A threshold session should never end in collapse.
- Keep some speed. Heavy threshold emphasis can blunt anaerobic capacity, so counterbalance it with hill sprints or short fast work.
Threshold is support, not the whole season
Threshold work is usually support for the race-specific training that comes later. It raises the ceiling on what you can sustain, but it is not the same as race readiness.
How Catherine applies this
Catherine sets threshold as a range from your effort, breathing, and splits, starts you just under it, and extends the work gradually. Threshold-heavy blocks always include speed work so your top end stays sharp.