ADS
Definition
ADS — Aerobic Deficiency Syndrome — is a condition in which the gap between AeT and AnT is too narrow: the aerobic system is underdeveloped relative to the anaerobic ceiling above it. A runner with ADS can often produce respectable short-distance performances, but the engine beneath the performance is thin.
The term was brought into coaching practice by Johnston and House. The diagnostic threshold they use — which Your Pacer uses — is the ratio AeT / AnT:
| Ratio | Classification | Coaching response |
|---|---|---|
< 0.75 | Severe ADS | Z1 only, Z2 minimal. No intensity. |
0.75 – 0.89 | ADS | Z1–Z2 only. No intensity prescriptions. |
0.90 – 0.94 | Standard | 80–90% aerobic, small Z3 doses permitted. |
≥ 0.95 | Developed | Full polarized distribution unlocked. |
Why it matters to runners
ADS is where well-intentioned athletes most often injure themselves. The signature pattern: a runner picks up a training plan from a magazine or an app that assumes a developed aerobic base, starts doing threshold work and intervals on an underdeveloped engine, and accumulates fatigue faster than adaptation. A few weeks in, something breaks — often a tendon, sometimes motivation.
The corrective path is not exotic. It is slow miles, at or below AeT, for long enough to raise the ratio. Weeks, sometimes months. Runners often report feeling worse before they feel better — the short-term gratification of harder sessions is gone, and the base-building work does not immediately translate to faster race times. Then, suddenly, it does.
When Your Pacer's diagnostic returns a ratio in the ADS bands, the coaching response is not negotiable. Intensity is withheld until the gate clears. This is one of the few places where the system takes an authoritative rather than autonomy-supportive stance — the physiology does not yield to preference.
How Your Pacer detects it
ADS is computed from your estimated AeT and AnT. Both are derived — ideally — from measured data in your last 90 days:
- AeT: heart-rate drift analysis on long, steady efforts, plus (where available) DFA-alpha1.
- AnT: from race or time-trial data (Daniels VDOT derivation), or from drift testing near AnT heart rate.
Both estimates carry a confidence score. Low confidence triggers an explicit request for a drift test before any intensity is prescribed.
Related terms
Further reading
- House & Johnston — the original framing of aerobic deficiency for mountain athletes (foundational coaching literature).
- Johnston, House & Jornet — ADS diagnostic protocols and corrective programs (published mountain-athlete methodology).