Four hard four-minute efforts separated by three easy minutes, raising peak oxygen-use capacity — the fitness measure most tightly linked to living longer. That gain is well established; the edge over steady moderate exercise is real but smaller than early studies suggested. Sessions are genuinely hard, and the usual failure is effort quietly dropping below what the format requires. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Maximal oxygen uptake (VO2max) | Above the 75th percentile for age and sex; roughly >45 (men) and >38 (women) mL/kg/min at 45–55 | Primary target of the protocol; strongest fitness-based predictor of survival |
| Resting heart rate | 50–65 bpm | Tracks cardiovascular adaptation; a multi-day rise signals inadequate recovery |
| Heart rate variability (HRV) | Stable or rising relative to personal 60-day baseline | Indicates autonomic recovery and whether training load is being absorbed |
| Blood pressure (home, seated) | 110–120 / 70–75 mmHg | Detects the antihypertensive effect and the additive low-pressure risk with medication |
| Fasting glucose and HbA1c | Fasting glucose 75–90 mg/dL; HbA1c 4.8–5.3% | Tracks the glycaemic effect, largest in those starting furthest from optimal |
| Fasting insulin and HOMA-IR | Insulin 2–5 µIU/mL; HOMA-IR below 1.0 | More sensitive than glucose to the insulin-sensitising effect |
| Apolipoprotein B (ApoB) | Below 80 mg/dL, or below 60 mg/dL where cardiovascular risk is elevated | Counts the atherogenic particles that drive cardiovascular events |
| High-sensitivity C-reactive protein (hs-CRP) | Below 1.0 mg/L | Tracks systemic inflammatory burden, which aerobic training tends to lower |
| Ferritin and full blood count | Ferritin 50–150 ng/mL; haemoglobin in the upper half of the reference range | Iron status and haemoglobin cap oxygen-carrying capacity and training response |
| Creatine kinase (CK) | Below 200 U/L at rest, measured 72+ hours post-exercise | Distinguishes normal training load from excessive muscle damage |
| Estimated glomerular filtration rate (eGFR) | Above 90 mL/min/1.73 m² | Establishes kidney function before repeated high-intensity exertion |
| Thyroid-stimulating hormone (TSH) and free T4 | TSH 1.0–2.0 mIU/L; free T4 in the upper half of the reference range | Unrecognised thyroid dysfunction blunts exercise tolerance and mimics poor response |
Cadence: Resting heart rate and sleep daily; home blood pressure weekly for 12 weeks then monthly; fitness reassessment at 12 weeks then every 6 months; full biomarker panel at 3 months then every 6–12 months. Baseline bloods drawn 72+ hours after hard exercise.