Zones & Thresholds
Zone 2, LT1/LT2, FTP, CTL/ATL/TSB, polarized vs pyramidal, aerobic decoupling.
10 articles · sorted by most recent
How Do I Calculate My Max Heart Rate? Why 220-Age Is Wrong
The 220-age formula was never validated. Its standard error is 12.4 bpm — meaning 1 in 20 people are off by more than 24 bpm. Here's what to use instead.
The Zone 3 Trap: Why Most Amateur Cyclists Lose a Full Season in the Grey Zone
Amateur cyclists spend 25–45% of training time in Zone 3 (76–90% FTP). Elites keep it under 11%. That gap explains a year of stalled fitness.
CTL Benchmarks for Ironman: What Fitness Score You Need for Your Finish Time
A sub-10-hour Ironman typically requires a race-day CTL of 120. Sub-9 hours needs 145–150. Here are the benchmarks, the ramp rate rules, and TSB taper targets by athlete tier.
Aerobic Decoupling: The Number That Tells You If Your Base Is Actually Working
Aerobic decoupling measures how much your heart rate drifts relative to pace or power. Below 5% means a race-ready aerobic base. Above 10% means your engine is leaking.
Polarized vs Pyramidal Training: The Research Has a Surprising Answer
Two 2024/2025 meta-analyses found no significant difference between polarized and pyramidal overall (SMD=-0.06). The better question is which model fits your athlete level and event distance.
VO2max Intervals: The 4x4 Rule and What Most Athletes Get Wrong
The Norwegian 4x4 protocol raised VO2max 7.2% in 8 weeks vs 1.8% for easy running. Most athletes do these sessions too often, too short, and at the wrong pace.
Zone 2 vs LT1: Why the 60–70% HRmax Definition Is Wrong
The '60–70% HRmax = Zone 2' shortcut is physiologically wrong. LT1 — your real Zone 2 ceiling — spans 69–94% HRmax across trained athletes. Here's how to find yours.
CTL, ATL, and TSB: The Mathematical Foundation of Training Load
CTL, ATL, and TSB are the three numbers that tell you whether to push harder or back off. Here's the math behind them and what they mean for your Ironman preparation.
TSS vs TRIMP: Which Training Load Metric Should You Use?
TSS uses power data; TRIMP uses heart rate. For multi-sport athletes managing three disciplines, the choice of metric determines whether your training load model is accurate or dangerously misleading.
Zone 2 Training: The Science Behind Slow Riding Making You Faster
Zone 2 is the physiological foundation of every elite endurance program. Here's the mitochondrial biology, the 80/20 data, and precise definitions that separate productive Zone 2 from glorified recovery.