Single-Session Spike Guard
No single run can exceed 110% of the longest run in the preceding 4 plan weeks. If a planned distance would spike above this threshold, it is automatically capped to the safe maximum.
Research: BJSM 2025 (n=5,200) found single-session spikes to be the strongest predictor of running injuries.
Acute:Chronic Workload Ratio (ACWR)
Pheidi continuously monitors your training load ratio by comparing your last 7 days (acute) against your last 28 days (chronic, averaged per week). A minimum of 3 weeks of completed workout data is required before the ratio becomes available.
| ACWR Range | Risk Zone | Guidance |
|---|---|---|
| < 0.8 | ● Under-training | You can safely increase load |
| 0.8 to 1.3 | ● Green | Sweet spot, building fitness safely |
| > 1.3 and ≤ 1.5 | ● Yellow | Caution, training load is ramping quickly |
| > 1.5 | ● Red | High injury risk, dial it back |
Safety guards run inside the Pheidi app, sign in to see your risk score.
Research & evidence
Science behind this feature from pheidi.training.
- Running Training Plan: The Complete Guide Pillar hub linking 48+ deeper dives, start here for the full picture.
- ACWR for Injury Prevention Acute:chronic workload ratio, the 0.8 to 1.3 safe zone and 1.5+ danger zone.
- Tracking ACWR in Practice How to compute and monitor workload ratio in day-to-day training.
- Session-Spike Injury Study Single-session spikes predict injury better than weekly jumps.
- Load Management Injury Research (2025) Current evidence on what actually reduces injury risk.
- Running Injury Rates: 2025 Review Modern prevalence data and what it tells us about prevention.
- The Weekly Volume Sweet Spot Injury rates minimize around 30 to 50 km/week for most runners.
- Wearables and Biofeedback for Injury Prevention Readiness metrics, recovery scores, and what they predict.
See also
- How Adaptive Progression Works How Pheidi increases your training volume safely: volume-aware increase rates, 3-up-1-down recovery weeks, and protection against rapid mileage spikes.
- How Load Redistribution Works What happens to the miles you remove from your plan, and how Pheidi safely reallocates load across future easy runs without breaching ACWR thresholds.
- How Injury Management Works How Pheidi adjusts your training plan when you report an injury: severity-based volume reductions, graduated return-to-running, and pain-based progression gates.