Which Training Phase Should I Be In? What About Deload Weeks?
Knowing what to train is one question. Knowing when to train what is another entirely. Periodisation, the systematic organisation of training into phases, is the framework that answers this question. It is one of the most robustly supported concepts in exercise science for endurance athletes.
The Phases of a Running Training Cycle
A 2022 systematic review of training periodisation in highly trained and elite distance runners (Casado et al., International Journal of Sports Physiology and Performance) confirmed that a structured, phased approach to training produces superior performance outcomes compared to unstructured programmes. The typical macrocycle for a runner preparing for a goal race is divided into four key phases:
Phase 1: Base / Preparation Phase
Duration: 8–20 weeks, depending on event and fitness level.
This phase builds the aerobic foundation. Training is characterised by high volume, low-to-moderate intensity, and a pyramidal training intensity distribution (TID), the majority of running below the first ventilatory threshold (easy/conversational pace). The objectives are to develop mitochondrial density, capillary networks, connective tissue strength, and running economy. Strength training during this phase should focus on foundational stability and general strength.
ACWR target: Build progressively, aiming to stay in the Building Phase. Avoid rapid spikes in this phase as tissues are not yet adapted to high-intensity stress.
Phase 2: Build / Pre-Competitive Phase
Duration: 6–12 weeks.
Intensity increases progressively. Threshold and tempo runs enter the programme, along with some race-specific work. Casado et al. (2022) noted that highly trained runners shift from a pyramidal TID in the preparation phase toward a more polarised TID (high volumes of easy running combined with targeted high-intensity sessions) as they approach competition. Volume typically peaks near the end of this phase. This is where the greatest fitness gains are made and where injury risk is highest if load monitoring is neglected.
ACWR target: Work within the full Building Phase, be careful - tempo sessions often increase internal load. The same mileage at tempo vs conversational pace does not have the same effect on the body.
Phase 3: Peak / Specific Phase
Duration: 2–4 weeks.
Race-specific workouts dominate. Sessions simulate race conditions: pacing, terrain, and effort. Volume begins to reduce slightly while intensity remains high or increases further. Recovery between sessions becomes critical. Research by Aubry et al. (2014) established the concept of "functional overreaching" during this phase, a brief but intentional increase in load that when followed by tapering, can produce a supercompensation effect and a performance peak.
Phase 4: Taper / Race Phase
Duration: 1–3 weeks.
Training volume reduces significantly, typically 40–60%, while intensity is maintained or slightly increased through short, sharp sessions. The taper allows accumulated fatigue to dissipate while fitness is preserved. ACWR trends naturally drop, as acute load falls while chronic load remains high, the ideal readiness state for performance.
Deload Weeks: When and Why
A deload week is a planned reduction in training volume, and sometimes intensity designed to allow accumulated fatigue to dissipate without losing meaningful fitness. It is distinct from a taper: a deload facilitates continued progression within a training block, while a taper prepares for peak performance at a specific event.
A 2024 cross-sectional survey of deloading practices in strength athletes (Haynes et al., Sports Medicine) found that practitioners most commonly implemented deload periods every 4–6 weeks, with a duration of approximately 6–7 days.
For experienced runners, the typical recommendation:
Frequency: Every 3–4 training weeks (a 3:1 build-to-deload ratio is most commonly applied).
Volume reduction: Reduce total distance by 30–40%. Maintain key sessions but shorten them.
Intensity: Maintain intensity in short doses. One tempo or interval session can be retained, shortened, to prevent detraining.
Deload weeks are not a sign of weakness. They are a scientific tool. Research on supercompensation theory is unambiguous: adaptation to training stress occurs during recovery, not during the stress itself. Skipping deloads delays progress and elevates injury risk.
Practical Application
Plan your phases backward from your goal race: identify your taper (2–3 weeks prior), your peak phase (2–4 weeks before that), your build (6–12 weeks), and your base (as long as you have). Insert a deload week every 3–4 training weeks throughout. Use your ACWR to fine-tune, but let the phase structure guide the big picture.
My bit of advice as a physio
There is a reason running coaches excist, the science behind phases, tapering, deload can be quite complex to manage and understand. A real life running coach can be incredibly beneficial as it is personalized. 10 people would need 10 different programs to make it to a finish line. Never underestimate the power of professional support.
