Cycling Anaerobic Capacity W' Training: The Science and Development of Explosive Power

Introduction

In the Critical Power model, a rider’s performance is determined by two parameters: CP (Critical Power, close to FTP) and W’ (W-prime, anaerobic work capacity reserve). If FTP is your “engine displacement,” then W’ is your “nitrous oxide system”—the decisive energy reserve for sprints above FTP, climbing attacks, and chasing down the peloton.

The Physiological Nature of W’

W’ refers to the total energy an athlete can expend above CP intensity (unit: joules, J). It is not merely the phosphocreatine (PCr) store, but also includes:

• Phosphocreatine (PCr): The most immediate energy source, capable of releasing large amounts of ATP within 5–10 seconds
• The anaerobic component of glycolysis: Supplies ATP while producing lactate, sustainable for 30–90 seconds
• Muscle buffering capacity: How much acidic environment can be tolerated before H⁺ accumulation

A typical amateur road cyclist’s W’ is approximately 12,000–20,000 J; well-trained athletes can reach 25,000–35,000 J.

The Dynamic Model of W’ Depletion and Recovery

W’ is not a one-time deposit; it is a dynamic “rechargeable battery”:

• When riding above CP, W’ is depleted at a certain rate
• When riding below CP, W’ recharges following an exponential function
• The recharge rate depends on the intensity differential: the further below CP the intensity, the faster the recharge

Research by Ferguson et al. (2010) indicates that the recovery time constant of W’ is approximately 300–600 seconds (5–10 minutes). This explains why, during group riding, after “resting” on descents or flat sections, the ability to attack on the next climb significantly recovers.

Testing Methods for W’

Method 1: Multiple All-Out Test Estimation

In a fresh state, measure separately:

• 5-second maximal power
• 30-second average power
• 5-minute maximal power

Estimate CP and W’ using the Critical Power model (power-duration relationship curve). Training Peaks’ WKO software can calculate this automatically.

Method 2: Three All-Out Tests (Burnley Protocol)

Over three separate days, perform 3-minute, 5-minute, and 10-minute all-out tests. Use the average power of the final 30 seconds and time to establish a regression line; the intercept is W’.

Training Strategies to Improve W’

Training 1: Phosphocreatine Supercompensation

• Format: 10–15 second all-out sprints, full recovery (5–10 minutes), repeat 5–8 sets
• Mechanism: After each all-out effort depletes PCr, adequate recovery promotes PCr supercompensation, gradually increasing storage capacity
• Frequency: Once per week, not more (PCr replenishment requires 3–5 days)

Training 2: Anaerobic Capacity Accumulation (Tabata Variation)

• Format: 30 seconds all-out (150–200% FTP) + 30 seconds very easy, repeat 10–15 sets
• Mechanism: Trains the total capacity of the glycolytic system and buffering ability
• Note: Intensity must truly reach “almost impossible to complete” levels; otherwise, the effect is greatly diminished

Training 3: Repeated Climbing Attacks

• Format: Choose a short climb of 2–3 minutes (e.g., the Yangmingshan Forestry Research Station section), attack at race pace, recover easily on the descent, repeat 6–10 sets
• Mechanism: Simulates race scenarios while training both W’ depletion and recharge
• Suitable for: Riders preparing for climbing challenge races across Taiwan

Training 4: Aerobic Base Support

Raising CP (i.e., FTP) itself indirectly improves the effective use of W’. The higher the CP, the higher the power at which the same W’ will be depleted. Therefore, Zone 2 base training also contributes indirectly to the “practical effectiveness” of W’.

Practical Recommendations

• Do not neglect W’ training: Most amateur riders over-focus on FTP improvement, overlooking the development of sprinting and explosive power
• Race pace management: In climbing races with timing (such as the Wuling Challenge), avoid frequent W’ usage in the early stages; save it for the final critical sections
• Limitations of trainers: Many smart trainers cannot simulate true short sprints; it is recommended to perform actual W’ training on outdoor slopes
• W’ and age: W’ is more influenced by fast-twitch fiber proportion and typically declines more significantly with age than CP; riders over 40 should especially preserve explosive power training

Conclusion

W’ is the most “underestimated superpower” in cycling training. It determines whether you can complete that attack, catch that acceleration, or hold your position in the group at the critical moment. Through a scientific W’ development plan, combined with a solid aerobic base, your cycling performance will no longer be merely “steady output”—you will be able to unleash true explosive power when it matters most.

Related Reading

• The W’ (W Prime) Model in Cycling: Training Implications of Anaerobic Work Capacity
• Critical Power (CP) vs FTP: Which Is Your True Threshold?
• Critical Power and W’: The Two-Parameter Model Explaining How Long You Can Hold On
• Improving Power-to-Weight Ratio (W/kg): Strategies to Increase Power While Managing Weight