Cycling Aerodynamics: A Scientific Analysis of VAM and Climbing Efficiency

Introduction

In Taiwan’s cycling community, “how many minutes to Wuling” is almost synonymous with the ultimate benchmark of training results. But performance on Wuling depends not only on FTP, but is also influenced by body weight, VAM, aerodynamics, and climbing strategy. Understanding the physics and physiology of climbing is the only way to truly plan training and race pacing scientifically.

VAM: A Universal Language for Measuring Climbing Ability

VAM (Velocità Ascensionale Media, Average Ascension Speed) was introduced by Italian team physician Michele Ferrari and is defined as the vertical elevation gained per hour (m/h).

VAM Calculation Formula

VAM = Elevation Gained (m) / Riding Time (h)

Example: The Hehuan Mountain East Wuling section (approximately 1,200 meters of climbing, typical finish time 2–3 hours)

• Completed in 2 hours: VAM = 600 m/h
• Completed in 3 hours: VAM = 400 m/h

VAM Reference Benchmarks

VAM and Gradient Relationship

At different gradients, the same power-to-weight ratio corresponds to different VAM values. The steeper the gradient, the smaller the proportion of aerodynamic drag, and the more accurately VAM reflects power-to-weight ratio:

• Gradient < 6%: Aerodynamic effects are significant, VAM has larger error
• Gradient 6–12%: VAM is a reliable indicator of climbing ability
• Gradient > 15%: Relies almost entirely on power-to-weight ratio; aerodynamic effects are negligible

The Physics of Climbing Decomposed

Total resistance while climbing consists of three components:

F_total = F_gravity + F_aero + F_rolling

• Gravitational Resistance (F_gravity): = m × g × sin(θ), is the primary resistance when climbing, accounting for approximately 80–85% of total resistance at an 8% grade
• Aerodynamic Drag (F_aero): Accounts for a smaller proportion at low climbing speeds, but remains non-negligible on gentle grades below 8%
• Rolling Resistance (F_rolling): Energy loss from tire deformation, related to bike weight and road surface, accounting for approximately 5–10% of total resistance

Key Strategies for Optimizing Climbing Efficiency

Strategy 1: Optimizing Power-to-Weight Ratio (W/kg)

This is the most direct determinant of climbing performance:

• Increase FTP: Systematic training to improve the power numerator
• Weight Management: Losing weight without sacrificing power is the fastest path to improving W/kg
• Losing 1 kg of body weight ≈ approximately 2–3 minutes faster on the East Wuling route (estimated based on a 70 kg rider with 250W FTP)

Strategy 2: Aerodynamic Position Adjustments (Gentle Grade Sections)

On gentle grades < 6% (such as the long gradual climbs in the early section of East Wuling), aerodynamics still has a noticeable impact:

• Lowering torso angle (dropping handlebars 2–3 cm) can reduce aerodynamic drag by approximately 5–10%
• Wearing a tight-fitting jersey (vs. loose clothing) can save 1–3W of aerodynamic loss
• Helmet selection: an aero helmet offers a 5–10W advantage at speeds of 30+ km/h

Strategy 3: Pacing Strategy

Research shows that Even Pacing is generally superior to starting fast and fading, or starting slow and finishing fast, on long climbs:

• The greater the power fluctuation, the higher the oxygen cost (each 10% increase in power variability increases oxygen consumption by approximately 3–5%)
• It is recommended to maintain power within ±5% of the target value throughout the climb (e.g., FTP 250W, climbing target 210W, maintain 200–220W)
• The early sections of Taiwan’s long climbs are often crowded, making it easy to get carried away and go out too fast; maintaining your own rhythm is the most important discipline

Strategy 4: Wheelset Selection

On true climbing sections with grades > 8%:

• Wheelset weight differences (1,200g vs. 800g) amount to approximately 5–8W at an 8% grade
• Rim depth offers almost no advantage for climbing (but does provide an aerodynamic advantage on gentle sections)
• Shallow-rim climbing wheelsets (< 30mm rim depth) are the best choice for Taiwan’s mountain races

Taiwan Climbing Data Reference

East Wuling (starting from Puli, 52 km, 3,275m elevation gain):

• Intermediate-advanced amateur target VAM ≈ 550–700 m/h
• Corresponding power-to-weight ratio approximately 2.8–3.5 W/kg
• Recommended race pacing: start at 92–95% FTP, maintain until exhaustion in the latter half

Practical Recommendations

• Use VAM to Track Progress: VAM on the same segment is the most intuitive metric for tracking climbing improvement, and it eliminates weather effects better than time
• Pay Attention to Aerodynamics on Gentle Grades: When encountering grades < 6%, remember to tuck low and don’t waste energy fighting wind resistance
• A Power Meter Is Essential Equipment for Climbing: Heart rate lags during climbing; only a power meter can tell you in real time whether you’re at your target intensity
• Timing of Weight Management: Consider a mild caloric deficit 4–6 weeks before a race, but avoid weight loss during high-volume training periods

Conclusion

Behind the VAM number lies the intersection of physics and physiology. To improve climbing ability, the core is raising your power-to-weight ratio, supplemented by sensible pacing and aerodynamic optimization. Taiwan’s abundant mountain terrain is a natural training ground for cyclists—every climb is an excellent opportunity to accumulate VAM data and analyze your own performance.

Related Reading

• Trail Running Training Load Calculation: Equivalent Conversion of Vertical Ascension (VAM)
• The Physics of Climbing: Mathematical Models of Power, Gravity, and Speed
• Climbing Weight Management: Strategies for Improving Power-to-Weight Ratio (W/kg)
• Climbing Power Distribution: A Wuling Comparison of Steady Watts vs. Steady Heart Rate