Climbing Performance: VAM, W/kg, Gradient Analysis

What Makes a Good Climber?

Climbing performance in cycling is fundamentally about power-to-weight ratio. Unlike flat riding where aerodynamics dominates, climbing is a battle against gravity. The lighter you are relative to your power output, the faster you'll ascend.

But weight alone doesn't tell the full story. Two key metrics reveal climbing ability:

• Power-to-Weight Ratio (W/kg): Your FTP divided by body weight
• VAM (Velocità Ascensionale Media): Vertical ascent rate in meters per hour

Power-to-Weight Ratio (W/kg): The Climber's Currency

Power-to-weight ratio is your Functional Threshold Power (FTP) divided by your body weight in kilograms. It's the single best predictor of climbing performance.

W/kg Categories by Level

The Weight Loss vs. Power Gain Trade-off

Power of Losing Weight

Every 1kg lost improves W/kg ratio without increasing power:

⚠️ Don't Lose Muscle

Aggressive weight loss can reduce FTP if you lose muscle mass:

• Healthy weight loss: Lose fat, maintain FTP → W/kg improves
• Unhealthy weight loss: Lose muscle, FTP drops 10-15% → W/kg may worsen

Safe approach: Lose 0.25-0.5kg per week through moderate calorie deficit while maintaining protein intake (1.6-2.2g per kg body weight) and training volume.

Building Power Without Weight Gain

Increasing FTP while maintaining weight is ideal:

Optimal Weight for Climbing

There's a point of diminishing returns. Ultra-light riders (<60kg) often have:

• Lower absolute power (harder to push big watts)
• Disadvantage on flats and into headwinds
• Weaker sprint power
• More fragile (injury prone, illness susceptible)

Sweet spot for most riders: 10-15% body fat for men, 15-20% for women. Lower body fat improves W/kg but becomes counterproductive below ~8% (men) or 12% (women) due to health and performance issues.

VAM (Velocità Ascensionale Media): Pure Climbing Rate

VAM measures how many vertical meters you ascend per hour. Unlike speed (km/h), which varies dramatically by gradient, VAM provides a gradient-independent metric of climbing performance.

VAM Benchmarks by Effort Level

Why VAM is Gradient-Independent

Speed (km/h) drops dramatically as gradient increases, even at constant power. VAM stays relatively consistent:

Factors Affecting VAM

1. Power-to-Weight (Primary)

Higher W/kg directly translates to higher VAM. This is the main driver.

2. Gradient (Secondary)

VAM naturally increases on steeper gradients because:

• Aerodynamic drag is lower at slower climbing speeds
• More power goes to lifting (gravity) vs. pushing air

However, very steep gradients (12%+) can reduce VAM if rider can't sustain power due to muscular fatigue.

3. Altitude

At elevation:

• Lower air density: Less aero drag → slightly higher VAM (1-2%)
• Lower oxygen: Reduced sustainable power → lower VAM (5-10% at 2000m)

Net effect: VAM typically decreases at altitude despite aero benefit.

4. Wind

Headwinds reduce VAM, tailwinds increase it. Strong headwind on a steep climb can reduce VAM by 10-20%.

Estimating W/kg from VAM

You can approximate power-to-weight from VAM and gradient using this empirical formula:

Accuracy Notes

• Best accuracy: 5-10% gradients, 15-25 km/h speeds
• Less accurate: Very steep (>12%) or shallow (<3%) gradients
• Affected by: Wind, drafting (reduces actual W/kg needed), bike weight

Use this formula as a rough estimate, not absolute measurement. Direct power meter data is always more accurate.

How Gradient Affects Power Requirements

Gradient has an exponential effect on power needed to maintain speed. Understanding this helps you pace climbs correctly.

Power Required by Gradient

Assumes 75kg rider + 8kg bike, sea level, no wind, smooth road

Why Aerodynamics Matter Less on Steep Climbs

At climbing speeds (<20 km/h), aerodynamic drag becomes a minor component of total resistance:

• 5% gradient at 20 km/h: ~15% aero, ~10% rolling, ~75% gravity
• 10% gradient at 12 km/h: ~8% aero, ~12% rolling, ~80% gravity
• 15% gradient at 9 km/h: ~5% aero, ~10% rolling, ~85% gravity

Practical implication: On steep climbs, sitting upright for better breathing and power is faster than staying aero. Comfort and power output > aerodynamics.

Pacing Strategies for Optimal Climbing

How you distribute power on a climb dramatically affects overall time. Even power is almost always fastest.

Even Power (Iso-Power) Pacing

Goal: Maintain constant power output throughout the climb, regardless of gradient changes.

Why it works:

• Avoids depleting W' (anaerobic capacity) with surges
• Maximizes sustainable effort
• Prevents early fatigue that compounds later

Using Gradient Changes Wisely

Shallow Sections Strategy

When gradient decreases (e.g., 9% → 5%), you have two options:

1. Maintain power: Speed increases, you get ahead of schedule (recommended for long climbs)
2. Reduce power slightly: Allows brief recovery while still making progress

Steep Sections Strategy

When gradient increases (e.g., 5% → 10%), avoid:

• ❌ Surging to "get it over with" → Depletes W', causes fade
• ✅ Maintain target power → Speed drops naturally, but effort stays sustainable

Standing vs. Sitting

Sitting (Default)

Pros:

• More aerodynamic
• Lower heart rate (~5-10 bpm)
• Sustainable for long durations

Cons:

• Can feel "locked in" on very steep sections
• Hamstrings/glutes may fatigue on long climbs

Standing (Strategic)

Pros:

• Engages different muscle groups (quads, calves, core)
• Allows body to stretch, blood flow to recover
• Can generate higher momentary power (attacks, steep kicks)

Cons:

• 5-10W higher power requirement at same speed (less aero)
• Higher heart rate
• Not sustainable for long periods

Best practice: Sit for majority of climb. Stand briefly (15-30 seconds) every 3-5 minutes to:

• Relieve pressure on sit bones
• Stretch hip flexors and lower back
• Engage fresh muscle groups

Training to Improve Climbing Performance

Climbing improvement comes from three areas: increasing FTP, reducing weight, and building specific muscular endurance.

1. Build Aerobic Base (Zone 2)

Long, steady rides at 60-70% FTP develop:

• Mitochondrial density
• Capillary network
• Fat oxidation (spares glycogen on long climbs)

Volume target: 70-80% of weekly training time in Zone 2 for endurance-focused riders. See Training Zones Guide.

2. Threshold Intervals (Zone 4)

Build FTP with sustained threshold efforts:

3. VO2max Repeats (Zone 5)

Short, hard intervals boost aerobic ceiling:

4. Long Climbs (Race Simulation)

Practice pacing on sustained climbs:

5. Weight Management

Reduce excess body fat strategically:

• Target: 0.25-0.5kg per week maximum
• Method: 300-500 calorie daily deficit
• Protein: Maintain 1.6-2.2g/kg body weight to preserve muscle
• Timing: Lose weight during base/build phase, not peak/race phase

Warning: Don't chase extreme leanness. Performance plateaus or declines below ~8% body fat (men) or ~12% (women).

Famous Climbs: Performance Analysis

Analyzing pro performances on iconic climbs reveals what W/kg looks like in practice.

Alpe d'Huez

• Distance: 13.8 km
• Elevation gain: 1100m
• Average gradient: 8.1%
• 21 hairpin turns

Mont Ventoux

• Distance: 21.5 km (from Bédoin)
• Elevation gain: 1600m
• Average gradient: 7.5%
• Final 6km: Exposed, often windy

Col du Tourmalet

• Distance: 18.8 km (from Luz-Saint-Sauveur)
• Elevation gain: 1400m
• Average gradient: 7.5%
• Highest paved pass in Pyrenees (2115m altitude)

Pro performances: 50-55 minutes (~6.0-6.3 W/kg, 1530-1680 VAM). Altitude affects these times—thinner air reduces power output by ~5-8%.

Frequently Asked Questions

Related Resources

• Functional Threshold Power (FTP) Testing
• Advanced Power Metrics (NP, IF, VI, W'bal)
• Training Zones for Climbing Improvement
• Aerodynamics: When It Matters vs. Climbs
• Getting Started with Power-Based Training