Trail Race Pacing: Why You Shouldn't Look at Your Garmin on the Trails

The Pacing Paradox of Trail Racing

On the road, you watch your Garmin and run 5:00/km; on the trails, watching your Garmin and running 5:00/km would be a disaster. Here’s why:

1. Pace is meaningless: Uphill 8:00, downhill 4:00, flats 5:30—the average has no reference value
2. GPS error is significant: Under tree canopy, GPS distance can underreport by 10-15%
3. Heart rate drifts faster: Terrain changes cause heart rate to spike wildly
4. Energy expenditure is non-linear: Steep climbs burn 2-3 times more calories per minute than flats

What You Should Look At Instead

Primary Metric: Rate of Perceived Exertion (RPE)

RPE on a 1-10 scale:

• 1-3: Warm-up pace
• 4-5: Can run and chat comfortably (suitable for 50K+ trail races)
• 6-7: Can speak short sentences (suitable for 25-50K trail races)
• 8-9: Can only utter single words (suitable for 10-25K trail surges)
• 10: Unable to speak (finish-line sprint)

In a trail race, you should maintain RPE 5-7 most of the time, adjusting based on distance.

Secondary Metric: Heart Rate

Heart rate is worth checking, but don’t chase the numbers. Focus on the “drift trend”:

• Heart rate steadily rising → intensity too high, need to slow down or refuel
• Heart rate stable → intensity is appropriate
• Heart rate dropping along with pace → accumulated fatigue, this is normal

Supporting Metric: Rate of Ascent

More meaningful than pace is “vertical ascent per hour” (VAM):

• Amateur trail runners climbing VAM: 500-800 m/h
• Elite trail runners climbing VAM: 1000-1200 m/h
• Hiking pace VAM: 300-400 m/h

Uphill Pacing Strategy

Gentle Slopes (3-6%)

• Maintain running form, shorten stride
• Pace may drop 20-40 sec/km
• Heart rate 5-8 bpm higher than on flats

Moderate Slopes (6-12%)

• Alternate between “power hiking” and short jogs
• Keep heart rate below 90% of max
• Use trekking poles (if allowed) to save 20% of effort

Steep Slopes (12%+)

• Power hike directly
• Push off with hands on knees for assistance
• Don’t force a run just to “save face”

Downhill Pacing Strategy

Gentle Downhills

• Let the speed out, but stay within your comfort zone
• Keep cadence at 180+, let stride extend naturally
• Make up time lost on the climbs

Steep Downhills

• Shorten stride, lean center of gravity back
• Watch your foot placement to avoid ankle rolls
• Heart rate may actually drop, but eccentric leg contractions take a toll
• Don’t bomb downhill excessively just to “save time”

Refueling Rhythm

Refueling matters more in trail races than road races:

• Every 30 minutes: 100-150 ml water + 50-100 mg sodium
• Every 45 minutes: 30-60g carbs (energy gels/chews/chewable food)
• At every aid station: Top off your bladder, stay 30-60 seconds (don’t skip this time)

Mental Pacing: Segment Thinking

For trail races over 25K, break the race into “aid station to aid station” segments:

• Don’t think about the finish line
• Only think about “getting to the next aid station”
• Set a small goal for each segment
• Reassess after completing each one

Conclusion

Trail racing is “the opposite of pacing philosophy”: let go of the pace numbers and feel the terrain with your body. Treat the watch as a recording tool, not a commander. Those who finish are the ones who have learned to “run without watching the pace.”

Related Reading

• Trail Running vs. Road Running: Why Pace Judgment Shouldn’t Rely Only on Kilometers
• Trail Running Heart Rate Training: Why Heart Rate Is Unreliable on Trails and You Should Look at RPE
• Road Running Heart Rate Pace vs. GPS Pace: Which Is More Accurate
• Road Running GPS Watch Pace Error: Why Your Pace Isn’t Accurate