Common Half-Marathon Training Mistakes: Not Enough Mileage, Too Much Speed, Too Little Rest

Introduction

Many runners train for months without seeing progress, or miss races due to injury, often for the same underlying reason: fundamental flaws in their training approach. These mistakes stem not from a lack of effort, but from a lack of proper training knowledge. This article focuses on the three most common problems in half-marathon training and provides specific corrective recommendations.

Mistake 1: Insufficient Weekly Mileage

Problem Description

Many runners only run 2–3 times per week, totaling just 15–20 km, yet expect to set a PB in a half marathon. The foundation of aerobic endurance is “accumulated mileage.” Without a sufficient mileage base, the effectiveness of speed training is extremely limited.

Recommended Mileage

How to Fix It

Don’t increase mileage drastically all at once; increase by no more than 10% per week. If your current weekly mileage is only 20 km, first spend 6–8 weeks steadily building up to 35 km before adding speed workouts to your schedule.

Mistake 2: Running Easy Runs Too Fast

Problem Description

This is the most common mistake among amateur runners. Many people go out each time and run at a moderate intensity where they’re “slightly breathless”—not easy enough (failing to allow adequate recovery), yet not fast enough (failing to achieve the benefits of speed training). Staying in this “gray zone” long-term leads to slow improvements in aerobic efficiency while injury risk continues to accumulate.

The correct pace for easy runs should be 60–90 seconds/km slower than your half-marathon goal pace, and you should be able to speak in full sentences easily. For most runners, this is much slower than their habitual pace, and it may initially feel “too slow,” but this is precisely the correct training stimulus.

How to Fix It

• Use heart rate monitoring: keep your easy-run heart rate at 65–75% of your maximum heart rate
• The running partner test: if you can chat comfortably with a companion, that’s the correct easy-run pace
• Accept the psychological adjustment period of “slowing down”: it typically takes 2–4 weeks to get used to running at the correct easy pace

Mistake 3: Too Few Rest Days or Neglecting Recovery

Problem Description

Many runners believe that “more running equals more progress,” running all 7 days of the week, or immediately following a high-intensity workout with a long run. What they fail to realize is that training adaptations occur during rest, not during the workout itself. Without adequate recovery time, training only accumulates fatigue rather than improving fitness.

Common signs of overtraining:

• Resting heart rate is 5–8 beats per minute higher than usual
• Easy-run pace continuously gets slower
• Declining sleep quality, waking up easily at night
• A noticeable drop in training motivation
• Minor aches and pains persisting for more than two weeks

How to Fix It

• Take at least 2 completely rest days per week (or active recovery, such as easy walking or swimming)
• Rest for 48 hours after interval workouts before your next high-intensity session
• Schedule a recovery week every 4 weeks: reduce mileage by 20–25% and lower the intensity of all high-intensity workouts

Other Common but Easily Overlooked Mistakes

• Skipping warm-ups and cool-downs: heading straight out the door without a 10–15 minute warm-up significantly increases the risk of muscle injury
• Insufficient fluid intake: you should consume body weight (kg) × 35 mL of water daily, with additional intake on training days
• Turning training into racing: pushing the pace on every long run prevents you from getting the maximum benefit from your training

Practical Advice

• Record a “rate of perceived exertion” (1–10) for each workout; tracking this over time helps you identify fatigue patterns
• Build the habit of a “training log”: mileage, pace, weather, and how you felt—reviewing it after a week will help you spot trends
• Don’t push through pain: pain is your body’s warning signal. Grinding through it for two weeks often costs far more than taking two weeks off

Conclusion

Common training mistakes often stem from “well-intentioned excess”—wanting to improve so badly that you overtrain. Truly effective half-marathon training requires three equally essential elements: a sufficient mileage base, proper intensity distribution, and adequate recovery time.

Related Reading

• Training Load for Ultramarathons: Recommendations for Weekly Mileage, Elevation Gain, and Long Run Distance
• Weekly Half-Marathon Training Structure: Arranging Long Runs, Intervals, and Easy Runs
• 12-Week Half-Marathon Plan: The Minimum Effective Training Volume for Light Mileage Runners
• Half vs. Full Marathon Training: Key Differences in Periodization and a Complete Breakdown of Common Training Volume Misconceptions