HIIT vs. Traditional Endurance Training: Which Is More Effective for Boosting FTP?

This Debate Has Been Around for a Long Time

“Should I ride more at low intensity, or less at high intensity?” This question has puzzled cyclists for decades. In recent years, a large body of scientific research has finally provided clearer answers.

Defining the Terms

HIIT (High-Intensity Interval Training):

• Intensity: > 85% VO2max or > 90% max heart rate
• Duration: 30 seconds to 5 minutes
• Total time: Usually 20-40 minutes (including rest)

Traditional Endurance Training (LSD):

• Intensity: 60-75% max heart rate (Zone 2)
• Duration: 1-4 hours
• Volume-based

What the Science Says

Norwegian Study (2007, Helgerud et al.)

An 8-week training comparison with athletes:

Scandinavian Polarized Training Research

Analysis of professional cyclists’ training shows:

• 75-80% of time at low intensity (Zone 1-2)
• 5-10% of time at high intensity (Zone 4-5)
• Almost no moderate intensity (Zone 3, Sweet Spot)

Physiological Mechanisms of Both

HIIT Adaptations:

• Increases VO2max (maximal oxygen uptake)
• Increases aerobic capacity of fast-twitch muscle fibers
• Improves lactate clearance rate
• Rapidly improves FTP

LSD Adaptations:

• Increases mitochondrial number and density
• Improves fat oxidation capacity (fat adaptation)
• Improves capillary density in muscles
• Builds a long-term aerobic base

Optimal Combination Strategy

The consensus in modern sports science: you need both—the ratio is key

Practical Application Recommendations

Limited Training Time (< 6 hrs/week):
Focus on HIIT, interspersed with Zone 2

• Weekdays: 2 HIIT sessions, 45 minutes each
• Weekend: 1 longer Zone 2 ride

Moderate Training Time (6-10 hrs/week):
Balanced approach

• Weekdays: 2 HIIT sessions
• Weekend: 1 long Zone 2 ride + 1 moderate-intensity ride

Adequate Training Time (>10 hrs/week):
LSD-based approach

• Plenty of Zone 2 to build the aerobic base
• 2 HIIT or Sweet Spot sessions per week

Short-Term vs. Long-Term Effects

Conclusion

For recreational riders with limited training time, HIIT is a more efficient tool for improving FTP; however, for long-term, sustained progress, you must also build a Zone 2 aerobic base. The smartest approach is to “combine both,” adjusting the ratio based on your available time.

Related Reading

• High-Intensity Interval Training (HIIT) for Cyclists: The Science of Improving Cardiorespiratory Efficiency in Less Time
• Applying High-Intensity Interval Training (HIIT) to Cycling: Designing 30/15 and 4x4 Intervals
• Exercise Intensity and Health Benefits: Is High Intensity Really Better? A Coach’s Guide to the HIIT vs. Moderate-Intensity Trade-off
• Sports Science: Application of High-Intensity Interval Training (HIIT) in Mountain Biking (MTB): Exploring Physiological Evidence of Stroke Volume and Anaerobic Endurance, with Training Plans: A Data-Driven Systematic Approach