Lactate Threshold Intervals: Periodized Application of Sweet Spot Training (88–93% FTP)

Introduction

In the language of power-based training, there is an intensity zone known as the “Sweet Spot,” which falls at approximately 88–93% of FTP. What makes this zone special is that it sits simultaneously within the high-efficiency output range of the aerobic energy system and near the critical point where lactate production begins to accelerate—providing sufficient training stimulus without imposing the heavy recovery burden associated with high-intensity intervals. Understanding the physiological mechanisms of the lactate threshold is the first step to mastering Sweet Spot training.

The Physiological Basis of the Lactate Threshold

The lactate threshold (LT) is not a fixed value but rather a continuous metabolic transition process, typically divided into two key nodes:

• LT1 (Aerobic Threshold): Lactate concentration begins to rise slightly, at approximately 2 mmol/L, corresponding to an easy pace where a rider can converse comfortably
• LT2 (Anaerobic Threshold / near FTP): The rate of lactate production begins to exceed the rate of clearance, with concentration climbing rapidly to approximately 4 mmol/L, corresponding to the power sustainable for about one hour of maximal effort

Sweet Spot training intensity falls between LT1 and LT2. In this zone, muscles still rely primarily on aerobic pathways, but sufficient lactate is produced to “train” the muscles and liver to accelerate lactate reutilization (the lactate shuttle mechanism). Consistent Sweet Spot training over time effectively raises the power corresponding to LT2—in other words, it increases your FTP.

Advantages and Limitations of Sweet Spot Training

The core advantage of Sweet Spot training is the “dual accumulation of training volume and training intensity.” Because the recovery burden is relatively manageable, riders can accumulate more “high-quality hours” within a week, which is particularly effective for improving FTP.

However, its limitation is that it cannot provide direct and intense stimulation to VO2max. If the goal is explosive speed or short-duration maximal power, the benefits of Sweet Spot training are relatively limited.

Periodization Strategy

Sweet Spot training is best used extensively during the Base Phase and the first half of the Build Phase. Below is an example periodization for a 12-week season preparation:

Weeks 1–4 (Base Phase):

• 2 Sweet Spot sessions per week, each 2×20 minutes (5 minutes rest between intervals)
• Paired with 2 long Z2 aerobic rides
• No high-intensity intervals

Weeks 5–8 (Build Phase):

• 2 Sweet Spot sessions per week, progressing to 3×15 minutes or 1×40 minutes
• Add 1 VO2max interval session per week
• Maintain or slightly reduce long rides

Weeks 9–12 (Peak Phase):

• Reduce Sweet Spot sessions to 1 per week (to maintain neuromuscular memory)
• Focus on high-intensity and race-simulation workouts

Progressive recommendations for Sweet Spot session formats:

• Beginner: 2×15 minutes, 5 minutes rest between intervals
• Intermediate rider: 2×20 minutes, or 1×40 minutes
• Advanced rider: 3×20 minutes, or 1×60 minutes (approaching tempo riding)

Practical Recommendations

1. A power meter is the best tool: The Sweet Spot range of 88–93% FTP spans only 5%; without a power meter, it is easy to ride too hard or too easy. Heart rate can assist but has a lag
2. Make use of Taiwan’s terrain: Taipei’s Muzha Zoo to Monkey Mountain (Hou Shan Yue), the entrance section of Hsinchu’s Beidalaman Forest Trail, and Taichung’s Dongfeng Bicycle Path are all suitable for maintaining steady power over extended periods
3. Don’t “push a little more” every session: The biggest pitfall in Sweet Spot training is gradually drifting toward near-FTP intensity, which erodes recovery capacity and disrupts the periodization plan
4. Record subjective feelings: After each session, rate your fatigue on a 1–10 scale. If the rating exceeds 7 for three consecutive sessions, schedule a reduced-volume workout

Conclusion

Lactate threshold intervals—especially Sweet Spot training—are among the most reliable tools for improving FTP. Their appeal lies in trading “sustainable stress” for “sustained physiological adaptation.” Accumulating them in the right position within a periodized plan will build a solid and robust power foundation. For Taiwanese riders, whether tackling Wuling, preparing for a 100 km cycling race, or improving efficiency in daily commuter rides, Sweet Spot training deserves to be the core framework of any training plan.

Related Reading

• Cycling Lactate Threshold Training: Interval Design for the Sweet Spot at 88–93% FTP
• Sweet Spot Training: Maximizing Benefits at 88–93% FTP
• Zone 4 Lactate Threshold Training: How to Precisely Hit the Sweet Spot to Improve FTP
• Lactate Threshold Training: How to Find Your Critical Cycling Pace