Double Threshold Training: Principles, Implementation, and Benefits for Endurance Athletes

How to Do Double Threshold Training?

Double threshold training involves performing two distinct, threshold-based workouts within the same day, typically separated by several hours, to maximize specific physiological adaptations for endurance performance.

What is Double Threshold Training?

Double threshold training is an advanced endurance training methodology characterized by executing two separate, high-quality training sessions in a single day, with each session targeting a specific physiological threshold. This approach, widely popularized by elite Norwegian endurance athletes, aims to accumulate a greater volume of work at or near an athlete's lactate thresholds than would be feasible or effective in a single, longer session.

The two primary thresholds targeted are:

• Aerobic Threshold (LT1 / Ventilatory Threshold 1 - VT1): The intensity at which lactate begins to accumulate above resting levels, but can still be cleared efficiently. This zone is characterized by sustainable, comfortably hard efforts where fat oxidation contributes significantly to energy production.
• Anaerobic Threshold (LT2 / Ventilatory Threshold 2 - VT2 / Functional Threshold Power - FTP): The intensity at which lactate production significantly exceeds lactate clearance, leading to a rapid and unsustainable rise in blood lactate. This zone represents the highest intensity an athlete can sustain for a prolonged period (typically 30-60 minutes) and is a strong predictor of endurance performance.

The Science Behind Double Threshold Training

The efficacy of double threshold training stems from its ability to provide specific, high-quality stimuli to the body's energy systems and physiological structures, leading to enhanced endurance capacity.

• Optimized Lactate Dynamics:
  • LT1 Sessions: These workouts primarily enhance the body's ability to clear lactate and improve mitochondrial efficiency. By spending time at LT1, the body becomes more adept at utilizing fat as fuel and improving capillary density, leading to a higher power output or pace at which lactate levels remain stable.
  • LT2 Sessions: These sessions push the upper limits of lactate tolerance and production, increasing the body's buffering capacity and improving the ability to sustain higher intensities. They directly raise the ceiling of an athlete's sustainable power or pace.
• Increased Training Volume at Specific Intensities: By splitting the threshold work into two sessions, athletes can accumulate a greater total volume at these crucial intensities without incurring the excessive fatigue, muscle damage, or risk of overtraining that a single, prolonged, very high-intensity session might induce. This allows for a more focused stimulus on different physiological pathways.
• Enhanced Adaptations: The repeated stimulus, especially when separated by a short recovery period, can amplify adaptations related to mitochondrial biogenesis, enzyme activity, and capillary growth, leading to improved oxygen delivery and utilization.

Who Can Benefit from Double Threshold Training?

Double threshold training is an advanced training strategy and is not suitable for all athletes. It is most beneficial for:

• Experienced Endurance Athletes: Runners, cyclists, triathletes, rowers, and cross-country skiers with a solid base of aerobic fitness and years of consistent training.
• Athletes with High Training Loads: Those who are already accustomed to significant weekly training volumes and can recover effectively from multiple demanding sessions.
• Individuals with Ample Recovery Resources: Adequate sleep, nutrition, and time for recovery are paramount due to the high stress placed on the body.
• Athletes Targeting Specific Performance Gains: Particularly those looking to improve their lactate threshold, sustained power output, and overall endurance capacity in competitive events.

It is generally not recommended for beginners or those new to structured training due to the high physiological stress and risk of overtraining or injury.

Key Principles of Double Threshold Training

Successful implementation of double threshold training hinges on adherence to several core principles:

• Precise Intensity Control: Both LT1 and LT2 sessions require accurate pacing and intensity monitoring to ensure the correct physiological stimulus. Guesswork can lead to sub-optimal training or excessive fatigue.
• Appropriate Volume: The total time spent at threshold in each session should be carefully managed. Typical LT1 sessions might involve 20-40 minutes of work at threshold, while LT2 sessions might involve 15-30 minutes of work at threshold (e.g., intervals).
• Strategic Frequency: Double threshold days are typically performed 1-2 times per week for advanced athletes, integrated into a broader training plan that includes lower-intensity aerobic work and recovery.
• Crucial Recovery: The time between the two sessions (typically 4-8 hours) and the recovery days following a double threshold day are critical for adaptation. Adequate sleep, nutrition (especially carbohydrate and protein intake), and hydration are non-negotiable.

How to Implement Double Threshold Training: Practical Application

There are several ways to structure a double threshold day, with the "Norwegian Model" being the most well-known.

Example 1: The Classic Norwegian Model (Morning LT1, Afternoon LT2)

This is the most common and effective approach for maximizing adaptations.

• Morning Session (LT1 Focus):

  • Goal: Improve aerobic capacity, fat oxidation, and lactate clearance at sustainable intensities.
  • Structure: Often a continuous run or ride with a significant portion at or just below LT1.
  • Example (Running): 60-90 minute run, including 20-40 minutes at a pace equivalent to your LT1 (comfortably hard, conversational pace, RPE 4-6/10). This might be structured as a 15-minute warm-up, 30-45 minutes at LT1, 15-30 minutes cool-down.
  • Example (Cycling): 90-120 minute ride, including 40-60 minutes at LT1 power.

• Afternoon Session (LT2 Focus):

  • Goal: Increase lactate tolerance, VO2max, and sustainable power/pace at higher intensities.
  • Structure: Interval-based, with repetitions at or just above LT2, followed by short recovery periods.
  • Example (Running): 10-15 minute warm-up, then 5-7 repetitions of 5-7 minutes at LT2 pace (hard, difficult to speak, RPE 7-8/10), with 1-2 minutes of easy jogging recovery between intervals. Follow with 10-15 minute cool-down.
  • Example (Cycling): 10-15 minute warm-up, then 4-6 repetitions of 8-10 minutes at LT2 power (FTP), with 2-3 minutes of easy spinning recovery between intervals. Follow with 10-15 minute cool-down.

Key considerations for the Norwegian Model:

• Allow 4-8 hours between sessions for partial recovery and fueling.
• Ensure adequate carbohydrate and protein intake between sessions to replenish glycogen and aid muscle repair.

Example 2: Combined Session Model (Less Common for "Double Threshold")

While not strictly "double threshold" in the traditional sense of two distinct sessions, some athletes might integrate both threshold zones into a single, longer workout. This is more of a "mixed threshold" session.

• Structure: A longer warm-up, followed by segments at LT1, then segments at LT2, or vice versa.
• Example (Running): 15-minute warm-up, 20 minutes at LT1 pace, 5 minutes easy recovery, then 3x5 minutes at LT2 pace with 2 minutes rest, 10-minute cool-down.
• Benefit: Time-efficient if two sessions aren't feasible.
• Drawback: May not allow for the same cumulative volume at each specific intensity as two separate sessions, and fatigue from the first threshold zone may compromise the quality of the second.

Monitoring Intensity: Finding Your Thresholds

Accurate determination of your individual thresholds is paramount for effective double threshold training.

• Lactate Testing:

  • Gold Standard: Laboratory-based testing involves taking blood samples at increasing exercise intensities to pinpoint the precise lactate concentrations corresponding to LT1 and LT2. This provides the most accurate data for setting training zones.
  • Typical Markers: LT1 often occurs around 2.0-2.5 mmol/L blood lactate, while LT2 (or OBLA – Onset of Blood Lactate Accumulation) is typically around 3.5-4.5 mmol/L, though individual variations exist.

• Heart Rate Zones:

  • Use: Once thresholds are determined via lactate testing or field tests, corresponding heart rate zones can be established.
  • General Guide (highly individual): LT1 often falls around 80-85% of Maximum Heart Rate (MHR) or 70-75% of Heart Rate Reserve (HRR). LT2 is typically around 90-95% MHR or 85-90% HRR.
  • Caution: Heart rate can be affected by fatigue, hydration, temperature, and stress, so it should be used in conjunction with other metrics.

• Pace/Power:

  • Running: Specific paces per kilometer or mile derived from field tests (e.g., 30-minute time trial for LT2).
  • Cycling: Specific power outputs (watts) derived from an FTP test (e.g., 20-minute maximal effort) or lactate testing. Power meters provide highly accurate and consistent intensity feedback.

• Rate of Perceived Exertion (RPE):

  • Subjective Scale (0-10):
    • LT1: RPE of 4-6/10 (comfortably hard, you can talk in short sentences).
    • LT2: RPE of 7-8/10 (hard, you can only utter a few words, breathing is labored).
  • Use: While subjective, RPE is a valuable tool, especially in conjunction with objective measures, as it accounts for daily variations in fatigue and readiness.

Progression and Periodization

Integrating double threshold training requires careful progression and fit within a broader periodized training plan.

• Start Conservatively: Begin with lower volumes and fewer intervals at threshold. For example, start with 3x5 minutes at LT2 instead of 5x7 minutes.
• Gradual Increase: Over several weeks, gradually increase the duration of intervals, the number of repetitions, or the total time spent at threshold.
• Placement in Periodization: Double threshold days are typically introduced during a "build" or "specific preparation" phase, after a solid aerobic base has been established, and before a "taper" or competitive phase.
• Listen to Your Body: The high stress of these sessions demands close attention to fatigue levels, sleep quality, and overall well-being.

Common Pitfalls and Considerations

While highly effective, double threshold training comes with risks if not managed properly.

• Overtraining: The cumulative stress of two high-intensity sessions can quickly lead to overtraining if recovery is insufficient or if the athlete is not adequately prepared. Symptoms include persistent fatigue, poor performance, irritability, and increased susceptibility to illness.
• Insufficient Recovery: Neglecting sleep, nutrition, and rest days will negate the benefits and increase injury risk.
• Incorrect Intensity: Training too hard during LT1 sessions can lead to excessive fatigue and compromise the LT2 session. Training too easy during LT2 sessions will not provide the necessary stimulus for adaptation. Precision is key.
• Poor Nutrition: Adequate carbohydrate intake before, during (for longer sessions), and especially between sessions is crucial for fueling performance and recovery. Protein intake aids muscle repair.
• Mental Fatigue: The demanding nature of these sessions can also lead to mental burnout if not managed with variety and appropriate rest.

Conclusion

Double threshold training is a potent and scientifically grounded method for advanced endurance athletes seeking to elevate their performance. By strategically targeting both aerobic and anaerobic thresholds in two distinct sessions within a single day, athletes can achieve a greater volume of high-quality work, leading to enhanced lactate dynamics, mitochondrial efficiency, and overall endurance capacity. However, its demanding nature necessitates a strong existing fitness base, meticulous attention to intensity, volume, recovery, and a willingness to listen closely to the body's signals to avoid the pitfalls of overtraining. When implemented correctly, double threshold training can be a cornerstone of a highly effective training plan, unlocking new levels of endurance performance.