Key Threshold Workouts to Boost Triathlon Fitness
Triathlon success hinges on the ability to sustain effort at your threshold—the point where your body produces and clears lactate at an equal rate. This balance allows you to perform at high intensity without hitting the dreaded wall. Training your threshold not only improves endurance and speed but also teaches your body to maintain efficiency under fatigue, a crucial skill for triathletes. Let’s explore the science behind threshold training, its benefits, and key workouts to elevate your triathlon fitness.
What is the Threshold, and Why is it Important?
Threshold, often referred to as lactate threshold (LT) or anaerobic threshold (AT), is the intensity at which your body starts to accumulate lactate faster than it can clear it. For most athletes, this occurs at about 80–90% of their maximum heart rate or roughly 85% of VO2 max.
In triathlons, especially long-distance races, your performance relies heavily on the ability to sustain effort just below your threshold. Improving this capacity allows you to race faster without expending excessive energy. Threshold training increases your body's efficiency in clearing lactate, improves oxygen delivery to working muscles, and delays fatigue.
The Science of Threshold Training
Threshold workouts target Zone 3–4 intensity, where your heart rate, pace, or power hovers just below your lactate threshold. Training in this zone pushes your body to adapt by:
Increasing mitochondrial density, which improves energy production.
Enhancing capillary networks to deliver more oxygen to muscles.
Boosting lactate clearance, delaying the onset of fatigue.
For triathletes, this means faster splits in all three disciplines while maintaining control and energy for the next leg.
Key Threshold Workouts for Swimming, Cycling, and Running
Swimming: Building Speed and Endurance
In swimming, threshold training focuses on maintaining a steady, challenging pace while refining technique under stress.
Example Swim Threshold Workout:
Warm-up: 400m easy swim, 200m drills (e.g., catch-up or fingertip drag), 4 x 50m build pace
Main Set: 5 x 400m at threshold pace, with 20 seconds rest between each
Cool-down: 200m easy swim
Why it works: Sustained efforts at threshold pace improve your ability to handle the intensity of open-water swimming and navigate variable conditions like currents or packs of swimmers.
Cycling: Power and Efficiency on the Bike
Cycling at threshold enhances your ability to sustain power over long durations, crucial for triathlon bike legs. Using a power meter or heart rate monitor ensures precise effort.
Example Bike Threshold Workout:
Warm-up: 15 minutes at Zone 2, with 4 x 30-second spin-ups (high cadence, low resistance)
Main Set: 3 x 15 minutes at 90% of FTP (functional threshold power) or Zone 4, with 5 minutes of easy spinning between intervals
Cool-down: 10 minutes at Zone 2
Why it works: Threshold intervals train your aerobic system to sustain high power outputs while improving pedaling efficiency. This workout prepares you for rolling terrain or windy conditions that demand steady effort.
Running: Maintaining Pace Under Fatigue
Threshold runs teach your body to clear lactate while sustaining race pace. These workouts improve running economy, ensuring you can hold form and speed even in the final miles of a triathlon.
Example Run Threshold Workout:
Warm-up: 10 minutes easy jog, 4 x 30-second strides (fast but controlled)
Main Set: 4 x 10 minutes at threshold pace (Zone 4), with 2 minutes of easy jogging recovery between intervals
Cool-down: 10 minutes easy jog
Why it works: Long intervals at threshold pace simulate race-day intensity, building mental toughness and pacing discipline for the run leg.
Combining Threshold Workouts in Brick Sessions
Triathletes can maximize training efficiency by incorporating threshold efforts into brick workouts, which simulate race conditions by combining two disciplines.
Example Brick Workout:
Bike: 60 minutes with 3 x 15 minutes at 90% FTP, 5 minutes easy recovery between intervals
Transition: Quick change into running gear
Run: 20 minutes at threshold pace
Why it works: This workout trains your ability to transition smoothly and sustain threshold effort under cumulative fatigue, a key skill for race day.
Tips for Effective Threshold Training
Know Your Zones: Use a lactate threshold test, power meter, or heart rate monitor to identify your threshold pace, power, or heart rate. Regular testing ensures accuracy as your fitness improves.
Focus on Quality: Threshold training is demanding; ensure you’re fully rested before key sessions to maximize benefits.
Incorporate Recovery: Space threshold sessions throughout your week to allow adequate recovery. Overtraining at this intensity can lead to burnout or injury.
Fuel Strategically: Threshold efforts deplete glycogen stores quickly. Consume a pre-workout snack rich in carbohydrates and refuel with a carb-protein mix post-workout.
Common Mistakes to Avoid
Going Too Hard: Training above your threshold turns a controlled workout into a VO2 max session, defeating the purpose. Stay disciplined and stick to your target intensity.
Skipping Recovery: Threshold work is taxing. Without proper recovery, you risk diminishing returns and increasing injury risk.
Neglecting Form: As fatigue sets in, it’s easy to let form slip. Focus on smooth technique, whether it’s stroke mechanics in swimming, pedaling efficiency on the bike, or proper posture while running.
How to Measure Progress
Improving your threshold takes time, but consistent training will yield measurable results. Indicators of progress include:
Faster swim, bike, or run paces at the same heart rate or power output.
Higher FTP (cycling) or threshold pace (running).
Lower perceived effort at previously challenging intensities.
Regularly testing your threshold every 6–8 weeks ensures your training zones remain accurate and reflects your fitness gains.
Conclusion
Threshold training is the foundation of triathlon fitness, bridging the gap between speed and endurance. By targeting this critical intensity in all three disciplines, you’ll develop the ability to sustain higher efforts, clear lactate efficiently, and maintain form under fatigue. Incorporate these workouts into your plan, monitor your progress, and stay consistent. With disciplined threshold training, you’ll be primed to race stronger, faster, and more efficiently, conquering each leg of the triathlon with confidence.