Swim Strong: 10 Threshold Sessions for Ironman 70.3!
Wondering how to swim faster and stronger in your Ironman 70.3 race?
Threshold swim training is the key to building the endurance, speed, and pacing control you need to crush the 1.9 km swim leg.
Why Threshold Swim Training Matters for Ironman 70.3
Threshold swimming develops the ability to sustain strong efforts without excessive fatigue — critical for maintaining form, speed, and energy into the bike.
By focusing on Critical Swim Speed (CSS) and lactate tolerance, you can improve aerobic endurance, stroke efficiency, and race-day confidence in the water.
Well-structured threshold sessions prepare you for the mental and physical demands of the swim leg.
These 10 essential swim threshold sessions will help you master consistent pacing, improve your Critical Swim Speed (CSS), and get race-day ready!
10 Key Swim Threshold Workouts for Ironman 70.3
1. Critical Swim Speed (CSS) Intervals
Purpose: Establish and sharpen your Critical Swim Speed.
Warm-up:
400m easy swim
Main Set:
5 x 200m at CSS pace (20–30 sec rest)
Cool-down:
200m easy swim
2. Threshold 400s
Purpose: Sustain strong pacing over longer distances.
Warm-up:
400m easy swim
Main Set:
4 x 400m at threshold pace (30–45 sec rest)
Cool-down:
200m easy swim
3. 100-200-100 Threshold Pyramid
Purpose: Build endurance with short, challenging sets.
Warm-up:
400m easy swim
Main Set:
100m + 200m + 100m at threshold pace, repeat 3x (2 min rest between sets)
Cool-down:
200m easy swim
4. 10 x 100m Threshold Intervals
Purpose: Improve pacing and lactate threshold.
Warm-up:
400m easy swim
Main Set:
10 x 100m at threshold pace (15–20 sec rest)
Cool-down:
200m easy swim
5. Threshold 3 x 500m Set
Purpose: Build endurance and fatigue resistance.
Warm-up:
400m easy swim
Main Set:
3 x 500m at threshold pace (1–2 min recovery)
Cool-down:
200m easy swim
6. Ladder Threshold Intervals
Purpose: Handle sustained efforts over increasing distances.
Warm-up:
400m easy swim
Main Set:
100m + 200m + 300m + 400m at threshold pace (1–2 min rest after set)
Cool-down:
200m easy swim
7. 5 x 300m Threshold with Rest
Purpose: Build strength and maintain consistent pacing.
Warm-up:
400m easy swim
Main Set:
5 x 300m at threshold pace (20–30 sec rest)
Cool-down: 200m easy swim
8. Broken 400m Threshold Intervals
Purpose: Improve speed endurance and mental toughness.
Warm-up:
400m easy swim
Main Set:
2 x 400m broken (200m + 10 sec rest, 100m + 10 sec rest, 100m)
1–2 min recovery between sets
Cool-down:
200m easy swim
9. Fast 50s and Threshold 200s
Purpose: Blend sprint speed with sustained threshold effort.
Warm-up:
400m easy swim
Main Set:
10 x 50m fast (Zone 5, 20–30 sec rest)
4 x 200m at threshold pace (30 sec rest)
Cool-down:
200m easy swim
10. Long Threshold Swim
Purpose: Build mental focus and aerobic capacity.
Warm-up:
400m easy swim
Main Set:
1500m straight at threshold pace
Cool-down:
200m easy swim
Final Tips for Swim Threshold Training
Pace Consistently: Use a swim watch or tempo trainer to maintain target CSS pace.
Focus on Technique: Good form saves energy at race pace — stay efficient throughout all sessions.
Simulate Race Conditions: Incorporate sighting and open-water sessions when possible.
Threshold swim sessions give you the stamina, speed, and confidence to start your Ironman 70.3 strong!
FAQs About Threshold Swim Training for Ironman 70.3
How often should I include threshold swim sessions?
Most athletes do 1–2 threshold sessions per week alongside longer aerobic swims.
What’s the best way to determine Critical Swim Speed (CSS)?
Complete a 400m and 200m time trial, then use a CSS calculator to set your pacing targets.
Should I practice threshold swimming in open water?
Yes — practicing continuous threshold swimming in open water is great for race-specific fitness.
Final Thoughts
Threshold swimming is the foundation for consistent pacing, strong finishes, and confident racing at Ironman 70.3.
Which threshold swim workout will you add to your plan to upgrade your swim performance?
Always consult with a medical professional or certified coach before beginning any new training program. The information provided is for educational purposes only and is not a substitute for personalized advice.