Triathlon Interval Workouts: Speed & VO2max Training

Triathlon interval workouts alternate between high-intensity efforts and recovery periods, improving your VO2max, lactate tolerance, and ability to surge during races.

While most triathlon training should be easy, interval work is where you build speed and top-end fitness. Done correctly, intervals make easy paces feel easier and raise your performance ceiling.

What Are Interval Workouts?

The Structure

Intervals consist of:

• Work period: Hard effort at high intensity
• Recovery period: Easy effort to partially recover
• Repetitions: Number of work/recovery cycles

Why Intervals Work

Types of Interval Workouts

By Duration and Intensity

The 80/20 Balance

Remember: intervals are only 10-20% of training

• 80% easy (Zone 1-2)
• 10% moderate (Zone 3)
• 10% hard intervals (Zone 4-5)

Learn more: Triathlon Training Zones Explained

Swimming Intervals

Short Intervals (Speed)

50m Sprints:

Warm-up: 300m easy + drills
Main: 10 x 50m fast, 20s rest
      Target: Near max effort
Cool-down: 200m easy
Total: 1,000m

100m Repeats:

Warm-up: 300m
Main: 8 x 100m hard, 20s rest
      Target: CSS pace -5 sec/100m
Cool-down: 200m
Total: 1,300m

Medium Intervals (VO2max)

200m VO2max Set:

Warm-up: 300m + 4x50m drill
Main: 6 x 200m at fast pace, 30s rest
      Target: CSS pace -3 sec/100m
Cool-down: 200m easy
Total: 1,900m

Descending Set:

Warm-up: 300m
Main: 400m moderate
      300m faster
      200m fast
      100m sprint
      (30s rest between)
      Repeat 2x
Cool-down: 200m
Total: 2,500m

Long Intervals (Threshold)

CSS Intervals:

Warm-up: 300m
Main: 5 x 300m at CSS pace, 15s rest
Cool-down: 200m
Total: 2,000m

Use our CSS Calculator to find your pace.

Cycling Intervals

Short Intervals (Neuromuscular)

30/30s:

Warm-up: 15 min easy
Main: 10 x (30s at 120% FTP + 30s easy)
      5 min easy
      Repeat 2-3 sets
Cool-down: 10 min
Total: 50-60 min

Tabata-Style:

Warm-up: 15 min
Main: 8 x (20s max + 10s easy)
      5 min easy
      Repeat 2 sets
Cool-down: 10 min
Total: 45 min

Medium Intervals (VO2max)

3-Minute Repeats:

Warm-up: 15 min
Main: 5 x 3 min at 115-120% FTP, 3 min easy
Cool-down: 10 min
Total: 55 min

5-Minute Repeats:

Warm-up: 15 min
Main: 4 x 5 min at 106-112% FTP, 4 min easy
Cool-down: 10 min
Total: 60 min

Long Intervals (Threshold)

8-Minute Repeats:

Warm-up: 15 min
Main: 4 x 8 min at 100-105% FTP, 4 min easy
Cool-down: 10 min
Total: 75 min

Calculate your FTP: FTP Calculator

Read more: Threshold Training for Triathlon

Running Intervals

Short Intervals (Speed)

200m Repeats:

Warm-up: 15 min + strides
Main: 8 x 200m at mile pace, 200m jog
Cool-down: 10 min easy
Total: ~40 min

400m Repeats:

Warm-up: 15 min + strides
Main: 6 x 400m at 5K pace, 90s jog
Cool-down: 10 min easy
Total: ~45 min

Medium Intervals (VO2max)

800m Repeats:

Warm-up: 15 min + strides
Main: 5 x 800m at 5K pace, 2 min jog
Cool-down: 10 min easy
Total: ~50 min

1km Repeats:

Warm-up: 15 min + strides
Main: 5 x 1km at 10K pace, 90s jog
Cool-down: 10 min easy
Total: ~55 min

Long Intervals (Threshold)

Mile Repeats:

Warm-up: 15 min + strides
Main: 3 x 1 mile at threshold pace, 3 min jog
Cool-down: 10 min easy
Total: ~55 min

Tempo Intervals:

Warm-up: 15 min
Main: 3 x 10 min at threshold, 3 min jog
Cool-down: 10 min easy
Total: ~60 min

Programming Intervals

Weekly Structure

Sample Build Phase Week

Progression Examples

Running 1km Repeats:

Interval Execution Tips

Pacing

The Right Approach:

• Even pacing across all repeats
• Last rep shouldn't be slowest
• Slight negative split is ideal

Common Mistake:

• Going out too fast
• Fading on later reps
• First interval best, last worst

Recovery Periods

Active vs Passive:

• Keep moving during recovery
• Very easy effort (walking/spinning)
• Allows partial but not full recovery

Recovery Duration:

• Shorter recovery = harder session
• Longer recovery = quality maintained
• Adjust based on workout goals

Mental Approach

During hard intervals:

• Break each interval into chunks
• Focus on technique under fatigue
• Use mantras ("smooth and fast")
• Stay present, don't think about remaining reps

Common Interval Mistakes

1. Too Many Intervals

Problem: Excessive high-intensity work

Signs:

• Persistent fatigue
• Declining performance
• Poor recovery between sessions

Solution:

• Maximum 2-3 interval sessions/week
• Balance with 80% easy training
• Include recovery weeks

2. Wrong Intensity

Problem: Too fast or too slow

Signs (too fast):

• Can't complete the session
• Significant fade in later reps
• Need days to recover

Signs (too slow):

• Feels too easy
• Could do many more reps
• HR doesn't reach targets

Solution:

• Use power/pace targets
• Aim for consistent repeats
• Adjust if needed mid-session

3. Inadequate Recovery Between Intervals

Problem: Not recovering enough during rest periods

Signs:

• Each rep harder than last
• HR doesn't drop during recovery
• Quality degrades quickly

Solution:

• Use prescribed recovery times
• Allow HR to drop 20-30 bpm
• Extend recovery if needed

4. Skipping Warm-Up

Problem: Going hard on cold muscles

Signs:

• First intervals feel terrible
• Injury risk higher
• Can't hit targets

Solution:

• 15+ min progressive warm-up
• Include strides before running intervals
• Arrive at first interval ready to go

Intervals in Race Preparation

Race Simulation Intervals

Combine intervals with race-specific work:

Bike: 60 min with 4 x 3 min race effort surges
T2: Quick transition
Run: 20 min with 3 x 90s at 5K pace

Brick Intervals

Practice running fast off the bike:

Bike: 45 min steady
Run: 4 x 400m at 10K pace, 200m jog

Read more: Brick Workouts for Triathlon

Related Resources

• Triathlon Training Zones Explained - Intensity guidance
• Threshold Training for Triathlon - Threshold intervals
• Triathlon Tempo Workouts - Moderate intensity
• Triathlon Build Phase - When to use intervals
• CSS Calculator - Swim targets
• FTP Calculator - Bike targets