Fasted Morning Open Water Swim: 60-Minute Aerobic Session

Session Overview

Swimming fasted — 8–12 hours after your last meal — trains your body to oxidise fat more efficiently, improving metabolic flexibility for long-course racing. This 60-minute open water session stays purely aerobic throughout, making it safe and effective for intermediate open water swimmers looking to build endurance adaptations.

What You’ll Need

• Wetsuit
• Bright tow float (non-negotiable when swimming solo)
• Sighting landmark or buoy course
• Post-swim snack and water bottle ready at the water’s edge

Warm-Up (10 minutes)

Easy breaststroke for 3 minutes to wake up your body. Follow with 7 minutes of easy front crawl building from very easy Zone 1 to Zone 2. Keep the effort honest — fasted training is undermined if you go out too hard.

Main Set

40 minutes of continuous Zone 2 swimming — heart rate at 60–70% of your maximum, breathing comfortably throughout.

• Minutes 0–20: Zone 2 front crawl, sight every 10 strokes, relaxed effort
• At minute 20: check in — if feeling strong, hold pace; if drifting low, refocus on stroke rate
• Minutes 20–40: continue Zone 2 effort, maintain stroke length and catch quality

Cool-Down (10 minutes)

Ease pace gradually over 5 minutes, then 5 minutes of easy backstroke if conditions allow. Exit the water and eat your post-swim snack within 10 minutes — a banana, gel or small bowl of porridge replenishes glycogen effectively.

Coaching Notes

• Only attempt fasted open water if you have prior OW experience — don’t combine an empty stomach with an unfamiliar environment
• Never swim fasted alone: always bring a buddy or use a highly visible tow float with an attached whistle
• Not recommended in water below 12°C — cold water burns glycogen faster, increasing hypoglycaemia risk
• To progress: extend the Zone 2 block by 5 minutes each week up to 60 minutes continuous