Five Weeks In. The Expedition Becomes the Norm.

There is a point in every ultra-endurance challenge where the extraordinary becomes ordinary. Team Nautilus have reached that point. Five weeks into their 2,000-mile row around Great Britain, the two-hours-on/two-hours-off rota is no longer something the crew are adapting to - it is simply how they live.

The Week Five data reflects that shift. Strain is high but beginning to settle. Energy expenditure is holding steady. The crew are not declining - they are enduring. And endurance, sustained over weeks rather than days, is a different kind of performance entirely.

This is Week Five.

A Note on This Week's Data

Sleep and recovery metrics remain unavailable due to limitations in data collection while at sea. This week's report continues to focus on workload, strain and energy expenditure.

Week Five Key Findings (June 30th - July 6th)

Strain

Average daily strain across the crew fell to 15.0 - down 16.7% on Week Four - though the crew remained under a consistently demanding workload throughout the period. A strain score of 15 still places every crew member in the upper reaches of what most athletes would consider a very hard training week. For Nautilus, it is simply another week at sea.

Energy Expenditure

Average calories burned held largely steady at 2,663 kcal per day - up just 1.8% on the previous week. Individual expenditure ranged from 2,155 to 4,066 kcal per day, continuing to highlight significant variation in the physical demands experienced across the six crew members.

The fact that energy expenditure has remained stable despite a reduction in recorded workouts suggests the crew are rowing fewer but harder sessions - each effort demanding more from the body than the last.

Workout Volume

Average recorded workouts fell to 20.2 per week - down 23.2%. As with the strain reduction, this does not indicate a drop in physical demand. It reflects the natural fluctuation of shift patterns, sea conditions and individual workload distribution across a crew of six operating around the clock.

What the Data Tells Us: The Physiology of Week Five

After five weeks of continuous rowing, the body is no longer responding to the expedition as a crisis. The acute stress response of the early weeks - sharp rises in strain, collapsing sleep metrics, plummeting recovery scores - has given way to a more stable, if still extreme, operating state.

This is both encouraging and important to understand. Stability in the data does not mean the body is fully recovered or that the physical cost of the challenge has reduced. It means the crew have found a sustainable level of output within their current physiological constraints - and that managing the inputs precisely is now what determines whether performance holds or begins to erode.

At this stage of the expedition, how the crew fuel matters more than how hard they row. The body's energy systems are continuously shifting between fuel sources depending on rowing intensity:

• Higher-intensity rowing draws heavily on carbohydrates, making consistent carbohydrate intake the primary performance lever for maintaining power output and delaying fatigue.
• Lower-intensity periods allow the body to utilise fat as a fuel source, preserving carbohydrate stores for the harder efforts ahead.

Maintaining regular carbohydrate intake across every 2-hour cycle - even during easier shifts - ensures the crew are never starting a hard rowing block on empty. By the time fatigue is felt, the deficit has already accumulated. The goal is to stay ahead of it.

Individual Highlights

• Highest energy demand: One crew member burned 4,066 kcal per day - up 36.6% on the previous week - despite completing slightly fewer sessions. Each shift is now requiring significantly more effort, likely reflecting more demanding sea conditions or sustained high-intensity output during rowing blocks.
• Most changed workload profile: One crew member saw both calorie expenditure and session count increase substantially - up 32.9% and 85.7% respectively - despite a slight reduction in average strain. A busier week with a different rhythm of effort.
• Reduced workload members: Two crew members recorded notably lower strain and session volumes this week. Lower output periods in an ultra-endurance environment are a natural part of the cycle - but maintaining nutrition and hydration discipline during easier periods is just as important as during peak load, to stay ready for the next high-demand block.

Week Five Focus: Fuel Use and Exercise Intensity

Our performance team's focus for this week centres on the relationship between rowing intensity and fuel selection:

• Keep carbohydrate intake consistent across every shift rotation, regardless of perceived effort level.
• Refuel within 30 minutes of finishing each rowing block to begin replacing glycogen stores before the next shift begins.
• Avoid prolonged gaps in energy intake between sessions. In a 2-on/2-off structure, the off period is a fuelling window, not just a rest window.
• Match food intake to individual demand. With crew members burning between 2,155 and 4,066 kcal per day, there is no single crew-wide target - each person's intake needs to reflect their own output.
• Maintain electrolyte replacement consistently across all conditions and all workload levels.

Follow the PEAK4 x Team Nautilus performance tracker for weekly updates throughout the GB Row Challenge 2026. The crew continue their circumnavigation of Great Britain - one shift at a time, one mile at a time.