Date: 7–9th July, 2025
‍Location: Bergen, Norway – Fyllingsdal Tunnel

Rider Profile

Name: Kristian Blummenfelt (@kristianblu)
Accolades:

• 2020 Olympic Triathlon Gold Medalist
• 2021 Ironman World Champion
• Ironman 70.3 World Champion

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‍Training Camp Objectives

Kristian returned to testing with Body Rocket during a focused three-day training camp in Bergen, Norway, joined by performance apparel brand Surpas, CORE Body Temperature and UK-based bike fitter Sam Barley. The goals of this session included:

• Evaluating the aerodynamic performance of a new Surpas suit being developed for the Ironman World Championships in Nice (September)
• Comparing helmet performance by testing the new Giant Rivet MIPS Aero helmet against Kristian’s older model
• Using Body Rocket’s aerodynamic data (CdA) to support data-driven refinement of his position and equipment
• Using the CORE body temperature sensor to validate the thermal performance of the new suit and help optimise Kristian’s heat adaptation strategy

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Test Venue & Protocol

Testing took place in the Fyllingsdal Tunnel, the world’s longest purpose-built tunnel for pedestrians and cyclists. The team used a 1km straight section of the tunnel for 2km out-and-back test runs, ensuring consistent conditions for accurate comparisons.

Each run isolated a single variable either a helmet or Surpas suit change with CdA values reviewed post-run to guide iterative refinement. This method ensured confidence in the validity of any aerodynamic gains or losses observed during testing.

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Testing Results

Figure 1: CdA vs. Gains

What the chart shows:

The aerodynamic drag (CdA) of different Surpas  suit and helmet configurations, including experimental modifications such as applied strips. Each combination is accompanied by the corresponding watts gained or lost.

Key Test Labels & Results:

• R3 – Baseline (New Helmet + New Surpas Suit): CdA = 0.175
  
• R4 – Old Helmet, New Surpas Suit: CdA = 0.178 → 3.6W lost
  
• R5 – New Helmet, Old Suit: CdA = 0.180 → 6.0W lost
  
• R6 – New testing strip 1: CdA = 0.178 → 3.6W lost
  
• R7 – New testing strip 2: CdA = 0.176 → 1.2W lost
  
• R8 – New testing strip 3: CdA = 0.178 → 3.6W lost
  
• R9 – New testing strip 4: CdA = 0.178 → 3.6W lost
  
• R10 – Vertical strip: CdA = 0.179 → 4.8W lost

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Key Takeaways

• The combination of new helmet and new Surpas suit (R3) was the most aerodynamic tested.
  
• The old helmet (R4) increased drag by 3.6 watts, validating the choice of Kristian's new Giant Rivet MIPS Aero helmet.
  
• The old suit (R5) cost Kristian 6.0 watts compared to the new Surpas suit, making a total 9.6W gain when combining the new helmet and suit.
  
  

Tests using additional aero strip variations (R6–R10) either increased drag or provided only minor benefits, indicating limited performance potential in those adjustments.

Conclusion

This three-day training camp in Bergen marked a key milestone in the build-up to Kristian Blummenfelt’s 2025 Ironman World Championship campaign. Leveraging Body Rocket’s aerodynamic testing tools, Kristian and his team made evidence-based decisions around kit and position unlocking a solid 9.6 watts in gains through the new Giant Rivet MIPS Aero helmet and Surpas suit.

Now, with the gains locked in and the hard work behind him, all eyes are on the World Championships in Nice and we’re wishing Kristian the very best as he takes on the next big challenge!