Ranks
Rank 1
Fitness
You have 10% more oxygen available.
Rank 2
Fitness
You have 20% more oxygen available.
Rank 3
Fitness
You have 30% more oxygen available.
Rank 4
Fitness
Sprinting and power attacks now use significantly less oxygen.
Challenges
Rank 1: Use up all available Oxygen and Carbon Dioxide 20 times.
Rank 2: Use up all available Oxygen and Carbon Dioxide 50 times.
Rank 3: Use up all available Oxygen and Carbon Dioxide 100 times.