"I used the mask system for around 8 weeks before Duathlon Worlds in NC.  After 4 weeks I found myself running and biking like I had 10 years ago, doing 34 min 10kms and sub 28min 20km rides at sub threshold heart rates.  Then in the horrible cold and pouring rain conditions, I raced to a World Silver Medal!  I believe that your altitude training system played a key role in this achievement and fitness, THANK YOU!"

- Shane Thread, World Duathlon Silver Medalist