The TrainingMask is a face mask designed to be worn while exercising to improve performance. The use of the mask was "engineered to apply variable levels of load to the respiratory muscles by controlling airflow pass through; this increases tension on your breathing - which makes you more powerful and efficient over a long workout."
The TrainingMask also improves the wearer's Respiratory Compensation Threshold (RCT), which is the boundary between high-intensity activity and severe intensity exertion. This shifts the body to use lactate levels instead of the customary carbon dioxide levels used in the body. This increases respiration and prompts a transition point to help push past fatigue and improve wearer's conditioning, strength, and power.
Image Credit: TrainnigMask