The level of resistance in the Trainer model is the highest level for most people, designed for those in good physical condition looking to benefit more from their training and exercise regime. This model is meant for the person who participates in activities such as swimming, tennis, running, golf or cycling at a high aerobic or endurance level. Advanced or professional performing artists specializing in high pressure instruments or professional singers with high lung volume will improve endurance and breath control while reducing risk of injury due to muscle strain or over performance. Recommended for Ages 13 and Up