In this study, we will test the hypothesis that preconditioning highly trained swimmers using skeletal muscle ischemia as the stimulus will improve exercise performance assessment.

The main purpose of this study is to determine if it is possible to precondition competitive swimmers and improve their exercise performance to provide further insight into the physiological mechanisms through which preconditioning may function. With four 5 minute inflation cycles of a blood-pressure cuff, we will induce skeletal muscle ischemia which is known to be a powerful method of preconditioning. Each swimmer will be blinded to the expected effect and randomly assigned to real preconditioning versus the sham intervention which will consist of four 5 minute cycles of blood pressure cuff inflation to 10mmHg. During a subsequent training session, the subjects will receive the intervention they have not received during the previous test session. Therefore, each subject will be part of both study groups and will serve as their own control. To evaluate the exercise performance, the subjects will perform an incremental swimming test protocol based on methods developed and reported by a member our research team. Swimming velocity, blood lactate level, heart rate, breathing frequency, dyspnoea and oxygen saturation will be measured during incremental exercise. Finally, we would like to determine the preconditioning effect of regular exercise training in an animal model.

Exercise performance is thought to be limited by skeletal, cardiac and respiratory muscle fatigue associated with episodes of exercise induced arterial hypoxemia. Preconditioning is defined as a period of brief lack of oxygen or ischemia in a tissue that protects the heart or any other organ from another sustained episode of ischemia. Preconditioning is believed to improve exercise performance by protecting the skeletal, cardiac and respiratory muscles against decreased oxygen and by-products of anaerobic metabolism that may limit an individual's exercise performance. Elite athletes, such as highly trained swimmers, may provide the research team with the opportunity to evaluate the effect of preconditioning during local tissue hypoxia and anaerobic metabolic by-products in healthy adolescents, which is otherwise not possible. With this study, we will show if it is possible to precondition competitive swimmers and improve their exercise performance using ischemia of the limb as a preconditioning stimulus.

Inclusion Criteria:

• Healthy male or female athlete volunteers
• Post-pubescent swimmers between the ages of 13 and 22 years (or healthy non-athletes (for the "equipment control" group and for the control arm for the animal model section)
• Members of competitive swimming teams
• Have achieved a swimming performance time within 5% of national qualification standards

Exclusion Criteria:

• Illness, surgery, or medical intervention within the last 48 hours
• Diabetes mellitus