Will, a 45-yr-old former collegiate swimmer turned lifelong triathlete, requests assistance with run training. His only significant medical history is a series of overuse injuries to his shoulders and Achilles tendon. In recent weeks, he notes his workouts are unusually difficult and reports feeling constriction in his chest with exertion – something he attributes to deficiencies in core strength. Upon further questioning, he explains that the chest constriction is improved with rest and that he often feels dizzy during recovery. What do you think is the underlying problem that could be causing Will’s symptoms during/after exercise?