Eccentric lower extremity training (ELET) programs are accepted as a viable way to help prevent injury in elite athletes (1). Additionally, blood flow restriction (BFR) has been reported in the clinical setting to help rehabilitate and prevent lower extremity injury in patients with orthopaedic conditions (2, 3), and has shown promise as a valuable tool for both athletic injury prevention and rehabilitation (4, 2). Additionally, subjective accounts suggest there is less resulting muscle damage and/or soreness compared to ELET (5). Hypothesis 1: A single bout of lower extremity eccentric exercise with BFR will reduce acute muscle damage in elite athletes and young healthy adults compared to a single bout of lower extremity eccentric exercise without BFR (1). Hypothesis 2: 6-week lower extremity eccentric training program with BFR will result in greater muscle hypertrophy, strength, and reduced fatigability in both elite athletes and young healthy adults when compared to a 6-week eccentric training program without BFR.