Muscle Regrowth During Physical Rehabilitation And Amino Acid Supplementation

BACKGROUND: Americans over the age of 65 represent the fastest growing segment of the U.S. population, thus it is not surprising to learn that the number of total knee arthroplasty (TKA) surgeries is predicted to increase as much as 673% by 2030, to 3.48 million procedures per year. By far the most significant clinical barrier following TKA surgery is persistent muscle atrophy and weakness. Previous research has demonstrated that essential amino acid (EAA) ingestion is a potent means to stimulate muscle protein synthesis in older adults. PURPOSE:To determine the effects of twice-daily ingestion of 20 grams of EAA before and after TKA surgery on muscle mass, strength and physical function. METHODS: Magnetic resonance imaging (MRI), isometric quadriceps strength and functional measures (stair climb, timed-up-and-go (TUG) and six-minute walk) were obtained at baseline and at 2 and 6 weeks post-TKA from older adults supplemented with EAA or placebo. RESULTS: Preliminary results indicate that muscle volume is significantly decreased at 2 and 6 weeks post (p<0.05). Timed stair assent and descent, and the timed-up-and-go (TUG) were increased at 2 weeks post relative to baseline (p<0.05), and the distance walked in 6 minutes decreased at 2 weeks post. Isometric quadriceps strength was significantly decreased at 2 weeks post relative to baseline (p<0.05). CONCLUSIONS: Our preliminary data demonstrate that TKA surgery is associated with significant muscle atrophy, declines in muscle strength and physical performance. These preliminary findings will help us to better understand the potential for EAA supplementation to attenuate loss and boost recovery of muscle mass, strength and function following TKA in older adults. This work was supported by the Eunice Kennedy Shriver National Institute for Child Health and Human Development K01HD057332 (HCD)