TABLE 2.

Muscle mass, strength, and function outcomes with protein-based interventions after orthopedic surgery¹

Study	Population	Age, y	Nutrition intervention	Muscle mass	Strength and function	Effect
Dreyer et al. 2018 (96)	TKA patients	∼64	20 g EAAs twice daily between meals for 7 d preoperatively and 6 wk postoperatively	13.4% vs. 8.5% ↓ quadriceps muscle volume in operated leg 6 wk postoperatively, control vs. intervention, (P < 0.05)	No difference between groups in functional measures or strength	Yes
Nishizaki et al. 2015 (98)	TKA patients	∼71	2.4 g HMB, 14 g l-arginine, 14 g l-glutamine twice daily for 5 d before and 28 d after TKA	No change in rectus femoris CSA from baseline at 42 d postsurgery, both groups	↓ Maximal knee extension strength in control group at 2 wk postsurgery, no change with intervention	Yes
Dreyer et al., 2013 (95)	TKA patients	∼69	20 g EAAs twice daily between meals for 7 d preoperatively and 6 wk postoperatively	14.3% vs. 3.4% ↓ quadriceps muscle volume in operated leg 2 wk postoperatively, 18.4% vs. 6.2% ↓ 6 wk postoperatively, control vs. intervention, (P < 0.05)	Intervention accelerated the return of functional mobility (i.e., timed up-and-go, stair-climb up, stair-climb down tests) at 6 wk	Yes
Ferrando et al. 2013 (97)	THA patients	∼55	15 g EAAs 3 times/d for 8 wk postoperatively	—	35% ↑quadriceps maximal voluntary contraction at 8 wk with intervention, no change in control group	Yes

¹CSA, cross-sectional area; EAA, essential amino acid; HMB, β-hydroxy-β-methylbutyrate; THA, total hip arthroplasty; TKA, total knee arthroplasty. ↑ indicates increase and ↓ indicates decrease.