Greater Protein Intake Emphasizing Lean Beef Does Not Affect Resistance Training-Induced Adaptations in Skeletal Muscle and Tendon of Older Women: A Randomized Controlled Feeding Trial

Chad C Carroll; Nathan Wc Campbell; Rebecca L Lewis; Sarah E Preston; Chloe M Garrett; Hannah M Winstone; Anna C Barker; Johnny M Vanos; Lucas S Stouder; Camila Reyes; Matthew A Fortino; Craig J Goergen; Zachary J Hass; Wayne W Campbell

doi:10.1016/j.tjnut.2024.04.001

Greater Protein Intake Emphasizing Lean Beef Does Not Affect Resistance Training-Induced Adaptations in Skeletal Muscle and Tendon of Older Women: A Randomized Controlled Feeding Trial

J Nutr. 2024 Apr 9:S0022-3166(24)00169-X. doi: 10.1016/j.tjnut.2024.04.001. Online ahead of print.

Affiliations

¹ Department of Health and Kinesiology, Purdue University, West Lafayette, IN, United States. Electronic address: carrol71@purdue.edu.
² Department of Health and Kinesiology, Purdue University, West Lafayette, IN, United States.
³ Department of Health and Kinesiology, Purdue University, West Lafayette, IN, United States; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States.
⁴ School of Nursing, Purdue University, West Lafayette, IN, United States; School of Industrial Engineering, Purdue University, West Lafayette, IN, United States; Regenstrief Center for Healthcare Engineering, Purdue University, West Lafayette, IN, United States.
⁵ Department of Nutrition Science, Purdue University, West Lafayette, IN, United States.

PMID: 38604504
DOI: 10.1016/j.tjnut.2024.04.001

Abstract

Background: Although experimental research supports that resistance training (RT), especially with greater dietary protein intake, improves muscle mass and strength in older adults, comparable research on tendons is needed.

Objectives: We assessed the effects of a protein-rich diet emphasizing lean beef, compared with 2 control diets, on RT-induced changes in skeletal muscle and tendon size and strength in older women.

Methods: We randomly assigned women [age: 66 ± 1 y, body mass index (BMI): 28 ± 1] to groups that consumed 1) 0.8 g total protein/kg body weight/day from mixed food sources (normal protein control, n = 16); 2) 1.4 g/kg/d protein from mixed food sources (high protein control, n = 17); or 3) 1.4 g/kg/d protein emphasizing unprocessed lean beef (high protein experimental group, n = 16). Participants were provided with all foods and performed RT 3 times/wk, 70% of 1-repetition maximum for 12 wk. We measured quadriceps muscle volume via magnetic resonance imaging (MRI). We estimated patellar tendon biomechanical properties and cross-sectional area (CSA) using ultrasound and MRI.

Results: Dietary intake did not influence RT-induced increases in quadriceps strength (P < 0.0001) or muscle volume (P < 0.05). We noted a trend for an RT effect on mean tendon CSA (P = 0.07), with no differences among diets (P > 0.05). Proximal tendon CSA increased with RT (P < 0.05) with no difference between dietary groups (P > 0.05). Among all participants, midtendon CSA increased with RT (P ≤ 0.05). We found a decrease in distal CSA in the 0.8 g group (P < 0.05) but no change in the 1.4 g group (P > 0.05). Patellar tendon MRI signal or biomechanical properties were unchanged.

Conclusions: Our findings indicated that greater daily protein intake, emphasizing beef, did not influence RT-induced changes in quadriceps muscle strength or muscle volume of older women. Although we noted trends in tendon CSA, we did not find a statistically significant impact of greater daily protein intake from beef on tendon outcomes. This trial was registered at clinicaltrials.gov as NCT04347447.

Keywords: MRI; clinical trial; dietary protein intake; tendon cross-sectional area; tendon modulus; ultrasound.

Associated data

ClinicalTrials.gov/NCT04347447