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Randomized Controlled Trial
. 2024 Jun;154(6):1803-1814.
doi: 10.1016/j.tjnut.2024.04.001. Epub 2024 Apr 9.

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  1 , Nathan Wc Campbell  2 , Rebecca L Lewis  2 , Sarah E Preston  2 , Chloe M Garrett  2 , Hannah M Winstone  2 , Anna C Barker  2 , Johnny M Vanos  2 , Lucas S Stouder  2 , Camila Reyes  2 , Matthew A Fortino  2 , Craig J Goergen  3 , Zachary J Hass  4 , Wayne W Campbell  5
Affiliations
Randomized Controlled Trial

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 et al. J Nutr. 2024 Jun.

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.

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Conflict of interest statement

Conflict of interest During the time this research was conducted, WWC received funding for research from NIH, USDA, Beef Checkoff, Foundation for Meat and Poultry Research and Education, Pork Checkoff, North Dakota Beef Commission, Barilla Group, Mushroom Council, National Chicken Council, and the Whey Protein Research Consortium. All other authors report no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Consort diagram.
FIGURE 2
FIGURE 2
Percent change in quadriceps muscle volume. Data presented as mean ± SE. Circles, squares, and triangles represent individual data points for each subject within a diet group.
FIGURE 3
FIGURE 3
Percent change in mean and regional patellar tendon cross-sectional area (CSA). Data presented as mean ± SE. Circles, squares, and triangles represent individual data points for each subject within a diet group. ∗P ≤ 0.05, the main effect of time. #P < 0.10, increase in the 1.4 g/kg/d group. aP < 0.05, a decrease in the 0.8 g/kg/d group.
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