Effect of Incorporating Lean Beef Into a Protein-rich Diet During Resistance Training Program on Skeletal Muscle and Connective Tissue Strength and Quality in Older Women

Loss of muscle mass and strength is a well-established outcome of normal aging. Muscle strength and mobility are also dependent on the quality and strength of connective tissue, which surrounds skeletal muscle. These layers, which are continuous with tendons, allow for the effective transfer of tension from skeletal muscle to bone to enable movement. Importantly, skeletal muscle strength is directly related to connective tissue strength. Greater tendon connective tissue cross-sectional area and stiffness optimize force transfer through tendon to maximize musculoskeletal function. As with skeletal muscle, tendon connective tissue quality declines with age. Previous research indicates that resistance training can improve muscle strength in older adults, but may not counter the effects of aging on tendon. The specific problem is that no approaches are available that benefit both skeletal muscle and tendon health to minimize loss of muscle mass and quality while also improving connective tissue quality and function in older adults. A critical need exists to assess approaches that improve both muscle and connective tissue strength and function. This need is highly relevant for older women, due to their higher risk of sarcopenia than men. Resistance training, especially when combined with higher protein intake, has been consistently shown to improve muscle mass and strength in older adults. Further, emerging research indicates that diets rich in total and indispensable amino acids (as in beef) augment exercise-induced improvements in tendon cross-sectional area in rodents and young humans. However, limited research exists on the impact of beef consumption combined with resistance training on muscle and tendon tissue outcomes, especially in older women. This research study will assess the effects of consuming a healthy, protein-rich diet emphasizing lean beef, compared to a healthy, normal-protein, lower beef diet (control 1), and a healthy protein-rich, lower beef diet emphasizing non-beef/red meat protein (control 2) on resistance training-induced changes in muscle and tendon tissue size, strength, and quality in older women.