Anabolic Resistance and Exercise in Older Adults
Muscle protein synthesis (MPS) is primarily driven by “physical activity and nutrient availability” (Atherton & Smith, 2012). Resistance training in particular can enhance the MPS response to protein intake by increasing the duration of the MPS process (e.g., heightening the “muscle full” threshold at which MPS returns back to postabsorptive rates, Deane et al., 2024) as well as sensitivity to nutrients (e.g., amplifying amino acid transporter expression for up to 24 hours; Moore, 2014).
Acute resistance exercise can increase MPS and promote hypertrophy if performed at proper volume and intensity (Atherton & Smith, 2012). Amino acid availability as well as mechanical overload (i.e., resistance exercise) are positively related to mTOR signaling pathway activity, which acts a stimulus for the MPS process in which, at the cellular level, a muscle protein is transcribed into mRNA (a single strand of nucleotides acting like a “blueprint” for building proteins), which is then translated by ribosomes and transfer RNA into a single strand of amino acids (i.e., a polypeptide chain), which is then translated by ribosomes and transfer RNA into a polypeptide chain that is finally folded and modified to form a functional protein (Miyazaki & Esser, 2009).
Regarding nutrition, amino acids are transferred from ingested protein to skeletal muscle proteins; this postprandial process serves to compensate for the muscle protein breakdown that occurs during fasting (Atherton & Smith, 2012). Thus, sufficient protein intake is necessary to trigger MPS. Most evidence suggests that approximately 20 grams (0.24 grams per kilogram of body weight) of protein per meal is an adequate amount for promoting MPS (Deane et al., 2024).
However, due to several factors related to the aging process, older adults may need twice as much protein to elicit an MPS response of the same magnitude (Deane et al., 2024). This blunted muscle protein synthesis response seen in older adults is generally referred to as “anabolic resistance” and can be defined as the “reduced ability of skeletal muscle to increase protein synthesis in response to amino acids and protein, insulin, or exercise” (Moro et a., 2018). Notably, inactivity is a likely contributor to anabolic resistance and the consequent loss of muscle mass that is characteristic of unhealthy aging (Moore, 2014).
Resistance training is an effective way to combat anabolic resistance and sarcopenia (muscle loss with aging), but certain considerations must be taken into account when programming for older adults undergoing or at risk of developing such dysfunctional processes. For instance, evidence suggests that older adults require greater regular loads in their training in order to maintain previous muscle growth than their younger counterparts (Bickel, et al., 2011). For this reason, periods of detraining may be especially detrimental to older adults regarding muscle mass. While traditional guidelines suggest that older adults train with moderate loads, emerging evidence claims that training at or above 80% of an individual’s one-rep max may provide additional benefit to older adults, especially since aging is associated with loss of muscle and strength (Tøien et al., 2025).
Improving strength and muscle mass can help promote mobility, general functionality, and preserve the independent lifestyle of older adults. Also, certain findings suggest that age does not necessarily impact the anabolic response to resistance exercise (Symons et al., 2011), and physical activity may have a protective effect against anabolic resistance (Perez-Castillo et al., 2025); therefore, regular, intense resistance training is of equal or greater importance to the health and well-being of older adults. However, older adults, especially those who have already experienced substantial muscle mass loss, are likely to be at a higher risk of injury during resistance training, so precautionary measures should be taken to prevent falls, to warm up and recover well, and to increase mobility.
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Citations
Atherton, P. J., & Smith, K. (2012). Muscle protein synthesis in response to nutrition and exercise. The Journal of Physiology, 590(5), 1049–1057. https://doi.org/10.1113/jphysiol.2011.225003
Bickel, C. S., Cross, J. M., & Bamman, M. M. (2011). Exercise dosing to retain resistance training adaptations in young and older adults. Medicine and Science in Sports and Exercise, 43(7), 1177–1187. https://doi.org/10.1249/MSS.0b013e318207c15d
Deane, C. S., Cox, J., & Atherton, P. J. (2024). Critical variables regulating age-related anabolic responses to protein nutrition in skeletal muscle. Frontiers in Nutrition, 11, Article 1419229. https://doi.org/10.3389/fnut.2024.1419229
Miyazaki, M., & Esser, K. A. (2009). Cellular mechanisms regulating protein synthesis and skeletal muscle hypertrophy in animals. Journal of Applied Physiology, 106(4), 1367–1373. https://doi.org/10.1152/japplphysiol.91355.2008
Moore D. R. (2014). Keeping older muscle “young” through dietary protein and physical activity. Advances in Nutrition (Bethesda, Md.), 5(5), 599S–607S. https://doi.org/10.3945/an.113.005405
Moro, T., Brightwell, C. R., Deer, R. R., Graber, T. G., Galvan, E., Fry, C. S., Volpi, E., & Rasmussen, B. B. (2018). Muscle Protein Anabolic Resistance to Essential Amino Acids Does Not Occur in Healthy Older Adults Before or After Resistance Exercise Training. The Journal of Nutrition, 148(6), 900–909. https://doi.org/10.1093/jn/nxy064
Pérez-Castillo, Í. M., Rueda, R., Pereira, S. L., Bouzamondo, H., López-Chicharro, J., Segura-Ortiz, F., & Atherton, P. J. (2025). Age-Related Anabolic Resistance: Nutritional and Exercise Strategies, and Potential Relevance to Life-Long Exercisers. Nutrients, 17(22), 3503. https://doi.org/10.3390/nu17223503
Symons, T. B., Sheffield-Moore, M., Mamerow, M. M., Wolfe, R. R., & Paddon-Jones, D. (2011). The anabolic response to resistance exercise and a protein-rich meal is not diminished by age. The Journal of Nutrition, Health & Aging, 15(5), 376–381. https://doi.org/10.1007/s12603-010-0319-z
Tøien, T., Berg, O. K., Modena, R., Brobakken, M. F., & Wang, E. (2025). Heavy Strength Training in Older Adults: Implications for Health, Disease and Physical Performance. Journal of cachexia, Sarcopenia and Muscle, 16(2), e13804. https://doi.org/10.1002/jcsm.13804
