{"doi":"10.1113/jp282877","title":"The secret to a long ‘musclespan’ is a little hard work","abstract":"Skeletal muscles’ ability to produce and transmit force is essential for movement and locomotion. Understanding the factors that control muscle mass and muscle function is therefore critically important to improve exercise performance and to prevent debilitating declines in physical function that are associated with age-related sarcopenia and have adverse effects on quality of life and mortality (Prado et al. 2018). In celebration of the publication of the 600th volume of The Journal of Physiology, we draw attention to the highly influential research published in The Journal in this area. It has long been known that muscle contraction is a key determinant of muscle size, because it activates muscle protein synthesis (Goldspink, 1977). Furthermore, it is well-established that muscle mass and function start to decline after people reach middle age (∼45 years and upwards) (Evans, 1995). Although reduced physical activity as people get older certainly contributes to these decreases, reduced activity alone is an insufficient cause, because muscle mass and function decline even in master athletes (∼50 years and older), albeit at a slower pace (Faulkner et al. 2008; Power et al. 2013). The nuanced nature of the relationship between muscle contraction and muscle protein synthesis and how it is affected by ageing remained elusive until the results from an elegant study by Kumar and colleagues (2009) appeared in The Journal of Physiology. Kumar and colleagues measured the rate of myofibrillar protein synthesis and muscle anabolic signalling in young (∼25 years of age) and older adults (average age: 70 years) who completed one of five unilateral knee-extension exercise protocols at increasing intensities, corresponding to 20%, 40%, 60%, 75% and 90% of their one-repetition maximum (1RM) workload. The duration of the exercise was adjusted so that the total volume of work was the same during all protocols. Myofibrillar protein synthesis was evaluated in the non-exercised leg and during several time periods during the immediate post-exercise recovery period (0−1 h, 1−2 h and 2−4 h) in the exercised leg. This innovative and sophisticated study design produced several seminal findings. First, the authors found that myofibrillar protein synthesis rate increased above rested values with increasing contractile intensity and was maximally stimulated at an exercise intensity of 60% 1RM in both young and older adults. Further increases in exercise intensity did not result in greater protein synthesis in either young or older adults. Second, although there was no difference in myofibrillar protein synthesis rate at rest between the young and older adults, the exercise-induced increase in myofibrillar protein synthesis at any exercise intensity was less in the older, compared with the young adults. And third, the increase in myofibrillar protein synthesis was preceded by greater phosphorylation (activation) of anabolic signalling proteins in the young, compared with older adults, which may partly explain the difference in the anabolic response between the young and old participants. In many regards, the observed muscle protein synthesis response to exercise was similar to the response to hyperaminoacidaemia and protein ingestion, because in both cases (exercise and nutrition) the response is dose-dependent and saturable (Bohé et al. 2001; Moore et al. 2009a) and blunted in older, compared with young adults (Kumar et al. 2009; Moore et al. 2015). This similarity supports the notion that factors intrinsic to skeletal muscle itself are key regulators of muscles’ growth potential (West et al. 2009) and therefore the underlying cause of age-associated sarcopenia. Another noteworthy observation was the short duration of the exercise-induced increase in myofibrillar protein synthesis, which reached peak values between 1 and 2 h after exercise and then returned to basal values. This temporal relationship between muscle work and myofibrillar protein synthesis ","journal":"The Journal of Physiology","year":2022,"id":305654,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":0,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9509,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":892686,"name":"Bettina Mittendorfer","orcid":"0000-0002-1746-8545","position":1,"is_corresponding":false},{"id":267705,"name":"Joseph W. Beals","orcid":"0000-0002-8813-4796","position":0,"is_corresponding":true}],"reference_count":21,"raw_metadata":null,"created_at":"2026-07-19T00:32:44.983506Z","pmid":"35100656","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}