Effects of older age on contraction-induced intramyocellular acidosis and inorganic phosphate accumulation in vivo: A systematic review and meta-analysis

• Published in: PloS one 2024-09, Vol.19 (9), p.e0308336
• Main Authors: Arieta, Luke R, Smith, Zoe H, Paluch, Amanda E, Kent, Jane A
• Format: Article
• Language: English
• Subjects: Accumulation; Acidification; Acidosis; Acidosis - metabolism; Acidosis - physiopathology; Adolescent; Adult; Age; Age Factors; Age factors in disease; Aged; Aging - metabolism; Aging - physiology; Analysis; Bioenergetics; Biology and Life Sciences; Demographic aspects; Development and progression; Energy demand; Fatigue; Health aspects; Humans; Hydrogen-Ion Concentration; In vivo methods and tests; Male; Medical research; Medicine and Health Sciences; Medicine, Experimental; Meta-analysis; Metabolites; Middle Aged; Missing data; Muscle Contraction; Muscle fatigue; Muscle Fatigue - physiology; Muscle, Skeletal - metabolism; Muscles; Muscular fatigue; Musculoskeletal system; Old age; Older people; pH effects; Phosphates; Phosphates - metabolism; Phosphorus imbalance; Physical Sciences; Research and Analysis Methods; Risk factors; Sensitivity analysis; Skeletal muscle; Software; Subgroups; Systematic review; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0308336

Although it is clear that the bioenergetic basis of skeletal muscle fatigue (transient decrease in peak torque or power in response to contraction) involves intramyocellular acidosis (decreased pH) and accumulation of inorganic phosphate (Pi) in response to the increased energy demand of contractions, the effects of old age on the build-up of these metabolites has not been evaluated systematically. The purpose of this study was to compare pH and [Pi] in young (18-45 yr) and older (55+ yr) human skeletal muscle in vivo at the end of standardized contraction protocols. Full study details were prospectively registered on PROSPERO (CRD42022348972). PubMed, Web of Science, and SPORTDiscus databases were systematically searched and returned 12 articles that fit the inclusion criteria for the meta-analysis. Participant characteristics, contraction mode (isometric, dynamic), and final pH and [Pi] were extracted. A random-effects model was used to calculate the mean difference (MD) and 95% confidence interval (CI) for pH and [Pi] across age groups. A subgroup analysis for contraction mode was also performed. Young muscle acidified more than older muscle (MD = -0.12 pH; 95%CI = -0.18,-0.06; p