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. 2019 Jan 1;126(1):257–262. doi: 10.1152/japplphysiol.00816.2018

Commentaries on Viewpoint: Rejuvenation of the term sarcopenia

PMCID: PMC6442659  PMID: 30694711
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

A MORE DYNAMIC NAME FOR AGE-RELATED FUNCTIONAL IMPAIRMENTS

Henning T Langer 1, Agata A Mossakowski 2, Keith Baar 1,3

to the editor: We agree with Bulow and colleagues (2) that “sarcopenia” should only be used to indicate the loss of muscle mass. Per the etymology of the word and its original intent, physical function should not be included within the definition. The loss of strength needs to be considered an independent measure so that clinicians can determine whether the muscle or its capacity for force generation is key for healthy aging. We suggest separating the terms, because in humans, muscle strength is lost three times faster than mass (3). Furthermore, in animal studies, old animals lose five times more strength than adult animals even when the decrease in muscle fiber cross-sectional area is identical (1). This suggests that muscle mass and strength are not directly related in old individuals. For force, we suggest the use of the term “dynopenia” from the Greek “dýnamis,” meaning power and “penia” meaning poverty or loss. Strength appears to have the greatest predictive capacity for longevity (5), possibly because older muscle loses innervation and force transfer (1, 4), which decreases specific force. Therefore, we agree with Bulow and colleagues that sarcopenia needs to continue to define only the loss of skeletal muscle mass. Furthermore, we propose that “dynopenia” be used to define the strength loss with age. Lastly, we endorse the notion that clinical practice should return to reliable measures of strength such as leg press or squat as opposed to simple functional tests (6-min walking) that do not accurately measure either strength or mass.

REFERENCES

  • 1.Baehr LM, West DW, Marcotte G, Marshall AG, De Sousa LG, Baar K, Bodine SC. Age-related deficits in skeletal muscle recovery following disuse are associated with neuromuscular junction instability and ER stress, not impaired protein synthesis. Aging (Albany NY) 8: 127–146, 2016. doi: 10.18632/aging.100879. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 3.Goodpaster BH, Park SW, Harris TB, Kritchevsky SB, Nevitt M, Schwartz AV, Simonsick EM, Tylavsky FA, Visser M, Newman AB. The loss of skeletal muscle strength, mass, and quality in older adults: the health, aging and body composition study. J Gerontol A Biol Sci Med Sci 61: 1059–1064, 2006. doi: 10.1093/gerona/61.10.1059. [DOI] [PubMed] [Google Scholar]
  • 4.Hughes DC, Marcotte GR, Baehr LM, West DWD, Marshall AG, Ebert SM, Davidyan A, Adams CM, Bodine SC, Baar K. Alterations in the muscle force transfer apparatus in aged rats during unloading and reloading: impact of microRNA-31. J Physiol 596: 2883–2900, 2018. doi: 10.1113/JP275833. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Rantanen T, Masaki K, He Q, Ross GW, Willcox BJ, White L. Midlife muscle strength and human longevity up to age 100 years: a 44-year prospective study among a decedent cohort. Age (Dordr) 34: 563–570, 2012. doi: 10.1007/s11357-011-9256-y. [DOI] [PMC free article] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

THE LACK OF COMMON DENOMINATORS DOES NOT PERMIT A BROADER DEFINITION OF SARCOPENIA

Julian Alcazar 1, Marcos Martin-Rincon 2, Luis M Alegre 3, Ignacio Ara 4, Jose A L Calbet 5

to the editor: As noted by Bulow, Ulijaszek, and Holm (3), we support the return to the original definition of sarcopenia, giving it the clinical relevance it has. Skeletal muscle power (i.e., force × velocity) is a crucial muscle function biomarker associated with physical function in older people. Besides muscle size, factors such as motor unit recruitment and firing frequency, muscle fiber phenotype, muscle architecture, and tendon properties contribute to muscle power generation. Impaired muscle function can be caused by a decreased contraction velocity, which is not associated with muscle size (1). The evolution of the term sarcopenia has complicated the adequate identification of these mechanisms, their regulatory pathways and its association with other clinical outcomes (e.g., frailty), with sarcopenia prevalence among frail people ranging 40–72% with distinct operational definitions (4). This fact would also entangle the differentiation among age-, disuse-, and disease-related muscle loss. Since muscle mass net loss depends upon the balance between protein synthesis-degradation, the problem becomes apparent as the specific role played by the major proteolytic pathways remains broadly inconsistent. While the ubiquitin-proteasome system seems to contribute primarily to muscle loss under disuse (5) and pathologic conditions, other systems predominate in the healthy aging muscle (2). Additionally, how exercise and other potential therapies could revert/compensate for the loss of muscle mass with age requires the identification of the molecular mechanisms regulating the muscle mass that are altered by aging. This task would be jeopardized by an overcomplicated term where distinct phenomena not inherently linked are present.

REFERENCES

  • 1.Alcazar J, Rodriguez-Lopez C, Ara I, Alfaro-Acha A, Rodríguez-Gómez I, Navarro-Cruz R, Losa-Reyna J, García-García FJ, Alegre LM. Force-velocity profiling in older adults: An adequate tool for the management of functional trajectories with aging. Exp Gerontol 108: 1–6, 2018. doi: 10.1016/j.exger.2018.03.015. [DOI] [PubMed] [Google Scholar]
  • 2.Bowen TS, Schuler G, Adams V. Skeletal muscle wasting in cachexia and sarcopenia: molecular pathophysiology and impact of exercise training. J Cachexia Sarcopenia Muscle 6: 197–207, 2015. doi: 10.1002/jcsm.12043. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 4.Davies B, García F, Ara I, Artalejo FR, Rodriguez-Mañas L, Walter S. Relationship between sarcopenia and frailty in the Toledo study of healthy aging: a population based cross-sectional study. J Am Med Dir Assoc 19: 282–286, 2018. [Erratum. J Am Med Dir Assoc 19: 566, 2018]. doi: 10.1016/j.jamda.2017.09.014. [DOI] [PubMed] [Google Scholar]
  • 5.Rudrappa SS, Wilkinson DJ, Greenhaff PL, Smith K, Idris I, Atherton PJ. Human skeletal muscle disuse atrophy: effects on muscle protein synthesis, breakdown, and insulin resistance-a qualitative review. Front Physiol 7: 361, 2016. doi: 10.3389/fphys.2016.00361. [DOI] [PMC free article] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

EVOLUTION OF THE DEFINITION OF SARCOPENIA

J Mathew Hinkley 1, Paul M Coen 1

to the editor: Baumgartner et al.(1), defined sarcopenia as the age-associated loss of skeletal muscle mass two standard deviations below a healthy population. Subsequent investigations using this definition more clearly described associations of sarcopenia with mobility disability, increased risk of falls, and reduced ability to perform activities of daily living (4). This complex, multifactorial etiology has led some to recognize sarcopenia as a geriatric syndrome rather than a traditional disease state (3). Like a geriatric syndrome, sarcopenia is caused by poorly understood interactions of age and disease that impacts multiple systems, resulting in a distinct pattern of clinical symptoms. While Baumgartner’s definition furthered our scientific understanding of sarcopenia, it has proved less useful for clinicians and for development of therapeutic strategies, as regulatory agencies have not recognized low muscle mass alone as a valid indication for treatment. For these reasons, the definition of sarcopenia needed to evolve. The contemporary definitions facilitated designation of an ICD-10 code in 2016, which will encourage wider adoption in clinical practice and has facilitated the development of therapeutics by the pharmaceutical industry. In their Viewpoint, Bülow et al. (2), argue that sarcopenia is caught in a tautological wrangle. We respectfully refute this suggestion as each element of sarcopenia (muscle mass, physical function, and muscle strength) is clearly distinct. A return to the original description focused exclusively on skeletal muscle mass, at a time when there is growing consensus on the contemporary definition of sarcopenia, would impede the development of effective therapeutic strategies for this serious health condition.

GRANTS

PMC is supported by research grants K01-AG044437 and R01-AG060153 from the National Institute on Aging.

DISCLOSURES

P.M.C. is a scientific consultant for Mitobridge Inc., an Astellas company. No other conflicts of interest, financial or otherwise, are declared by the authors.

REFERENCES

  • 1.Baumgartner RN, Koehler KM, Gallagher D, Romero L, Heymsfield SB, Ross RR, Garry PJ, Lindeman RD. Epidemiology of sarcopenia among the elderly in New Mexico. Am J Epidemiol 147: 755–763, 1998. doi: 10.1093/oxfordjournals.aje.a009520. [DOI] [PubMed] [Google Scholar]
  • 2.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 3.Cruz-Jentoft AJ, Baeyens JP, Bauer JM, Boirie Y, Cederholm T, Landi F, Martin FC, Michel J-P, Rolland Y, Schneider SM, Topinková E, Vandewoude M, Zamboni M; European Working Group on Sarcopenia in Older People . Sarcopenia: European consensus on definition and diagnosis: Report of the European Working Group on Sarcopenia in Older People. Age Ageing 39: 412–423, 2010. doi: 10.1093/ageing/afq034. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Rolland Y, Czerwinski S, Abellan Van Kan G, Morley JE, Cesari M, Onder G, Woo J, Baumgartner R, Pillard F, Boirie Y, Chumlea WMC, Vellas B. Sarcopenia: its assessment, etiology, pathogenesis, consequences and future perspectives. J Nutr Health Aging 12: 433–450, 2008. doi: 10.1007/BF02982704. [DOI] [PMC free article] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

SARCOPENIA IN THE ERA OF PRECISION MEDICINE

Brian A Irving 1,2, Timothy D Allerton 2, K Sreekumaran Nair 3

to the editor: From a purist’s perspective, “sarcopenia” refers to the progressive loss of muscle mass that directly contributes to age-related declines in strength and power. The progressive nature of sarcopenia differentiates itself from other myopathies (i.e., cachexia, etc.).

However, declines in muscle mass, strength, and power do not follow the same trajectories with age. Indeed, the loss of muscle strength is more rapid than the reduction in muscle mass, which is not prevented when muscle mass is maintained (1).

Sarcopenia profoundly impacts muscle strength and power, but also fits nicely into the broader picture of the muscle’s biological age (2). Indeed, aging is associated with declines in the number and cross sectional area of individual muscle fibers, especially type II fibers, declines in protein synthesis, and motor unit innervation and firing rates (2, 3). Collectively, these declines in neuromuscular function also contribute to reductions in muscle strength and power. Moreover, aging in sedentary people is accompanied by the loss of mitochondrial density, mtDNA abundance, oxidative capacity, and protein synthesis, which are highly associated with reduced exercise capacity (5). Age-related loss of muscle strength combined with the loss of muscle contractile units and mitochondrial function creates a perfect storm leading to the loss of independence in a rapidly aging population. Most age–related changes in muscle are reversible with rigorous exercise training demonstrating highly specific phenotype and molecular changes (4). Targeted interventions directed to the loss of muscle mass and the loss muscle function represent the future of precision medicine in this field.

REFERENCES

  • 1.Delmonico MJ, Harris TB, Visser M, Park SW, Conroy MB, Velasquez-Mieyer P, Boudreau R, Manini TM, Nevitt M, Newman AB, Goodpaster BH, Health A; Health, Aging, and Body . Longitudinal study of muscle strength, quality, and adipose tissue infiltration. Am J Clin Nutr 90: 1579–1585, 2009. doi: 10.3945/ajcn.2009.28047. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Irving BA, Robinson MM, Nair KS. Age effect on myocellular remodeling: response to exercise and nutrition in humans. Ageing Res Rev 11: 374–389, 2012. doi: 10.1016/j.arr.2011.11.001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Manini TM, Clark BC. Dynapenia and aging: an update. J Gerontol A Biol Sci Med Sci 67: 28–40, 2012. doi: 10.1093/gerona/glr010. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Robinson MM, Dasari S, Konopka AR, Johnson ML, Manjunatha S, Esponda RR, Carter RE, Lanza IR, Nair KS. Enhanced protein translation underlies improved metabolic and physical adaptations to different exercise training modes in young and old humans. Cell Metab 25: 581–592, 2017. doi: 10.1016/j.cmet.2017.02.009. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Short KR, Bigelow ML, Kahl J, Singh R, Coenen-Schimke J, Raghavakaimal S, Nair KS. Decline in skeletal muscle mitochondrial function with aging in humans. Proc Natl Acad Sci USA 102: 5618–5623, 2005. doi: 10.1073/pnas.0501559102. [DOI] [PMC free article] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

COMMENTARY ON VIEWPOINT: REJUVENATION OF THE TERM SARCOPENIA

Ricardo M Lima 1

to the editor: Bulow et al. (1) are to be congratulated for their insightful commentary regarding the use of the term sarcopenia, which was introduced to describe the age-related decline in skeletal muscle mass (5) and has since become widely used. Currently, there is broad support for the concept that strength and function are more clinically meaningful than is muscle mass (2–4), and hence these measures were incorporated into sarcopenia definitions. Based on this background, Bulow et al. (1) postulate that the use of the term sarcopenia rests upon tautological association and suggest a return to its original definition (i.e., solely loss of muscle mass).

Although I entirely agree with the framework raised by our well-respected colleagues (1), I believe that changing sarcopenia definition now would lead to further confusion in research and clinical settings. Since its first description (5), numerous research has emerged and tremendous advances have been made in understanding the link between muscle-related phenotypes and outcomes in older people. At least two annual conferences and one peer-reviewed journal aim at advancing the state of knowledge in the field. Therefore, sarcopenia is already a widely known entity. Other conditions have emerged from it, for example, sarcopenic obesity (3) and osteosarcopenia (4). Perhaps more important than redefining terminology would be to disseminate effectively the latest knowledge, including that sarcopenia is not characterized only in terms muscle mass. Increased awareness of sarcopenia signs will optimize detection and treatment of this disabling condition and ultimately contribute to improve quality of life in the elderly population.

REFERENCES

  • 1.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 2.dos Santos EP, Gadelha AB, Safons MP, Nóbrega OT, Oliveira RJ, Lima RM. Sarcopenia and sarcopenic obesity classifications and cardiometabolic risks in older women. Arch Gerontol Geriatr 59: 56–61, 2014. doi: 10.1016/j.archger.2014.03.012. [DOI] [PubMed] [Google Scholar]
  • 3.Lima RM, Bezerra LM, Rabelo HT, Silva MA, Silva AJ, Bottaro M, de Oliveira RJ. Fat-free mass, strength, and sarcopenia are related to bone mineral density in older women. J Clin Densitom 12: 35–41, 2009. doi: 10.1016/j.jocd.2008.10.003. [DOI] [PubMed] [Google Scholar]
  • 4.Menant JC, Weber F, Lo J, Sturnieks DL, Close JC, Sachdev PS, Brodaty H, Lord SR. Strength measures are better than muscle mass measures in predicting health-related outcomes in older people: time to abandon the term sarcopenia? Osteoporos Int 28: 59–70, 2017. doi: 10.1007/s00198-016-3691-7. [DOI] [PubMed] [Google Scholar]
  • 5.Rosenberg IH. Summary comments. Am J Clin Nutr 50: 1231–1233, 1989. doi: 10.1093/ajcn/50.5.1231. [DOI] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

SHOULD WE REJUVENATE THE (ROSENBERG) DEFINITION OF SARCOPENIA? A RESPONSE BASED ON THE POPULATION HEALTH SCIENCE

Juan Pablo Rey-López 1

to the editor: Bullow et al. (2) make a case for bringing back the original term of sarcopenia, whereby a decline in lean body mass may exceed a critical threshold that lead to poor health. Before expressing my comments about the piece of Bullow et al. (2), I was astonished that the original definition of sarcopenia proposed by Rosenberg (5) (which has received 395 cites in Web of Science) did not include any scientific reference to support their arguments. Thus, the criticisms raised by Bullow et al. (2) in relation to the lack of clear theoretical frameworks contained in recent definitions of sarcopenia, should also be extensive to the first definition coined by Rosenberg (5). Nonetheless, I agree with the suggestion that the current algorithms used to identify sarcopenia are misleading for three reasons: First, sarcopenia is used to describe both the loss of function and muscle mass, which is intrinsically inaccurate. Second, rather than thinking in sarcopenia as a dichotomous category, clinicians should not overlook that most health indicators are distributed along a continuum (4). This approach forces us to downplay any quest for accurately defining sarcopenia as what matters most is to optimize the functional capability and muscle mass maintenance of the entire population (population strategy) (4). Critically, these efforts should start early in life (1). Finally, in a world where one-third of the global population exceeds normal weight (3), body fat loss remains our most important public and clinical health priority. For all the reasons above, a rejuvenated definition of sarcopenia is largely irrelevant.

GRANTS

J.P.R.L. is supported by a post-doctoral fellowship from the University of Sydney (Australia).

REFERENCES

  • 1.A Sayer A, Stewart C, Patel H, Cooper C. The developmental origins of sarcopenia: from epidemiological evidence to underlying mechanisms. J Dev Orig Health Dis 1: 150–157, 2010. doi: 10.1017/S2040174410000097. [DOI] [PubMed] [Google Scholar]
  • 2.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term Sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 3.Afshin A, Forouzanfar MH, Reitsma MB, Sur P, Estep K, Lee A, Marczak L, Mokdad AH, Moradi-Lakeh M, Naghavi M, Salama JS, Vos T, Abate KH, Abbafati C, Ahmed MB, Al-Aly Z, Alkerwi A, Al-Raddadi R, Amare AT, Amberbir A, Amegah AK, Amini E, Amrock SM, Anjana RM, Ärnlöv J, Asayesh H, Banerjee A, Barac A, Baye E, Bennett DA, Beyene AS, Biadgilign S, Biryukov S, Bjertness E, Boneya DJ, Campos-Nonato I, Carrero JJ, Cecilio P, Cercy K, Ciobanu LG, Cornaby L, Damtew SA, Dandona L, Dandona R, Dharmaratne SD, Duncan BB, Eshrati B, Esteghamati A, Feigin VL, Fernandes JC, Fürst T, Gebrehiwot TT, Gold A, Gona PN, Goto A, Habtewold TD, Hadush KT, Hafezi-Nejad N, Hay SI, Horino M, Islami F, Kamal R, Kasaeian A, Katikireddi SV, Kengne AP, Kesavachandran CN, Khader YS, Khang YH, Khubchandani J, Kim D, Kim YJ, Kinfu Y, Kosen S, Ku T, Defo BK, Kumar GA, Larson HJ, Leinsalu M, Liang X, Lim SS, Liu P, Lopez AD, Lozano R, Majeed A, Malekzadeh R, Malta DC, Mazidi M, McAlinden C, McGarvey ST, Mengistu DT, Mensah GA, Mensink GBM, Mezgebe HB, Mirrakhimov EM, Mueller UO, Noubiap JJ, Obermeyer CM, Ogbo FA, Owolabi MO, Patton GC, Pourmalek F, Qorbani M, Rafay A, Rai RK, Ranabhat CL, Reinig N, Safiri S, Salomon JA, Sanabria JR, Santos IS, Sartorius B, Sawhney M, Schmidhuber J, Schutte AE, Schmidt MI, Sepanlou SG, Shamsizadeh M, Sheikhbahaei S, Shin MJ, Shiri R, Shiue I, Roba HS, Silva DAS, Silverberg JI, Singh JA, Stranges S, Swaminathan S, Tabarés-Seisdedos R, Tadese F, Tedla BA, Tegegne BS, Terkawi AS, Thakur JS, Tonelli M, Topor-Madry R, Tyrovolas S, Ukwaja KN, Uthman OA, Vaezghasemi M, Vasankari T, Vlassov VV, Vollset SE, Weiderpass E, Werdecker A, Wesana J, Westerman R, Yano Y, Yonemoto N, Yonga G, Zaidi Z, Zenebe ZM, Zipkin B, Murray CJL; GBD 2015 Obesity Collaborators . Health effects of overweight and obesity in 195 countries over 25 years. N Engl J Med 377: 13–27, 2017. doi: 10.1056/NEJMoa1614362. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Rose G. Sick individuals and sick populations. Int J Epidemiol 30: 427–432, 2001. doi: 10.1093/ije/30.3.427. [DOI] [PubMed] [Google Scholar]
  • 5.Rosenberg IH. Summary comments. Am J Clin Nutr 50: 1231–1233, 1989. doi: 10.1093/ajcn/50.5.1231. [DOI] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

SHOULD SARCOPENIA DEFINITIONS CONSIDER MUSCLE QUALITY AS WELL AS QUANTITY?

David Scott 1,2, Robin M Daly 3, Peter R Ebeling 1, Alan Hayes 2,4

to the editor: The Viewpoint of Bülow et al. (1) is symptomatic of the ongoing confusion and debate surrounding the definition of sarcopenia. While we contend that the inclusion of functional assessments in current sarcopenia operational definitions improves accessibility for clinicians, we concur that this may inadvertently reduce the perceived clinical relevance of muscle itself.

Nevertheless, measures of muscle mass are not closely associated with the muscle functional declines that are strong predictors of disability, falls, fractures, and mortality. This may be explained in part by the fact that mass alone does not reflect age-related changes in “muscle quality,” which incorporates muscle composition and neuromuscular function.

Osteoporosis, which is inextricably linked to sarcopenia, is defined as low bone mass with a deterioration of bone microarchitecture (3). Conversely, muscle quality receives little attention in current sarcopenia definitions.

Increased muscle fat infiltration, measured by computed tomography or magnetic resonance imaging (MRI), is associated with poor physical performance and also metabolic dysfunction (including insulin resistance and type 2 diabetes) (4). Bioelectrical impedance spectroscopy may be sensitive to age-related muscle composition changes, including fiber size atrophy and increased muscle fibrosis and fat infiltration (5). Neuromuscular activation, representing the ability to recruit motor units for force production, can also be estimated by tools including electromyography, T2-weighted MRI, and neuromuscular electrical stimulation (2).

Although each of these measurements have limitations, including their limited availability for clinicians, ongoing research and future technological advances may support qualitative assessments of skeletal muscle that improve clinical diagnosis and treatment of sarcopenia.

GRANTS

D.S. is supported by a NHMRC RD Wright Biomedical Career Development Fellowship (GNT1123014).

REFERENCES

  • 1.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 2.Clark DJ, Fielding RA. Neuromuscular contributions to age-related weakness. J Gerontol A Biol Sci Med Sci 67: 41–47, 2012. doi: 10.1093/gerona/glr041. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Kanis JA, Kanis JA; WHO Study Group . Assessment of fracture risk and its application to screening for postmenopausal osteoporosis: synopsis of a WHO report. Osteoporos Int 4: 368–381, 1994. doi: 10.1007/BF01622200. [DOI] [PubMed] [Google Scholar]
  • 4.Scott D, Trbojevic T, Skinner E, Clark RA, Levinger P, Haines TP, Sanders KM, Ebeling PR. Associations of calf inter- and intra-muscular adipose tissue with cardiometabolic health and physical function in community-dwelling older adults. J Musculoskelet Neuronal Interact 15: 350–357, 2015. [PMC free article] [PubMed] [Google Scholar]
  • 5.Yamada Y, Buehring B, Krueger D, Anderson RM, Schoeller DA, Binkley N. Electrical properties assessed by bioelectrical impedance spectroscopy as biomarkers of age-related loss of skeletal muscle quantity and quality. J Gerontol A Biol Sci Med Sci 72: 1180–1186, 2017. [DOI] [PMC free article] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

UPROOTING SARCOPENIA FROM ITS ORIGINS BY INTRODUCING BODY FAT TO ITS DEFINITION

Anne-Julie Tessier 1,2, Stéphanie Chevalier 1,2,3

to the editor: We are in complete agreement with the Viewpoint of Bulow et al. (1) and wish to raise another argument in favor of rejuvenating the term sarcopenia. Not only is the consensus definition confusing enough by combining two distinct—although related— entities, lean mass and physical function, but new cut points for low lean mass involving measures of body fat further confuses defining the condition. Indeed, the FNIH Sarcopenia Project suggested to normalize ALM to BMI as an indicator of low lean mass (4). Because excess body fat negatively impacts physical function, especially gait speed, balance, and any weight-bearing physical test, lower ratio of lean mass relative to body weight or BMI best predicts poor physical function, logically. Largely influenced by high BMI, a low ratio masks the absolute estimation of lean mass, which may be normal in many. This could lead to misidentification of true sarcopenia, i.e., low ALM relative to height, which in itself carries significant morbidity and mortality risks in several clinical conditions. In contrast, having some degree of excess fat with normal muscle mass may be impeding physical function but may be protective for survival in older adults (5) and in clinical conditions, such as in cancer (3). We strongly support reserving the term sarcopenia for defining low lean mass relative to height, which would resonate in geriatrics but other clinical fields as well, and using dynapenia, as suggested by others (2), to define low strength. The term sarco- dynapenia could then be self-explanatory to all.

REFERENCES

  • 1.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 2.Clark BC, Manini TM. Sarcopenia =/= dynapenia. J Gerontol A Biol Sci Med Sci 63: 829–834, 2008. doi: 10.1093/gerona/63.8.829. [DOI] [PubMed] [Google Scholar]
  • 3.Martin L, Senesse P, Gioulbasanis I, Antoun S, Bozzetti F, Deans C, Strasser F, Thoresen L, Jagoe RT, Chasen M, Lundholm K, Bosaeus I, Fearon KH, Baracos VE. Diagnostic criteria for the classification of cancer-associated weight loss. J Clin Oncol 33: 90–99, 2015. doi: 10.1200/JCO.2014.56.1894. [DOI] [PubMed] [Google Scholar]
  • 4.Studenski SA, Peters KW, Alley DE, Cawthon PM, McLean RR, Harris TB, Ferrucci L, Guralnik JM, Fragala MS, Kenny AM, Kiel DP, Kritchevsky SB, Shardell MD, Dam TT, Vassileva MT. The FNIH sarcopenia project: rationale, study description, conference recommendations, and final estimates. J Gerontol A Biol Sci Med Sci 69: 547–558, 2014. doi: 10.1093/gerona/glu010. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Winter JE, MacInnis RJ, Wattanapenpaiboon N, Nowson CA. BMI and all-cause mortality in older adults: a meta-analysis. Am J Clin Nutr 99: 875–890, 2014. doi: 10.3945/ajcn.113.068122. [DOI] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

SARCOPENIA: SKELETAL MUSCLE MASS IS NOT SYNONYMOUS WITH MUSCLE STRENGTH

Brandon A Yates 1,2,3, LeAndra R Brown 4, Thomas W Storer 5, Wayne L Westcott 6

to the editor: We agree with Bülow et al. (1) that rejuvenation of the original definition of sarcopenia is necessary to further advance both science and clinical practice. By focusing attention on the age-related loss of lean body mass (LBM), appropriate interventions can be developed for use in clinical environments and research settings. However, we offer precautions to the authors’ statement that the two definitions are a tautological association.

Sarcopenia is characterized by a progressive (3–8% per decade) decrease in LBM and is associated with reduced muscle strength and function (4). Currently, progressive resistance exercise training (RET) is the best prophylactic and rehabilitative treatment for sarcopenia (3). Although increases in LBM, strength, and physical function are positive adaptations to RET, changes in LBM can occur independently of strength and function (5). LBM is the phenotypic expression of cellular responses to anabolic and catabolic stimuli resulting in changes in protein turnover; whereas, muscle strength is reflective of changes in neural activation and the intrinsic force-generating capacity (5). Collectively, these contribute to physical function along with several other factors, including cognition and aerobic fitness (5). Therefore, RET interventions should be designed to stimulate the physiological and neural responses that are specifically associated with muscle strength and LBM (2).

Given the physiological differences and developmental processes between muscle strength and LBM, we recommend that dynapenia (5) be adopted to define the age-related reduction in muscle strength and function and that sarcopenia return to its original definition of age-related reduction in LBM.

REFERENCES

  • 1.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 2.Burd NA, West DW, Staples AW, Atherton PJ, Baker JM, Moore DR, Holwerda AM, Parise G, Rennie MJ, Baker SK, Phillips SM. Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men. PLoS One 5: e12033, 2010. doi: 10.1371/journal.pone.0012033. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Fiatarone MA, Marks EC, Ryan ND, Meredith CN, Lipsitz LA, Evans WJ. High-intensity strength training in nonagenarians. Effects on skeletal muscle. JAMA 263: 3029–3034, 1990. doi: 10.1001/jama.1990.03440220053029. [DOI] [PubMed] [Google Scholar]
  • 4.Flack KD, Davy KP, Hulver MW, Winett RA, Frisard MI, Davy BM. Aging, resistance training, and diabetes prevention. J Aging Res 2011: 127315, 2010. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Heymsfield SB, Gonzalez MC, Lu J, Jia G, Zheng J. Skeletal muscle mass and quality: evolution of modern measurement concepts in the context of sarcopenia. Proc Nutr Soc 74: 355–366, 2015. doi: 10.1017/S0029665115000129. [DOI] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

ON SARCOPENIA: THE CONVOLUTION OF THE TERM

Artemissia-Phoebe Nifli 1

to the editor: For a few millennia, the Greek term λιπόσαρκος (lacking flesh) has been used to designate probable medical conditions: the extremely pale gaunt figure of Democritus, as well as his erratic antisocial behavior, impelled the city senate to invite Hippocrates to treat the philosopher (5). Similarly, poor eating habits and nocturnality, indicative of vitamin D deficiency, might cause Socrates’ student Chaerephon’s pale and pathetic physique; it is not surprising that 19 bat species were named after him since 1800!

In 1989, in “his plea,” Irwin H. Rosenberg coined two compound lexemes of Greek origin, sarcomalacia (feeble flesh) and sarcopenia (flesh deficit), to describe the dramatic age-related muscle mass decline and its ramifications, while sarcopenia was soon endorsed by the scientific community (2, 3). So far, because of the reciprocation among muscle wasting, mobility, and nutrition, supplementation and supervised physical activity were shown to improve the latest agreed measures: muscle mass, strength, and performance, especially in older individuals (3). However, as the departed gerontologist and psychiatrist Bob Butler advocated, a functional and comprehensive approach would be preferable to the elderly (1, 4). From our viewpoint, Greek laic terms, such as atrophy, marasmus, cachexia, and sarcopenia, as well as fatigue, malnutrition, debilitation, and senility are essential for patient-health caregiver communication. On the other hand, there is strong scientific evidence of redundancy and comorbodity. Therefore, priority should be given to the refinement of the diagnostic tools, and the improvement of their prognostic and predictive value, toward a responsible dependency in advanced age.

REFERENCES

  • 1.Andrew MK, Fisk JD, Rockwood K. Psychological well-being in relation to frailty: a frailty identity crisis? Int Psychogeriatr 24: 1347–1353, 2012. doi: 10.1017/S1041610212000269. [DOI] [PubMed] [Google Scholar]
  • 2.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 3.Michel JP. Sarcopenia: there is a need for some steps forward. J Am Med Dir Assoc 15: 379–380, 2014. doi: 10.1016/j.jamda.2014.03.016. [DOI] [PubMed] [Google Scholar]
  • 4.Okabe D, Tsuji T, Kondo K. [The Comprehensive Geriatric Assessment predicts healthy life expectancy better than health checkups in older people: JAGES cohort study]. Nippon Ronen Igakkai Zasshi 55: 367–377, 2018. doi: 10.3143/geriatrics.55.367. [DOI] [PubMed] [Google Scholar]
  • 5.Sakalis DT. Iπποκρά τους επιστολαί. Έκδοση κριτική και ερμηνευτική. Faculty of Medicine, University of Ioannina, 1989, p. 401. [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

THE IMPORTANCE OF AN INTEGRATIVE APPROACH TO ADDRESS AGE-RELATED SKELETAL MUSCLE DYSFUNCTION

Robert V Musci 1, Adam R Konopka 2, Karyn L Hamilton 1

to the editor: As Bülow and colleagues (1) indicated, the definition of sarcopenia has evolved to characterize broadly age-related skeletal muscle dysfunction. Recognition from the World Health Organization that “sarcopenia” impacts health will stimulate greater funding and research focused on muscle aging. However, reducing the multifaceted nature of age-related muscle dysfunction into a term originally intended to describe age-related muscle mass loss may muddle communication. As such, it may promote clearer communication if the term sarcopenia is limited to uses that are closest to the Greek meaning “poverty of flesh,” or age-related loss of skeletal muscle mass. However, it is also critical to retain an integrative perspective on the ever-expanding knowledge about the many factors contributing to age-related muscle dysfunction.

Should sarcopenia return to define age-related lean mass loss, we suggest a new umbrella-term that better encapsulates the phenomenon and factors of age-related loss of muscle function than sarcopenia currently does. Like other conditions (e.g., cancer), this term should encompass the variety of underlying, discrete processes of age-related muscle dysfunction, such as mitochondrial dysfunction (4), neuromuscular degradation (5), impaired lipid metabolism (2), and inflammation (3). The term should also broadly characterize and define the typical pathological progression (e.g., sarcopenia, dynapenia, and metabolic dysfunction) and functional outcomes (e.g., disability, comorbidities, and mortality). Such a term that characterizes age-related skeletal muscle dysfunction would provide necessary clarity as we continue to elucidate the consequences of and solutions for this phenomenon.

REFERENCES

  • 1.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 2.Coen PM, Goodpaster BH. Role of intramyocelluar lipids in human health. Trends Endocrinol Metab 23: 391–398, 2012. doi: 10.1016/j.tem.2012.05.009. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Franceschi C, Campisi J. Chronic inflammation (inflammaging) and its potential contribution to age-associated diseases. J Gerontol A Biol Sci Med Sci 69, Suppl 1: S4–S9, 2014. doi: 10.1093/gerona/glu057. [DOI] [PubMed] [Google Scholar]
  • 4.Holloway GP, Holwerda AM, Miotto PM, Dirks ML, Verdijk LB, van Loon LJC. Age-associated impairments in mitochondrial adp sensitivity contribute to redox stress in senescent human skeletal muscle. Cell Reports 22: 2837–2848, 2018. doi: 10.1016/j.celrep.2018.02.069. [DOI] [PubMed] [Google Scholar]
  • 5.Vasilaki A, Richardson A, Van Remmen H, Brooks SV, Larkin L, McArdle A, Jackson MJ. Role of nerve-muscle interactions and reactive oxygen species in regulation of muscle proteostasis with ageing. J Physiol 595: 6409–6415, 2017. doi: 10.1113/JP274336. [DOI] [PMC free article] [PubMed] [Google Scholar]
J Appl Physiol (1985). 2019 Jan 1;126(1):257–262.

SARCOPENIA: LOST IN TRANSLATION?

Russell T Hepple 1

to the editor: Bulow and colleagues (1) make a point that resonates with many in the aging muscle research community. As they eloquently state, recent consensus definitions of sarcopenia have lost touch with the phenomenon that originally defined the term sarcopenia coined by Arthur Rosenberg (2), age-related muscle atrophy. The switch in focus to physical function generates confusion of priorities in basic science pursuing the mechanisms of sarcopenia. Following the original coining of the term sarcopenia by Rosenberg, basic scientists appropriately focused upon identifying pathways that could cause muscles to atrophy with aging. However, in studies using recent consensus definitions of sarcopenia, selection of subjects meeting these criteria will result in recruitment of many individuals within the sample who do not have aging muscle atrophy at all. Adding to this issue, is the fact that in recent years many clinical fields have interpreted the operational definitions of muscle atrophy included in clinical definitions of sarcopenia to mean any muscle atrophy at all, and as such many studies characterize relatively young patients who have muscle atrophy as being sarcopenic (3). Clearly, changes need to be made if the term sarcopenia is going regain the spirit of the original definition: aging muscle atrophy.

REFERENCES

  • 1.Bulow J, Ulijaszek SJ, Holm L. Rejuvenation of the term sarcopenia. J Appl Physiol (1985); doi: 10.1152/japplphysiol.00400.2018. [DOI] [PubMed] [Google Scholar]
  • 2.Rosenberg IH. Summary comments. Am J Clin Nutr 50: 1231–1233, 1989. doi: 10.1093/ajcn/50.5.1231. [DOI] [Google Scholar]
  • 3.Echeverría P, Bonjoch A, Puig J, Estany C, Ornelas A, Clotet B, Negredo E. High prevalence of sarcopenia in HIV-infected individuals. BioMed Res Int 2018: 5074923, 2018. doi: 10.1155/2018/5074923. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Journal of Applied Physiology are provided here courtesy of American Physiological Society

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