There is a lot of discussion concerning the normal cut-off points of skeletal mass among different populations worldwide. Genetic and environmental differences most probably lead to different measurements. Defining muscle mass in healthy young adults in Greece will provide information that can be used to determine normal ranges of muscle mass of both sexes and consequently define sarcopenia.

The aim of the study is to define appendicular skeletal muscle mass reference measurements in healthy young adults in Greece. These values can be used to determine sarcopenia cut-offs according to recommendations.

Introduction

The reduction of muscle mass in humans is obvious after the age of fifty, with a reduction rate of 3-8% every ten years. The rate of loss accelerates with chronic diseases, sedentary lifestyle, low physical activity, nutritional, environmental and socioeconomic factors .

Sarcopenia has been officially recognized as a disease according to World Health Organization. European Working Group on Sarcopenia in Older People 2 has revised the definition and diagnostic criteria of sarcopenia aiming to encourage more research in the field. In Greece, there are no reference values for muscle strength and muscle mass. Defining these values will permit the investigators to provide a tool that will help to establish country - specific measurements of sarcopenia in Greek population.

Study population-Methods

The study site will be the Outpatient Geriatric Assessment Unit and the Radiology Department of Henry Dunant Hospital Centre, in Athens-Greece.

The study population will be healthy adults that meet the inclusion criteria. The recruitment will be performed using the snowball sampling technique (for instance, through printed material, the marketing department of the hospital, social media, advertising banners, etc.). Stratified random sampling technique will be used to achieve a representative sample size.

Evaluation of the appendicular muscle mass of the limbs will be performed by Dual-Energy X-ray Absorptiometry, using a QDR-4500 A fan Beam densitometer (Hologic, Inc., Bedford, MA). Hologic Discovery W configured with software version 12.1 (Hologic, Bedford, MA).

Body composition analysis will be evaluated with TANITA Body Composition Analyzer device,model BC-418MA. Analysis concerns calculation of body consistency (body fat mass, lean mass water and predicted muscle mass) using Bioelectric Impedance Analysis. Bioelectric Impedance Analysis measures the body composition using a constant power source (high frequency current 50kHz, 90 μA).

Muscle mass will also be measured by ultrasound -U/S. U/S determines the thickness and transverse incisions of a superficial muscle group. It can measure basic parameters such as muscle volume and spectrum length through the B-Mode imaging with Linear 7-12MHz frequency heads that can reliably determine the thickness and transverse incisions of the superficial muscular Groups.

Statistical analysis

It will be performed using the Statistical Package for the Social Sciences -SPSS Version 26.0 (IBM), and R Version 3.6.2.

Descriptive statistics will be presented in percentage proportions, mean values and Standard Deviations (SD) of the variables. In addition, Z-score will be calculated (e.g. Dual-energy X-ray absorptiometry , Bone Mineral density, Dual-energy X-ray absorptiometry % fat, etc.) and T-score ± 2 standard deviations.

Chi-square - χ2 tests or non-parametric tests will be produced to compare qualitative variables. T-test, Analysis of Variance- ANOVA and non-parametric tests will be used in the statistical analysis of quantitative variables within the categories of qualitative variables.

Approval

The protocol has been approved by the Scientific Committee of the Henry Dunant Hospital Centre, in Athens -Greece, and is in accordance with the Code of Ethics of the World Organization for Medical Sciences (CIOMS) as formulated in the Helsinki Declaration on Biological Research.

Informed consent

All participants will be informed in written for the purpose of the research, and the way their personal data are processed (name, address, telephone, e-mail), under the provisions of 2016/679 according to the General Data Protection Regulation (GDPR).

The consent form will describe the legal and transparent way of processing their data, stating the specific purpose for data collection, as well as information about storage of their data. It will also contain a written description of the rights of the participants concerning their data and their ability to revoke consent for the processing of their data. The processing, transfer and storage of data, will also be described, as well as who will have access to their data, and how long the data will be stored for.

Finally, all participants will sign the written informed consent and confidentiality form.

Inclusion Criteria:

1. Healthy Greek young adults (20 - 44 years old), with Caucasian characteristics.
2. Able to read and write in Greek language.

Exclusion Criteria:

1. Chronic diseases, such as, heart diseases, type II diabetes mellitus and autoimmune diseases.
2. Hyperthyroidism or hypothyroidism (persons with normal thyroid function for six months are included).
3. Malignancies.
4. Seizures of epilepsy, neurodegenerative diseases.
5. Asthma and/or chronic respiratory pulmonary disease-Chronic Obstructive Pulmonary Disease.
6. Metal prefixes.
7. Pacemaker.
8. Systematic medication intake (such as hypolipemic drugs, antihypertensive drugs, antidepressants, glucocorticoids and any other hormonal treatment).
9. Protein formulations and anabolic intake.
10. Hormone intake (testosterone, estrogen, contraceptive, growth hormone, dehydroepiandrosterone.
11. Professional athletes and people with intense physical activity, intensive exercise with weights, long-distance runners (Marathons).
12. Substance use or abuse (cocaine, heroin, amphetamines).
13. Pregnancy.
14. History of hospitalization in Intensive Care Unit
15. History of serious injury
16. Considerable body weight alterations during the previous year (increase or decrease)
17. History of Bariatric surgery
18. Any dietary restriction due to disease (sprue), choice (vegan), or eating disorder (anorexia nervosa).

Gender identity

The study population will be healthy adults that meet the inclusion criteria and can have access to the study site. The recruitment will be performed using the snowball sampling technique (for instance, through printed material, the marketing department of the hospital, social media (Facebook/Instagram/Twitter), advertising banners, etc.). We will also invite participants from nearby academic institutions, organizations, municipalities, etc. It is foreseen to include 500 participants in the study.