Lifestyle, Fitness, and Plasma Biomarkers in Healthy Young Adults

Plasma concentrations of BDNF and pTau217 will be assessed using ELISA kits. Fasting venous blood samples will be collected by a qualified nurse from the antecubital vein into EDTA-treated vacutainers and centrifuged at 1500g for 10 minutes. Plasma will then undergo a second centrifugation at 2500g for 15 minutes and be stored in cryogenic vials at -80ºC. BDNF will be measured using the Human/Rat BDNF ELISA Kit (Proteintech Europe; sensitivity: 0.1 pg/mL; range: 12.5-800 pg/mL). PTau217 will be measured using the Human Phosphorylated Tau 217 ELISA Kit (GenoChem World; sensitivity: 0.1 pg/mL; range: 0.8-40 pg/mL).

An accelerometer (ActiGraph GT3X, Actigraph Corporation, Pensacola, FL) will be provided to all participants one week prior to the assessments to monitor physical activity levels during all waking hours, except during the shower or bath. Registration will take place over a seven-day period, including at least three weekdays (Monday through Friday) and two days during the weekend. The accelerometer will be positioned on the right hip of each participant through the use of an elastic belt. Their position will be reviewed before and after the registration period and participants will be provided with a diary to indicate the hours of use.

Participants will be provided with a Xiaomi® Smart Band 9 activity bracelet to monitor sleep quality. The device will record sleep cycle phases and data, as well as detailed data on heart rate and oxygen saturation.

Will be calculated using the waist circumference (in centimeters) and the hip circumference (in centimeters)

Hip circumference will be assed in centimeters (cm)

Waist circumference will be assed in centimeters (cm)

Sleep quality will also be assessed by completing the Spanish version of the questionnaire Pittsburgh Sleep Quality Index (PSQI). This questionnaire consists of 24 items, of which 19 questions are self-assessed, while the remaining five are questions assessed by the patient's partner or roommate (the latter are not scored and are used only as clinical information). The total score ranges from 0-21 points, where a higher score indicates a worse subjective quality of sleep.

By monitoring the heart rate of the participants, heart rate variability will be assessed, which involves the variation of the time intervals between beats (R-R intervals) and which is shown to be a useful tool in the control of the patient's health since it is an estimator of the balance between the activity of the sympathetic and parasympathetic autonomic nervous system . To evaluate heart rate variability, a polar H10 band and heart rate monitor (Polar Electro Oy, Kempele, Finland) and a mobile application, specifically Elite HRV will be used. Heart rate variability will be monitored daily for the week prior to the initial assessment visits. To do this, participants will be instructed to take the measurement the first 5 minutes as soon as they wake up and on an empty stomach.

The level of perceived stress will be assessed through the perceived stress questionnaire (PSQ). This questionnaire consists of 30 items and is carried out autonomously in the presence of the evaluator (score goes from 0 to 120 points, with higher score indicating more perceived stress levels). In addition, the Perceived Stress Scale (Perceived Stress Scale (PSS)) in its version of 14 items that are carried out in a self-administered way (score goes from 0 to 56, with higher scores indicating more stress levels).

Plasma testosterone/cortisol ratio using ELISA kits. Fasting venous blood samples will be collected from the antecubital vein into EDTA-treated vacutainers and centrifuged at 1500g for 10 minutes. Plasma will then undergo a second centrifugation at 2500g for 15 minutes and be stored in cryogenic vials at -80ºC. Sample collection will be performed by a qualified nurse. Testosterone will be measured using the Invitrogen™ High Sensitivity Competitive ELISA Kit (Life Technologies; sensitivity: 2.97 pg/mL; range: 317.0-8440.5 pg/mL). Cortisol will be assessed with the Invitrogen™ Cortisol Competitive ELISA Kit (Life Technologies; sensitivity: 27.6 pg/mL; range: 8.5-23.8 µg/mL).

Adherence to the Mediterranean diet will be assessed through the Mediterranean Diet Quality Index in childhood and adolescence (KIDMED) questionnaire. This quiz It consists of 16 questions that evaluate adherence to this diet in children and young people (from 2 to 24 years old) and can be performed self-administered or conducted by an interviewer. The score goes from -4 to 12, with higher score indicating better adherence to Mediterranean diet.

Handgrip strength will be assessed using the hand-held Jamar® Plus Smart Dynamometer (Patterson Medical Ltd., Sammons Preston, Nottinghamshire, UK). Manual grip strength will be recorded on both limbs and the dynamometer will be adjusted to hand size prior to testing. The participant's elbow should be in 90° flexion and the forearm fully supported on a table.

The values of mean and peak gas exchange (ml·kg-1·min-1) during a stress test. The gas analyzer that will be used in this study (Cortex Metalyzer 3B, Leipzig, Germany).

The basal metabolic rate (ml·kg-1·min-1) will be determined by recording the variables mentioned above for 15 minutes in supine position.

The values of mean and peak heart rate (beats per minute) will be assessed using a polar H10.

The Excess Post-exercise Oxygen Consumption (EPOC) post-exercise will be recorded on ml·kg-1·min-1. This will be calculated every minute for 12 min after the end of the exercise.

Weight will be assess on kilograms (kg)

Height will be assess on centimeters (cm)

Weight and height will be combined to report body surface area (BSA) in kg·cm-1

The NUTRILAB bioimpedance device (AKERN Srl, Florence, Italy) will be used. This non-invasive method measures the body's resistance and reactance of the body to the passage of a low-intensity electric current and enables the determination of various body parameters. Bioimpedance provides accurate data on body composition. Users will be instructed to remove all metal-containing objects and remain in a supine position on a couch during the measurements, with the legs in 45° abduction, the shoulders in 30° abduction relative to the center of the body and the hands in pronation. After cleaning the skin with alcohol, two adhesive electrodes (Biatrodes Akern Srl, Florence, Italy) will be placed on the surface of the right hand and two on the right foot. The measurement results will be given in different unit measures depending on the specific variable assessed.

Cognitive performance will be assessed through the questionnaire Frontal Assessment Battery (FAB). This questionnaire allows for rapid assessment of executive function through six tests that correspond to each specific cognitive or behavioral domain related to the frontal lobes. The scores ranges from 0 to 18 where higher scores indicating better cognitive function.