The project aims to explore the mechanisms by which lifelong exercise can promote healthy aging and slow down the negative impact of aging on the muscular system, immunity and the circadian system. The main goal of the project is to investigate the effect of lifelong endurance exercise on physical fitness, body composition, bone density and selected hormonal, biochemical, histological and molecular indicators of metabolic health and circadian clock function based on blood, immune cell and skeletal muscle tissue analyses in volunteers differentiated by age and weekly volume of physical activity.

It is hypothesized that lifelong endurance exercise may have beneficial effects on the circadian system stability and many, but not all health outcomes. Osteopenia/osteoporosis and low-grade malnutrition may be more prevalent in the group of endurance-trained senior runners.

In order to achieve the above research aims, sixty male subjects in total will be recruited according to inclusion and exclusion criteria. Four groups of subjects will differ according to their age and physical activity levels:

• a group of endurance-trained seniors (age range 65 - 75 year old, n=15) ● a group of sedentary seniors (age range 65 - 75 year old, n=15)
• a group of well endurance-trained young men (age range 20 - 30 year old, n=15) ● a group of sedentary young men (age range 20 - 30 year old, n=15).

Subjects must meet the following inclusion criteria:

1. for athletes' groups: defined as more than 150 minutes of running activity per week; for young athletes at least 3 years and for master athletes at least 15 years history of running.
2. for groups less active than recommended: no history of regular physical activity training and no more practice than 150 minutes of moderate or 75 minutes of vigorous intensity per week.

The standard inclusion criterion for every group will be body mass index (range 18.5-30 kg/m2).

No experimental study has been published on the potential of life-long exercise to attenuate the aging-induced disorganization of the circadian system and thus to promote healthy aging. In this aspect, the proposed study is original and up-to-date. Moreover, also other aspects of the study, e.g. exercise and inflammaging or the risks (besides the benefits) of the long-life endurance training on bone tissue etc. have been studied only scarcely. Therefore, more scientific information is needed before it can be safely prescribed to the aging population

Inclusion Criteria:

for athletes' groups (master - 65 - 75 years old, and young athletes - 20 - 30 years old)

• more than 150 minutes of running activity which is by ACSM considered as vigorous intensity of endurance running for young athletes at least 3 years and for master athletes at least 15 years
• body mass index (BMI index) - range 18.5-30 kg/m2

for groups less active than recommended (sedentary young and elderly)

• no history of regular physical activity training and no more practice than 150 minutes of moderate or 75 minutes of vigorous intensity per week
• body mass index (BMI index) - range 18.5-30 kg/m2

Exclusion Criteria

• recent or current infection
• malignant disease
• uncontrolled hypertension (higher than 160 / 95mmHG)
• congestive heart failure (NYHA grade III and IV)
• unstable angina pectoris
• recent myocardial infarction (during the last 6 months)
• severe cardiac arrhythmia (anamnestic)
• chronic obstructive pulmonary disease
• presence of severe pulmonary, pleural or pericardial disease
• severe asthma
• recent sudden stroke (during the last 6 months)
• epilepsy
• insulin-dependent diabetes mellitus
• unstable bone lesions with a high risk of fractures
• other chronic diseases, at the discretion of the responsible doctor
• states of mental incompetence (severe anxiety and depression, dementia, alcoholism , or other dependencies, mental retardation)
• conditions complicating regular physical activity (uncontrollable pain, severe arthritis, planned knee / hip endoprosthesis, pathological fractures (last 6 months), amputation, use of walker, wheelchair
• pharmacological interference (e.g., steroids, nonsteroidal anti-inflammatory agents, immunosuppressive and antineoplastic drugs, beta blockers, statins)
• the use of performance-enhancing drugs in the past and during the study period

Inhabitants of Bratislava city (Slovakia) and those living within one hour drive by car from the laboratory (Faculty of Physical Education and Sport, Comenius University in Bratislava)