0_4559 Thanks to medical advancements, life expectancy has been increasing, and with it the number of elderly people. One of the main factors associated with the development of morbidities in later stages of life is neuromuscular decline, which mainly entails a loss of skeletal muscle mass and power.  These changes accelerate starting from 50 years of age and can lead to the decrease of mobility and an increased risk of bone fractures. Monitoring the insurgence of such condition is critical for a timely treatment. The “Trajector-AGE” project (PRIN2020-2020477RW5) aims to track the progression of neuromuscular decline in middle-aged (55-60 years) and old (75-80 years) populations through a 2-year period, with time points every 6 months. To comprehensively characterize the muscular status and its evolution, several conventional techniques (such as biopsy, ultrasound, electromyography and magnetic resonance imaging) are being employed. In addition, innovate diffuse optics methods allow to non-invasively assess muscle oxidative metabolism and perfusion. In particular, Time Domain (TD) NearInfrared Spectroscopy (NIRS) allows to retrieve absolute values for oxygenated and deoxygenated hemoglobin concentration; Diffuse Correlation Spectroscopy (DCS) enables to quantify blood flow. The hemodynamic and microvascular responses of the vastus lateralis muscle are monitored with 1 Hz sampling rate, yielding time series for the following quantities: oxy- (O₂Hb), deoxy- (HHb) and total- (tHb) hemoglobin concentrations (expressed as absolute values in mM) tissue oxygen saturation (StO₂=O₂Hb/tHb, expressed as %), blood flow index (BFI) (expressed as % variation from the baseline). 47 volunteers have been evaluated so far, out of a total of 100 planned, according to three measurement protocols: an arterial occlusion in rest conditions, a cycling exercise followed by intermittent arterial occlusions during recovery, and an incremental cycling exercise up to exhaustion. Preliminary results show trends in agreement with the existing literature. However, while hemoglobin concentration and oxygen saturation responses to occlusion tests are well known, there is a lack of studies on BFI variations during cycling, likely due to the sensitivity of DCS to motion artifacts. The measurements carried out within this project will therefore be used to develop data analysis models to filter out these unwanted contributions. Furthermore, in these acquisitions, a single inter-fiber distance between source and detector has been employed, making difficult a clear discrimination between the contributions of superficial layers (derma and fat) and deeper ones (muscle). To address this limitation, a new multi-distance device is currently being developed and will be soon exploited in the second time point to refine the analysis model.