Background: The pioneering female physiologist Frances Hellebrandt first highlighted the significance of the skeletal muscle pump in circulation in the 1930s. However, the mechanisms underlying the muscle pump’s function remain elusive, particularly in older individuals. It is thought that during muscle contraction, increased intramuscular pressure facilitates the expulsion of blood from the muscle’s veins, aiding venous return. This contraction-induced pressure gradient assists in pushing blood towards the heart, increasing preload, and subsequently stroke volume (SV). In this study we investigated muscle pump activity using continuous measurements of thigh muscle activity, thigh total haemoglobin concentration (Hb), and cardiac SV. Methods: 22 individuals (aged 70.8±5.3 years, 77.3% female) recruited from a Falls and Syncope Unit (St James’s Hospital, Dublin) underwent non-invasive measurements of Hb (NIRS PortaLite, Artinis Medical Systems, The Netherlands), electromyography (EMG) (Shimmer3, Research Ltd, Ireland), and SV (Finapres Nova, Finapres Medical Systems, The Netherlands) during a 10-second thigh squeeze test. Pre-processing involved data quality checks, alignment, and resampling. 60-second regions of interest were extracted, normalised, and processed using MATLAB (R2023a, TheMathWorks, Inc., Natick, MA, USA). Cross-correlation and Granger causality analyses were conducted to explore relationships between signals. Results: Thigh Hb and EMG signals lagged 8.4 and 8.5 seconds behind SV, respectively. Granger Causality analysis revealed a significant causal relationship from both Hb and EMG to SV in 68% of participants at measured lags. Conclusion: The observed ~8.5-second lag between thigh measurements and SV implies a plausible temporal relationship between muscle activation and venous return, further supported by significant causal relationships found in a substantial portion of participants using Granger causality analysis. These findings underscore the importance of continued research in this area, not only for advancing our understanding of physiological mechanisms but also for informing potential clinical applications aimed at optimising cardiovascular health and function.