This present project is composed of three distinct but related studies which employed a novel thumb resistance-exercise protocol common to each study. The overall aim was to address the following needs in exercise-centred research: i) to understand the biological and affective implications of a very low-dose (micro-dose) of resistance-exercise on resistance-trained and untrained men; ii) to improve the standardisation of exercise protocols used in resistance-exercise research and therefore the validity of outcomes; iii) to explore the multidimensional consequences of resistance-exercise on host (human) biology which will lead to safer, more efficacious exercise prescription and monitoring practice. Study 1 examined the effects of a micro-dose of thumb resistance-exercise on leukocyte redistribution, thumb pinch-strength, and reported fatigue. The effect of training status was also studied. Developing on the findings of study 1, study 2 investigated the effects of the thumb exertion on lymphocyte subpopulation trafficking, and explored the potential role of blood lactate in regulating lymphocyte-selective redistribution. Study 3 examined the effects of the thumb exertion on serological dehydroepiandrosterone-sulfate (DHEA-S), interleukin (IL)-6 and mood-state determinants. Potential relationships between mood and the biomarkers were studied with the aim of directing research on safer, non-invasive exercise-monitoring methods.