Wearable sensors help us in taking corrective steps that will make us healthier than yesterday. Wearable sensors empower people to be productive, active and attentive by instilling in them, the need to take care of themselves. Now, smart phone users can monitor their health and fitness on their mobile devices. Smart watches, performance monitoring, virtual coaching, body temperature management, activity tracking are few applications worth mentioning. A continuous estimation of fitness level, employing these wearable devices, can potentially help users in setting personalized short and long-term exercise goals leading to positive impact on one's overall health. Efficiency, life span, power consumption and performance are among the key issues in desiring a wearable device. Where a device needs longer life, bigger battery can be used but large size leads to discomfort in wearable sensors usage, so we concentrate on smaller sized batteries and smaller devices. Smaller the size of wearable sensor goes; bigger the longevity problem arises in terms of maintaining the power to use wearable sensor efficiently. Bluetooth used as a wireless link communication between wearable sensor and handheld devices or computer drains wearable device power faster. In this context prolonging battery life is one among major challenges that needs to be addressed in a wearable system. In this study, we address various efficient power management techniques for wearable sensors and decisions taken during designing a software algorithm, since software is also one among key factors that drives the hardware of a wearable sensor. This thesis is organized as follows: first, the wearable sensor hardware and firmware are described. Next, power management techniques, provided by the manufacturer are presented. Finally, power budget analysis and efficient power management methods are illustrated with results. Chapter 1 details the importance of wearable sensor and uses in variety of fields.