Vibration stimulation has been used as a tool to relieve muscle pain and spasm in physical therapy for many years. However recently, vibration, mainly Whole Body Vibration (WBV), has been increasingly studied and used as an exercise intervention in sports and rehabilitation. Although the physiological mechanisms which guide the body's response to this exercise modality are relatively poorly understood, evidence indicates that vibration can enhance muscle strength, power, and flexibility as well as increase bone mineral density in the general population. Evidence also suggests that the neuromuscular response to vibration stimulation depends on muscle length, stretch level (contraction) along with the vibration characteristics. One way to alter muscle length and contraction levels while receiving vibration is to superimpose the stimulation on graded isometric contraction. However, current WBV device designs cannot facilitate the delivery of vibration stimulation superimposed on graded isometric voluntary contraction. The aim of this PhD project was twofold, firstly to develop and evaluate a prototype WBV device which enables the delivery of vibration stimulation that can be superimposed on graded isometric contraction and secondly, to assess the neuromuscular responses to vibration superimposed on graded isometric contractions in lower limbs using this device. Due to the novelty of the device design and the method of the delivery, this study initially investigated the effects of different vibration frequencies and amplitudes combined with various effort levels on neuromuscular responses in lower limbs. The results of this study confirm that isometric contraction superimposed on vibration stimulation induce enhanced neuromuscular activity in the lower limbs. The results also confirm that although the neuromuscular responses to vibration depend on multiple factors the main determinants seem to be the vibration frequency, amplitude and muscle contraction /forc The results also confirm that although the neuromuscular responses to vibration depend on multiple factors the main determinants seem to be the vibration frequency, amplitude and muscle contraction /force level. Another limitation of most existing vibration devices is that they are not capable of delivering frequency of the vibration independent of amplitude and vice versa. Further, the evidence suggests that vibration amplitude can play an important role in neuromuscular response to vibration, especially when superimposed with graded contraction/force levels. To address the above limitation, the second aim of this PhD project was to develop and evaluate a prototype miniature upper limb vibration device capable of delivering precise and independent vibration frequency and amplitude stimulation. The miniature upper limb vibration (ULV) device with piezo actuators developed for this thesis, enables precise vibration stimulation to be delivered in a seated position with graded voluntary contraction superimposed. The neuromuscular responses to vibration superimposed on graded isometric contractions in upper limbs were also assessed by investigating the fatiguing effects of superimposed vibration stimulation using this newly developed device. This study is the first to investigate and compare the fatiguing effects of superimposed vibration stimulation pre and postvibration exercise in upper limbs. The results of this study confirm that isometric contraction superimposed on vibration stimulation lead to increased fatigue levels and neuromuscular activity in upper limbs. The results also indicate that post-vibration treatment the muscles display enhanced force generation capability associated with lower fatigue levels. In summary, two (WBV and ULV) novel vibration exercise devices were successfully developed and evaluated for this thesis. The results of the studies on these devices confirm that vibration stimulation superimposed on graded isometric contraction can induce higher neuromuscular activity compared to isometric contraction alone in both upper and lower limbs. However the effects of vibration frequency, amplitude and contraction/force levels seem to differ between the upper and lower limbs.