Doctor of Philosophy (PhD)


School of Kinesiology

Document Type



The primary focus of this dissertation was to understand the motor control strategy used by our neuromuscular system for the multi-layered motor tasks involved during smartphone manipulation. To understand this control strategy, we recorded the kinematics and multi-muscle activation pattern of the right limb during smartphone manipulation, including grasping with/out tapping, movement conditions (MCOND), and arm heights.

In the first study (chapter 2), we examined the neuromuscular control strategy of the upper limb during grasping with/out tapping executed with a smartphone by evaluating muscle-activation patterns of the upper limb during different movement conditions (MCOND). There was a change in muscle activity for MCOND and segments. We concluded that our neuromuscular system generates the motor strategy that would allow smartphone manipulation involving grasping and tapping while maintaining MCOND by generating continuous and distinct multi-muscle activation patterns in the upper limb muscles.

In the second study (chapter 3), we examined the muscle activity of the upper limb when the smartphone was manipulated at two arm heights: shoulder and abdomen to understand the influence of the arm height on the neuromuscular control strategy of the upper limb. Some muscles showed a significant effect for ABD, while some muscle showed a significant effect for SHD. We concluded that the motor control strategy was influenced by the arm height as there were changes in the shoulder and elbow joint angles along with the muscular activity of the upper limb. Further, shoulder position helped in holding the head upright while abdomen reduced the moment arm and moment and ultimately, muscle loading compared to the shoulder.

Overall, our neuromuscular system generates motor command by activating a multi-muscle activation pattern in the upper limb, which would be dependent upon the task demands such as grasping with/out tapping, MCOND, and arm heights. Similarly, our neuromuscular system does not appear to increase muscle activation when there is a combined effect of MCOND and arm heights. Instead, it utilizes a simple control strategy that would select an appropriate muscle and activate them based on the levels of MCOND and arm heights.



Committee Chair

Van Gemmert, Arend W. A.