Postural monitoring and neuromuscular synergies related to damages due to a sedentary lifestyle

Each year, there is a growing prevalence of sedentary behaviors and an increment of pathologies linked to bad lifestyle habits and physical inactivity. If we consider the typical day of a person who works in an office sitting for several hours in front of the computer, we understand how he or she may be susceptible to developing neuromuscular pathologies both at the trunk and upper limb level. At the level of the trunk, low back pain (LBP) is certainly the most present, while at the level of the upper limbs, the hand is the most exposed, and the scribe's cramp is an example of this. The great challenge today in preventing and treating these pathologies lies in the difficulty in performing a clear diagnosis due to the lack of understanding of the main causes, as they often stem from a complex interplay among biomechanical, behavioural, neurophysiological, and environmental factors. This complexity makes it difficult to identify targeted and comprehensive intervention strategies. A possible approach to addressing these issues is to study the behavior resulting from the pathology by applying the motor control perspective, which enables the analysis of how the neuromuscular system, through the muscle synergies, anticipates, adapts, and compensates in the face of perturbations. In this context, two complementary studies were conducted: the first focused on analyzing postural and compensatory strategies in individuals with chronic and latent LBP, and the second explored the postural control of a hand in the act of producing force in multi-finger tasks by analysing the muscular synergies and the fine motor control mechanisms. The first study aimed to test the motor anticipation and adaptation patterns in subjects who were affected by low back pain (LBP) but in the absence of pain for more than 10 days. The task was to maintain an upright posture while self-inducing perturbations through the release of a weight positioned either in front of or behind the body. Muscle activity was registered with a system made of 14 sensors of electromyography (EMG). When compared with healthy subjects, the analysis revealed that individuals affected by LBP pre-programmed a more conservative control of action by increasing the amount of muscle co-contraction. These findings underline the presence of differences between healthy and LBP individuals, even if the latter were tested in the absence of pain. It is worth mentioning that differences were particularly present for the synergies applied in preparation for the action. The second study focused on understanding how hand muscle synergies contribute to force stabilization during a task. The experiment analyzed force exertion on customized cells designed to measure the force produced by the index, middle, ring, and little fingers, along with sensors to monitor motor unit (MU) activity in two key agonist-antagonist muscles controlling these fingers. Through the application of motor control theories and techniques, it was possible to identify stabilizing synergies at different levels of control: at the level of force production, at the level of individual agonist and antagonist muscles considered separately, and at the level of the interaction between these muscles analyzed as a single functional entity. These studies highlight the value of testing the control of movements for a better understanding of muscle synergies developed during action preparation and action performance. The findings might provide a foundation for developing more effective prevention and rehabilitation strategies, focused on personalized and innovative approaches. Finally, this work emphasizes the importance of integrating motor control knowledge into clinical and therapeutic programs, with the goal of improving quality of life and reducing the risk of recurrence.