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Physical and neurophysiological factors influencing dynamic balance

Abuzayan, K J (2010) Physical and neurophysiological factors influencing dynamic balance. Doctoral thesis, Liverpool John Moores University.

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Static and dynamic balance are essential in daily and sports life. Many factors have been identified as influencing static balance control, two of which are carrying additional weight and localized muscle fatigue but their influence on dynamic balance in sport activities has not been fully established. Therefore, the aim of this thesis was to investigate the characteristics of dynamic balance in sport related activities, with specific reference to the influence of body mass changes and muscular fatigue. Study one: The objectives of study one (methodological study, n = 5) were to apply the extrapolated Centre of Mass (XCoM) method and other relevant variables (centre of pressure, CoP; Centre of Mass, CoM; shear forces, Fh; kinetic energy, KE; momentum, P; and angular impulse, AI) to investigate sport related activities such as hopping and jumping. Many studies have represented the CoP data without mentioning its accuracy so several experiments were done to establish the agreement between the CoP and the projected CoM in a static condition. It was found that there was an inaccuracy with the average difference about 4mm. This meant that the angular impulse could not be reliably calculated. Its horizontal component, representing the Friction Torque (Q), could be reliably computed for dynamic balance. The implementation of the XCoM method was found to be practical for evaluating both static and dynamic balance. The general findings were that the CoP, the CoM, the XCoM, Fh, and Qwere more informative than the other variables (e.g. KE, P, and AI) during static and dynamic balance. The XCoM method was found to be applicable to dynamic balance as well as static balance. Study 2: The objectives of study two (baseline study, n =20) were to implement Matlab procedures for quantifying selected static and dynamic balance variables, establish baseline data of selected variables which characterize static and dynamic balance activities in a population of healthy young adult males, and to examine any trial effects on these variables. The results indicated that the implementation of Matlab procedures for quantifying selected static and dynamic balance variables was practical and enabled baseline data to be established for selected variables. There was no significant trial effect. Recommendations were made for suitable tests to be used in later studies. Specifically it was found that one foot-tiptoes tests either in static or dynamic balance are too challenging for most participants in normal circumstances. A one foot-flat eyes open test was considered to be representative and challenging for static balance, while adding further vertical jump and landing tests (two feet flat and one foot flat vertical jump) to the horizontal jumping and hopping for dynamic balance was considered to be more representative of sports situations. The main differences between horizontal and vertical jumping were in anterior-posterior direction. Study 3: The objectives of study three (differentiation study, n =20) were to establish the influence of physical (external added weight) and neurophysiological (fatigue) factors on static and dynamic balance in sport related activities. This was typified statically by the Romberg test (one foot flat, eyes open) and dynamically by jumping and hopping in both horizontal and vertical directions. Statically, added weight increased body's inertia and therefore decreased body sway in anterior-posterior direction though not significantly. Dynamically, added weight significantly increased body sway in both mideo-lateral and anterior-posterior directions, indicating instability, and the use of the counter rotating segments mechanism to maintain balance was demonstrated. Fatigue on the other hand significantly increased body sway during static balance as a neurophysiological adaptation primarily to the inverted pendulum mechanism. Dynamically, fatigue significantly increased body sway in both mideo-lateral and anterior-posterior directions again indicating instability but with a greater use of counter rotating segments mechanism. Differential adaptations for each of the two balance mechanisms (inverted pendulum and counter rotating segments) were found between one foot flat and two feet flat dynamic conditions, as participants relied more heavily on the first in the one foot flat conditions and relied more on the second in the two feet flat conditions. Conclusion: Results from this thesis are expected to aid towards advancing the understanding of balance in sport related activities, and can provide a solid foundation for future work in this area. In particular, a method was established to assess static and dynamic balance, baseline data for these associations was provided, and differential adaptations to physical or neurophysiological constraints were found. Valuable associations between specific variables and the first two mechanisms of balance were demonstrated.

Item Type: Thesis (Doctoral)
Subjects: Q Science > QM Human anatomy
Q Science > QP Physiology
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions: Sport & Exercise Sciences
Date Deposited: 16 Mar 2017 09:21
Last Modified: 16 Mar 2017 09:21
URI: http://researchonline.ljmu.ac.uk/id/eprint/5965

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