Browsing by Author "Costello, Kerry E."

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    Independent effects of adding weight and inertia on balance during quiet standing
    Costello, Kerry E.; Matrangola, Sara L.; Madigan, Michael L. (2012-04-16)
    Background Human balance during quiet standing is influenced by adding mass to the body with a backpack, with symmetrically-applied loads to the trunk, or with obesity. Adding mass to the body increases both the weight and inertia of the body, which theoretically could provide counteracting effects on body dynamics and balance. Understanding the independent effects of adding weight and inertia on balance may provide additional insight into human balance that could lead to novel advancements in balance training and rehabilitation. Therefore, the purpose of this study was to investigate the independent effects of adding weight and inertia on balance during quiet standing. Methods Sixteen normal-weight young adult participants stood as still as possible on a custom-built backboard apparatus under four experimental conditions: baseline, added inertia only, added weight only, and added inertia and weight. Results Adding inertia by itself had no measurable effect on center of pressure movement or backboard movement. Adding weight by itself increased center of pressure movement (indicated greater effort by the postural control system to stand as still as possible) and backboard movement (indicating a poorer ability of the body to stand as still as possible). Adding inertia and weight at the same time increased center of pressure movement but did not increase backboard movement compared to the baseline condition. Conclusions Adding inertia and adding weight had different effects on balance. Adding inertia by itself had no effect on balance. Adding weight by itself had a negative effect on balance. When adding inertia and weight at the same time, the added inertia appeared to lessen (but did not eliminate) the negative effect of adding weight on balance. These results improve our fundamental understanding of how added mass influences human balance.
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    Understanding the Independent Effects of Inertia and Weight on Balance
    Costello, Kerry E. (Virginia Tech, 2011-06-03)
    While human balance is known to be affected by altered sensory feedback, altered dynamics may also contribute to balance deficiencies in certain populations. The goal of this study was, therefore, to investigate the effects of altered dynamics, namely increased inertia and increased weight, on standing balance. Sixteen normal-weight male participants completed quiet standing in a custom-built backboard under four conditions: baseline, increased inertia only, increased weight only, and increased inertia and weight. Increased inertia did not affect body center of mass movement (COM) or center of pressure (COP) movement, suggesting that no additional ankle torque was necessary to control the increased inertial forces. Increased weight caused increased body COM movement (increased backboard angle range and angular speed) and greater acceleration of the COM (as evidenced by increased COP-COM), requiring an increased level of corrections needed to maintain upright posture (as evidenced by increased COP speed) and increased ankle torques (as evidenced by increased range of COP position). Increasing inertia and weight simultaneously had the same effects as increasing weight except that there was no increased COM movement when both inertia and weight were increased. This indicates that there may be a slight mediating effect of increasing inertia on the extreme changes in balance observed when only weight is increased. These results indicate that altered dynamics of the body have an effect on human standing balance, just as altered sensory function has an effect on balance.