# Impact of Differing Instability Devices on Postural  
Sway Parameters  
[PERSON]  
1 School of Kinesiology and Nutrition, University of Southern Mississippi, Hattiesburg, MS 39406, USA; [EMAIL_ADDRESS] (X.M.W. ); [EMAIL_ADDRESS] (J.C.M. ); [EMAIL_ADDRESS] (A.K.M.) [PERSON]  
2 Department of Physical Therapy, University of Mississippi Medical Center, Jackson, MS 39216, USA; [EMAIL_ADDRESS] (M.R.B. ); [EMAIL_ADDRESS] (J.B.D. ); [EMAIL_ADDRESS] (J.C.G.) [PERSON]  
2 Department of Physical Therapy, University of Mississippi Medical Center, Jackson, MS 39216, USA; [EMAIL_ADDRESS] (M.R.B. ); [EMAIL_ADDRESS] (J.B.D. ); [EMAIL_ADDRESS] (J.C.G.) [PERSON]  
2 Department of Physical Therapy, University of Mississippi Medical Center, Jackson, MS 39216, USA; [EMAIL_ADDRESS] (M.R.B. ); [EMAIL_ADDRESS] (J.B.D. ); [EMAIL_ADDRESS] (J.C.G.) [PERSON]  
1 School of Kinesiology and Nutrition, University of Southern Mississippi, Hattiesburg, MS 39406, USA; [EMAIL_ADDRESS] (X.M.W. ); [EMAIL_ADDRESS] (J.C.M. ); [PERSON]@usm  
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.edu (A.K.M.) ++  
As has been stated throughout the literature pertaining to injury, the primary predictor of future injury is current/past injury [12; 13]. Thus, the importance of creating not only rehabilitation but injury prevention programs centered on the improvement of balance parameters is paramount to reducing not only the number of injuries that occur but also the long-term effects of these injuries. Many times, an instability device is used in these training programs to create this unstable surface condition and provide a progressive overload in the training. Previous research has found that training on unstable surfaces can improve both static and dynamic balance, as well as perceptual outcomes [14; 15; 16; 17; 18]. A common issue with this training is the variability between the degrees of instability experienced across differing instability devices. Therefore, assessing the differences between commonly used instability devices is essential. [PERSON] et al. [7] reported no differences in the postural sway parameters between two different foam pad conditions in groups of faller and non-faller older adults. [PERSON] et al. [11] found that foam pads of a similar size but different densities had statistically different impacts on anterior-posterior (AP) torque variance during a bilateral stance with eyes closed. However, no differences were observed between medium- and soft-density foams and a solid surface under eyes-open conditions. Lastly, they observed differences in the medial-lateral (ML) direction torque variance across all conditions (visual and surface). During a single-limb stance, [PERSON] et al. [6] also found differences in the ML direction among instability devices commonly used by practitioners. Specifically, they found that a half-foam roller had significantly less mediolateral displacement than a BOSU ball. Additionally, the BOSU ball had a significantly greater sway area and average sway velocity than the other three devices. However, no statistical differences were observed between the half-foam roller and foam pad conditions across any variables. The lack of consistent findings across studies regarding the instability devices creating changes in postural sway points to the need for further investigation to better design training programs in the future. Since unstable surfaces challenge the somatosensory systems responsible for postural stability, they can be used to assess postural sway and are frequently implemented during balance training interventions to introduce a progressive overload during rehabilitation [14; 15; 16; 17; 18]. Rehabilitation professionals (physical therapists, athletic trainers, and strength and conditioning coaches) often use unstable surfaces such as foam pads, wobble boards, and BOSU trainers to create instability during training sessions. This is largely done to train neuromuscular qualities to prevent future injuries.