The School of Health Sciences Motion Analysis Lab is located in the HSC building, Room 014. The lab allows us to investigate human movement with the goal of optimizing motor control and motor learning for recovery and for wellness.

Proactive and Reactive Balance

Falling is a serious problem, impacting a high proportion of older adults and resulting in profound mortality and morbidity as well as loss of function and independence.  Balance can be defined as the ability to maintain the center of mass (COM) within the base of support (BOS).  While COM and BOS are easier to define in a static positions such as standing, their definition is more challenging in dynamic functional activities, such as walking or reaching, where both the COM as well as the BOS may be in continuous motion. Recent research supports that control of both COM and the BOS are critical to fall prevention, rather than just COM control, and that older adults are able to learn the combined control of COM and BOS with training.  In addition, research supports that exercise protocols for strength and balance are the most effective community intervention for falling.

Many community fitness and wellness programs, as well as most physical therapy interventions, utilize proactive balance training; which is an anticipatory and self-initiated approach of strength and balance exercises to improve balance for the prevention of falls.  Reactive balance training, on the other hand, is the practice of responses to unexpected perturbations that cause losses of balance, such as a slip, trip, or nudge.  Proactive balance training is more prevalent clinically due to its ease of use, lower perceived safety threat, greater acceptance by participants, and lower cost.  However, falls generally occur due to inadequate reactive responses to external perturbations.  Due to the closer similarity of reactive balance training and falls occurring in real-life, reactive perturbation training is being studied much more and research suggests that it has more effective, long term results than proactive training. 

The degree to which skills gained under proactive conditions transfer to reactive conditions is unknown.  Research is needed to assess this transfer and which types of training are more efficient and effective at preventing falls.  Since proactive training is self-initiated, it may be less intense (lower amplitude perturbations, less challenging to the person’s balance control systems) than reactive tasks.  It is possible that, at similar intensities, the efficacy of the two types of training would be closer.  Another important question then, is whether proactive balance training can be structured to match the intensity of reactive training, while retaining its advantages of lower cost, easier administration, lower perceived threat and greater acceptance.  In order to compare the intensity of different balance activities, we developed the Rate of Perceived Stability Scale (RPS). 

We are investigating the potential to use off-the-shelf video gaming to create high-intensity proactive balance training.  The immersive nature of the games leads to greater engagement and attention and more practice repetitions, and the variety of games and platforms available allows modulation of many therapeutic aspects of the tasks and environment that are not necessarily available in non-virtual settings.  We have done extensive work with the Xbox system with Kinect and the Wii system and have designed a protocol and progression of games and surfaces that provides high intensity proactive balance training.   

(Top) Games and various balance surfaces for greater intensity of
proactive balance training.  (Bottom) Game being played on foam mats with fall arresting harness.

In conjunction with MASS Rehab in Dayton, OH, we designed and had fabricated standing slip platforms (Slip Trainers.)  We have developed a protocol of slip testing and reactive balance training for this device, along with a fall arresting harness and load measuring device.  This allows us to administer repeated slip perturbations of a consistent and known intensity safely and efficiently.  Among young adults, we have found that subjects learn to recover from the induced slips over repeated trials and we have identified a decreasing reliance on the harness as the fall avoidance task is learned. 


(Top Left) Longer standing slip induction plate with harness for reactive balance testing and training.   (Bottom Left) Subject with  markers, on shorter slip induction plate, for motion capture and analysis.  (Top Right) Cortex figures of subject's motion during a fall (upper) and a recovery (lower) trial. 

We have also developed a walking slip set-up and protocol to test responses to gait slips in addition to standing slips.  The rail and harness system allows us to perturb subjects anywhere along a walkway while still monitoring and protecting the subjects and collecting data.  (Picture at left shows slipping walkway and rail system)

We believe that a properly designed protocol of active video games with different balance surfaces may challenge people’s balance to a similar degree as the reactive (slipping) task. The slip device and protocol, the RPS, the harness and load cell system, and the active gaming and balance surfaces protocol have all been developed with an eye towards implementation among older adults as this is the population for whom falls are of great concern.  We have completed pilot and feasibility testing of the equipment (including a more mobile harness system from Enliten, Neward, DE) and protocols for a larger scale study among older adults.  

Reinthal A and Espy D. CSU Undergraduate Research Engaged Learning Grant: 2016 “Aggressive harnessed balance training with balance impaired adults.” $9,565.00  

Espy D  and Reinthal A. CSU Undergraduate Research Engaged Learning Grant: 2015 “Can we increase the intensity of proactive balance exercises?”  $6,721  

Espy D and Rashidi M.  CSU Undergraduate Research Engaged Learning Grant: 2013 “Design, build and testing of a surface translation balance training device” $5484 

Espy D.  CSU Undergraduate Research Engaged Learning Grant: 2012 “Comparison of Responses in Proactive vs. Reactive Balance Control.”  $ 5058,
Espy D, Reinthal A and Walsh J.  CSU Undergraduate Research Engaged Learning Grant: 2011 “Development and Validation of Methods to Rate Components of a Balance Training Program” $ 6052 

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