Effects of EMG-Biofeedback Balance Training on Hoffman's Reflex

Injuries caused by falls are a major worldwide issue and the most serious injuries include hip fractures and trauma to the brain. In-depth analysis of the risk factors for falls have discovered that balance disorders and abnormal gait are the strongest contributors. It is not a surprise that neural control of posture is altered as a function of age. Falls among the elderly has become an increasing issue and are leading to an escalating number of medical conditions, mortality and utilization of health care services. In Canada, 32 to 42% of older adults who are 70 years or older fall each year. Balance is the key ability needed to avoid falls because maintaining upright balance is needed to complete individual daily activities. Quantitative assessments are needed when evaluating the postural balance of participants. The force plate is a piece of equipment that is a reliable balance assessment method which is used widely in both laboratory and clinical settings. Despite the many research studies over the last three decades analyzing the effects of age and postural control, the number of deaths caused by falling and fall-related injuries has continued to increase. More studies are needed to highlight how old age affects neural mechanisms of postural control. Specifically, we need to understand the mechanisms by which balance training can lead to improved postural control to decrease falls among older adults.

A valuable neurophysiological measurement known as the Hoffman (H) reflex, has a high sensitivity to posture. Measuring the H-reflex amplitude can be used to detect whether changes in spinal excitability accompany balance training. It is a relatively simple technique which makes it an intriguing tool for research. The H-reflex has been used for decades in motor control studies which emphasize spinal mechanisms. It is commonly used as a tool for analyzing spinal excitability, or how effectively synaptic transmission occurs between motor neurons and 1a afferents.

For balance training, electromyography (EMG) biofeedback can be implemented which would involve the participants controlling objects on a screen through the electrical signals of their muscles while standing. The sensors used for EMG are not painful or invasive and can be applied to target the impairment of specific muscles or muscle groups. The EMG-Biofeedback system creates a classifier that predicts the user's intended game control inputs through real-time EMG signals. This innovation would be achieved by placing the sensors on the upper leg and arms to collect data for the signals of the lower and upper extremities, so the motor performance and successful game execution can be focused on the balance of participants. Eighteen sessions (40 minutes each) of EMG-biofeedback training of the lower body (tibialis anterior muscle) over three weeks in participants suffering with chronic stroke was shown to improve motor control outcomes including balance and strength.

To gain a further understanding of the neurophysiological effects of EMG-biofeedback, we will be analyzing changes in spinal reflex excitability by measuring H-reflex amplitudes, and balance board test results before and after 4 weeks of balance training in the aging population. While there have been published studies regarding this intervention improving balance, there have not been any studies exploring whether EMG-biofeedback training also changes spinal reflex excitability. This intervention has the potential to improve spinal reflexes and balance of older adults and prevent future falls. This intervention can possibly decrease major injuries across the healthy older adult population, and changes in H-reflex amplitudes can be associated with balance changes. Studies which have explored changes in H-reflex amplitude after one-month long balance training, have not done a follow-up assessment to confirm the longevity of improvements in balance and decreased amplitudes of the H-reflex.

Methods:

During the participants' first visit to the laboratory, they will complete 3 functional assessments, and one neurophysiological assessment. The functional assessments will measure balance in a standing position. These balance assessments will take approximately 10 min. to complete. The measurement of muscle activity will involve non-invasive stimulation behind the knee which will evoke a muscle twitch in the calve (soleus) muscle. This Hoffman Reflex assessment will be completed for each leg and reflects the activity of circuits within the spinal cord that are thought to contribute to balance. This procedure requires approximately 20 minutes for each leg.

The participants will be randomly assigned to the balance training or biofeedback balance training group by the lead investigator of this study, and the participant will not be told which group they have been assigned to. Irrespective of which group the participant has been assigned to, they will have electrodes placed on upper and lower body muscles which will be attached to the EMG system using leads and you will be completing a computer game that requires your balance for 30 min. each of your training sessions. Assistive devices such as canes, walkers etc. will not be used during the balance training. The participants can take breaks and sit down occasionally during the balance training. This training will take place 4 times per week for a total of 16 times. Both groups will experience the computer game during standing balance training.

The day after their last session, they will complete a follow-up assessment session which will also involve completion of the 3 functional balance tests and measurement of muscle activity for each leg, which will follow the same procedure as the first assessment session.

The second follow-up assessment will take place 2 weeks after the final training session. All assessments from the first follow-up will be repeated.