The Departments of Physical Therapy, Mechanical Engineering, and Health and Nutrition Sciences at the University of Delaware, have recently received funding from the National Institutes of Health to start a new and exciting 5 year study to determine the effects of having stroke survivors walk on a treadmill while using functional electrical stimulation ( FES) of the ankle muscles. There are two major parts to the project. The overall goal of study one, “Fast Treadmill Training/Functional Electrical Stimulation to Improve Walking: Study #1- Development of Training Protocols”, is to demonstrate the effects of fast treadmill training combined with FES on walking patterns of stroke survivors. Study two, which will commence in approximately 2 years, will assess the impact of the training protocols when compared to a control group.
Background and Significance
According to the American Heart Association, 7.7 million people are living with the effects of stroke and over 700,000 people will experience a stroke or recurrence of a stroke annually. One of the primary concerns for patients who experience stroke is the ability to regain walking function. Walking after a stroke is characterized by decreased walking speed, endurance, and symmetry. Over the years, a variety of approaches to gait retraining have been suggested. Recently, treadmill training (with or without body weight support) has emerged as an intervention that improves walking performance in people who have had a stroke. Lamontagne and Fung (2004) found that patients with hemiparesis following stroke can safely walk up to 156% of the self-selected speeds and that fast walking induces marked speed-related improvements in body and limb kinematics and muscle activation patterns. Functional electrical stimulation ( FES) has long been used to improve walking function in stroke survivors (Liberson et al., 1961) and may assist in increasing walking speed for those stroke survivors who cannot otherwise reach their maximally efficient walking speed.
Inclusion and Exclusion Criteria:
*** Individuals with stroke who are only able to ambulate with orthotic support, may be able to participate in a portion of the study
There are three stages to the FastFES study.
Stage 1: Clinical Testing with Muscle Evaluation, Motion Analysis on Treadmill without Electrical stimulation, and Energy Efficiency Testing
During clinical testing, researchers will document the subject’s status on multiple clinical measures: range of motion, motor control, proprioception, coordination, sensation, balance and gait. The impact of the subject’s stroke on activity and participation will also be documented. During the Muscle Evaluation, researchers will be able to obtain information about the subjects’ muscles that will enable our mathematical muscle models to predict the stimulation patterns accurately. These stimulation patterns will then be used to help subjects walk more efficiently so they will be able to walk longer distances without fatigue. For each subject, data will be collected from the ankle dorsiflexor and plantarflexor muscles. All electrical pulses will be delivered via self-adhesive electrodes placed over the muscles being tested. The adhesive is a water-soluble hypoallergenic conductive gel that has little risk of causing skin irritation. Electrical pulses will be delivered using a Grass stimulator.
To test the ankle muscles, subjects will be positioned supine on the force dynamometer with their hips extended to approximately 0 0 and their knees fully extended (0 0). The muscles will be first tested isometrically at four different angles. After confirming good electrode placements, the subject’s maximum twitch isometric force will be determined using a series of single stimulation pulses. Subjects will be then tested under nonisometric conditions where the limb is allowed to move freely in response to electrical stimulation. Each testing train will last a maximum of 1 sec or contain 50 pulses, whichever yields the shorter train duration. In addition, stimulation within each train will be terminated whenever the ankle reaches 0 o of dorsiflexion or 25 o plantarflexion. Following the testing protocol, a 10 minute rest will be given to the subject, after which a similar procedure will be followed for the remaining muscles.
During Motion Analysis with electrical stimulation, subjects will be asked to walk on a treadmill and over ground while stride dimensions (cadence, velocity, stride and step lengths), ground reaction force (GRF), joint kinematics, and kinetics are recorded. Heart rate, blood pressure, and rate of perceived exertion will be monitored at each rest break. Elastic bands will be wrapped around the thighs and calves to which small, reflective markers will be attached. Additional markers will be taped to the subjects’ sneakers and on the upper back, shoulder, pelvis, hip, knee and ankle joints with adhesive tape. The location of the markers will be recorded with an 8 camera 3-D motion analysis system (Vicon MX, Vicon, Lake Forest, CA). With a safety harness and possibly holding onto a handrail, subjects will walk at different speeds on a split belt 6 degree of freedom instrumented treadmill (AMTI, Watertown, MA). The speeds selected include the self-selected walking speed, slower than self-selected walking speed, the fastest possible walking speed, and 2-3 incremental speeds between self-selected and fastest walking speed.
During energy efficiency testing, oxygen uptake will be measured while walking on the treadmill using the exact walking speeds determined from the previous session and the protocol described above. Subjects will wear a nose clip and breathe through a mouthpiece (Hans Rudolph Inc., Kansas City, MO) to collect expired air as they walk on the treadmill. Subjects will initially sit quietly as collection and analysis of expired gas will be completed using the ParvoMedics TrueOne 2400 Metabolic Measurement System. Subjects will maintain their stationary position for 5 minutes and a pre-exercise zero-work VO2 will be quantified from the last 2 min of the 5-min collection. During the stationary and walking periods expired air will be sampled continuously from a mixing chamber, passed through a drying tube, and analyzed for O2 and CO2 concentration as well as ventilation volume. Energy expenditure per meter walked will be calculated from the VO2 data. This will be used to generate a speed-energy expenditure curve to assess changes in energy expenditure with speed changes.
Stage 2: Treadmill Walking with FES
During this stage, you will do similar tasks as those described in treadmill walking above. The differences are that you will walk on the treadmill at different speeds while receiving electrical stimulation to the muscles on the front of your leg and your calf. Stimulation to the front of the leg will help to lift your toes as you swing your paralyzed leg during walking. Stimulation to the calf muscle will help you to push down on the treadmill belt during walking. These electrical stimulations will last no more than 1 second and should not be painful. This stage allows the researchers to determine the best stimulation parameters to use for Stage 3.
Stage 3: Training with FES
The training phase of this study will help us develop procedures that may allow stroke survivors to walk more efficiently and become less tired. In this phase, you will undergo training on the treadmill and over ground with and without electric stimulation 3 times per week for a total of approximately 36 training sessions. Every 4 weeks, you will undergo the evaluation sessions again as mentioned during Stage 1 which will allow us to document your progress. When you have finished all the training sessions, we will ask you to come back in 3 months to undergo the evaluations again to see how you have been walking since you finished the study.
Lamontagne A, Fung J. Faster is better: implications for speed-intensive gait training after stroke. Stroke 2004; 35:2543-2548.
Liberson WT, Holmquist HJ, Scot D, Dow M. Functional electrotherapy: stimulation of the peroneal nerve synchronized with the swing phase of gait in hemiplegic patients. Arch Phys Med Rehabil 1961; 42:101-105.
Perumal R, Wexler AS, Binder-Macleod SA. Mathematical model that predicts lower leg motion in response to electrical stimulation. J Biomech. 2006; 39( 15): 2826-36.
Perumal R, Wexler AS, Ding J, Binder-Macleod SA. Modeling the length dependence of isometric force in human quadriceps muscles. J Biomech. 2002 Jul; 35( 7): 919-30.
Fast FES Grant-1R01NR010786-01