Student Scholar Symposium

Physical Therapy

The Effect Of Muscle Fatigue On The Lower Extremity's Muscle Activation
Presenter(s): Christopher (CJ) De Leon, Christopher Hoang, Michael Shiraishi, Shannon Toy, Tiffany Lubrino, Armond Gray
Advisor(s): Dr. Rahul Soangra
The purpose of this research study is to examine the changes in electromyogram (EMG) signals of the agonistic muscle and antagonistic muscles during fatigue. Muscle fatigue occurs when a muscle is affected by strenuous or acute activity that decreases its performance (Enoka and Stuart 1992). This study collects data from eight college students and the materials used are twenty-six reflective markers that are placed throughout the body, four EMGs, and four Xsens inertial measurement unit (IMU). We have our patients perform walking trials, heel raises, and steady standing. The fatigue portion of this study is introduced by having our participant perform ankle plantarflexion and dorsiflexion on the Biodex Dynamometer, an isokinetic muscle testing machine that fatigues the lower right extremity by performing multiple sets of plantarflexion and dorsiflexion ankle movement until 60% of their maximum voluntary contraction (MVC) is achieved. The fatiguing of the calf muscles during this phase shows differing rates of the antagonistic and agonistic muscle decline in muscle activity during co-activation, an event where both muscles activate simultaneously to smooth movements and provide fine-motor control (Patikas et. al 2002). In terms of our data, we can accurately measure the activity level of the gastrocnemius and anterior tibialis by synchronizing Vicon, a motion capture program, with Delsys EMG collection to observe functional tasks such as walking or doing heel raises. In post-processing, we will separate low/high EMG frequencies to distinguish unique motor unit activation within the tibialis anterior and gastrocnemius. We hypothesize that tibialis/gastrocnemius co-activation ratio will vary in post-fatigue compared to pre-fatigue. If we find this to be true, then it may be an indicator that simultaneous motor unit recruitment of agonistic/antagonistic muscles will adjust post-fatigue to attempt smooth motion.

The Effects of Muscle Fatigue on Postural Stability
Presenter(s): Armond Gray, Shannon Toy, Tiffany Lubrino, Christopher Hoang, Michael Shiraishi 
Advisor(s): Dr. Rahul Soangra
The main goal of this research study is to compare the relationship between muscle fatigue and postural stability using postural, gait and functional analyses. Focusing on the postural analysis, a force plate is used to determine the center of pressure during pre and post fatigue activities. The plate provides a way to measure steadiness, stability, and the net force between the left and right force plates. Furthermore, the force plates allow us to see if one side of the body is more fatigued than the other depending on the location of the subject’s center of pressure (Murray, MP., et al., 1975). Fatigue is induced by Biodex, an isokinetic muscle testing machine, and allows us to fatigue the lower right extremity so that we can fatigue a given subject in order to assess their postural stability. One parameter of stability is postural sway velocity, the sway speed of one’s torso while maintaining balance. In general, postural sway velocity is significantly increased when the lower extremities are fatigued, as determined by infrared motion capture markers. Fatigue is defined as the reduction in maximal force-generating capability during exercise (Harkins, K., et al., 2005). This aligns with our hypothesis that fatigue will negatively affect the gait and postural performance tested on 8 different subjects. From this study, we can expect significant variations in postural sway velocity and center of pressure travel between pre- and post- fatigue trials. For pre-fatigue tests, we expect the motor units to not be fatigued and activated. However, we expect in post fatigue that there will be decreased postural stability resulting from the Biodex exercises and decreasing activation of motor units in the right lower extremity. Overall, the data will quantify the increase in postural sway velocity and variations in center of pressure travel due to muscle fatigue. 

The Effects of Muscle Fatigue on Gait Parameters
Presenter(s): Tiffany Lubrino, Amir Memarian, Shannon Toy, Armond Gray, Christopher Hoang, Michael Shiraishi
Advisor(s): Dr. Rahul Soangra
The central purpose of this study is to observe the effects of muscle fatigue through performance based on gait parameters, muscle function, and postural stability. When fatigue increases, muscle function decreases. We predicted that fatigue negatively affects gait performance. Gait parameters are used in our experiment to measure the line of progression between the left and right foot. We also measure the subject’s step and stride length, base of support, gait velocity, and gait asymmetry. The relationship to walking stability and gait strategies will contribute to our understanding of gait patterns, and to ultimately minimize the risk of falls (Alamoudi, R., 2020). Depending on the impact of an altered gait cycle, an abnormal gait can lead to more significant health issues. In a study observing how gait parameters affected Parkinson patients, these patients have increased variations in gait parameters in walking speed and stride length within average values (Medijainen, K. et al., 2019). In terms of our data, we can accurately measure the gait parameters by using Vicon, a motion capture program to observe walking cycles when the subjects walk on the treadmill. We recruited eight subjects in a healthy condition throughout this biomechanical research and observed how their pre and post stages of fatigue had affected their gait parameters over time. The gait parameters are influenced by using twenty-six reflective spherical markers, four EMGs (electromyography) to evaluate the activity of nerves and motor neurons, and four Xsens under IMU. These devices were applied at various bony landmarks to obtain walking, heel raise, and standing data through motion capture. We can identify a person’s unique movements, and can ultimately observe fatigue based on their gait parameters and walking patterns. As a result, this experiment can benefit physical therapy research in the future because we can recognize and identify how muscle fatigue can impact walking performance.

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