Tag: Human Physiology

How Smartphone Use during Walking Affects Ability to React to an Unexpected Event in Young Adults

Presenter: Deborah Wang

Mentors: Li-Shan Chou and On-Yee Lo, Human Physiology

Poster: C8

Major: Human Physiology

College students often engage in risky mobile phone behaviors. Though texting while driving has been an extensively studied, the issue of texting or other smartphone usage while walking has only been recently examined as a daily hazard. This project focused on how smartphone usage affected a person’s response to an unexpected event when the subject was looking intently at the screen. This study examined the failure rate as the subject stopped in front of a projected line, and associated gait characteristics including stride length, center of mass (COM) velocity and COM medial-lateral sway. In this experiment, whole body motion was collected with 29 reflective bony landmark markers and a 10-camera system. Subjects first stopped in front of a projected line at the same location, and with the same timing for 5 trials (expected condition, EX). Subjects were then asked to stop in front of the line projected at different times or locations for 10 trials (unexpected condition, UN), and then simultaneously completing a Stroop test on an iPod touch under the same unexpected condition for another 10 trials (UN_Stroop). A Stroop test has subjects pick the ink color a word of a color (IE green, blue or red) is written in (IE green, blue or red). This made the UN_Stroop condition the most challenging. UN and UN_Stroop had a higher failure rate than the 0% of EX (33% and 17% respectively). Furthermore, with smartphone usage, gait velocity and stride length decreased while medial-lateral sway increased, which could negatively impact pedestrian safety.

Age-Related Differences in Healthy Male Runners

Presenter: Justine Silberberg

Mentors: JJ Hannigan and Li-Shan Chou, Human Physiology

Poster: 60

Major: Human Physiology

Previous research suggests that older males display less ankle plantar flexion and greater hip flexion during gait compared to younger individuals. Differences in running gait between younger and older individuals, however, are largely unknown. This study investigated differences in strength, flexibility, and range of motion between younger runners (n = 15; age range = 18-21) and older runners (n = 10; age range = 40-51). All subjects were males who ran at least 20 miles per week. For testing, subjects ran continuous laps of approximately 40-meters in the Motion Analysis Laboratory. Running kinematics were collected using a 10-camera motion capture system, strength was measured using a Biodex System 3 dynamometer, and flexibility was measured statically by a trained clinician. Independent sample t-tests were used to examine group differences. Older individuals were found to have increased hamstring flexibility, increased first metatarsal-phalangeal joint range of motion, decreased quadriceps flexibility, and decreased trunk flexion compared to younger runners (p < 0.01). Limitations include the relatively small sample size and cross-sectional nature of this study. Understanding age-related differences in running gait may help clinicians better treat injuries in older runners. Future studies exploring age-related differences in running should recruit a wider age range and follow these individuals over time.

Analysis of Dynamic Balance Control in Below-Knee Amputees with Use of Powered Prosthetic Foot

Presenter: Shaun Resseguie

Mentors: Michael Hahn and Jake Hinkel-Lipsker, Human Physiology

Poster: 55

Major: Human Physiology 

The powered prosthetic foot (PPF) is designed to provide below-knee amputees (BKA) with active propulsion and plantar flexion similar to that of the biological limb. Previous studies have demonstrated the PPF’s ability to increase BKA walking speeds, while reducing the energetic costs, however, little is known about its effects on dynamic balance control. The purpose of this study was to assess dynamic balance control in a sample of BKA subjects during level-ground walking and obstacle crossing tasks. Control subjects (n=5) and BKA subjects (n=4) were instructed to complete a series of functional walking tasks during each lab visit. The BKA subjects completed the walking protocol twice, first in their traditional passive prosthetic foot and again in the prescribed PPF after two weeks of acclimation. Motion data were collected via a 10-camera system with a 53-marker and 15-segment body model. Center of mass (CoM) motion and peak velocity within the frontal plane were analyzed and used as functional indicators of dynamic balance control. Preliminary findings from the study indicate that BKA subjects wearing the PPF generally experienced a greater mediolateral CoM motion and peak velocity, thus signifying a reduced ability to maintain dynamic balance control. Our findings may be of particular interest to clinicians and PPF designers working to improve the amputee population’s quality of life. Further data analysis is needed to support these initial findings.

Effects of Chronic Passive Heating on Resting Heart Rate, Blood Pressure, and Body Core Temperature

Presenter: Kaitlin Livingston

Mentors: Christopher Minson and Vienna Brunt, Human Physiology

Poster: 44

Major: Human Physiology 

Repeated bouts of exercise in the heat are known to decrease resting body core temperature (Tc), mean arterial pressure (MAP) and resting heart rate (HR). Although exercise in the heat produces these cardiovascular changes, it is currently unknown whether passive chronic heating provides the same benefits. Our research sought to examine the effects of passive chronic heating on resting Tc, MAP, and HR. Five sedentary, college-aged subjects (4 females, 1 male) were assigned to an 8-week hot water immersion program (4-5 sessions/week). Subjects were submerged to the clavicle in 40.5°C water until a rectal temperature (Tre) of 38.5°C was reached. Subjects maintained a Tre between 38.5-39.0°C during an hour of partial immersion. HR and Tre were measured with a HR monitor and rectal thermistor both at rest and at 5-minute intervals during the heat stress. MAP was measured on another day with brachial auscultation after ≥20 minutes of supine rest. Both resting MAP (81±1 vs. 76±2 mmHg, p=0.02) and resting Tre (37.4±0.5 vs. 36.8±0.4°C, p=0.03) decreased after 8 weeks of passive heat stress with no change in resting HR (63±5 vs. 63±6 beats/min, p=0.26). Chronic passive heat stress reduces resting MAP and Tre similarly to what is observed with exercise heat in the heat. This suggests that chronic passive heat stress could be used to benefit cardiovascular health similarly to exercise in the heat.

Differences in Functional Recovery Following Concussion between Males and Females

Presenter: Rachel Klas

Mentors: Li-Shan Chou and Quinn Peterson, Human Physiology

Poster: 38

Major: Human Physiology

Concussion, a brain trauma resulted from linear or rotational acceleration to the head, represents a majority of the traumatic brain injuries (TBI) sustained each year. To understand if there are recovery differences between males and females post-concussion, this research examined males and females with matched controls for two months following the injury. In this study, a 3-dimensional motion analysis system was used to observe the trajectory of 29 anatomical locations in order to determine the peak anterior velocity of each subject’s center of mass (COM, the point where the mass is equally distributed) and the medial-lateral COM sway. Symptom severity was assessed based on a 22-symptom inventory and a scale similar to the Likert scale for each symptom (ranking each symptom from 0-6). A three-way analysis of variance, or ANOVA, was performed to analyze the data in order to determine the effect of concussion, sex (male and female), time (72 hour, one week, two week, one month, and two month post-injury), and the interactions between these independent variables. It was revealed that males and females do not objectively differ in terms of the peak anterior COM velocity or COM medial-lateral displacement across the 2-month study, but that females reported more severe symptoms than males. The findings suggest that subjects of both sexes follow the same general gait balance recovery trends and that both sexes report heightened symptoms for at least two months after experiencing a concussion. Across all time points, females reported more symptoms than males, so either males are underreporting their symptoms or females are experiencing more symptoms than males.

The Effect of Chronic Passive Heat Therapy on Forearm Reactive Hyperemia

Presenter: Andrew Jeckell

Mentors: Christopher Minson and Vienna Brunt, Human Physiology

Poster: 31

Major: Post-baccalaureate 

Reactive hyperemia is a transient increase in blood flow that occurs following a period of ischemia (e.g. arterial occlusion) and is indicative of microvascular health. Regular exercise is a critical preventive measure in maintaining reactive hyperemia; however, consistent exercise is difficult or impossible for some people. Recent evidence suggests chronic passive heat therapy (CHT) may result in improvements to cardiovascular health similar to exercise. To examine the effects of 8 weeks of CHT on forearm post-occlusive reactive hyperemia, six healthy university students (21 ± 1 years) underwent hot water immersion 4-5 times per week to maintained rectal temperature of 38.5°C
for 1 hour per session. Before and after 8 weeks of CHT, brachial artery blood flow was measured via Doppler ultrasonography for 3 minutes following a 5-minute forearm arterial occlusion. Data presented as mean ± SE vascular conductance (VC, blood flow divided by mean arterial pressure). In preliminary subjects, change in peak VC from baseline, indicating structural microvascular changes, increased following CHT from 1.77 ± 0.24 to 2.26 ± 0.20 ml/ min/mmHg (p = 0.09). Area-under-the-curve of the hyperemic response, indicating functional changes, increased from 59.7 ± 9.0 to 111.9 ± 13.0 sec.ml/min/mmHg (p = 0.11). CHT appears to produce structural and functional microvasculature changes comparable to that of exercise, and could potentially serve as an alternative method for improving cardiovascular health.

Chronic Passive Heat Therapy Improves Microvascular Nitric Oxide-Dependent Dilation during Skin Local Heating

Presenter: Taylor Eymann

Mentors: Christopher Minson and Vienna Brunt, Human Physiology

Poster: 21

Major: Human Physiology

Vascular dysfunction, often caused by deficient nitric oxide (NO) production, is present in the majority of cardiovascular disease and is first detectible in the microcirculation. Heat stress can increase NO production via
heat shock protein expression. Therefore chronic passive heat therapy (CHT) may improve microvascular health
and lower cardiovascular risk. The cutaneous circulation is easily accessible and represents overall microvascular health. PURPOSE: To observe the effects of 8wks of CHT on cutaneous NO-dependent dilation. METHODS: Seven healthy, sedentary subjects were immersed in either 40.5°C (N=5; CHT) or 36.5°C (N=2; sham group) water for 90min 4-5 times per week for 8 weeks. Before and after the 8wks, two intradermal microdialysis fibers were inserted into the forearm and infused with lactated Ringer’s solution (control) and a nitric oxide synthase competitive inhibitor (L-NNA), to inhibit NO synthase. Increased skin blood flow responding to local skin heating to 39°C, which is a test of microvascular health, was measured at each site using laser-Doppler flowmetry. NO-dependent dilation, calculated as the difference between control and L-NNA sites, was expressed as percent maximal cutaneous vascular conductance (%CVCmax; flow/mean arterial pressure). RESULTS: CHT increased NO-dependent dilation from 27±4 to 36±5%CVCmax (p<0.05). No improvement was observed in sham subjects. CONCLUSION: Our findings suggest heat therapy increases NO production and vasodilation in the human microcirculation. Continued exposure to passive heat may lower cardiovascular risk.

Correlations between Static and Dynamic Asymmetry in Runners

Presenter: Varneet Brar

Mentors: Li-Shan Chou and JJ Hannigan, Human Physiology

Poster: 6

Major: Human Physiology 

Asymmetry between limbs can be assessed statically, as measured by passive flexibility and range of motion (ROM), and dynamically, as measured by joint angle ROM during gait. Both types of asymmetry have been suggested as possible factors in developing a lower limb injury. The purpose of this study was to identify if there is a correlation between static and dynamic asymmetry. Sixty healthy subjects running at least 20 miles per week participated in the study. Dynamic joint angle ROM for the hip and knee was collected as subjects ran continuous laps in the UO Motion Analysis Laboratory using a 10 camera motion capture system. Static flexibility and ROM were measured by a trained clinician using a goniometer. Static and dynamic asymmetry between limbs was then calculated using an established method: the symmetry index (SI). Pearson correlation coefficients were used to test the strength of the relationships between static and dynamic SI. A moderate, significant correlation was found between static hip internal rotation ROM and dynamic hip internal rotation ROM (r = 0.296, p = 0.035). No additional significant correlations were found. As internal hip rotation has been linked to lower limb injury, future studies should investigate whether clinical correction for static asymmetry, especially for hip internal rotation, alters asymmetry during running gait. Correcting these asymmetries may help prevent injury setbacks for both recreational and competitive runners.

Rpb1 Mutations and Interactions with Backtracked RNA in RNA Polymerase II in Yeast

Presenter: Mandi Severson

Faculty Mentor: Diane Hawley

Presentation Type: Poster 82

Primary Research Area: Science

Major: Biology, Human Physiology

Funding Source: NICHD Summer Research Program, National Institutes of Health, $3800

RNA Polymerase II (RNAP II) is an enzyme that catalyzes the synthesis of all mRNA in eukaryotic cells. The Rpb1 subunit participates in RNA elongation in the active site of the enzyme. However, residues in Rpb1 have also been identified as having a potential role in backtracking and arrest. Backtracking occurs when RNAP II moves backward along the DNA, causing the 3’ end of the RNA to dislodge from the active site and bind to nearby RNAP II residues. If the polymerase has not backtracked extensively, RNAP II can spontaneously resume transcription; however, if the polymerase has backtracked too much, elongation stops and RNAP II arrests. This study focuses on creating mutations in Rpb1 residues that interact with backtracked RNA. The point mutations being investigated change nucleophilic amino acid residues into residues that theoretically should have reduced ability to bind to backtracked RNA. If RNAP II residues and backtracked RNA are interacting this way, it may induce less extensive backtracking and decreased incidence of arrest. Currently we are using site-directed mutagenesis to create and isolate mutants, which are then tested in transcription assays to observe the effects on speed and incidence of arrest of RNAP II. Mutants are still being isolated and tested at this time. Results from this study will contribute to our knowledge about backtracking and its function in the transcription cycle, which could help us combat viral proliferation and genetic disease.

Implementation of Artificial Intelligence in Motor Learning

Presenter(s): Sydney Bright − Human Physiology

Faculty Mentor(s): Mike Hahn

Poster 25

Research Area: Human Physiology

Motor control of the forearm flexors and extensors can be impaired due to trauma, such as a stroke, which can hinder the ability to perform daily tasks. In this study, the effects of an Artificial Intelligence (AI) controller on the ability of healthy subjects to learn a novel computer game control task were examined. By using the electromyography sensors of a Myoband in tandem with a Scratch program of Flappy bird, a program was created that adapts to player specific skills. Purpose: The purpose of this experiment was to determine the motor learning outcomes given an adaptive AI motor learning environment. Hypothesis: It was hypothesized that an adaptive AI will result in less motor learning. Methods: Subjects played a modified Flappy Bird game with a multi-channel EMG sensor that fits around the forearm (Myoband). The experiment requires two consecutive days of participation. During the first day, subjects had a 2-minute warm up period followed by 20 rounds of playing the game. The second day consisted of a similar 2-minute warm up period followed by 3 rounds of the game. Results: 46 of 48 subjects have been recorded. So far, the AI group has an average 17 point improvement, linear group has 31 points and the random group has 33 point improvement. Discussion: No statistical test have been done, but from preliminary analysis of the data, the hypothesis seems to be supported.