<p> Recent motor control literature has demonstrated that using verbal cues to direct a performer&rsquo;s attention externally (i.e. toward movement outcome) enhances motor skill performance. The purpose of this study was to investigate how an athlete&rsquo;s focus of attention impacts kinematic performance of the snatch. 12 competitively trained athletes performed blocks of 3 snatch repetitions at 80% 1RM following internal and external instructions. The results indicated that athletes adopting an internal focus increased elbow velocity relative to an external, while an external focus increased horizontal barbell velocity. Internal cues resulted in larger BCH angles at the max height (MH), relative to external, indicating that the athletes are squatting under the barbell too soon. This information adds to the literature suggesting small changes in coaching cues can impact performance significantly. It is recommended that coaches use cues that direct an athlete&rsquo;s attention externally, toward the movement outcome, rather than the action itself. </p>

<p> The purpose of this study was to determine if a single inertial measurement unit (IMU) could be used to estimate the vertical ground reaction force (vGRF) of a vertical jump. To do this 16 college-age participants (8 female, 8 male) preformed three counter movement jumps, three drop jumps, and three squat jumps. All jumps were simultaneously recorded with a force plate (1250 Hz) and an IMU (128 Hz) placed on the sacral-L5 junction. The peak rate of force development, reactive strength index, jump impulse, jump height determined from impulse (h_imp), jump height determined from flight time, and peak force were measured using both the force plate and IMU. There was a significant difference between measuring devices for all dependent variables (p &lt; 0.05) except the h_imp (p = 0.341). In conclusion, this study does not provide a means of accurately estimating vGRF using an IMU.</p>

<p>Trahan, Brittany A. Bachelor of Science, University of Louisiana at Lafayette, Spring 2011; Master of Science, University of Louisiana at Lafayette, Spring 2015 Major: Kinesiology Title of Thesis: Evaluation of the Effects of an Elastic Hamstring Assistance Device During Downhill Running Thesis Director: Dr. Randy Aldret Pages in Thesis: 72; Words in Abstract: 207 ABSTRACT This investigation determined the benefits of the Hamstrong device after downhill running. Sixteen healthy college-aged males volunteered to participate in the repeated measures experimental study. They were assigned to either run with or without the device. They ran for forty minutes at 75% of their calculated VO2 Max speed. The effects of the device or absence of the device were examined as well as the PROM and isometric hamstring strength. The subjects had to repeat the protocol (minus the running) at three different time periods following the exercise. Repeated measures ANOVA did not reveal a significant (F=0.119, p=0.705) effect for the left leg PROM, nor a significant (F=0.016, p=0.977) effect for the right leg PROM. Repeated measures ANOVA did not reveal a significant effect (F=0.578, p=0.128) for the right leg at 90 degrees of extension during isometric strength testing, but there was a significant effect (F=1.027, p=0.032) for the left leg at the same angle. Repeated measures ANOVA did not reveal a significant effect (F=0.797, p=0.063) for the right leg at 135 degrees of extension during isometric strength testing, nor a significant effect (F=0.227, p=0.467) for the left leg at the same angle. There were no other changes regarding the effects of the device regarding myoglobin concentration.

Purpose. The purpose of this dissertation was to determine the effects of chronic plantar fasciitis on intrinsic foot structures with respect to biomechanics, muscle atrophy and muscle energetics. This was accomplished in three parts. Methods. In Part I, a three-dimensional motion capture system with a synchronized force platform quantified multi-segment foot model kinematics and ground reaction forces associated with walking. Healthy individuals were compared to individuals with chronic plantar fasciitis feet. Typical kinematic variables, measures of coupling, phase and variability were examined in rearfoot, forefoot and hallux segments. In Part II, foot and leg magnetic resonance images were taken in subjects with unilateral plantar fasciitis so that within each subject, the healthy limb could be compared to the plantar fasciitis limb. Cross sectional areas (CSA) of the plantar intrinsic foot muscles (PIFM) and tibialis posterior muscle were computed from user-digitized images. In Part III, the metabolic demands of the PIFM were evaluated using phosphorous magnetic resonance spectroscopy at rest and after barefoot walking. Muscle pH and the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) were compared in healthy and plantar fasciitis feet. Results. In comparison to healthy feet, plantar fasciitis feet exhibited significantly (p < 0.05): (1) greater rearfoot motion, (2) greater sagittal plane forefoot motion, (3) fewer rearfoot-forefoot frontal anti-phase movements, (4) reduced rearfoot-forefoot transverse coordinative variability, (5) greater first metatarsophalangeal (FMPJ) joint dorsiflexion, (6) greater FMPJ-medial longitudinal arch (MLA) coupling variability, and (7) decreased vertical ground reaction forces at propulsion. Also, plantar fasciitis feet had 5.2% smaller PIFM CSA at the forefoot compared to contralateral healthy feet. No CSA differences were seen in the rearfoot PIFM or at the tibialis posterior muscle. The PIFM of healthy and PF feet were not significantly different in resting intracellular levels of pH or Pi/PCr, and there were no significant differences in the increase of Pi/PCr from rest to post-walking. Conclusions. In Part I, it was concluded that plantar fasciitis feet exhibit kinematics which are consistent with theoretical causation of the plantar fasciitis injury, that is, the plantar fasciitis foot exhibits excessive motion. Fewer number of anti-phase movements exhibited by plantar fasciitis feet may be an indication of pathology. The ground reaction force results suggested a compensatory pain response. In Part II, it was concluded that atrophy of the forefoot PIFM may destabilize the medial longitudinal arch and prolong the healing process. Lastly in Part III, it was concluded that resting energetics were consistent with muscle free of systemic disease or neuromuscular pathology. The presence of plantar fasciitis did not elicit systematic asymmetries in the metabolic response in comparison to healthy feet. Clinical Relevance. These kinematic results provided some evidence to support the clinical assertion that excessive motion is related to plantar fasciitis. These results also support treatment modalities which clinicians currently use to reduce rearfoot eversion, flattening of the medial longitudinal arch and dorsiflexion of the FMPJ (e.g. foot orthoses, insoles, taping, rocker soles). When treating plantar fasciitis patients, clinicians should assess for PIFM and tibialis posterior muscle atrophy and prescribe targeted exercises when appropriate.

The forefoot (FF) running pattern has been recently advocated to improve running economy and prevent overuse injuries compared to the rearfoot (RF) pattern. However, these claims have not been supported by empirical evidence. The purpose of this dissertation was to investigate the potential advantages of RF and FF patterns to improve running economy and reduce injury risk in 20 natural RF and 20 natural FF runners. The first study found that the RF group was more economical when performing the RF pattern at a slow, medium, and fast speed vs. FF running. Only running at the fast speed resulted in a difference in economy between footfall patterns in the FF group in which RF running was more economical. Therefore, there is no advantage of FF running for improving running economy. The results of the second study indicated that there was a weak to moderate relationship between Achilles tendon (AT) moment arm length and running with either RF or FF patterns. AT force was greater during FF running, which may increase the risk of developing tendon injury. The third study used a modeling approach to find that FF running resulted in greater elastic energy recoil in the gastrocnemius (GA) and the soleus (SO). However, greater mechanical work overall with FF running resulted in no difference in metabolic cost of the GA between footfall patterns but greater metabolic cost of the SO compared to RF running. The fourth study found that shock attenuation was greater during RF running compared to FF running. Greater shock attenuation during RF running was a result of an increased load imposed on the system. Decomposing the vertical ground reaction force in the frequency domain revealed that RF running may have a greater reliance on passive shock attenuation mechanism whereas the FF pattern may have a greater reliance on active shock attenuation mechanisms. These results suggest that previous speculation that the FF running pattern is more economical was not substantiated. It is likely that each footfall pattern exposes a runner to different types of injuries, rather than one footfall pattern being more injurious than another.

Many people with multiple sclerosis (MS) have difficulty with walking, which can decrease their sense of mobility. Gait stability was investigated by studying stride parameters and head movements at preferred and fixed speeds in those with MS. First, walking gait data were recorded at preferred and fixed walking speeds from 19 individuals with MS and 19 controls. Traditional gait parameters were compared, as was swing foot to center of mass (CoM) timing at mid-swing. Second, walking gait data in healthy young adults (n=20) were recorded at preferred speed and while stepping over an obstacle. Study 2 developed novel swing definitions, measures of coordination between the swing foot and body CoM, and head movements as they pertain to field of view orientation during walking. Third, these novel measures were used to study the swing phase of walking in people with MS. The first investigation revealed that the MS group walked with lengthened dual support times across all speeds, but shortened swing time and altered swing foot timing at fixed speeds in comparison to controls. Those with MS adopted a gait strategy with increased dual support time, despite forcing changes to swing that may reduce gait stability. In the second investigation, novel measures of swing showed alterations to phases of swing and in coordination between the swing foot and CoM under different gait tasks. This study also showed that the field of view was closer to the body during obstacle condition steps compared with unobstructed gait. In the third study, these novel measures showed that at all speeds the MS group shortened early swing and lengthened mid swing while late swing remained unchanged compared with controls. Coordination measures illustrated adaptations in swing foot dynamics that may partially ameliorate altered swing foot timing. The MS group oriented the field of view closer to the body earlier in swing compared with controls. Those with MS have functionally adapted swing to increase time over the stance foot and rely more on visual perception, yet shorter early swing may afford fewer opportunities to plan a step or cope with gait disturbances while walking.

<p> Deviations in foot posture, such as pes cavus or pes planus, may be a risk factor for lower limb injury due to compensatory motion of the lower extremity. Due to these compensatory motions dynamic balance has been reported to decline; with decreased dynamic balance risk of injury is increased. Assessing athletes to determine if they present characteristics related to higher risk of injury could potentially reduce the amount of athletes enduring injuries. Therefore, the purpose of the current study was to investigate if history of lower limb injury in the athletic population has a stronger association with foot posture or dynamic balance. A secondary purpose was to determine if foot posture relates to dynamic balance performance. Sixty collegiate athletes participated. Data analyses concluded female athletes had increased injury frequency and severity with severely pronated foot posture while male athletes had increased injury frequency and severity with moderately pronated foot posture.</p>