16 participants participated in a 4 week (12 session) balance training protocol. Pre and post-testing used a gait assessment to examine margin of stability and center of pressure. Senaptec sensory ...station was used to examine the relationship between variables of interest and visual skills. 4 groups were distinguished by stable and unstable surfaces and eyes open and eyes closed. There was no relationship between variables of interest and surface type or visual condition.
Introduction: During the development of endurance athletes, it is important to be able to achieve consistent progression of abilities while simultaneously avoiding overtraining. While generic models ...of training fit many athletes, they also cause other athletes to overexert themselves or prevent them from maximizing adaptations to training. Current methods of estimating the intensity of workouts for individuals involve access to an exercise performance lab, relatively expensive equipment, and performing in lab conditions. Many endurance athletes do not have a practical way of performing these tests and others do not desire to be regularly tested in a lab. Alternative methods to determine training intensity outside of a lab setting are scarce. Purpose: The purpose of this study was to develop a practical way for endurance runners to determine the training intensity that they should be training at to allow for consistent physiological adaptation without causing the onset of overtraining syndrome. More specifically, this thesis sought to determine whether the minimum exercise intensity required to promote physiological adaptation could be found and whether this minimum intensity could be found at different altitudes. Methods: The minimum intensity of each participant was found by performing pre-and post-testing of stimulus workouts to determine if a 15-second or greater per mile faster running pace was achieved from the beginning of the study. The pre-and post-testing consisted of four days of 50-minute runs at a heart rate average of 150 bpm. The average running pace of the first four easy running days was compared to the average running pace of the third and fourth easy days after each stimulus run. Each stimulus run was 50 minutes in length and consisted of the first 25 minutes being run in a similar way to every easy run, which meant that the participants often had a heart rate average under 150 bpm for this section. The second 25 minutes of the first stimulus run was performed at a heart rate intensity of 160 bpm and if no adaptation to that stimulus run was observed, then the intensity of the last 25 minutes was increased by 5 bpm. This pattern was repeated until a physiological adaptation was observed or until the participant could no longer perform the study. Results: The researcher found the minimum intensity heart rate for seven of the nine participants (171 bpm, 175 bpm, 170bpm, 175 bpm, 164 bpm, 161 bpm, and 160 bpm for participants 1, 2, 3, 5, 6, 7, and 8 respectively). For these seven participants, an increase in the easy day running pace after the physiological adaptation ranged from 2.73% faster to 6.24% faster than the pre-test easy day running pace. The average number of stimulus runs to cause physiological adaptation was 2.57 with a range of one to four stimulus runs. The minimum intensity heart rate for participants 4 and 9 could not be determined. Conclusion: From the findings of this study, it is possible to determine the minimum intensity to promote overload over the course of a short-term endurance program. Further, it is possible to find this minimum intensity for most athletes and there may be greater potential to find the minimum intensity of more athletes if the protocol is modified to include participants that may adapt to heart rate intensities lower than 160 bpm. The minimum intensity to promote overload could be found at different altitudes, however, the researcher suggests that a larger sample size of case studies would be more effective in supporting these findings.
Approximately 1 out of 3 patients fail to return to previous levels of sport participation after anterior cruciate ligament reconstruction (ACLR), with injury-related fear identified as a potential ...barrier for return to sport. However, we do not know how injury-related fear is associated with other meaningful psychological responses to injury, or how patient perceptions of these psychological responses relate to their rehabilitation experiences. The purpose of this cross-sectional, explanatory sequential mixed-methods study was to explore how perceptions of self-determined motivation, athlete burnout, and injury-related fear affected psychological experiences during ACLR rehabilitation in patients between 4- and 6-months post-ACLR. 13 participants were recruited and completed questionnaires measuring self-determined motivation, athlete burnout, perceived stress, and injury-related fear. A sub-sample of 5 participants participated in a semi-structured interview to further underline patient experiences during ACLR rehabilitation. A strong, positive relationship was observed between perceived stress and injury-related fear (rho = 0.70, p = 0.008). Thematic analysis revealed five themes related to the rehabilitation experience: 1) struggling with the recovery process, 2) acknowledging negative emotional states, 3) drive to return to sport and normal life, 4) understanding and finding purpose in rehabilitation, and 5) successfully navigating the recovery process. These preliminary data suggest that negative emotional states, such as injury-related fear and athlete burnout, may be related to self-determined motivation and perceived stress after ACLR.
This study aims to improve a soccer player’s shot on goal by applying a core exercise intervention to determine its influence on balance, absolute strength, and shot accuracy. Collegiate soccer ...players (N=20) were tested at baseline and after twenty days. Balance was measured using the Star Excursion Balance Test (SEBT) and the Y Balance Test (YBT). Participant shot accuracy was measured using an accuracy net that includes multiple targets. Absolute strength was measured using a one repetition maximum (1RM) bench press test and squat test, and endurance measured using a plank hold test. The control group (CTRL, n=10) continued with activities of daily living (ADL), including regular soccer practices, without implementing a core exercise intervention. The intervention group (INT, n=10) completed a core exercise intervention program consisting of unilateral, dynamic balance exercises. Following the twenty-day intervention period, both groups were tested in all metrics again to determine if any changes occurred. Data were analyzed to determine if balance improved in the core intervention group in the posterior and lateral reaches, as well as their overall strength. Although the results did not indicate significant differences in shot accuracy, the study encourages further research because posterior balance significantly improved in the INT group but not CTRL in all balance tests. Future core intervention may include exercises to improve anterior and medial balance to determine if accuracy is improved by a core intervention program.
Murine and cell culture models have identified Notch1 as a novel endothelial mechanosensor that may exert a protective role for vascular adjustments in response to changes in vascular wall shear ...stress. However, in vivo studies in humans are lacking. Accordingly, we sought to characterize the concentrations of Notch1 extracellular domain (ECD) prior to, during, and following 20-min of altered shear stress in the brachial artery of ten young and healthy adults (6M/4F). Alterations in shear were induced by placing a pneumatic cuff inflated to 220mmHg around the left wrist. Cuffs were also placed below the axilla of both arms and inflated to 40mmHg to trap the released Notch1 ECD. The right arm (no wrist cuff) was treated as a time control. Blood samples were collected from a superficial antecubital vein of both arms at baseline, 20-min of wrist cuff inflation, as well as 1-min and 15-min following wrist cuff release. The Notch1 ECD was quantified from plasma using a commercially available ELISA kit. Duplex ultrasound was used to confirm alterations in shear stress. In the experimental arm, concentrations of Notch1 ECD remained statistically similar to baseline values following 20-min of reduced antegrade shear stress, but were significantly elevated by ~50% (P=0.033) immediately following cuff release, coinciding with a ~100% increase in antegrade shear. Concentrations of Notch1 ECD remained unchanged in the control arm and were statistically similar to baseline values at 15 min recovery in both the control and experimental arm. These data indicate that Notch1 may be an important mechanistic regulator of vascular function, particularly in response to increased antegrade shear.
The purpose of this study was to examine the influential factors involved in Division III college football recruiting. Furthermore, both Division III college football players and coaches rated a ...variety of factors to determine if any discrepancies exist between what players and coaches rate as influential during the college-selection process. Statement of ProblemThere is a considerable amount of research for college football recruiting and general college sports recruiting. However, most of the data in the current literature consists of studies that examined recruiting and the different choice factors from the perspectives of student-athletes choosing among Division I institutions. None of these studies include the perspectives of college coaches and what they determine to be influential factors for players during recruiting. Sources of DataAn anonymous 6-point Likert Scale survey was created using a list of 27 pre-determined choice factors and then distributed via email to 246 Division III college football head coaches across the United States. In the emails, coaches were asked to participate in the study by sharing the attached survey with all members of their current football staff and player roster. For data analysis, a Mann-Whitney U test was done using SPSS software to compare the responses of the two groups. Conclusion ReachedThe players’ and coaches’ ratings of eight of the 27 choice factors were significantly different. Furthermore, the players appeared to place more value in academic-related factors whereas the coaches seemed to value athletic-related ones. This may indicate that a disconnect exists between what NCAA Division III college football players and coaches find important in the college-selection process.
Cancer cachexia (CC) is a devastating wasting syndrome characterized by marked weight loss including skeletal muscle atrophy that affects approximately 80% of cancer patients. Current therapeutic ...treatments including pharmacological and nutritional intervention are insufficient to prevent or reverse it. Prior studies demonstrated lower muscle mass, impaired muscle function, and mitochondrial health in the development of CC. Specifically, mitochondrial fusion protein, Optic atrophy 1 (OPA1) which plays a significant role in skeletal muscle health, is suppressed in the development of CC. Furthermore, most pre-clinical CC studies were mainly focused on males although there are distinct phenotypical differences in skeletal muscle between males and females. Therefore, these studies were set to investigate two independent research questions (Chapter 3 & 4). The purpose of this dissertation project was to investigate skeletal muscle alterations during the development of CC in female tumor-bearing mice (Chapter 3) and determine the efficacy of OPA1 as a therapeutic target for cancer-induced muscle atrophy (Chapter 4). To accomplish this research plan, I completed a series of studies using both cell culture and animal models of CC. For the Chapter 3 experiments, 60 female mice were given either an IP injection of PBS or Lewis Lung Carcinoma (LLC) injection and the tumors were allowed to grow for 1, 2, 3, or 4-wk to assess the time course of cachectic development. We found a dichotomous effect on tumor mass between 3- and 4-wk animals where approximately half of mice between the two groups exhibited low tumor (LT) mass (<1.2 g) while the other half developed higher tumor (HT) mass (>2 g). Furthermore, HT mice revealed greater protein degradation, impaired muscle contractility, and mitochondrial degeneration. These alterations are relatively modest when compared to male data from previous studies. For the Chapter 4 experiments, I utilized both pharmacological (in vitro & in vivo) and genetic overexpression of OPA1 (OPA1 TG) in LLC-conditioned media (LCM) and LLC-induced CC. 72 hours of LCM intervention induced smaller myotubes, which was normalized by BGP-15 treatment and this effect appeared to be driven by suppressed inflammatory cytokine and autophagic-lysosomal pathway (ALP) activity at the mRNA level. 4-wk of LLC implantation was sufficient to induce cachectic phenotype while this effect was normalized in OPA1 overexpression in tumor-bearing mice. In conclusion, my dissertation data suggests both biological sex as an important variable and OPA1 as a novel therapeutic target for cancer-induced muscle wasting.
Within-subject training models, whereby researchers apply an exercise condition to one limb, and a separate exercise condition to the opposing limb, have become routine amongst the exercise ...literature. However, no study has directly tested whether exercising one limb with a high-load condition will influence strength adaptations within the opposing limb, even when the opposite limb is training. Furthermore, muscle post-activation performance enhancement (PAPE) is representing local level changes, however, more research is warranted to understand if this can be differentially impacted with different types (e.g. low load vs. high load) of resistance training. The purpose of this study was to determine if unilateral high-load training influences strength adaptations within the contralateral limb. A secondary purpose was to discern whether PAPE could be increased with resistance training. 116 participants were randomized to one of three intervention groups, and completed 18 training sessions involving isotonic elbow flexion exercise. Group 1 trained their dominant arm only, with a one-repetition maximum (1RM) test (maximum five attempts), followed by four sets of traditional exercise at an 8–12 RM. Group 2 completed the same training as Group 1 in their dominant arm, whilst the non-dominant arm completed four sets of low-load exercise (30–40 RM). Group 3 trained their non-dominant arm only, performing the same low-load exercise as Group 2. Participants were compared for changes in muscle thickness, isotonic elbow flexion 1RM, and postactivation performance enhancement (PAPE). Groups 1 (Δ 1.5 kg) and 2 (Δ1.1 kg) presented the greatest changes in non-dominant strength, as compared to Group 3 (Δ 0.3 kg). Only the arms being directly trained saw changes in muscle thickness, when compared to the untrained limbs. There were no differences amongst groups for changes in PAPE. Unilateral high-load training appears to influence strength changes in the contralateral arm, despite the contralateral arm training with a low-load exercise. Results of this study have broader implications for future research, and suggest that within-subject training models cannot be used when the primary outcome is strength changes.
Statement of the Problem: Previous research has focused on mitigating head impacts to improve sport safety through rule changes and enforcing tackling techniques. However, there is limited ...information on pre-season factors that could be modified to further reduce head impact severity. We aimed to predict head impact biomechanics on factors such as: (1) head protection time, (2) cervical strength, and (3) anthropometric characteristics and helmet dimensions.Methods: Twenty-seven youth tackle football players (age=12.2±0.4yrs, height=161.5±9.7m, mass=55.5±15.2kg) participated in this study. Participants completed a pre-season protocol to analyze all objectives. The first objective included a motion capture analysis of a head protection reaction time and eye movement time protocol during a single- and dual-task performance using a light stimulus. The head protection time consisted of a player strategy, head turn, and hand reaction time (s) while eye movement time (s) was recorded using videography. The second objective used a Multi-Cervical Unit to assess cervical isometric strength (N/kg) and time to peak (s) in flexion, extension, left and right lateral flexion. We also captured time to peak in all 4 directions. The third objective captured anthropometric characteristics and helmet dimensions. We used univariate linear regression model with random intercepts to determine if there were associations between our predictors and head impact outcomes. We also performed separate linear regression models to determine the association of predictors and number of impacts.Results: Our results from the first aim suggests slower eye movement time is associated with an increase in rotational velocity. Our results for aim two indicated stronger cervical strength in the left and right lateral flexion were associated with decreased peak rotational velocity. Slower time to peak left lateral flexion was associated with increased linear acceleration. Lastly, slower time to peak flexion and extension were associated with increased rotational velocity. For our third aim we discovered several anthropometric characteristics and helmet dimensions to influence head impact severity and frequency.Conclusions: Several factors were found to be associated with increased head impact frequency and severity. Our study found potential modifiable factors, interventions, and designs to improve sport safety and mitigate head impacts among youth players.
This study examined the effect of repetitions per set as a function of changing load (percentage of one-repetition maximum) on the accuracy of intraset repetitions in reserve (RIR) predictions in the ...back squat and bench press. Twelve resistance trained men completed three multi-set back squat and bench press training sessions that differed in the number of target repetitions (session 1: 10 repetitions; session 2: 8 repetitions; session 3: 6 repetitions). The last set of each session was performed until muscular failure in which subjects verbally indicated when they perceived 4 RIR and 1 RIR. For each RIR prediction, RIRDIFF perceived RIR - actual RIR was calculated. Differences in RIRDIFF were analyzed using both raw RIRDIFF (including positive and negative values) and absolute RIRDIFF (absolute values) via MANOVA and factorial ANOVA. The model controlled for the covariates session-type, percentage of 1RM, and total repetitions per set. Overall, RIR accuracy at the predicted 1 RIR was significantly greater (i.e., lower absolute RIRDIFF) than at the predicted 4 RIR in both the bench press (4 RIR: 1.00 ± 0.18 vs. 1 RIR: 0.69 ± 0.12; p = 0.028) and the squat (4 RIR: 1.43 ± 0.31 vs. 1 RIR: 0.79 ± 0.26; p = 0.007). No covariates significantly affected RIR accuracy (p = 0.085 – 0.518) at the predicted 1 RIR. However, at the predicted 4 RIR, the covariate repetitions per set affected raw RIRDIFF in both the squat (p = 0.007) and bench press (p < 0.001), indicating that subjects tended to overpredict RIR in lower repetition sets and underpredict RIR in higher repetition sets.These results indicate that trained men can predict RIR close to failure within <1 repetition of error and under various conditions. Further, trained men may overpredict RIR in lower repetition sets and underpredict RIR in higher repetition sets when training further from failure.
