Browsing by Subject "Force"

Now showing 1 - 5 of 5
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    Aerobic training effects on rate of force production
    (2013-05) Carroll, Christopher K.
    Aerobic training has been negated as a training modality for many anaerobic sports and their participating athletes. The trend is due to a growing theory that aerobic training has the potential to inhibit strength, power, and/or overall anaerobic performance. However, there are studies that have produced conflicting as well as inconclusive findings when aerobic conditioning is performed concurrently with strength training. PURPOSE: The primary purpose of this research was to investigate the effects of aerobic training on anaerobic output defined by vertical jump (VJ), broad jump (BJ), and Wingate testing results in male and female recreationally trained runners over a period of 16 weeks. Additionally, body weight (BW), percent body fat (PF), pre-exercise resting heart rate (RHR), VO2max and anaerobic threshold (AT) were examined as exploratory measures. METHODS: A 16-week observational pre- and posttest design was used to determine the effects of a single phase aerobic training specific to preparing for a marathon on measures of anaerobic power as well as anthropometric measures and body composition. RESULTS: The primary findings demonstrated that after 16 weeks of a specified aerobic training for a marathon, there was no change in VJ (p = 0.307) and there was an increase in BJ (p = 0.011). There was no change in peak power (males p = 0.08, females p = 0.114). There was an improvement in fatigue index (males p = 0.017, females p = 0.006) during the 30-second Wingate cycle test among study subjects, however there was a decrease in PF (p=0.0001). In addition, marginal increases in VO2max (p = 0.055) as well as decreases in PF (p = 0.001) and RHR (p = 0.001) were observed. CONCLUSION: The findings do not support the notion of the universal nature that aerobic training has a negative effect in the development of rate of force production. However, the adverse effect may hold true in regards to explosive strength due to limited neural activation. The interference effect may also be present in a concurrent setting where aerobic and anaerobic training protocols are assessed in exclusively aerobically trained subjects. However, in a sport performance setting, as well as in general public health, the training for physical fitness requires the development of muscle strength, power and endurance. The present findings indicate that the influence of aerobic training is an important factor for not only overall fitness, but it does not appear to constrain anaerobic performance.
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    Effect of Gingival Margin Design on Clear Aligner Material Strain and Force Delivery
    (2021-06) Brown, Brooke
    Aim: To evaluate the effect of the gingival margin design on strain distribution and forces and moments delivered from Essix ACE and Zendura FLX to a maxillary central incisor during labial tipping about a simulated center of rotation.Methods: Clear aligners (CAs) were prepared from two materials, Essix ACE and Zendura FLX, in 0.030 mil (0.75 mm) thickness. For each material, three margin designs—scalloped, straight cut 0.75 mm above gingival zenith and straight cut 1.5 mm above gingival zenith—were fabricated with no tooth movement and 2.4 degrees of labial tipping about a simulated center of rotation, for a total of 12 designs. Three CAs were manufactured for each of the 12 designs, for a total of 36 aligners. Forces and moments were recorded with a force measuring device in all six degrees of freedom, from the center of the crown and the center of resistance (COR).
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    Force reflecting pneumatic hand tools.
    (2009-12) Johnson, Peter Knox
    Pneumatic hand tools have been used for many decades. These tools help users accomplish tasks with much less effort than is required with manual tools. However, one significant drawback of pneumatic tools compared with manual hand tools is that the user is disconnected from the output forces the tool is creating. This has various safety and functionality issues. A pair of pneumatic powered loppers was developed to demonstrate the potential of force-multiplying, pneumatically powered hand tools with haptic control. A purely mechanical control system was tested and found to provide proportional feedback over the range of operating conditions. The work required to cut through different sizes of dowels and branches was also calculated and tested against the prototype to determine the amount of compressed air needed to operate the loppers. It was determined that the loppers could have an onboard, high pressure tank that could provide enough energy for average homeowner use. For commercial use a larger external tank would be required.
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    Hand force profiles of women with hand osteoarthritis during sealed jar opening
    (2014-10) McGee, Corey Weston
    Purposes: Joint protection strategies are often recommended for individuals with hand arthritis. However, there is little research regarding their effectiveness or on the use of measures in evaluating the effects of joint protection strategies. The purposes of this study were to 1) evaluate the effects of the type of grasp, the hand grasping the lid, and the use of non-skid material on the hand forces acting upon a jar lid when breaking a jar's seal, 2) examine the hand forces requirements when opening a sealed jar and 3) investigate relationships between several measures of hand function and the actual hand forces used during the everyday task of opening a sealed jar in order to validate their use in measuring the effectiveness of joint protection strategies such as using a counterforce such as a table or opposing extremity and using a nonskid material.Methods: A novel jar device created by McGee, Nuckley, and Mathiowetz was used to gather measurements of grip force, compressive force down through the lid's axis of rotation (Fz) and compressive force perpendicular to the side of the lid (Fx/Fy) when attempting to open a `sealed jar'. The jar lid's torque requirement was set to 4.24 N*m, a torque commonly imposed by the manufacturer when creating a seal on larger diameter jars. Thirty-one women with hand osteoarthritis were asked to complete 16 jar opening simulations by alternating three different factors: hand turning the jar lid, position (supinated/vertical and oblique/diagonal), and use of a non-skid material. After each jar turning simulation, participants were asked to report their perceived level of pain and exertion using the 0 to 10 scales of the NRS and Borg CR10, respectively. Additional measures of hand function were quantified to determine if and to what extent they predicted success and the capacity to generate forces when opening a sealed jar.Results: The impact of arthritis on our sample's function was modest (AIMS2-SF2 Total Health Score; x = 10.62) and the distribution of arthritis between hands was not dissimilar. Use of the supinated grasp required less force/time in Fx [F(1,419)=30.5, p<.0001], Fy [F(1,419)=34.5, p<.0001], and Fz than power grasp [F(1,419)=23.5, p<.0001]. Participants used less grip force to twist the lid with their left hand than with their right hand [F(1,419)=21.7, p<.0001]. Participants also perceived their effort to be less when using their left hand, a supinated grasp, and non-skid material. Additionally, participants rated their pain as lower when using their left hand and when using a supinated grasp. Lastly, a left supinated grasp with a non-skid material was a significantly more successful strategy to open jars than was any other (χ2=9.4, p<.001). Across all approaches, participants who were successful used 149.2±6.2 N of grip force and 47.8±2.8 N of `compensatory' forces when opening the sealed jar. Perceived effort was a significant positive predictor of grip force across time and is a significant negative predictor of peak M(z). Palmar abduction of the stabilizing thumb was a significant positive predictor of torque and a negative predictor of grip forces. Total active motion of the stabilizing and turning thumbs was a positive predictor of grip force and an increase in pain from baseline was a significant negative predictor of grip force and a positive predictor of torque.Conclusions: The counterforce offered by the supinated `stabilizing' hand results in the use of fewer compensatory forces by the turning hand. The left hand requires less grip force to successfully open a sealed jar and pain as well as perceived effort were least among those who used a non-skid material when opening. This data supports that women with hand arthritis will know more success, perceive less pain and effort, use less grip force, and will more efficiently generate the forces required to break the seal of a large jar when using a left hand, supinated counterforce, and non-skid material. These findings validate the use of non-skid material to reduce hand forces with jar turning but only when combined with a supinated approach. Perceived effort, and a change in pain from baseline are strong predictors of the forces used during jar opening and thus should be considered when considering the effectiveness of joint protection strategies used by women with hand osteoarthritis when attempting to open sealed jars. Other measures of hand function were also predictive of the hand forces generated when opening a sealed jar and these factors should be considered during assessment and intervention planning.
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    Human iPSC-Derived Cardiac Myocytes: Toward an In Vitro Model of Cardiac Physiology
    (2017-05) Wheelwright, Matthew
    Cardiovascular Disease is a growing public health issue in the modern world, with a high incidence rate that continues to increase, and poor mortality rates. Recent technological advances have made it possible to efficiently derive cardiac myocytes from human induced pluripotent stem cells (hiPSC-CMs). These have been seen as a model for human heart disease, as well as a potential source for cellular transplantation into failing diseased heart tissue. Many laboratories have devoted substantial effort to examining the functional properties of hiPSC-CMs, including electrophysiology, intracellular calcium handling, and gene/protein expression and force. In the first part of this thesis, we utilize traction force microscopy (TFM) to determine the maximum force production of isolated hiPSC-CMs under varied culture and assay conditions. We elucidate here the relationship between cell morphology and force production, and find a significant relationship between cell size and force. HiPSC-CMs developing in culture for two weeks produce significantly less force than cells cultured from one to three months and hiPSC-CMs cultured for three months resemble the cell morphology of neonatal rat ventricular myocytes. Unexpectedly, hiPSC-CMs produce less force when assayed on increasingly stiff substrates, and generate less strain energy. Finally, hiPSC-CMs cultured in conditions of physiologic calcium concentrations are larger and produce more force than cells cultured in standard media. In the second part of this thesis, we address the concept of immaturity in hiPSC-CMs, and attempt to accelerate maturation. We use genome editing to engineer hiPSC-CMs that contain an inducible gene expression cassette, in order to overexpress two proteins associated with maturity: SERCA2a and cardiac troponin I (cTnI). We find that we are able to overexpress both proteins in differentiated hiPSC-CMs after two weeks of treatment with doxycycline. SERCA2a-overexpressing cells showed significant alterations in physiologic function, including increased chronotropy and decreased time to peak in calcium transients following treatment with isoproterenol, a β-adrenergic agonist. Furthermore, using an impedance-measuring system to track contractility kinetics, we found that SERCA2a-overexpressing cells had shortened time to peak and time to baseline after gene induction, with continued response to isoproterenol. As a sign of maturation, SERCA cells also expressed increased cTnI, a key marker of maturity. Using RNAseq, we found that cTnI-overexpressing cells had marked, global changes in their gene expression profile. Key findings include upregulation of genes associated with cardiac contractility and development, such as cardiac myomesin and tropomyosin and ryanodine receptor, and downregulation of genes associated with pacemaker and ventricular cell types, such as HCN and GREM2, and genes associated with skeletal myocytes, such as skeletal muscle actin. Overall, our findings show that hiPSC-CMs have physiologic function similar to that of immature cardiac myocytes, but that we are able to induce maturation by overexpression of genes associated with maturity.