Una Anàlisi matemàtica del moviment d'una pilota de futbol durant el vol

En aquest article es presenta un estudi analític i numèric de les equacions tridimensionals que descriuen el moviment d'una pilota que gira a l'aire. L'anàlisi inicial considera coeficients de fregament constants i després s'estén al cas d'un fregament que depèn de la velocitat de rotació de la pilota. S'observa una coincidència excel.lent entre els resultats numèrics, els analítics i els experimentals. La solució analítica ens mostra de manera explícita com el moviment de la pilota depèn de paràmetres com la rugositat, la velocitat i les condicions atmosfèriques. Es demostra la importància d'aplicar models tridimensionals en comptes d'aproximacions bidimensionals.In this paper an analytical and numerical study of the three-dimensional equations describing the motion through the air of a spinning ball is presented. The initial analysis involves constant drag coefficients but is later extended to involve drag varying with the spin ratio. Excellent agreement is demonstrated between numerical and analytical results. The analytical solution shows explicitly how the balls motion depends on parameters such as ball roughness, velocity and atmospheric conditions. The importance of applying three-dimensional models, rather than two-dimensional approximations, is demonstrated

EFFECT OF RUNNING SPEED AND SURFACE INCLINATION ON MUSCLE ACTIVATION DURING TREADMILL RUNNING BY WOMEN

The current study examined muscle activity of the biceps femoris (BF), semimembranosus (ST), vastus lateralis (VL), vastus medialis (VM), lateral gastrocnemius (GL), and medial gastrocnemius (GM) during treadmill running. Female college runners (n=15) ran at speeds of 1.79, 2.24, and 2.68 m·s-1 at 3 different grades of incline (0, 10, and 15%). Right leg Muscle activity was assessed via electromyography and normalized to maximal voluntary isometric contraction. Results indicated muscle activity increased with speed and grade except for SM which showed only grades of 0 and 15% being different; and that for GL and SM only 2.68 m·s-1 differed from other speeds. Muscles of the posterior thigh (BF and SM) were different from the posterior shank (GL and GM); while anterior thigh muscles (VL and VM) did not differ from the others. There were no differences in medial/lateral aspects

Quadriceps function in elderly patients after proximal femoral fracture

The aims of this thesis were twofold. The first was to investigate the practicability, reproducibility and the validity of measurement of leg extensor power (LEP) in Osteoporotic and frail elderly people, in order to determine the changes associated with repeated measurements, and the ability of LEP to discriminate between different patient groups (an Osteoporotic group, frail elderly and patients who have sustained a fractured neck of femur). This was an observational study, using a convenience sample. A series of 10 measurements of LEP (using the Nottingham power rig) were made, with a 30 second rest between measurements. Ten repeated series of measurements were made at 3-day intervals in the Osteoporotic and in the PFF groups. All measurements were made by a single observer. There was a progressive increase in measured LEP over the first 5 attempts at a single visit in all the patient groups, after which performance stabilised and was relatively constant. There were also significant increases in LEP in the Osteoporotic and PFF groups when measured on a second occasion 3 days later, with a mean change of 3.8 Watts (SE 1.6, P=0.02) and 2.1 Watts (SE 0.5, P=0.02) respectively. There was no further significant improvement between a second and third series of measurements in the Osteoporotic group (mean change of -0.5, SE 2.8, P= 0.87). This study found significant increases in LEP with repeated measures at a single visit. This may have been due to a learning effect or a warming up effect of the muscle groups. We have taken the mean of the 6th to 10th measurements at a single visit as the summary measure of LEP. There were also significant increases in LEP when measurements were repeated after a 3-day interval. This was likely to be due to a learning effect. The second, and main aim of the work presented in this thesis was to determine whether systematic progressive high intensity quadriceps training increases leg extensor power and reduces disability in patients rehabilitating after proximal femoral fracture. This study was an open parallel group randomised controlled trial comparing 6 weeks of quadriceps training (40 patients) plus standard rehabilitation versus standard rehabilitation alone (40 patients). The training group exercised twice weekly, with 6 sets of 12 repetitions of knee extension (both legs), progressing up to 80% of their one- repetition maximum. The main outcome measures were leg extensor power (Nottingham Power Rig), functional mobility (Elderly Mobility Scale, which includes Functional Reach and a measure of gait speed), disability (Barthel Index) and perceived health status (Nottingham Health Profile). These were made at baseline, after 6 weeks (at the end of the intervention) and at 16 weeks. Leg extensor power increased significantly in the quadriceps-training group (fractured leg mean improvement at 6 weeks 157% (standard error 16), non-fractured leg 80% (12)) compared to the control group (63% (11) and 26% (8) respectively, unpaired Student t-test P=0.001 and P=0.001 for between group comparisons). Significant improvements in LEP in the quadriceps-training group were maintained at 16 weeks. The data from the intervention study was also used to examine the relationship between LEP/Kg and functional capacity. Correlations between LEP/Kg (fractured leg alone, and combined LEP, (fractured leg plus non-fractured leg)) and disability (Barthel) and functional scores (Elderly Mobility Scale, Sit to Stand, Timed Up and Go, Functional Reach and Gait Speed) and grip strength were determined by calculating Spearman's rank correlation. There were statistically significant correlations for LEP/Kg of the fractured leg and all functional scores with r values ranging between 0.39 and 0.65 for the quadriceps trained group at week 6. The strongest correlations were seen between LEP/Kg and the Elderly Mobility Scale (r=0.65). Similar results were seen for combined LEP/Kg at week 6 for the quadriceps trained group. When training induced changes in LEP/Kg and functional measures were analysed there was a significant correlation between change in LEP/Kg and change in gait speed (r=0.69). This was not the case for combined LEP/Kg. Therefore progressive high-intensity quadriceps training in elderly proximal femoral fracture patients increased leg extensor power and reduced disability. This was accompanied by an increase in energy as measured by the Nottingham Health Profile. This intervention may provide a simple practical way of improving outcome in these patients

CHANGES IN RUNNING GAIT PARAMETERS DURING A 161 KM TRAIL RACE

The current study examined changes in running speed and technique during a 161 km trail race and their relationship to performance. Sixteen participants were video recorded during continuous running for each of the five 32 km loops of the race. Participant’s stride length (SL), stride rate (SR), and speed were calculated. Lap and finish times were also collated from the race results. All variables changed significantly during the race (i.e. Speed?, Lap time?, SL? and SR?). Increased consistency in stride rate and length across the five laps, as well as speed, correlated positively with performance. Increased stride length in laps one, two and four correlated positively with performance. Results indicated that fatigue during the race decreased both speed and SL. Better performers ran faster with a longer SL and were able to maintain their initial speed for longer

Holmes Tremor due to Artery of Percheron Infarct: Clinical Case and Treatment Using Deep Brain Stimulation of the Vim and ZI Targets

Background: Holmes tremor (HT) arises from disruption of the cerebellothalamocortical pathways. A lesion can interrupt the projection at any point, resulting in this tremor. We describe a case of HT due to the rare artery of Percheron infarct and its successful treatment using deep brain stimulation. Case report: A 62-year-old woman with a right medial cerebral peduncle and bilateral thalamic stroke developed HT. Ventral intermediate nucleus (Vim) zona incerta (ZI) deep brain stimulation (DBS) surgery was performed, with improvement in her tremor. Discussion: Our case supports the theory that the more caudal ZI target in combination with Vim is beneficial in treating poorly DBS-responsive tremors such as HT

“Because we have really unique art”: Decolonizing Research with Indigenous Youth Using the Arts

Indigenous communities in Canada share a common history of colonial oppression. As a result, many Indigenous populations are disproportionately burdened with poor health outcomes, including HIV. Conventional public health approaches have not yet been successful in reversing this trend. For this study, a team of community- and university-based researchers came together to imagine new possibilities for health promotion with Indigenous youth. A strengths-based approach was taken that relied on using the energies and talents of Indigenous youth as a leadership resource. Art-making workshops were held in six different Indigenous communities across Canada in which youth could explore the links between community, culture, colonization, and HIV. Twenty artists and more than 85 youth participated in the workshops. Afterwards, youth participants reflected on their experiences in individual in-depth interviews. Youth participants viewed the process of making art as fun, participatory, and empowering; they felt that their art pieces instilled pride, conveyed information, raised awareness, and constituted a tangible achievement. Youth participants found that both the process and products of arts-based methods were important. Findings from this project support the notion that arts-based approaches to the development of HIV-prevention knowledge and Indigenous youth leadership are helping to involve a diverse cross-section of youth in a critical dialogue about health. Arts-based approaches represent one way to assist with decolonization for future generations

Return to Sport and Athletic Function in an Active Population After Primary Arthroscopic Labral Reconstruction of the Hip

Background: Labral reconstruction has been advocated as an alternative to debridement for the treatment of irreparable labral tears, showing favorable short-term results. However, literature is scarce regarding outcomes and return to sport in the nonelite athletic population. Purpose: To report minimum 1-year clinical outcomes and the rate of return to sport in athletic patients who underwent primary hip arthroscopy with labral reconstruction in the setting of femoroacetabular impingement syndrome and irreparable labral tears. Study Design: Case series; Level of evidence, 4. Methods: Data were prospectively collected and retrospectively analyzed for patients who underwent an arthroscopic labral reconstruction between August 2012 and December 2017. Patients were included if they identified as an athlete (high school, college, recreational, or amateur); had follow-up on the following patient-reported outcomes (PROs): modified Harris Hip Score (mHHS), Nonarthritic Hip Score (NAHS), Hip Outcome Score–Sport Specific Subscale (HOS-SSS), and visual analog scale (VAS); and completed a return-to-sport survey at 1 year postoperatively. Patients were excluded if they underwent any previous ipsilateral hip surgery, had dysplasia, or had prior hip conditions. The proportions of patients who achieved the minimal clinically important difference (MCID) and patient acceptable symptomatic state (PASS) for mHHS and HOS-SSS were calculated. Statistical significance was set at P =.05. Results: There were 32 (14 females) athletes who underwent primary arthroscopic labral reconstruction during the study period. The mean age and body mass index of the group were 40.3 years (range, 15.5-58.7 years) and 27.9 kg/m2 (range, 19.6-40.1 kg/m2), respectively. The mean follow-up was 26.4 months (range, 12-64.2 months). All patients demonstrated significant improvement in mHHS, NAHS, HOS-SSS, and VAS (P \u3c.001) at latest follow-up. Additionally, 84.4% achieved MCID and 81.3% achieved PASS for mHHS, and 87.5% achieved MCID and 75% achieved PASS for HOS-SSS. VAS pain scores decreased from 4.4 to 1.8, and the satisfaction with surgery was 7.9 out of 10. The rate of return to sport was 78%. Conclusion: At minimum 1-year follow-up, primary arthroscopic labral reconstruction, in the setting of femoroacetabular impingement syndrome and irreparable labral tears, was associated with significant improvement in PROs in athletic populations. Return to sport within 1 year of surgery was 78%

Application of the combined integral method to Stefan problems

In this paper we present a new, accurate form of the heat balance integral method, termed the Combined Integral Method (or CIM). The application of this method to Stefan problems is discussed. For simple test cases the results are compared with exact and asymptotic limits. In particular, it is shown that the CIM is more accurate than the second order, large Stefan number, perturbation solution for a wide range of Stefan numbers. In the initial examples it is shown that the CIM reduces the standard problem, consisting of a PDE defined over a domain specified by an ODE, to the solution of one or two algebraic equations. The latter examples, where the boundary temperature varies with time, reduce to a set of three first order ODEs

Improving the accuracy of heat balance integral methods applied to thermal problems with time dependent boundary conditions

In this paper the two main drawbacks of the heat balance integral methods are examined. Firstly we investigate the choice of approximating function. For a standard polynomial form it is shown that combining the Heat Balance and Refined Integral methods to determine the power of the highest order term will either lead to the same, or more often, greatly improved accuracy on standard methods. Secondly we examine thermal problems with a time-dependent boundary condition. In doing so we develop a logarithmic approximating function. This new function allows us to model moving peaks in the temperature profile, a feature that previous heat balance methods cannot capture. If the boundary temperature varies so that at some time t > 0 it equals the far-field temperature, then standard methods predict that the temperature is everywhere at this constant value. The new method predicts the correct behaviour. It is also shown that this function provides even more accurate results, when coupled with the new CIM, than the polynomial profile. Analysis primarily focuses on a specified constant boundary temperature and is then extended to constant flux, Newton cooling and time dependent boundary conditions