A Mathematical Model of Human Dynamic Locomotion: Theoretical Bases of the Model

The most current models of dynamic locomotion involve the use of a simple or damped spring-mass system (McMahon and Green, 1979 and Blickhan, 1989). Each of these models uses rather simple approximations (point-like mass, and massless spring) of the complex human anatomy. They use the dynamic variables but neglect the control process completely. These models do not describe a realistic behavior of the system at some instant in time. For example, previous models have kept the system stiffness k, as a constant during the support phase. In reality, however, a complicated process depending on anatomy, posture, and muscle control gives rise to a wide variation in system stiffness as the takeoff leg moves over the support foot. Therefore, the problem faced in developing an analytical approach for coaching is to develop a mathematical model that accurately describes support phase mechanisms. The purpose of this study is to create a mathematical model that reflects all features that determine jump distance. In order to create a more realistic model, it has been necessary to derive equations of motion in a spring-mass system with stiffness k, as a function of time and posture. System stiffness k(t) was calculated from jump data collected using a Bertec force plate. Jump data was also used to test the accuracy of the model by comparing calculations to measurements of a 3D Motion Analysis System. The input parameters used for our model were the touchdown angle, the velocity at touchdown, the mass of the subject, the leg and foot length, and the system stiffness kW. We found the actual jump distance and the calculated distance in agreement. Also the calculated coordinates and velocities as functions of time match the measured data. The very first tests suggest a relative deviation of less than 5%. This refined model is more accurate than previous models of dynamic locomotion. It contains all the features necessary to accurately predict flight distance as a function of initial value parameters and support phase parameters. This model now becomes a tool for coaches to design individual performance in a heuristic manner

A Mathematical Model of Human Dynamic Locomotion: The Development and Application of the Model

Human walking is characterized by a progression of steps such that contact with the ground is never broken. More dynamic activities such as running, hopping, and jumping are characterized by a cycle that includes a phase of support as well as a ballistic flight phase. The objective of individuals engaged in dynamic locomotor activities is to produce and control desired movements in order to achieve a determined performance goal. The problem confronted by teachers, coaches, and trainers is to devise a systematic procedure based on scientific principles which can be used to evaluate motor skills. One solution to this problem is the traditional trial and error approach used by most coaches. In this study the authors have developed a systematic analytical approach using mathematical modelling as the tool. This tool permits the coach to systematically vary the input parameters thus moving toward an ideal technique for that individual without continually stressing the athlete. More specifically, the purposes of this presentation are to: 1) highlight the coaching demands that a realistic mathematical model of dynamic locomotion must meet and 2) show the development of a model that meets all features necessary to calculate the flight distance correctly given various input parameters. Therefore, the presentation will focus on: 1) features necessary for a realistic model of dynamic locomotion, which are anatomy, posture, dynamic variables, control processes, and stochastic, 2) the advantages and disadvantages of existing models, 3) the steps taken in developing our model, and 4) how our model can be used as a tool for coaches to evaluate and design individual performance in a heuristic manner

Effects of a Mindfulness-Based Intervention on Distress, Weight Gain, and Glucose Control for Pregnant Low-Income Women: A Quasi-Experimental Trial Using the ORBIT Model.

BackgroundStress can lead to excessive weight gain. Mindfulness-based stress reduction that incorporates mindful eating shows promise for reducing stress, overeating, and improving glucose control. No interventions have tested mindfulness training with a focus on healthy eating and weight gain during pregnancy, a period of common excessive weight gain. Here, we test the effectiveness of such an intervention, the Mindful Moms Training (MMT), on perceived stress, eating behaviors, and gestational weight gain in a high-risk sample of low income women with overweight/obesity.MethodWe conducted a quasi-experimental study assigning 115 pregnant women to MMT for 8 weeks and comparing them to 105 sociodemographically and weight equivalent pregnant women receiving treatment as usual. Our main outcomes included weight gain (primary outcome), perceived stress, and depression.ResultsWomen in MMT showed significant reductions in perceived stress (β = - 0.16) and depressive symptoms (β = - 0.21) compared to the treatment as usual (TAU) control group. Consistent with national norms, the majority of women (68%) gained excessive weight according to Institute of Medicine weight-gain categories, regardless of group. Slightly more women in the MMT group gained below the recommendation. Among secondary outcomes, women in MMT reported increased physical activity (β = 0.26) and had lower glucose post-oral glucose tolerance test (β = - 0.23), being 66% less likely to have impaired glucose tolerance, compared to the TAU group.ConclusionA short-term intervention led to significant improvements in stress, and showed promise for preventing glucose intolerance. However, the majority of women gained excessive weight. A longer more intensive intervention may be needed for this high-risk population. Clinical Trials.gov #NCT01307683

Yearbook I - PhD research in progress July 2007

An edited volume with contributions from five PhD researchers in the school of Humanities and Social Sciences at the University of East London. Each contributor details their research work in progress. Topics in this volume include: sexuality narratives of women in Turkey, post-apartheid South African culture, Turkey and the European information society, conceptualising feminism in Africa, and discourses of Europeanised cosmopolitanism

Linkage analyses of cannabis dependence, craving, and withdrawal in the San Francisco family study

Cannabis is the most widely used illicit drug in the United States. There is ample evidence that cannabis use has a heritable component, yet the genes underlying cannabis use disorders are yet to be completely identified. This study's aims were to map susceptibility loci for cannabis use and dependence and two narrower cannabis-related phenotypes of “craving” and “withdrawal” using a family study design. Participants were 2524 adults participating in the University of California San Francisco (UCSF) Family Alcoholism Study. DSM-IV diagnoses of cannabis dependence, as well as indices of cannabis craving and withdrawal, were obtained using a modified version of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA). Genotypes were determined for a panel of 791 microsatellite polymorphisms. Multipoint variance component LOD scores were obtained using SOLAR. Genome-wide significance for linkage (LOD > 3.0) was not found for the DSM-IV cannabis dependence diagnosis, however, linkage analyses of cannabis “craving” and the cannabis withdrawal symptom of “nervous, tense, restless or irritable” revealed five sites with LOD scores over 3.0 on chromosomes 1, 3, 6, 7, 9. These results identify new regions of the genome associated with cannabis use phenotypes as well as corroborate the importance of several chromosome regions highlighted in previous linkage analyses for other substance dependence phenotypes

Initiation of a stable convective hydroclimatic regime in Central America circa 9000 years BP

Many Holocene hydroclimate records show rainfall changes that vary with local orbital insolation. However, some tropical regions display rainfall evolution that differs from gradual precessional pacing, suggesting that direct rainfall forcing effects were predominantly driven by sea-surface temperature thresholds or inter-ocean temperature gradients. Here we present a 12,000 yr continuous U/Th-dated precipitation record from a Guatemalan speleothem showing that Central American rainfall increased within a 2000 yr period from a persistently dry state to an active convective regime at 9000 yr BP and has remained strong thereafter. Our data suggest that the Holocene evolution of Central American rainfall was driven by exceeding a temperature threshold in the nearby tropical oceans. The sensitivity of this region to slow changes in radiative forcing is thus strongly mediated by internal dynamics acting on much faster time scales

Heritability of MMPI-2 Scales in the UCSF Family Alcoholism Study

The present study evaluated the heritability of personality traits and psychopathology symptoms assessed by the Minnesota Multiphasic Personality Interview 2nd edition (MMPI-2) in a family-based sample selected for alcohol dependence. Participants included 950 probands and 1204 first-degree relatives recruited for the UCSF Family Alcoholism Study. Heritability estimates (h2) for MMPI-2 scales ranged from .25–.49. When alcohol dependence was used as a covariate, heritability estimates remained significant but generally declined. However, when the MMPI-2 scales were used as covariates to estimate the heritability of alcohol dependence, scales measuring antisocial behavior (ASP), depressive symptoms (DEP), and addictive behavior (MAC-R) led to moderate increases in the heritability of alcohol dependence. This suggests that the ASP, DEP, and MAC-R scales may explain some of the non-genetic variance in the alcohol dependence diagnosis in this population when utilized as covariates, and thus may serve to produce a more homogeneous and heritable alcohol dependence phenotype

Genome-wide linkage scan of antisocial behavior, depression, and impulsive substance use in the UCSF family alcoholism study

Epidemiological and clinical studies suggest that rates of antisocial behavior, depression, and impulsive substance use are increased among individuals diagnosed with alcohol dependence relative to those who are not. Thus, the present study conducted genome-wide linkage scans of antisocial behavior, depression, and impulsive substance use in the University of California at San Francisco Family Alcoholism Study

Cannabis dependence in the San Francisco Family Study: Age of onset of use, DSM-IV symptoms, withdrawal, and heritability

Cannabis is the most widely used illicit drug in the United States, yet the role of genetics in individual symptoms associated with cannabis use disorders has not been evaluated. The purpose of the present set of analyses was to describe the symptomatology and estimate the heritability of DSM-IV criteria/symptoms of cannabis dependence in a large sample of families. Participants were 2524 adults, participating in the University of California San Francisco (UCSF) Family Study of alcoholism. Seventy percent of the sample had ever used cannabis and 13.9% met DSM-IV criteria for cannabis dependence. Younger age at first cannabis use was found to be significantly associated with a shortened survival to becoming cannabis dependent. Although a greater percentage of men met criteria for cannabis dependence, women were found to demonstrate “telescoping” as indexed by a shorter survival time from initial use to dependence as compared to men. A cannabis withdrawal syndrome was identified in users, the primary symptoms of which were nervousness, appetite change, and sleep disturbance. Cannabis use (h2 = 0.31) and dependence (h2 = 0.20), age at first use, individual DSM-IV criteria for dependence, and cannabis-use associated symptoms of depression, trouble concentrating and paranoia were all found to be heritable. These findings suggest that within this population that cannabis use and dependence, as well as individual cannabis dependence symptoms have a significant heritable component, that cannabis dependence is more likely to occur when use begins during adolescence, and that the cannabis dependence syndrome includes a number of heritable untoward psychiatric side effects including withdrawal

Age at Regular Drinking, Clinical Course, and Heritability of Alcohol Dependence in the San Francisco Family Study: A Gender Analysis

We examined gender differences in age of onset, clinical course, and heritability of alcohol dependence in 2524 adults participating in the University of California San Francisco (UCSF) family study of alcoholism. Men were significantly more likely than women to have initiated regular drinking during adolescence. Onset of regular drinking was not found to be heritable but was found to be significantly associated with a shorter time to onset of alcohol dependence. A high degree of similarity in the sequence of alcohol-related life events was found between men and women, however, men experienced alcohol dependence symptoms at a younger age and women had a more rapid clinical course. Women were found to have a higher heritability estimate for alcohol dependence (h2 =0.46) than men (h2 =0.32). These findings suggest that environmental factors influencing the initiation of regular drinking rather than genetic factors associated with dependence may in part underlie some of the gender differences seen in the prevalence of alcohol dependence in this population