Simulation models of obesity : a review of the literature and implications for research and policy

Simulation models (SMs) combine information from a variety of sources to provide a useful tool for examining how the effects of obesity unfold over time and impact population health. SMs can aid in the understanding of the complex interaction of the drivers of diet and activity and their relation to health outcomes. As emphasized in a recently released report of the Institute or Medicine, SMs can be especially useful for considering the potential impact of an array of policies that will be required to tackle the obesity problem. The purpose of this paper is to present an overview of existing SMs for obesity. First, a background section introduces the different types of models, explains how models are constructed, shows the utility of SMs and discusses their strengths and weaknesses. Using these typologies, we then briefly review extant obesity SMs. We categorize these models according to their focus: health and economic outcomes, trends in obesity as a function of past trends, physiologically based behavioural models, environmental contributors to obesity and policy interventions. Finally, we suggest directions for future research.

Too little exercise and too much sitting : inactivity physiology and the need for new recommendations on sedentary behaviour

Moderate-to vigorous-intensity physical activity has an established preventive role in cardiovascular disease, type 2 diabetes, obesity, and some cancers. However, recent epidemiologic evidence suggests that sitting time has deleterious cardiovascular and metabolic effects that are independent of whether adults meet physical activity guidelines. Evidence from “inactivity physiology” laboratory studies has identified unique mechanisms that are distinct from the biologic bases of exercising. Opportunities for sedentary behaviors are ubiquitous and are likely to increase with further innovations in technologies. We present a compelling selection of emerging evidence on the deleterious effects of sedentary behavior, as it is underpinned by the unique physiology of inactivity. It is time to consider excessive sitting a serious health hazard, with the potential for ultimately giving consideration to the inclusion of too much sitting (or too few breaks from sitting) in physical activity and health guidelines.

The ethics of surrogate decision making in medicine : autonomy, paternalism, or a different approach?

Knowing who to involve in treatment decisions when a patient is incapacitated has been the subject of discussion in bioethical, health law and clinical research. The major issues tend to revolve around the tension between exercising a degree of medical paternalism and respecting patient autonomy. Patients are encouraged to exert their autonomy even when they may not be capable of doing so, by means of surrogate consent or advanced directives. While liberal concepts of autonomy are exemplified in western bioethics and legal systems, clinically these decisions remain difficult, and input from medical professionals is sought, raising the issue of paternalism. A framework of bioethics, which places the patient in a relational context rather than a strictly autonomous one, may be a more helpful way of deliberating these difficult decisions

Cane toad or computer mouse? Real and computer-simulated laboratory exercises in physiology classes

Traditional practical classes in many countries are being rationalised to reduce costs. The challenge for university educators is to provide students with the opportunity to reinforce theoretical concepts by running something other than a traditional practical program. One alternative is to replace wet labs with comparable computer simulations. These virtual experiments involve no harm to animals and require little ongoing expenditure. This study documents second-year physiology students' perceptions of and attitudes to simulations by incorporating several computer simulations into the practical program. Computer simulations met the conceptual and, to some extent, the motivational goals of university practical programs. While students enjoyed both wet labs and computer-simulated exercises, overwhelmingly the wet lab provided the more memorable and stimulating learning experience. Based on this study, students suggested that computer simulations could be effectively used to complement rather than replace practical classes where students gain laboratory skills.

Cross-adaptation and bitterness inhibition of L-Tryptophan, L-Phenylalanine and urea : further support for shared peripheral physiology

A previous study investigating individuals' bitterness sensitivities found a close association among three compounds: L-tryptophan (L-trp), L-phenylalanine (L-phe) and urea (Delwiche et al., 2001, Percept. Psychophys. 63, 761-776). In the present experiment, psychophysical cross-adaptation and bitterness inhibition experiments were performed on these three compounds to determine whether the bitterness could be differentially affected by either technique. If the two experimental approaches failed to differentiate L-trp, L-phe and urea's bitterness, then we may infer they share peripheral physiological mechanisms involved in bitter taste. All compounds were intensity matched in each of 13 subjects, so the judgments of adaptation or bitterness inhibition would be based on equal initial magnitudes and, therefore, directly comparable. In the first experiment, cross-adaptation of bitterness between the amino acids was high (>80%) and reciprocal. Urea and quinine-HCl (control) did not cross-adapt with the amino acids symmetrically. In a second experiment, the sodium salts, NaCl and Na gluconate, did not differentially inhibit the bitterness of L-trp, L-phe and urea, but the control compound, MgSO4, was differentially affected. The bitter inhibition experiment supports the hypothesis that L-trp, L-phe and urea share peripheral bitter taste mechanisms, while the adaptation experiment revealed subtle differences between urea and the amino acids indicating that urea and the amino acids activate only partially overlapping bitter taste mechanisms.

Are unilateral and bilateral patellar tendinopathy distinguished by differences in anthropometry, body composition, or muscle strength in elite female basketball players?

Background: Overuse injury to the patellar tendon (patellar tendinopathy) is a major reason for interrupted training and competition for elite athletes. In both sexes, the prevalence of unilateral and bilateral tendinopathy has been shown to differ. It has been proposed that bilateral pathology may have a different aetiology from unilateral pathology. Investigation of risk factors that may be unique to unilateral and bilateral patellar tendinopathy in female athletes may reveal insights into the aetiology of this condition.
Objectives: To examine whether anthropometry, body composition, or muscle strength distinguished elite female basketball players with unilateral or bilateral patellar tendinopathy.
Methods: Body composition, anthropometry, and muscle strength were compared in elite female basketball players with unilateral (n = 8), bilateral (n = 7), or no (n = 24) patellar tendinopathy. Body composition was analysed using a dual energy x ray absorptiometer. Anthropometric measures were assessed using standard techniques. Knee extensor strength was measured at 180°/s using an isokinetic dynamometer. z scores were calculated for the unilateral and bilateral groups (using the no tendinopathy group as controls). z scores were tested against zero.
Results: The tibia length to stature ratio was approximately 1.3 (1.3) SDs above zero in both the affected and non-affected legs in the unilateral group (p<0.05). The waist to hip ratio was 0.66 (0.78) SD above zero in the unilateral group (p<0.05). In the unilateral group, leg lean to total lean ratio was 0.42 (0.55) SD above zero (p<0.07), the trunk lean to total lean ratio was 0.63 (0.68) SD below zero (p<0.05), and leg fat relative to total fat was 0.47 (0.65) SD below zero (p<0.09). In the unilateral group, the leg with pathology was 0.78 (1.03) SD weaker during eccentric contractions (p<0.07).
Conclusions: Unilateral patellar tendinopathy has identifiable risk factors whereas bilateral patellar tendinopathy may not. This suggests that the aetiology of these conditions may be different. However, interpretation must respect the limitation of small subject numbers.

The limits of medicine and the social consequences for sufferers of chronic fatigue syndrome

Chronic fatigue syndrome (CFS) appears to be made up of several clusters of illness categories acting alone or in tandem to cause the decline of health through; fatigue/exhaustion, sensitivity/allergies, pain, general muscle and joint pains, cognitive impairment and gastrointestinal problems. This study investigated how patients interpret, evaluate and respond to the complex and varied symptoms of chronic fatigue syndrome. Data were collected from persons with CFS using a survey (n=90) and an interview (n=45). The researchers investigated how chronic fatigue syndrome is diagnosed by medical practitioners, how the label of CFS is determined and the social consequences for the patient. The results confirm the limited ability of the biomedical paradigm to diagnose adequately and treat effectively 'socially constructed' and medically ambiguous illnesses like CFS. In the absence of a legitimated regime of medical treatment for CFS, a range of often expensive treatments are employed by CFS sufferers, from formal use of pharmaceutical drugs through to 'alternative' therapies, including herbal, vitamin, homeopathic, esoteric meditative techniques, spiritual healing and general counselling are taken in no particular order.

When does physiology limit the foraging behaviour of freely diving mammals?

Diving animals offer a unique opportunity to study the importance of physiological constraint and the limitation it can impose on animal's behaviour in nature. This paper examines the interaction between physiology and behaviour and its impact on the diving capability of five eared seal species (Family Otariidae; three sea lions and two fur seals). An important physiological component of diving marine mammals is the aerobic dive limit (ADL). The ADL of these five seal species was estimated from measurements of their total body oxygen stores, coupled with estimates of their metabolic rate while diving. The tendency of each species to exceed its calculated ADL was compared relative to its diving behaviour. Overall, our analyses reveal that seals which forage benthically (i.e. on the sea floor) have a greater tendency to approach or exceed their ADL compared to seals that forage epipelagically (i.e. near the sea surface). Furthermore, the marked differences in foraging behaviour and physiology appear to be coupled with a species demography. For example, benthic foraging species have smaller populations and lower growth rates compared to seal species that forage epipelagically. These patterns are relevant to the conservation and management of diving vertebrates.

What do we mean by the term "inflammation"? A contemporary basic science update for sports medicine

Most practicing sports medicine clinicians refer to the concept of "inflammation" many times a day when diagnosing and treating acute and overuse injuries. What is meant by this term? Is it a "good" or a "bad" process? The major advances in the understanding of inflammation in recent years are summarised, and some clinical implications of the contemporary model of inflammation are highlighted.

Purchase commitments : Big business bias or solution to the 'neglected diseases' dilemma?

Miniscule research resources are allocated to researching the diseases of developing countries such as malaria, tuberculosis (TB), dengue fever, river blindness, Chagas disease and leishmaniasis, and the strains of HIV prevalent in Africa. Plainly, the patent system and the commercial model of drug research fail to respond to the needs of the poor for the simple reason that the poor exercise little purchasing power. But pressures are mounting on governments and corporations to tackle the ‘neglected diseases’ calamity. An important argument in an intense global debate is that corporations would respond to the needs of developing countries if the diseases of the poor could be made profitable. This is the idea developed by Kremer and Glennerster in a crisply written book, Strong Medicine: Creating Incentives for Pharmaceutical Research on Neglected Diseases.

Investigating women's preference for sildenafil or tadalafil use by their partners with erectile dysfunction : the partners' preference study.

Introduction: Several preference studies comparing a short-acting with a longer-acting phosphodiesterase type 5 inhibitor have been conducted in men. Most men in those studies preferred tadalafil rather than sildenafil, and recent post hoc analysis of one study described several factors associated with men’s treatment preference. No prospective studies have investigated the woman partners’ preferences.

Aim: To investigate the treatment preference of women who were partners of men using oral medications for erectile dysfunction (ED) in a single-center open-label crossover study.

Methods: One hundred heterosexual couples in stable relationships, with male partners having ED based on the erectile function subscale of the International Index of Erectile Function, were randomly assigned to receive sildenafil or  tadalafil for a 12-week phase, followed by another 12-week period using the alternate drug. Male and female participants completed sexual event diaries during both study phases, and the female participants were interviewed at  baseline, midpoint, and end of study.

Main Outcome Measures: Primary outcome data were the women’s final  interviews during which they were asked which drug they preferred and their reasons for that preference.

Results: A total of 79.2% of the women preferred their partners’ use of tadalafil, while 15.6% preferred sildenafil. Preference was not affected by age or treatment order randomization. Women preferring tadalafil reported feeling more relaxed, experiencing less pressure, and enjoying a more natural or spontaneous sexual experience as reasons for their choice. Mean number of tablets used, events recorded, events per week, and days between events were not significantly different during each study phase.

Conclusion: Women’s preferences were similar to men when using these two drugs. While the women’s reasons for preferring tadalafil emphasized relaxed, satisfying, longer-lasting sexual experiences, those preferring sildenafil focused on satisfaction and drug effectiveness for their partner.

Physiology and biochemistry of budburst in Vitis vinifera

Both the physiological and biochemical control of budburst in the grapevine, Vitis Vinifera L. were investigated. It was found that the accuracy of a predictive model for grapevine budburst based on ambient temperature was limited under the experimental conditions. There was a significant correlation of 4.7 ± 0.3 days between the days of maximal xylem exudation and budburst over the 3 years of investigation. The co-relationships between daily xylem exudate volume and a range of environmental parameters were considered. It was found that soil temperature was highly correlated against daily xylem exudation. Ambient temperature and soil moisture were significantly correlated with xylem exudation, however the coefficients of correlation were much lower than that of soil temperature. Rainfall showed only a very limited correlation with daily xylem exudate flow. Seasonal variations in the pH and the carbohydrate and inorganic nutrient concentrations of xylem exudate were investigated. Exudate carbohydrate concentrations fell from 660 µM before the day of maximal xylem exudation to zero levels within 4 weeks. Xylem exudate pH was found to consistently fall to a minimum at the time of maximal exudate flow. Exudate concentrations of the metallic cofactors Ca, K, Mg, Mn and Zn varied directly with daily exudate flow, suggesting some sort of flow-dependent mobilisation of these nutrients. A growth promontory oligosaccharide fraction was prepared by partial acid hydrolysis of grapevine primary cell wall material. This fraction significantly increased control growth of the Lemna minor L. bioassay over a limited ‘window’ of bioactivity. A growth inhibitory oligosaccharide fraction, similar in activity to abscisic acid was isolated from grapevine xylem exudate prior to budburst. The exudate concentration or efficacy of this substance declined after budburst such that there was no apparent growth inhibition. A model is proposed for grapevine budburst whereby an oligosaccharide growth inhibitor is gradually removed from the xylematic stream under the effects of soil temperature, allowing the surge of metabolic activity and vegetative growth that constitute budburst.

Descriptive epidemiology of Australian football injuries presenting to sports medicine clinics

Sports injury prevention has been the focus of a number of recent public health initiatives due to the acknowledgement that sports injuries are a significant public health problem in Australia Whilst Australian football is one of the most popular participation sports in the country, only very limited data is available about football injuries The majority of sports injury data available for this sport is from hospital emergency departments and elite-level injury surveillance Overall there is a paucity of data from treatment settings other than hospitals In particular, there is a lack of information about the injuries sustained by community-level, junior and recreational Australian football participants. One good potential source of football injury data is sports medicine clinics. Analysis of injury presentations to sports medicine clinics was undertaken to provide a detailed description of the epidemiology of Australian football injuries that present to this treatment setting and to determine the implications for injury prevention in this sport. In addition, the data from sports medicine clinics was compared with existing sources of Australian football injury data to determine how representative sports medicine clinic data is of other football injury data sources and to provide recommendations for future injury surveillance n Australian football. The results contained in this thesis show that Australian football is the sport most associated with injury presentation at sports medicine clinics. The majority of injured Australian football players presenting to sports medicine clinics are community-level or junior participants which suggests that sports medicine clinics are a good source of information on the injuries sustained by sub-elite football participants. Competition is the most common context in which Australian football players presenting to sports medicine clinics are injured. The major causes of injuries to Australian football players are being struck by another player, collisions and overuse. Injuries to Australian football players predominantly involve the lower limb. Adult players, players who stopped participating immediately after noticing their injury and players with overuse injuries are the most likely to sustain a more severe injury (i.e. more than four weeks before a full return to football participation and a moderate/significant amount of treatment expected). The least experienced players (five or less years of participation) are more likely to require a significant amount of treatment than the more experienced players. The prevention of lower limb injuries, injuries caused by body contact and injuries caused by overuse should be a priority for injury prevention research in Australian football due to the predominance of these injury types in the pattern of Australian football injuries Additionally, adult players, as a group, should be a focus of injury prevention activities in Australian football due to the association between age and injury severity. Overall, the pattern of Australian football injuries presenting to sports medicine clinics appears to be different than reported by club-based and hospital emergency department injury surveillance activities. However, detailed comparison of sports medicine clinic Australian football data with other sources of Australian football injury data is difficult due to the variable methods of collecting and reporting injury information used by hospital emergency department and club-based injury surveillance activities. The development of a standardised method for collecting and reporting injury data in Australian football is strongly recommended to overcome the existing limitations of data collection in this sport. In summary, sports medicine clinics provide a rich source of Australian football injury data, especially from the community and junior levels of participation. The inclusion of sports medicine clinic data provides a broader epidemiological picture of Australian football injuries. This broader understanding of the pattern of Australian football injuries provides a better basis for the development of injury prevention measures in this sport.

Hypertrophic signalling in human skeletal muscle

Ý-lactoglobulin enriched whey protein isolate, but not carbohydrate, increased growth signalling in human skeletal muscle when consumed in conjunction with resistance exercise. Ageing did not impair the anabolic signalling response; however this response was attenuated after training. These findings help identify strategies to prevent, or delay the onset of sarcopenia.