WAVE DRAG IN FRONT CRAWL SWIMMING

When swimming at the surface, swimmers will experience wave drag. It is observed that above a certain speed, wave height grows rapidly with further speed increase, suggesting that wave drag cannot be neglected at high speed. Therefore, the magnitude of this component of total drag was estimated. Total drag was decomposed in 2 parts; wave and pressure drag. Assuming wave drag to be negligible below 1.6 m/s, the velocity dependence of pressure drag was assessed by drag determinations at speeds below 1.6 m/s. By subtracting the estimated pressure drag from total drag values measured at higher speeds, wave drag was estimated. At a mean speed of 1.89 m/s, mean wave drag was 11.5 N, amounting to 12.1 % of total drag. These results underline the importance of reducing wave drag by diving under the surface after start and turns

The working mechanisms of an environmentally tailored physical activity intervention for older adults: a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>The aim of this study was to explore the working mechanisms of a computer tailored physical activity intervention for older adults with environmental information compared to a basic tailored intervention without environmental information.</p> <p>Method</p> <p>A clustered randomized controlled trial with two computer tailored interventions and a no-intervention control group was conducted among 1971 adults aged ≥ 50. The two tailored interventions were developed using Intervention Mapping and consisted of three tailored letters delivered over a four-month period. The basic tailored intervention targeted psychosocial determinants alone, while the environmentally tailored intervention additionally targeted environmental determinants, by providing tailored environmental information. Study outcomes were collected with questionnaires at baseline, three and six months and comprised total physical activity (days/week), walking (min/week), cycling (min/week), sports (min/week), environmental perceptions and use and appreciation of the interventions.</p> <p>Results</p> <p>Mediation analyses showed that changes in cycling, sports and total physical activity behaviour induced by the environmentally tailored intervention were mediated by changes in environmental perceptions. Changes in environmental perceptions did not mediate the effect of the basic tailored intervention on behaviour. Compared with the basic tailored intervention, the environmentally tailored intervention significantly improved cycling behaviour (τ = 30.2). Additionally, the tailored letters of the environmentally tailored intervention were better appreciated and used, although these differences did not mediate the intervention effect.</p> <p>Discussion</p> <p>This study gave some first indications of the relevance of environmental perceptions as a determinant of changing physical activity behaviours and the potential effectiveness of providing environmental information as an intervention strategy aimed at enhancing physical activity behaviour among older adults.</p

Reduction in sugar-sweetened beverages is not associated with more water or diet drinks

Objective The Dutch Obesity Intervention in Teenagers (DOiT) is a school-based randomised controlled trial that was effective in decreasing the consumption of sugar-sweetened beverages among adolescents. The present study examined, using mediation analysis, whether this decrease in consumption of sugar-sweetened beverages could be explained by an increase in the consumption of water or diet drinks.Design Participants completed a questionnaire about their beverage consumption at baseline and at 8 months (immediately post-intervention), 12- and 20-month follow-ups. A series of multi-level linear regression analyses were performed to examine water and diet drink consumption as potential mediators of the intervention effect on the consumption of sugar-sweetened beverages.Setting Eighteen Dutch secondary schools.Subjects A total of 747 adolescents (mean age: 12&middot;7 years).Results In addition to the DoiT intervention effect of a reduction in the consumption of sugar-sweetened beverages at 8 months (&minus;284 ml/d; 95 % CI &minus;420, &minus;148) and 12 months (&minus;260 ml/d; 95 % CI &minus;360, &minus;160), there was also a significant reduction in diet drinks at 8 months (&minus;52 ml/d; 95 % CI &minus;89, &minus;16). There was no significant difference in water consumption at any follow-up. The decrease in sugar-sweetened beverage consumption could not be explained by an increase in water or diet drink consumption at any time point.Conclusions Interventions aimed at reducing sugar-sweetened beverage consumption may be effective without changing consumption of other beverages. Reducing sugar-sweetened beverages was, however, a main message of the DOiT intervention. It is possible that a concomitant promotion of water may have resulted in a greater increase in water intake and replacement of sugar-sweetened beverages with water.<br /

The Active plus protocol: systematic development of two theory- and evidence-based tailored physical activity interventions for the over-fifties

<p>Abstract</p> <p>Background</p> <p>Limited data are available on the development, implementation and evaluation processes of physical activity promotion programmes among older adults. More integrative insights into interventions describing the planned systematic development, implementation and evaluation are needed.</p> <p>Methods and design</p> <p>The purpose of this study is to give an integrative insight into the development of the Active <it>plus </it>programme applying the six-step Intervention Mapping protocol. The Active <it>plus </it>programme consisted of two theory- and evidence-based tailored physical activity promotion interventions, both comprising three tailored letters delivered over four months and aimed at raising awareness of insufficient physical activity, and stimulating physical activity initiation and maintenance among the over-fifties.</p> <p>The first intervention, the basic tailored intervention, provided tailored letters that intervened on the psychosocial determinants of physical activity. The second intervention, the intervention <it>plus</it>, provided the same tailored information but additionally provided tailored information about physical activity opportunities in the specific environment in which the older adults lived. This environment-based component also provided access to a forum and e-buddy system on a website. A plan for implementation and evaluation is also described.</p> <p>Discussion</p> <p>The planned development of the Active <it>plus </it>programme resulted in two theory- and evidence-based tailored physical activity interventions targeted at the over-fifties.</p> <p>Trial Registration</p> <p>Dutch Trial Register NTR 920</p

The neighborhood social environment and body mass index among youth: a mediation analysis

BackgroundThis study aimed to examine associations between aspects of the neighborhood social environment and body mass index (BMI) in youth both cross-sectionally and prospectively; and whether this association was mediated by physical activity, screen-time and sedentary time.MethodsData were collected in 2004 and 2006 in high and low socio-economic areas of Melbourne, Australia. In 2004, 185 children aged 8-9 years (47% boys) and 359 children aged 13-15 years (45% boys) participated. Parents reported their perceptions of aspects of the social environment (i.e. social networks and social trust/cohesion), and physical activity (i.e. time spent outdoors by their children; and their younger children\u27s walking and cycling trips) and screen-time (i.e. TV viewing, computer use). The older children self-reported their walking and cycling trips and their screen-time. All children wore an accelerometer to objectively assess outside-school hours moderate- to-vigorous physical activity and sedentary time. BMI was calculated from height and weight measured in 2004 and 2006. Multilevel linear regression analyses were conducted to examine associations between the social environment and BMI. Mediation analyses using the products of coefficient method were conducted to determine whether associations between the social environment and BMI were mediated by the time spent in a range of physical activity and sedentary behaviors.ResultsCross-sectional and prospective regression analyses showed that a more positive social network and higher social trust/cohesion was related to lower BMI among children. There was no evidence that time spent in physical activity or sedentary behaviors mediated this relation, despite significant associations between social networks and screen-time and between screen-time and BMI.ConclusionsThe findings suggest that the neighborhood social environment may be important for preventing overweight and obesity in children. Further research investigating the mechanisms through which the neighborhood social environment exerts its effect on BMI is needed. <br /

Toward the optimal strategy for sustained weight loss in overweight cancer survivors:A systematic review of the literature

Purpose: To gain more insight into the optimal strategy to achieve weight loss and weight loss maintenance in overweight and obese cancer survivors after completion of initial treatment, this systematic review aimed to provide an overview of the literature on intervention effects on weight, to describe intervention components used in effective interventions, to identify and synthesize behaviour change techniques (BCTs) and to assess the frequency with which these BCTs were used in effective interventions. Methods: Six databases were searched for original research articles describing weight changes in adult overweight cancer survivors after participation in a lifestyle intervention initiated after completion of initial treatment. Two researchers independently screened the retrieved papers and extracted BCTs using the BCT Taxonomy version 1. Results: Thirty-two papers describing 27 interventions were included. Interventions that were evaluated with a robust study design (n = 8) generally showe

Stakeholder views on taxation of sugar-sweetened beverages and its adoption in the Netherlands

An increasing number of governments worldwide have introduced a tax on sugar-sweetened beverages (SSB) for public health. However, the adoption of such a policy is still debated in many other countries, such as in the Netherlands. We investigated Dutch stakeholder views on taxation of SSB and perceived barriers and facilitators to its adoption in the Netherlands. Semi-structured interviews were conducted in 2019 with 27 stakeholders from health and consumer organizations, health professional associations, trade associations, academia, advisory bodies, ministries and parliamentary parties. Data were analysed using a thematic content approach. The findings reveal that, between and within sectors, stakeholders expressed contradictory views on the effectiveness, appropriateness and (socio)economic effects of an SSB tax. Perceived barriers to the adoption of an SSB tax in the Netherlands included an unfavourable political context, limited advocacy for an SSB tax, a strong lobby against an SSB tax, perceived public opposition, administrative load and difficulties in defining SSB. Perceived facilitators to its adoption included an increasing prevalence of overweight, disappointing results from voluntary industry actions, a change of government, state budget deficits, a shift in public opinion, international recommendations and a solid legal basis. In conclusion, this study shows that several challenges remain to be overcome for the adoption of an SSB tax in the Netherlands. Similar research on stakeholder views in other countries may further inform SSB tax policy processes

Do financial constraint and perceived stress modify the effects of food tax schemes on food purchases: moderation analyses in a virtual supermarket experiment

Objective: To investigate whether financial constraint and perceived stress modify the effects of food-related taxes on the healthiness of food purchases. Design: Moderation analyses were conducted with data from a trial where participants were randomly exposed to: a control condition with regular food prices, an sugar-sweetened beverage (SSB) tax condition with a two-tiered levy on the sugar content in SSB (5-8 g/100 ml: €0·21 per l and ≥8 g/100 ml: €0·28 per l) or a nutrient profiling tax condition where products with Nutri-Score D or E were taxed at a 20 percent level. Outcome measures were overall healthiness of food purchases (%), energy content (kcal) and SSB purchases (litres). Effect modification was analysed by adding interaction terms between conditions and self-reported financial constraint or perceived stress in regression models. Outcomes for each combination of condition and level of effect modifier were visualised. Setting: Virtual supermarket. Participants: Dutch adults (n 386). Results: Financial constraint or perceived stress did not significantly modify the effects of food-related taxes on the outcomes. Descriptive analyses suggest that in the control condition, the overall healthiness of food purchases was lowest, and SSB purchases were highest among those with moderate/high levels of financial constraint. Compared with the control condition, in a nutrient profiling tax condition, the overall healthiness of food purchases was higher and SSB purchases were lower, especially among those with moderate/high levels of financial constraint. Such patterns were not observed for perceived stress. Conclusion: Further studies with larger samples are recommended to assess whether food-related taxes differentially affect food purchases of subgroups

Direct and indirect associations between the family physical activity environment and sports participation among 10-12 year-old European children: testing the EnRG framework in the ENERGY project

BACKGROUND: Sport participation makes an important contribution to children’s overall physical activity. Understanding influences on sports participation is important and the family environment is considered key, however few studies have explored the mechanisms by which the family environment influences children’s sport participation. The purpose of this study was to examine whether attitude, perceived behavioural control, health belief and enjoyment mediate associations between the family environment and 10–12 year-old children’s sports participation. METHODS: Children aged 10–12 years ( = 7234) and one of their parents (n = 6002) were recruited from 175 schools in seven European countries in 2010. Children self-reported their weekly duration of sports participation, physical activity equipment items at home and the four potential mediator variables. Parents responded to items on financial, logistic and emotional support, reinforcement, modelling and co-participation in physical activity. Cross-sectional single and multiple mediation analyses were performed for 4952 children with complete data using multi-level regression analyses. RESULTS: Availability of equipment (OR = 1.16), financial (OR = 1.53), logistic (OR = 1.47) and emotional (OR = 1.51) support, and parental modelling (OR = 1.07) were positively associated with participation in ≥ 30mins/wk of sport. Attitude, beliefs, perceived behavioural control and enjoyment mediated and explained between 21-34% of these associations. Perceived behavioural control contributed the most to the mediated effect for each aspect of the family environment. CONCLUSIONS: Both direct (unmediated) and indirect (mediated) associations were found between most family environment variables and children’s sports participation. Thus, family-based physical activity interventions that focus on enhancing the family environment to support children’s sport participation are warranted