physical activity, child fitness, and the obesity epidemic greg welk weimo zhu

PHYSICAL ACTIVITY, CHILD PHYSICAL ACTIVITY, CHILD FITNESS, AND THE OBESITY FITNESS, AND THE OBESITY

EPIDEMICEPIDEMIC

Greg Welk Greg Welk Weimo ZhuWeimo Zhu

§15.1 MODEL OF HEALTH RELATED FITNESS Physical activity and physical fitness are

often considered to be synonymous terms but they are fundamentally differences and unique implications for health.

Bouchard & Shepard ， 1997

身体活动休闲活动执业活动家务

与健康有关的体能心肺功能、心态素质新陈代谢能力动作素质、肌肉素质

健 康身心无疾疾病死亡

遗传

Definitions and Descriptions of Physical Activity and Inactivity

Physical activity (PA) is typically defined as “any bodily movement produced by skeletal muscles that results in energy expenditure”(11).

The term exercise is often used interchangeably with the term physical activity but “exercise” refers to a more structured (and planned) form of physical activity that is done with a specific purpose in mind

Longitudinal studies have demonstrated that activity levels decline by about 20-25% during the period from 12-18 (Kemper, Post, Twisk, & van Mechelen, 1999); (Kimm et al., 2000) .

In any case, there is no denying the importance of regular physical activity for youth.

Descriptions and Definitions of Physical FitnessPhysical fitness’s current model : morphological fitness cardiorespiratory fitness metabolic fitness motor fitness and neuromuscular fitness (Bouchard & Shepard, 1994).

Cardiorespiratory fitness Cardiorespiratory fitness includes : Categories of aerobic power, Heart functions (blood pressure) Lung function.

Participation in physical activity that challenges the cardiovascular system (aka aerobic activity) helps to improve cardiorespiratory fitness but the associations between habitual physical activity and aerobic fitness are lower in youth than in adults (Morrow & Freedson, 1994).

Morphological fitness Morphological fitness refers to indicators that

represent the structure and composition of the body such as subcutaneous and visceral adipose tissue, body fat distribution, and bone mineral density.

The primary component of interest is typically body fatness

Low levels of physical activity and high levels of inactivity are causally associated with changes in overweight in children

(Berkey et al., 2000; Gordon-Larsen, Adair, & Popkin, 2002)

Metabolic fitness Metabolic fitness includes biochemical indicators

that are associated with a reduced risk of cardiovascular disease and type II diabetes.

These indicators are known to be influenced by physical activity and to relate directly to health. Many of the Indicators of metabolic fitness cluster together as part of an overall ‘metabolic syndrome’ that predisposes individuals to cardiovascular disease (Lakka, Laaksonen, and Lakka, 2002).

Motor fitness Motor fitness, in this model, refers to

components that can improve the ability to learn and perform complex skills required in some sports and physical activities.

Muscular fitness Muscular fitness includes the

related dimensions of power, strength and endurance.

Muscle endurance and muscle strength are typically considered to be dimensions of health related fitness because there are direct links to health.

Power (the combination of speed and strength), on the other hand, is often considered to be a dimension of skill related fitness (Corbin, Welk, Corbin, Welk, 2007)

Speed is more genetically linked and less responsive to training.

A LIFESPAN MODEL OF PHYSICAL ACTIVITY AND HEALTH

Blair (1989)

An important message in the model is that physical activity and health-related risk factors can both track from childhood into adulthood.

The relationships between physical activity and health outcomes are reciprocal (bi-directional arrows).

Relationships Between Physical Activity, Physical Fitness, and Health

Physical activity has effects on a variety of physiological systems and has been shown to impact each of the different components of HRF.

Activity and inactivity are both important in obesity prevention in youth.

§15.3THE YOUTH PHYSICAL ACTIVITY PROMOTION MODEL Youth Physical Activity Promotion (YPAP)

Model is a social-ecological model that was developed to facilitate the targeting of variables known to influence children’s physical activity behavior (Welk, 1999).

(Welk,1999)青少年身体活动促进模型

Factors Influencing Physical Activity in Youth – Description of the YPAP Model

Predisposing Factors Predisposing factors refers to factors that

may predispose a child to be physically active.

Enabling Factors Enabling factors refers to factors that enable a

child to be physically active. These can include environmental variables such as access to facilities, equipment, and programs that provide opportunities for physical activity.

Reinforcing Factors Reinforcing factors refers to support that a child

receives from significant others to be physically active. Parents, peers and teachers/coaches can all act to directly influence children’s interest and involvement in physical activity by providing opportunities for children to be active through the day.

Strategies for Promoting Physical Activity - Application of the YPAP Model

School Based Physical Activity Promotion Family and Community Based Programming