Distinguishing Between Physical Fitness, Exercise and Physical Activity
Caspersen, Powell, and Christenson (1985) define physical activity as any bodily movement produced by skeletal muscles that result in energy expenditure. The energy expenditure is usually measured in kilocalories, or what is better known as calories. Physical activity can be categorized into four areas: occupational, sports, conditioning, and household.
Exercise is a subset of physical activity (Caspersen et al., 1985). Although physical activity and exercise have similar components (both involve bodily movements performed by working muscles resulting in an energy expenditure or the expenditure of calories), the latter is considered unique because it is planned, structured, and repetitive and has as its main aim to improve or maintain physical fitness. A person who goes to a health club, plays basketball, jogs or walks for a structured time frame is considered to be performing exercise. A person who gardens, mows the lawn, climbs a flight of stairs, or performs housework is said to be performing physical activity. The major difference, however, is that structured exercise usually involves a greater increase in physical fitness than general physical activity because it is performed at a higher intensity level. Nonetheless, both types of movement are needed during the day to confer optimum health benefits.
Physical fitness is defined as a state characterized by an ability to perform daily activities with vigor, as well as the demonstration of traits and capacities associated with low risk of premature development of the hypokinetic diseases, including such diseases as obesity, Type II diabetes, coronary heart disease and osteoporosis (Pate, 1988). The three primary components of physical fitness include cardiovascular endurance, muscle strength and endurance, and flexibility. The primary emphasis of this chapter will be on improving physical fitness. However, it is important to note that although fitness enhancement produces the greatest overall gains in health, any type of movement - exercise or physical activity - in an inherently sedentary population will confer substantial health benefits.
Health and Fitness Research with Persons Who Have Developmental Disabilities Persons with developmental disabilities generally have poor health profiles (Fernhall et al., 1996; Fernhall, 1997). Pitetti and Campbell (1991) noted in a paper entitled, "Mentally Retarded Individuals-A Population at Risk," that adults with developmental disabilities can be considered a high-risk group for developing secondary conditions. In their report they noted the following:
- Adults with developmental disabilities have a lower limit for the onset of old age and a higher mortality rate than the general population.
- Young adults with developmental disabilities living in community residences have cardiovascular fitness levels representative of a sedentary lifestyle.
- Significantly more cardiovascular disorders were seen among individuals with developmental disabilities than the general population.
Data on the health and activity patterns of adults with developmental disabilities, including persons with Down syndrome, indicate that activity levels within this group are far below the general population. In a study by Rimmer, Braddock and Marks (1995) it was noted that less than 10% of adults with developmental disabilities engage in physical activity a minimum of three days a week. In another study by Hoge and Dattilo (1995), adults with developmental disabilities living in the community did not participate in leisure-time activity at nearly the same level as the general population. Most of the activities that the subjects chose to participate in during their leisure time were sedentary in nature, such as watching television or listening to the radio.
In a recent study evaluating the cardiorespiratory fitness of young individuals with developmental disabilities, including Down syndrome, researchers concluded that the peak VO2 levels (the most important measure of fitness) of persons with developmental disabilities with and without Down syndrome were significantly below those of the general population (Fernhall et al., 1996). They concluded that cardiorespiratory fitness must be greatly improved in this population in order to lower the risk of cardiovascular disease. Fernhall et al. (1998) also recently found that the fitness levels of children with developmental disabilities were also very poor, predisposing them to greater health risks in adulthood.
Obesity rates are also high among persons with Down syndrome and developmental disabilities. In one investigation it was noted that more than 75% of female adults with developmental disabilities were obese (Rimmer et al., 1993). Frey and Rimmer (1995) also found that there was a much higher rate of obesity among American adults with developmental disabilities compared to German adults with developmental disabilities. The incidence of obesity among the American sample was 43%, compared to only 16.7% of the German subjects. The investigators concluded that one of the reasons for the major differences in obesity between the two countries was due to lifestyle. The German cohort was more involved in regular physical activity and relied less on vehicular transportation to get to places.
Rubin et al. (1998) found that in a sample of 290 subjects with Down syndrome, 45% of men and 56% of women were overweight using the criteria established in the Healthy People 2000 report of a Body Mass Index (BMI) > 27.8 kg/m2 for men and 27.3 kg/m2 for women. This is substantially higher than the general population, which is 33% for men and 36% for women. Overweight levels were highest in persons who lived at home with their families compared to those residing in a group home.
In two related studies, Rimmer, Braddock and Fujiura (1992, 1994) studied the blood lipid levels of 360 adults with developmental disabilities, including persons with Down syndrome. The investigators concluded that 32% of the female subjects and 54% of the male subjects had cholesterol levels greater than 200 mg/dl. In addition, the total cholesterol to HDL-C ratio was greater than 4.5 in over half the sample. The investigators concluded that a significant percentage of individuals with developmental disabilities, including Down syndrome, could benefit from an exercise program and appropriate counseling on diet and nutrition to lower the incidence of secondary conditions in this population.
In a recent study investigating the strength levels, body composition, and bone mineral density in 16 pre-menopausal women with developmental disabilities, Felix, McCubbin, and Shaw (1998) reported very low levels of strength and higher levels of obesity compared to age-matched controls. Strength levels were approximately 50 percent lower for the adults with developmental disabilities, and the incidence of obesity was 50 percent compared to only 25 percent for the age-matched cohort without developmental disabilities. Despite not finding significant differences in bone mineral density between the two groups, the investigators noted that there were meaningful differences. Femoral bone mineral density was 7.14 percent lower and whole body density was 3.61 percent lower in the adults with developmental disabilities. The mean age of the sample was 28 years, and the researchers noted that in an older population, these differences were likely to be much greater. The low strength levels, high body fat, and lower bone mineral density reported in women with developmental disabilities support previous findings.
Center, Beange, and McElduff (1998) studied the incidence of osteoporosis in 94 adults with developmental disabilities (41 males, 53 females) who lived in Australia. The investigators found that bone mineral density was significantly lower in adults with developmental disabilities compared to an age- and gender-matched control group of women without developmental disabilities. Only 32 percent of the sample participated in vigorous exercise. The investigators concluded that in relatively young persons with developmental disabilities (M age = 36 yrs), low bone mineral was a major concern among this cohort.
In summation, the literature is replete with studies that have reported inferior health and fitness levels among persons with developmental disabilities. This is likely to predispose them to greater health complications as they reach older adulthood. There is an urgent need for health professionals to begin to identify fitness intervention models that effectively increase the physical activity and fitness levels of persons with developmental disabilities.
Developing a Fitness Program for Persons with Developmental Disabilities Persons with developmental disabilities have the same essential needs as the general population in terms of improving their health and fitness. An exercise program should include the three common elements: cardiovascular endurance, strength and flexibility. Each of these is described below.
The most important component of a fitness program is cardiovascular endurance (Oja & Tuxworth, 1995). Most of the research on the benefits of exercise has shown that improving the capability of the heart, blood vessels and lungs to transport oxygen to working muscles is the key element in reducing cardiovascular disease (e.g., stroke, heart disease). Therefore, a fitness program should employ the 3-2-1 principle. This principle states that in a 1-hour block of time, 30 minutes should be spent on cardiovascular activity, 20 minutes on strength, and 10 minutes on flexibility. If time is limited to a half hour, it is best to skip the strength and flexibility components and perform 30 minutes of cardiovascular activity. (Strength only needs to be performed three days a week.) Although the 3-2-1 principle will depend on the individual's greatest needs, the emphasis for most people will remain highest for cardiovascular activity and lowest for flexibility.