EXERCISE IN PEDIATRICS: PHYSIOLOGIC IMPACT
It is widely accepted that exercise and physical activity (PA) have many physical and psychological benefits. Much research has been done to support this in adults. Only recently has data been presented to describe the benefits of exercise in both healthy children and those with chronic disease.
Exercise programs in healthy children have resulted in quantifiable improvements in aerobic endurance, static strength, flexibility, and equilibrium (2). Regular physical activity in adolescence is associated with lower mean adult diastolic blood pressures (3). However, a survey of middle school children showed that the majority are not involved in regular physical activity or physical education (PE) classes in school (4). Despite this, school days are associated with a greater level of PA in children at all grade levels than free days (5). Requiring PE classes in school improves the level of PA in children, but does not lower the risk for development of overweight or obesity (6) without dietary education and modification (7). Children attending after-school programs participate in greater amounts of moderate and vigorous physical activity than their peers (8).
Obesity is increasing in epidemic proportions among children in developed countries. It has been linked to development of the metabolic syndrome (defined as having three or more of the following conditions: waist circumference ≥ 90th percentile for age/ sex, hyperglycemia, elevated triglycerides, low high- density lipoprotein [HDL] cholesterol, and hypertension) (9); both obesity and metabolic syndrome are more common in adolescents with lower levels of physical activity (10). Insulin resistance is reduced in youth who are physically active, reducing the risk of developing type 2 diabetes (11). Exercise in obese children can improve oxygen consumption and may improve cardiopulmonary decrements, including resting heart rate (12).
An eight-week cycling program has been shown to improve HDL levels and endothelial function (13), though in the absence of weight loss, had little effect on adipokine levels (14).Exercise has positive effects on bone mineralization and formation. Jumping programs in healthy pre- pubescent children can increase bone area in the tibia (15) and femoral neck, and bone mineralization in the lumbar spine (16). The effects of exercise and weight bearing may be further enhanced by calcium supplementation (17). The effects on postpubertal teens are less clear.
In children with chronic physical disease and disability, the beneficial effects of exercise are beginning to be studied more systematically. Historically, it was believed that children with cerebral palsy (CP) could be negatively impacted by strengthening exercises, which would exacerbate weakness and spasticity. Recent studies show this to be untrue. Ambulatory children with CP who participate in circuit training show improved aerobic and anaerobic capacity, muscle strength, and health-related quality-of-life scores (18).
In ambulatory adolescents with CP, circuit training can reduce the degree of crouched gait and improve perception of body image (19). Performing loaded sit-to-stand exercises results in improved leg strength and walking efficiency (20,21).
Percentage body fat is greater, and aerobic capacity (VO2/kg) is lower in adolescents with spinal cord dysfunction than healthy peers. Their levels mirror those in overweight peers. They also reach physical exhaustion at lower workloads than unaffected controls (22). Participation in programs such as BENEfit, a 16-week program consisting of behavioral intervention, exercise, and nutrition education, can produce improvements in lean body mass, strength, maximum power output, and resting oxygen uptake (23).
Supervised physical training can safely improve aerobic capacity and muscle force in children with osteogenesis imperfecta (24).
Patients with cystic fibrosis who participate in stationary cycling for aerobic conditioning dislike the tedium of the exercise, but improve their muscle strength, oxygen consumption, and perceived appearance and self-worth (25). Pediatric severe-burn survivors have lower lean body mass and muscle strength compared with nonburned peers; however, both are significantly improved following exercise training (26).Children with polyarticular juvenile idiopathic arthritis have safely participated in aerobic conditioning programs, with improvements noted in strength and conditioning. Those with hip pain may be negatively impacted, having increased pain and disability (27). The exercise prescription in children experiencing hip pain should be modified to reduce joint forces and torques.
Joint hypermobility and hypomobility syndromes commonly result in pain. These patients demonstrate lower levels of physical fitness and higher body mass indexes, likely secondary to deconditioning (28). These and other children with pain syndromes benefit from increased exercise and physical activity.