7. Sport for special groups

Preventing obesity: There has been a marked decline in sports participation among Australian children since 1985, when 86% of children aged 5–14 years were active in sport. In 2003, these levels had fallen to 69% of boys and 54% of girls.1,2 During this same period there has also been an increase in the incidence of childhood overweight and obesity.

Obesity affects 19%–23% of Australian children and adolescents.3 Obesity in adolescence is associated with increased risk of mortality from all causes (independent of adult weight).4 To date, exercise interventions aimed at reducing childhood obesity have been disappointing. Preventing obesity through daily physical activity appears to be a more rewarding approach.

Bone mineral accrual: Recent research suggests that the greatest bone mineral accrual occurs when weight-bearing exercise is performed in the early pubertal years5 (evidence level II; based on the National Health and Medical Research Council system for assessing evidence6). Inactivity during these years may result in children failing to realise their potential for peak bone mass.

Lipid profile and insulin sensitivity: The incidence of type 2 diabetes in children and adolescents is increasing.7 Aerobic exercise improves insulin sensitivity in overweight children (evidence level II),8 and may produce beneficial changes in blood lipid profiles (increased level of high-density lipoprotein [HDL] and decreased level of low-density lipoprotein [LDL]) in children. Cross-sectional studies in young athletes show a positive correlation between aerobic fitness (VO2 peak) and HDL levels.9 With life expectancy potentially falling for the first time in many years because of the effect of the obesity epidemic on adult disease, measures need to be taken earlier to improve insulin sensitivity and blood-lipid profiles.10

Psychological and social reasons: Involvement in team sports is beneficial in promoting socialisation skills and in enabling children to function in a team environment. Physical activity and sport are also very important in children with chronic illness or disability, as a means of “normalising” their lifestyle and improving quality of life.

How much is too much? There are few sports with evidence-based guidelines on this issue. In baseball, however, it was observed that many promising pitchers in the junior baseball leagues were not progressing to senior ranks because of upper limb overuse injuries.11,12 As a result of these findings, there are now strict guidelines on how many balls it is safe to pitch at various ages. Unfortunately, guidelines for other children’s sports are based on “best practice” rather than scientific evidence. Improved injury surveillance in children’s sport will help in the development of such guidelines.

Sports injuries: Trauma produces different injuries in children compared with adults. The cartilaginous growth plates in the immature human skeleton close at different ages, and are more vulnerable to injury at certain times, depending on times of peak growth and age of closure. Mechanisms of injury that tear ligaments in adults are also more likely to cause growth-plate injuries or avulsion fractures in children.

Osteochondroses: These are a group of conditions that affect the growing skeleton and articular cartilage. They are more common in boys than girls, and they may be intra-articular (eg, osteochondritis dissecans), physeal (eg, Scheuermann disease) or extra-articular (eg, traction apophysitis).

They vary in their aetiology and frequency of occurrence. Although the causative factors are not fully understood, it appears that stress, ischaemia and genetics are all implicated to varying degrees. The osteochondroses differ in their treatment and prognosis, with some resolving spontaneously while others require surgical intervention.

Traction apophysitis is common in active children, and is caused by the combination of growth and excessive loading of the vulnerable tendon growth-plate interface, resulting in traction of a muscle–tendon unit on the apophysis. Osgood–Schlatter disease (affecting the tibial tuberosity) is the commonest traction apophysitis followed by Sever disease (affecting the calcaneum; see Case study 1).

Fractures: Peak fracture risk in children coincides with the adolescent growth spurt in both sexes. This is thought to be the result of increased cortical bone turnover at this time of high calcium demand for longitudinal bone growth.14 While weight-bearing activity in childhood may be protective against fractures in adult life, participating in sports at higher levels is associated with increased risk of fracture in prepubertal children.15

Heat-related illness in children: Children are more susceptible than adults when exercising in the heat because they have:

• a higher surface-area to body-mass ratio, so that children absorb more heat from the environment (and, conversely, experience greater heat loss in a cold environment);

• lower exercise efficiency, producing more heat for a given work load;

• a higher sweating threshold and lower sweat rate;

• slowness to acclimatise; and

• a tendency to dehydrate, requiring reminders to drink while exercising.

The risk of heat-related illness in children is increased by obesity, medications such as antihistamines, phenothiazines and anticholinergics, and some diseases (diabetes, cystic fibrosis and cardiac conditions). The risk is also increased in a child who gives a history of previous heat-related illness.

Implementation of injury prevention strategies requires injury surveillance data in children’s sport. One area where successful preventive strategies have been implemented as a result of injury data is in the sport of rugby union. Changes in the scrummaging rules were made in Under-19 rugby in response to a review of spinal cord injuries, which showed an increased number of paralysing injuries in Australian schoolboy rugby since the introduction of the power scrum.16

Improved injury surveillance will enable the establishment of evidence-based guidelines on safe levels of activity and will identify risk factors for injury.

Weight training in children has always been a controversial topic. Its detractors say that it is injurious and does not produce strength improvements in the pre-adolescent child. However, studies now show that weight training can produce strength gains, even in prepubertal children, and that the injury risk is low when training is well supervised (evidence level III-2).17

Strength gains in prepubertal children are thought to be a result of neuromuscular adaptations in the absence of muscle hypertrophy. High-repetition (13–15 repetitions), moderate-resistance programs produce greater increases in strength than low-repetition (6–8 repetitions), high-resistance programs (evidence level III-2).18

Part of the controversy surrounding weight training in children stems from confusion as to the difference between weight training and weight lifting. Weight lifting is a competitive sport where maximal lifts are performed and is unsuitable for children before adolescence.19 Weight training (also called strength training or resistance training) involves repetitive submaximal muscle contractions with the aim of improving strength.

There is currently no good evidence that weight training improves performance or prevents injury in children’s sport.

Primary prevention of cardiovascular disease: In 2001, physical inactivity was second only to tobacco smoking as a cause of total disability and death in Australia.20 Sedentary patients have a 1.5–2.0 times greater risk of cardiovascular events. Recent activity rather than being active earlier in life confers greater benefit.21 Box 1 illustrates the high prevalence of physical inactivity as a cardiovascular risk factor when compared with other well accepted risk factors.

Physical activity can provide benefits in a number of these risk factors:

• Diabetes — exercise increases insulin sensitivity and reduces the incidence of type 2 diabetes.22

• Obesity — activity has had a more significant impact in men than in women, and is generally more easily achieved in men; its effect is greater in overweight rather than in severely obese patients for whom mobility is difficult.

• Lipids — activity lowers triglyceride levels, increases HDL levels and lowers total cholesterol levels.23

• Hypertension — sustained exercise (of at least 50% of achievable activity) typically produces a 5–10 mm fall in both diastolic and systolic blood pressure, although it is less effective in those who are normotensive.

Secondary prevention of cardiovascular disease: While supervised cardiac rehabilitation programs have been shown to improve survival and well being after a cardiac event,24 there is evidence (level II) that continued exercise reduces mortality in patients after myocardial infarction.24

Habitual physical activity improves functional capacity and well being in patients with cardiovascular disease. Recent studies suggest that physical activity improves functional capacity and survival in patients with heart failure.25

Other benefits of physical activity: These include reduced risk of mortality from all causes, and improved quality of life after myocardial infarction (evidence level II).21,26 Physical activity may also reduce depression.27

Musculoskeletal injury: This is the most common adverse outcome associated with adults participating in exercise programs. Injuries occur in both men and women, affecting the lower limbs and, in particular, the knee. Sports participation is associated with a higher incidence of musculoskeletal injuries than involvement in a tailored exercise program (eg, walking, jogging).28

Sudden cardiac death or acute cardiac event: Although habitual physical activity reduces the risk of sudden cardiac death in the asymptomatic population, the increased risk of sudden death during an acute bout of physical activity is well documented.29

People with the following cardiovascular problems should be advised against exercising:

• unstable angina;

• dyspnoea or chest pain with low activity;

• arrhythmia at rest;

• uncontrolled hypertension;

• severe aortic stenosis; or

• uncontrolled heart failure.

Patients with established coronary artery disease should not undertake competitive sports unless they have normal left ventricular function and have received appropriate revascularisation therapy.30

Patients should be advised to stop exercising if they experience:

• chest tightness, discomfort or pain;

• dizziness or light-headedness;

• difficulty breathing or shortness of breath;

• nausea;

• claudication; or

• palpitations or exercise tachycardia.

There are three identified levels of physical activity:

• Low — no noticeable increase in breathing and heart rate with constant movement (eg, slow walking or playing bowls). One could easily whistle while undertaking a low-intensity activity.

• Moderate — slight but noticeable increase in breathing and heart rate, and possible light sweating (eg, brisk walking or slow swimming). One would be able to talk during this activity, but not whistle.

• Vigorous — hard breathing, such as puffing (eg, singles tennis or jogging) making it difficult to talk.

Acute cardiac disease: Following an acute myocardial infarction, a supervised cardiac rehabilitation program is recommended. There is good evidence (level II) that these supervised, exercise programs improve quality of life, reduce total cholesterol levels and reduce subsequent cardiac mortality.24

The exercise program will depend on the patient’s clinical condition. It should commence in a hospital setting, and will usually involve a graded walking activity. The duration and intensity of walking should gradually increase over a 6-week period, building up to 30–60 minutes of exercise a day (see Case study 2).

Chronic cardiac disease: Commence with short-duration (5–10 minutes), low-to-moderate-intensity exercise with regular rest periods interspersed. Gradually increase the duration of exercise if the patient remains asymptomatic. The higher the premorbid level of fitness, the more rapid the progression.

The aim of exercise in this population is to increase the volume of existing activity, and not to introduce new or more intense activities. If symptoms occur, then referral should be arranged.

Since the first epidemiological studies on the benefit of physical activity on cardiovascular disease, it has been well documented that physical inactivity is an important risk factor in population health.31 Further, it is estimated that as much as half of the functional decline associated with ageing is actually a result of disuse and, in the case of the decline in muscle function, is at least partially reversible by resistance training.32

A combination of aerobic and resistance exercise can help counteract a number of the changes that occur in the human body with ageing (see Box 2). The degree of benefit achieved by physical activity depends on:

• the extent of any pre-existing medical condition;

• the type of program provided; and

• the frequency, duration and intensity of exercise (see previous section).

Encouraged by government-sponsored campaigns such as “Active Australia”, “Participation” (Canada) and “Active for Life” (New Zealand), there has been a revolution in sport, with large numbers of older Australians participating in exercise and sport programs, including veterans’ and masters’ sporting competitions around Australia and worldwide.

Masters’ competitors show great diversity across all social groups, medical status and history of sporting participation, with the rate of ageing shown to be a highly individual process.35,36

• Exacerbation of cardiac ischaemia (either asymptomatic or diagnosed);

• Cardiac arrhythmia, with sudden cardiac death (although the absolute risk of sudden cardiac death during any episode of vigorous exertion is extremely low29);

• Dehydration and electrolyte imbalance (may be exacerbated by medications such as diuretics);

• Deterioration of chronic medical condition, such as pulmonary and coronary artery disease, especially if associated with exposure to air pollution in urban environments;37 and

• Musculoskeletal injury (this is the main medical cost of involvement in masters’ competitions38,39 — about one in 10 participants are injured to a degree sufficient for medical assessment; most injuries are acute and are associated with running and pivoting sports, most frequently involving the knee40).

In addition to the usual guidelines for a person commencing sport, the older person should be advised about the following:

• Medical control of pre-existing health problems should be maximised, and older people should be aware of how their medications may affect their response to exercise. Medical assessment of cardiovascular risk factors before commencing an exercise program or sporting activity is advised.

• There should be appropriate graduated progression of training before competition.

• People need to monitor themselves and cease the activity if there are any associated symptoms such as excessive dyspnoea, palpitations, chest pain, syncope, or fatigue. Such symptoms need to be fully assessed before return to sport.

• Older people should avoid training excesses, and allow adequate recovery. They should aim for 10%–15% increments in training load.

• People need to allow adequate time for acclimatisation before competing in new environments.