Youth and Adolescents
Children and adolescents experience a decrease in physeal strength during pubescence.56 The cross-sectional area of muscle and isokinetic muscle strength have been shown to increase with age and training, with youth athletes having decreased size, strength, and composition of muscle.57a
In childhood, muscle and bone growth can affect injury incidence. Sullivan et al57b found that players younger than 10 years were rarely affected by injury (< 1 injury/100 participants), whereas the injury rate among older players was reported to be 7.7/100 players. There is an increase in the incidence of overuse injury in adolescents. This increase can be attributed to participation in year-long sport, early specialization, and participation in multiple sports simultaneously as athletes grow older.24 Overuse injuries occur as a result of repetitive submaximal forces to the musculoskeletal system. Coupled with inadequate rest, injury can result. Injury can occur at the musculotendinous unit, bone, bursa, neurological system, and physes. Apophyseal and physeal stress injuries are of particular concern in youth athletes.4 Soft tissue injuries and fractures are common in younger patients because of involvement in physical activity, sports, and accidents. The increased exposure but incomplete development of the musculoskeletal system are likely reasons for increased soft tissue injury. Children aged 10 to 14 years accounted for more than half (56.6%) of SRIs evaluated in the emergency department. The majority (71.1%) of SRIs occurred in boys, and, overall, males had a greater number of injuries.58 The Public Health Agency of Canada reported that 68% of SRIs occur in children aged 10 to 14 years.59 Some injuries more commonly found in patients younger than 20 years include injury to the forearm/hand extensor tendon, thumb ulnar collateral ligament, forearm/hand flexor tendon, acromioclavicular joint, meniscus, ACL, posterior cruciate ligament, MCL, lateral collateral ligament, and peroneal tendon. Middle Age Matheson et al64 examined overuse injury in older and middle-aged athletes. A study of 1407 cases revealed that common injury-associated activities with the younger group (mean age, 30.4 years) were running, fitness classes, and field sports, whereas racquet sports, walking, and low-intensity sports were more commonly associated with injury in the older group (mean age, 56.9 years). The frequency of tendinitis was similar in both age groups, but groups displayed increased frequency of other conditions. The younger group displayed a high frequency of patellofemoral pain syndrome and stress fracture/periostitis, whereas the older group displayed an increased frequency of metatarsalgia, plantar fasciitis, and meniscal injury. Changes in physiology and anatomy caused by aging can increase the incidence of injury. Injuries such as Achilles tendon rupture, patellar tendon rupture, and quadriceps tendon rupture are most commonly seen in middle-aged men. Mallet finger is most commonly seen in middle-aged men and women. This pattern is likely due to degenerative changes in the tendons of patients who remain active.60 Muscle mass decreases approximately 3% to 8% per decade after the age of 30 years.61 The degenerative changes in the tendon that occur with aging include changes in the collagen and noncollagen matrices, decreased tensile strength, and a decrease in volume density. For example, shoulder pain was reported in 24% of high-level tennis players from ages 12 to 19 but increased to 50% for middle-aged participants.62 Older Adults [gallery ids=",236794,236795,,236796,,,,236800,,236797,,236798,236799,236801"] There are many negative effects of the aging process on the function of the musculoskeletal system. Bones become brittle and break more easily. Joints become inflamed, stiff, and deformed, causing painful motion. Older adults may experience more severe effects, including reduced activity tolerance, decreased height due to compressed intervertebral disks, altered posture, reduced reflexes, tremors, weakness from disuse, and contractures from prolonged limited range of motion (ROM). Luckily, physical activity and proper diet can slow or prevent many of these problems because bones and muscles adapt to the stresses placed upon them. As people age, cartilage between bones gradually loses fluid and becomes thinner, therefore resulting in increased compressive forces on the bones. Joints grow stiffer and less flexible, with a decreased amount of fluid present to lubricate the joints. Calcification can occur in the joints, resulting in decreased ROM. Lean body mass decreases, partially because of loss of muscle tissue. Fat is increasingly deposited in the muscle tissue, muscle fibers shrink, and muscle tissue is replaced more slowly. Lost muscle tissue may eventually be replaced with fibrous tissue, which does not contribute to force generation. Eventually, changes in the muscle tissue, coupled with changes in the function of the nervous system, result in decreased muscular force generation, control, and contractile capability.63 These adaptive mechanisms become less effective, and the body becomes more susceptible to injury. Osteoarthritis was 2.5 times higher in older adults compared to a middle-aged group.64 It could be speculated that decreased fluid in the joint, changing biomechanics, decreased extensibility and resilience, and degeneration of connective tissue contribute to the increased frequency of the injuries seen in older adults. Fall prevention has been increasingly popular as the medical community has realized the frequency and financial burden associated with such incidences. Millions of adults, aged 65 years and older, experience a fall each year. Falls are the leading cause of fatal and nonfatal injuries, and it was estimated that, in 2012 alone, the direct medical costs from falls was $30 billion.65 Exercise has been widely recommended as a fall-prevention method. This may be a double-edged sword. Although exercise is recommended for fall prevention and as a remedy for many health issues that arise commonly in the last decades of life, some speculate that soft tissue injuries will increase as older adults remain active later into the lifespan.60 The safety margin of exercise dosage declines with age. Exertional injuries are common in older individuals and are connected to the degenerative process that occurs with aging. Acute injuries in older, active adults are most often associated with activities that require a high amount of coordination, reaction time, and balance. It is recommended that consideration be made regarding activity type and a proper match between ability and requirement be made. Muscle is the most commonly acutely injured tissue among active elderly athletes, and the lower extremities are the most widely affected.66 The benefits of exercise and risk of injury must be weighed appropriately.