Table 1.

Systems review with overview of impairments, prevalence, implications, and possible interventions.

Impairments	Prevalence in Population with Ds	Implications	Possible Interventions
Cardiovascular/pulmonary
Impaired Heart Rate Regulation [28]	Unknown	Lower than expected heart rates at all intensities [28].	Ds-specific formula to predict maximal heart rate: 179 − (0.56 × age) [28]
Cardiovascular Dysfunction [11]	Unknown	Decreased endurance, ability to perform daily activities [11].	3–7 days/week at 40–80% of VO2R or HRR, 30–60 total min/day, preferably walking; or running, swimming, stationary cycling [49] When sedentary, ‘start low and go slow’ [51]
Impaired Blood Pressure Regulation [29]	Unknown	Low blood pressure [29], lightheadedness, orthostatic hypotension [52].	If symptoms are present: changes in diet and fluid intake, awareness of body position changes, or medication [30]
Impaired Heart Valve Structure [7]	Mitral valve disease (prolapse or regurgitation) 36%, tricuspid disease (insufficiency or regurgitation) 10%, aortic disease (insufficiency or regurgitation) 8% [7]	Valve dysfunction [7], shortness of breath, difficulty catching your breath, fatigue, weakness, or inability to maintain regular activity level, lower cardiovascular capacity [53].	Surgery; post-surgical rehabilitation with cardiac therapy [53]. Possible need for exercise intensity modifications.
Impaired Pulmonary Pressure Regulation [54]	Associated with congenital heart disease or upper airway obstruction [54]	Pulmonary hypertension [54], fatigue, decreased energy and participation [55]. Possible supplemental oxygen needs.	Surgery for heart defects and treatment of airway obstruction, vasodilator therapies, supplemental oxygen [54]. Possible need for exercise intensity and duration modification.
Musculoskeletal
Impaired Metabolism [7,56]	Overweight: 38% Obese: 34% [7]	Obesity, impacted gait [56], decreased energy, decreased motivation, decreased physical activity [57].	Multifactorial interventions including physical activity, diet and behavioral change [56]
Ligamentous Laxity [22,23]	100% [23]	Increased range of motion at all joints, plays a role in flat feet, hip disorders, patellar instability, atlanto-axial instability, poor grip strength, difficulty with dexterity and fine motor activities, atypical gait [40,41].	Strength exercises to strengthen the muscles surrounding the joints for added support [33,36]. To improve gait: treadmill interventions, orthoses [58]
Pes Planus [22,23,31]	60–76% [23]	Increased risk for hallux valgus, bunions, great toe abduction, atypical gait, decreased gait speed, decreased step length, fatigue with walking/standing, knee pain, decreased motivation to move [31].	Orthotic foot support, insoles, inserts and proper shoes [23,59]
Hypotonia (low tone) [23]	At least 80% [23]	Resting muscle tone, commonly confused with inability to build strength.	Support for PT and OT interventions focused on improving strength and motor planning [36]
Scoliosis [22]	4.8% [22]	Decreased abdominal strength and endurance, decreased trunk strength and endurance, decreased scapular strength and endurance, decreased glenohumeral joint range of motion, compensation patterns for upper extremity movement, leg length discrepancy, atypical gait pattern, radicular pain, pain in neck, back, hip, knee or leg [35].	Remediate: Core strengthening, trunk musculature strengthening, scapular strengthening. Compensate: foot support, shoe lift, bracing [35].
Hip Disorders [7,60]	Between 5 and 20% [7], 28% [60]	Dislocation, dysplasia, and impingement [7].	Strengthen dynamic stabilizers, or surgical treatment [34,61], total hip replacement [7]
Patellar Instability/Dislocation [32]	4–8% [32]	Usually associated with ligamentous laxity. Knee pain, decreased gait endurance, decreased gait speed, fear of participating in dynamic activities.	Functional/asymptomatic: conservative rehabilitation [37] Severe/affecting functioning: surgical intervention [37].
Atlanto-Axial Instability [7]	2–20% [7]	Avoid activities that increase risk for atlanto-axial dislocation [38].	Surgery/Avoid activities that increase risk for atlanto-axial dislocation [38]
Spondylosis or Degenerative Change of the Cervical Spine	33–64% (age-dependent) [7]	Possible pain, possible decreased muscle strength.	Surgical decompression-stabilization, specific exercises to maximize function and decrease pain; Modifications to exercise positions and movement ranges to protect cervical spine and nerves.
Decreased Muscle Strength [8]	Unknown	Decreased ability to perform daily activities [8].	Progressive strength exercise training program targeting major muscle groups following ACSM guidelines [49]
Osteoporosis [7,9]	Increased risk compared to peers in general population [7]	Increased risk of fracture [62].	Multifactorial interventions focused on physical activity, sunlight exposure and vitamin D [7] Dynamic (active) weight bearing [62]
Arthritis [22,24]	7% inflammatory arthritis in children with Ds [22]	Stiffness, pain, avoidance of physical activities [63].	Medication [63], moderate exercise
Neuromuscular
Impaired Balance [47]	Unknown	Impaired static balance, problems with altered somatosensory input [47], atypical gait [40,41].	Various exercise programs to improve balance in anteroposterior and mediolateral directions, treadmill walking, core stabilization, visual-vestibular integration [47,64] Core stability exercises, isokinetic strengthening, and treadmill training [65,66,67,68]
Visual Impairment [43,44]	78% in adults with Ds [69] Increased incidence of nystagmus and strabismus	Issues with focus [43], depth perception, color discrimination, and reduced sensitivity [44].	Appropriate eye wear and/or accommodations
Hearing/Vestibular Impairments [42,45,46]	Hearing impairment up to 73% [45]	Documented differences in inner ear anatomy/shape may impact vestibular function [42,46].	Appropriate hearing aids and/or accommodations. For vestibular impairments: visual-vestibular exercises [70]
Impaired Proprioception [47]	Unknown	Children with Ds have difficulty interpreting somatosensory input to achieve postural control for maintaining balance [47]. Decreased feedback from proprioceptive sensors in joints with ligamentous laxity [71].	Balance training, visual-vestibular exercises [64,70]
Seizures [72]	1–13% [72]	Can develop in infancy but also in the third decade of lifespan [72].	Medication, safety measures [72]
Cognitive, language, and learning abilities
Cognitive Impairment [48,49,50]	Majority of individuals with Ds. Varied degree of cognitive impairment [48]	Slower processing time [48]. Varied degree of cognitive impairment [48]. Difficulty with expressive speech language, speech intelligibility [48]. Potentially reduced and delayed pain responses, not insensitive to pain, but expression of pain is often is delayed and less precise [48]. Preference for sameness and routine [48]. Preference for routines and ‘grooves’ [48]. Difficulty with generalization Excellent visual learners [48].	Motivated by positive social encouragement [48]. Effective strategies include positive reinforcement [50]. Use simple, one-step instructions [49]. Appropriate familiarization and practice needed [49]