Down syndrome is the most commonly identified genetic cause of intellectual disability [1
] with over 1 million people with Down syndrome living worldwide. Physical impairments commonly associated with Down syndrome include a higher prevalence of heart defects, muscle weakness and hypotonia, and low cardiovascular fitness [2
Muscle strength is important for young adults with Down syndrome. Due to their intellectual disability, their workplace activities typically emphasise physical rather than cognitive skills such as packing boxes of confectionery, sorting and cutting clothing, and assembling automotive parts [6
]. These physical work tasks can be problematic for young adults with Down syndrome as they typically have muscle weakness, hypotonia, and low cardiovascular fitness [2
]. Their upper [7
] and lower limb [3
] muscle strength is up to 50% lower than their peers with typical development and their peers with intellectual disability without Down syndrome [8
]. Muscle weakness contributes to a reduced ability to perform activities of daily living [9
], and can negatively impact their vocational and social development in the workforce [10
] as well as their quality of life [13
A systematic review [14
] suggested progressive resistance training (PRT) improves muscle strength in people with Down syndrome. PRT is a form of strength training where relatively high loads are lifted for a relatively low number of repetitions before muscular fatigue, and the load is progressed as the person gets stronger [15
]. PRT is regarded as the best way to improve muscle strength when implemented with sufficient intensity and progression of load [15
]. PRT is an appropriate intervention for adolescents and young adults with Down syndrome as they can master the repetitive skills required by this form of exercise and it can be conducted in an integrated and social community setting. Participation in team sports can be difficult for the majority of this group as they do not possess the coordination or agility to keep up with their peers without disability.
Only 3 published trials [6
] have investigated the effects of a stand-alone PRT training programme in people with Down syndrome. Two of these trials [16
] found improved upper and lower-limb muscle strength with training but neither reported the effects of the programmes on functional activities. The findings of these two trials were also limited because neither employed an assessor who was blind to group allocation nor did they include a control group so the effects of the training might have been due to series effects. The third trial is the only published RCT to investigate the effect of a stand-alone PRT programme and found it significantly improved upper limb muscle endurance for adults with Down syndrome (mean difference chest press repetitions at 50% 1 RM was 16.7, 95% CI 7.1 to 26.2, p = 0.002) [6
]. The 10-week community based PRT programme was compared with usual care in 20 adults with Down syndrome (13 men, 7 women; mean age 26.8 ± 7.8 years) and also observed improvement in upper limb muscle strength (mean difference, chest press 1 RM 8.6 kg, 95% confidence interval -1.3 to 18.5 kg, p = 0.08) and upper limb functional activity at 10 weeks (mean difference grocery shelving task -20.3 s, 95% CI -45.7 to 5.2 s, p = 0.11) that approached but did not reach statistical significance. A limitation of this trial [6
] was that the small sample size meant that it lacked power to detect clinically significant differences between the groups.
Research on barriers and facilitators for exercise has found people with Down syndrome require close supervision from a support person to participate in a high intensity exercise programme. Supervision is necessary to ensure they exercise at the correct intensity, to provide physical and motivational support and to help keep them focused [18
]. Similar findings have been reported in studies on aerobic training for people with Down syndrome where constant encouragement was necessary to keep the participants going, as if left to themselves they would stop immediately especially if there were any distractions or diversions [19
]. Social interaction has also been identified as the main reason people with Down syndrome participate in exercise. Similar themes have been identified by other researchers [20
Improving community participation in exercise is a priority for young people with Down syndrome as they typically do not participate in the recommended levels of activity. A recent study suggests 75% of adolescents with Down syndrome do not meet the Australian guidelines on activity levels compared to 15-25% for their peers with typical development [21
]. Muscle weakness is a specific impairment that contributes to a low level of fitness and a reduced ability to complete daily activity in people with Down syndrome [9
]. Therefore, apart from the effect of muscle weakness on meaningful activities like work task performance, a related and important issue for people with Down syndrome is the extent to which their muscle weakness contributes to their low level of physical activity.
While an increase in muscle strength might be expected to improve the amount of physical activity they undertake, no studies have investigated this to date. Strength in people with Down syndrome has been associated with higher levels of physical activity. A study of people with Down syndrome who trained for Special Olympics events an average of 4.9 hrs per week had significantly greater isometric muscle strength of the lower back and limbs compared to people with Down syndrome who were sedentary. Decreased muscle strength is believed to impact on the ability of young adults with Down syndrome to perform everyday activities, including walking and running [22
]. Therefore, improving muscle strength could potentially increase the amount of activity they undertake.
Implementing an exercise programme during adolescence is advantageous. Good exercise habits established early in life are important predictors of healthy activity patterns in adulthood [23
]. Children with Down syndrome become less active during adolescence [25
]. Their low levels of activity is concerning because of its association with obesity, type 2 diabetes, osteoporosis and cardiovascular disease [26
]. Over 80% of people with Down syndrome are overweight [27
] and people with Down syndrome are 10 times more likely to die from diabetes than the general population [28
]. Therefore, it is important that young adults with Down syndrome are encouraged to engage in physical activity and exercise [29
A student-led community-based PRT programme for young adults with Down syndrome is innovative and provides the supervision and social interaction people with Down syndrome need to exercise. Typically developing adolescents often exercise at a gym [30
] and so this is a reasonable recreation option for adolescents with Down syndrome. Physiotherapy students make the ideal support people for adolescents with Down syndrome as they have an understanding of the principles of exercise training, and are close enough in age that the social relationship between the pair is meaningful. An additional beneficial outcome of this arrangement is that physiotherapy students have an opportunity to gain a unique experience of disability, something that is often missing from their professional training due to a lack of appropriate placements.
In summary, the published literature provides evidence that PRT can improve muscle strength and endurance in people with Down syndrome. There is now a need for a fully powered randomised controlled trial to investigate the effects of PRT on work task performance and level of physical activity for young adults with Down syndrome. We hypothesise that a community-based strength training programme will improve work task performance in adolescents and young adults with Down syndrome. The primary aim of this study, therefore, is to investigate if a community-based strength training programme can improve work task performance in adolescents and young adults with Down syndrome. The secondary aims are to investigate: (a) if the exercise programme leads to an improvement in muscle strength, and (b) if the exercise programme leads to an increase in the amount of moderate and vigorous level physical activity undertaken by adolescents and young adults with Down syndrome.