Exercise as it relates to Disease/The impact of resistance training on young people with cerebral palsy

Progressive resistance training and mobility-related function in young people with cerebral palsy: a randomized controlled trial
This is a review of research presented in the Journal of Developmental Medicine & Child Neurology in 2013.

Background
Cerebral palsy (CP) is the most common cause of physical disability in children in developed countries, with 2-2.5 affected per 1000 live births.

CP is a collection of syndromes notably characterised by abnormal movement patterns and postures. Cerebral palsy is often caused by a lesion on the brain but may also be caused by genetic factors, infections in-utero, and premature or complicated births. Brain lesions are irreparable but do not usually change across a lifetime, however resultant clinical musculoskeletal syndromes may change in nature and severity as the child ages. Physical abnormalities are not usually evident at birth but develop during periods of rapid growth in childhood

There are several types of CP, collectively known as the cerebral palsies; identified by their topographical brain location. Approximately 80-85% of diagnoses constitute spastic and mixed motor disorders. with dyskinetic and ataxic cerebral palsies much less common. Spastic hemiplegia, spastic diplegia, and spastic quadriplegia are most common, with the nomenclature coinciding with the severity of the condition, and capacity for independent or assisted walking, or no functioning gait

During early childhood, the primary focus of treatment is on improving the function of affected limbs**. The focus shifts to avoidance of pain in adolescence and adulthood. A key feature of the conditions is the insufficient growth of longitudinal skeletal muscles, leading to contracture, poor balance, weakness, muscle spasticity, and consequent inactivity. Spasticity commonly leads to contracture in the gastrocnemius (calf muscle) and deformities of the foot and ankle. In many cases persons with cerebral palsy will experience torsion on long bones, joint instability, and joint dislocation, resulting in premature joint degradation and pain.

The primary treatment for the cerebral palsies is orthopedic surgery to incrementally lengthen affected tendons however, Botox injections, used to reduce muscle activation in spastic skeletal muscle, thereby facilitating new muscle and neural pathway development, have proven successful in numerous trials; with many children receiving the treatment soon after birth. Commonly, Botox is used to treat dynamic equinus (toe walking), adductor spasticity (scissor gait), and hamstring spasticity (crouching gait). Spasticity in upper limbs and management of pain following surgery has also been successful.

It is generally accepted that physiotherapy is required to regain strength and function following surgery, but little research has been done into the effectiveness of resistance training programs outside of surgical rehabilitation.

Research
This study was a single-blind randomised controlled trial comprising two groups: progressive resistance training and a control group receiving their usual level of care and recreational activity. Participants, aged between 14 and 22 years, were recruited through a major metropolitan children's hospital. All 48 participants (26 male; 22 female; mean age 18 years, one month) were required to be classified as level II or III on the Gross Motor Function Classification System (GMFCS) and had not participated in strength training programs for the preceding six months, nor had surgery in the preceding two years.

Participants were randomly assigned to control (usual activity) or experimental (progressive resistance training twice a week) groups for a period of 12 weeks

Method
Separate randomisation steps were implemented for both GMFCS II and III, with participants in the experimental group undertaking physiotherapist-supervised resistance training twice a week for 12 weeks. Three sets of 10-12 repetitions of exercises, with a two minute break between sets. Participants were instructed to 'work hard', or a minimum of 5 on the 0-10 Borg Perceived Exertion Scale, which was evaluated at the end of each session. Exercises were individualised to address issues identified during gait analysis. Following 12 weeks of resistance training, participants were instructed to take a rest from resistance training until the final testing at 24 weeks. Control group participants were required to continue with their usual recreational activities, provided they did not include resistance training.

Results
Outcome measures were evaluated at baseline, at 12 weeks (immediately following the intervention), and 12 weeks from the end of the trial. Participants' subjective reports, measured against a Functional Assessment Questionnaire and the Functional Mobility Scale indicated that resistance-trained individuals noticed an improvement in mobility, whereas fewer control group participants reported notable change (10 out of 23, and 4 out of 25 participants respectively). Importantly, whilst targeted muscle strength increased by 27%, it did not result in improvement in gait or walking speed, nor objective measures of mobility.

Discussion
The results of this study suggest that individualised progressive resistance training does not directly affect mobility or gait in young people with CP. There are some notable limitations of this particular study, including its small sample size; that the recreational activity undertaken by the control group was not documented; and that the program delivery timeframe was short. This may account for the negligible impact on gait and mobility measures, despite the increase in targeted muscle strength. The training protocol was delivered in a local gym, so whilst not performed under laboratory conditions, was representative of the ways training is undertaken in practice. Walking is a complex combination of movement patterns, with skill components as well as musculature requirements. The current study assumed that muscular strength and gait share a linear relationship, however, future research should consider the possibility that strength training combined with specific gait skill-based training may yield more significant results. Future research should also consider evaluation of participants of resistance training programs in longitudinal format in order to note the long term ramifications. The authors of this study took care to note that the benefits of resistance training may go beyond improved mobility, as participants experienced the physical and mental health benefits of undertaking exercise and increased strength. The combination of surgery and strength training; Botox and strength training; or a combination of all three was beyond the scope of this study but should also be considered before dismissing the potential for improved gait through individualised resistance training programs.