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Exercise and cerebral palsy

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A cerebral palsy child in her standing wheelchair.

Specialty	Pediatrics, Neurology, Orthopedics, Physiatry
Causes	Abnormal development or damage in the brain
Symptoms	Motor function disorder
Complications	Intellectual disability, epilepsy, gastrointestinal complication, speech disorder
Usual onset	Early childhood
Diagnostic method	Clinical diagnosis
Treatment	Occupational, physical, speech therapies and surgery
Frequency	1.5 to 3 in 1000 live births

Physical exercise interventions, consistent with prescription standard, have shown to improve health and fitness of cerebral palsy patients.

Cerebral palsy (CP) refers to a group of lifelong disorder with motor dysfunction attributed to perinatal or postnatal damage of the central nervous system. Up to date, many studies have suggested that cerebral palsy patients tend to demonstrate poor muscle strength and cardiorespiratory endurance. With lower degree of health-related fitness, they tend to experience repeated cycles of deconditioning, in which reduced physical activities lead to further decline in physical functions. In the long term, such physical inactivity would substantially increase the risk of mortality due to chronic disorders. To minimize secondary complications, there is a need to promote higher level of physical exercise in CP patients in accordance with the standards.  

Physical exercise interventions generally focus on resistance training and endurance training. General guidelines on exercise prescription have been recommended by different studies, but the severity of disease and progress of each individual still need to be taken into considerations to achieve expected functional implications. To date, different rehabilitation therapies (physiotherapy, hippotherapy and aquatic therapy) have involved the clinical use of exercises in the restoration physical function and mobility in CP.The adaptation of muscle size and length to different therapeutic exercise interventions have been discussed in recent studies.

Types of exercise

This article will focus on the treatment of CP on the young, as congenital CP makes up 85-100% of cases and symptoms that are noticeable in early childhood. Resistance training and cardiovascular endurance exercise are the major categories of exercises amongst CP children and adolescents.

Resistance training

Resistance (strength) training has shown to improve the balance, gait speed muscle strength, and gross motor skills in teenagers and kids with CP in Gross Motor Function Classification System levels I, II, and III. In a systematic review, repeated findings have demonstrated that strength training can increase muscle strength in the knee flexors and extensors as well as plantar flexors and extensors. However, the efficacy of such programmes hinges upon consistency, as it is challenging for anyone let alone children to be disciplined through regular training. Albeit to accumulate long lasting benefits.

The right of amount of exercise

According to the journal of developmental medicine & child neurology, the optimal resistance exercise regime for CP patients consists of 1 to 3 sets of 6 to 15 repetitions of strength training exercises that progresses from single-joint, machine assisted exercises, to the addition of free weights for multi-joint exercises. The same exercises are repeated in 2-4 sessions per week, at an intensity of 50-85% of an individual’s maximum strength, on non-consecutive days for a minimum of 12 consecutive weeks.

Endurance training

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Assisted treadmill walking as an example of endurance training for people with cerebral palsy.

Endurance training is often used to improve motor control in the lower body in exercise programs. It simultaneously develops strength in lower extremity muscles, decreases the energy required to walk, and enhances gross motor skills of teenagers with spastic CP.

The upper body is an unexpected beneficiary in terms of cardiovascular exercise, as it aids dynamic postural control, in addition to walking speed and endurance in children with spastic CP. This is achieved when the treadmill speed increases to encourage heavier weight bearing in the legs, thus promoting muscular function to maintain a good posture sustainably.

The right of amount of exercise

The ideal endurance exercise plan for adolescents and children involves rhythmic movements of major muscle groups, with an intensity between 60-95% of an individual’s peak heart rate, for a minimum of 20 minutes, for 2 or 3 times per week for 16 to 8 consecutive weeks, respectively.

The long-term benefits of exercise and physical activities are not limited to the typical physical and mental benefits of the average person. Since exercise allows CP patients to regain strength and muscle control, just like most aspects of body building, the “use it or lose it” principle applies. If exercise is a life-long habit, the symptoms of CP such as uncoordinated, and jerky movements will be minimized.

Clinical use of exercise

The total number of sessions below hinges on the severity i.e., spastic, quadriplegic CP and the progress of patients during each session. Therapeutic exercises can help patients regain functional motor skills and mobility until independence is achieved.

Physiotherapy

Physiotherapy is widely practiced in paediatric rehabilitation to treat young patients, symptoms such as scoliosis and elevated muscle tone are managed by a combination of therapeutic intervention and physical activities.

School-aged children with bilateral spastic CP can benefit from physiotherapy. As seen in a research, individuals who undertook a physiotherapy program consisting of manipulation of objects beyond limb’s length, stretching muscles of the lower limbs as well as walking on uneven terrain are more independent, have a better sense of balance and strengthened motor skills. This is evident in the Kids mini-bestest balance test, WeeFIM independency test, and GMFM-88 motor skills test gross motor ability of children which shows improvements in postural control, functional independence and gross motor skills of children with CP as demonstrated by the 3 tests respectively.

NDT- neurodevelopmental therapy is a branch of physiotherapy that utilizes techniques to prevent the formation of abnormal muscle tone and control of reflexes. This is achieved by the practice of functional movements and skills, that ultimately aids postural alignment and self-organization.

CIMT - constraint induced movement therapy, is an alternative form of physiotherapy that is geared towards hemiplegic children. In which the unaffected limb is restrained (by a cast) and the affected limb undergoes intensive and repetitive shaping activities, thereby targeting affected arm.

For young patients that are about to take their first steps, body weight support treadmill training could be beneficial. This improves the gait cycle of infants and newborns before they begin to bear weight or stand, as they attempt to walk on a low-speed treadmill while closely monitored and supported by the physiotherapist. This therapy has shown to help children with cerebral palsy gain independence by improving their mobility and gait pattern, thus improving balance and build strength in their lower limbs simultaneously.

Hippotherapy has been utilized as an occupational and physical therapy to improve physiological and mental functions of cerebral palsy patients.

Hippotherapy

Hippotherapy is a form of occupational and physical therapy that utilizes movements of horses to provide patients with motor and sensory stimuli. This treatment involves three therapeutic principles that help in physiological and mental rehabilitation of the patients.

Firstly, it involves equine heat transmission to human. As exercising horses could achieve a body temperature of 38°C to 38.8°C, the temperature difference allows flows of thermal energy to human body. With slightly higher temperature, sensitivity of sensory perception increases, promoting extension and relaxion of muscles and ligaments.

Secondly, rhythmic impulses generated during ambulation create an anterior-posterior oscillation in the patient’s pelvis. While riders are trained to maintain an upright posture in disequilibrium state, their balance, coordination, and development of paraspinal muscle will improve.

Thirdly, the three-dimensional locomotion of horse replicates the motion of human pelvis when walking. Such multidirectional movements allow enhancement in flexibility of pelvic ligament as well as head and trunk control.

Other than physical improvements, socialization and self-perception of patients have improved through continuous contact with the horses, and thus developing patients’ independence for daily living activities.

To overcome spatiotemporal and weather constraints of conventional hippotherapy, robotic hippotherapy has been recently integrated into clinical applications. Nonetheless, further research and development are needed to evaluate the efficacy and reliability of robotic hippotherapy system.

Aquatic therapy

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Early intervention with aqua therapy, by minimizing the impact of gravity on the body, which promotes good posture without increasing muscle tone, despite the muscles are exerting the same strength.

Aquatic therapy (aqua therapy) is a series of water-based exercises that aids musculoskeletal rehabilitation in paediatric CP patients. Unlike land-based training, water buoyancy reduces gravitational effect on musculoskeletal system, thus increasing joint flexibility and postural support even when the trunk is supported by uneven muscle tone. Meanwhile, the thermal and viscosity properties of water allow muscle strengthening with minimal pain, spasticity and joint stress.

Although this therapy has been recently discovered in the last 2-3 decades, its benefits are demonstrated through a plethora of studies. In a 2019 study, children who were subjected to a gym based passive stretching and functional training routine had a statistically significant (p<0.05) lowered gross motor function in several aspects compared to the group who had undergone aquatic therapy. However, the intergroup differences in walking, running and jumping did not show statistically significant results.

Apart from the physical benefits, aqua therapy has been known to improve the mental wellbeing of pediatric CP patients. This is evident in a study conducted, where parents and patients have both reported a consensus of experiencing positive effect. Since the novelties of aqua therapy cannot be undermined, most research have concluded that its safety concerns, effects of exercise on fitness remains unknown. Therefore, aquatic therapy is often used in conjunction with conventional land-based interventions.

Effects on muscle structure and function

Numerous skeletal muscle fibers bundle together to form muscle fascicles.

In cerebral palsy, the most critical symptoms are manifested in skeletal muscle, with structural alterations including smaller muscle size, shorter fascicle length and overstretched sarcomeres. As a result, CP patients tend to experience limited range of motion and force production. Nevertheless, the average human muscle exhibits remarkable plasticity which show adaptation to voluntary exercise. This section will primarily discuss the effects of physical training on muscle function and architecture in CP patients.

Effects on muscle size

Muscle strength is primarily determined by the anatomical cross-sectional area of muscle fibers. With greater fiber area, actin-myosin interaction in muscle increases, hence generating greater muscular force with each contraction. However, in many studies, muscle sizes are often determined by measuring muscle volume and muscle thickness, instead of fiber areas, owing to their less demanding and non-invasive measurement procedures.

With physical training interventions under supervision, muscle hypertrophy in CP children has been reported to show similar magnitude as typically developing adults, ranging from 3% to 10%.A 12-to-14-week knee extensor training in CP children has been shown to increase the cross-sectional area of quadricep muscles by 3%-10% and its thickness by 7%-12%. Plantarflexor strengthening in children has also resulted in a 19.7%-30.5% gastrocnemius muscle volume gain with moderate functional improvement.

In contrast, for several studies with home-based exercise interventions, muscle sizes have remained relatively stagnant. Unlike the previous studies, these training were primarily delivered by parents without expert guidance. This therefore emphasizes the importance of professional supervision and provision in training interventions to optimize muscle plasticity.

Effects on muscle fascicle length

Muscle fascicle refers to a bundle of muscle fibers composed of numerous sarcomeres as contractile units in a highly organized manner. While parallel addition of sarcomeres increases the fiber areas, serial addition of sarcomeres elongates the length of muscle fascicles. CP patients’ muscles would usually consist of overstretched sarcomeres, that were frequently accompanied with shortened muscle fascicle, suggesting a reduction of sarcomere in series.

Muscles with reduced serial sarcomeres experience greater sarcomeric shortening velocity during muscle contraction. Higher shortening velocity reduces actin-myosin interactions, thus generating lower force in CP muscles. Hence, most training interventions aim to prevent loss of serial sarcomeres which has important implications on the force-velocity property of muscle.

Theoretically, eccentric contraction allows the lengthening of muscles under tension. However, eccentric backward-downhill treadmill training has not contributed to muscle fascicle lengthening as expected. Kalkman et.al then hypothesized that a combination of resistance training and stretching would be more effective in fascicle elongation than stretching alone. This was proven in a study with ankle robot interventions involving stretching and resistance components that lead to fascicle elongation and force transmission improvements in CP children. Additionally, a 10-week plantarflexor training increases fascicle length in CP children through the enhancement of tendon stiffness.

Tendon stiffness refers to the resistance of tendon to length change. As tendon stiffness increases, stiffness of muscle relative to tendon decreases, enabling stronger transmission of stretching stimuli to the fascicles. Meanwhile, stiffer tendons also recoil more quickly, releasing energy faster with greater force. 

However, there is no universal consensus suggesting whether contraction mode, range or velocity is the actual stimulus for fascicle elongation. Further studies in this area are required to promote better interventions in increasing CP fascicle length.

In summary, the effects of physiotherapy have been well documented and implemented in the present day, yet the effects of aqua therapy and hippotherapy on muscle structure remain as a direction for future research.