The hereditary ataxias are a group of genetic disorders characterized by slowly progressive incoordination of gait and balance impairments in sitting and standing. Trunk local stability during gait is lower in patients with degenerative ataxia than that in healthy adult population.

Given the fact that drug interventions are rare in degenerative diseases and limited to only specific type of diseases and symptoms, physiotherapy is a major cornerstone in current therapy of ataxic gait. Core stability exercises training could be included as an adjunct to conventional balance training in improving dynamic balance and gait. Due to the nature of the interventions, the study will have a single blind design.

The hereditary ataxias are a group of genetic disorders characterized by slowly progressive incoordination of gait and often associated with poor coordination of hands, speech, and eye movements. Prevalence of the autosomal dominant cerebellar ataxias (ADCAs) is estimated to be approximately 1-5:100,000 populations. Hereditary ataxia may result from: dysfunction of the cerebellum and its associated system, lesions in the spinal cord and/or peripheral sensory loss.

Clinical manifestations of hereditary ataxia are poor coordination of movement and a wide-based, uncoordinated, unsteady gait. Poor coordination of the limbs and of speech (dysarthria) are often present. Ataxia patients perceive impairments in balance, coordination and speech as the symptoms with greatest impact, as well as fatigue.

Postural disorders in cerebellar ataxia constitute a major cause of poor balance. Local stability of the trunk during gait in patients with cerebellar degenerative ataxia is lower than that in controls. To compensate for this instability, walkers increase the width of the base of support, take smaller steps and increase the duration of foot contact to the floor, sacrificing swing phase. They progress forward slower, with a lower cadence and preferred walking pace. This lack of stability is in turn correlated with the history of falls. Local stability of the trunk may thus be useful when planning gait and balance rehabilitation in patients with ataxia. Developing core strength is essential for everyday health and well-being, as a strong core protects the spine, reduces back pain, enhances movement patterns, and improves balance, stability and posture. However, while motor training programs have been shown to be beneficial in other neurodegenerative diseases (e.g., Parkinson's disease or stroke, their effectiveness remains controversial in the field of degenerative hereditary ataxias.

There's emerging evidence that rehabilitation may improve function, mobility, ataxia and balance in genetic degenerative ataxia. Although these conclusions are based primarily on moderate to low-quality studies, the consistency of positive effects verifies that rehabilitation is beneficial. Intensive rehabilitation (with balance and coordination exercises) improves the patients' functional abilities (level of proof: moderate). Although techniques such as virtual reality, biofeedback, treadmill exercises with supported body weight and torso weighting appear to be of value, their specific efficacy has yet to be characterized. This body of literature is limited by the wide range of underlying conditions studied and methodological weaknesses (small sample sizes, poorly described rehabilitation protocols, etc.

The aim of this study is that a program of core stability exercises could improve sitting and standing balance and gait in hereditary ataxia patients. Secondary objectives are activities of daily living, lower limb strength and health status of quality of life. After giving informed consent, participants will be randomly assigned (at a ratio 1:1) to core stability group or control group. Concealed treatment allocation will be performed via opaque envelopes.

The study will be carried out in accordance with the principles enunciated in the current version of the Declaration of Helsinki and the requirements of Spanish law and the Spanish regulatory authority.

• Inclusion criteria: suffer a degenerative hereditary ataxia. spinocerebellar ataxia (SCA), Friedreich's ataxia (FRDA), idiopathic sporadic cerebellar ataxia, and specific neurodegenerative disorders in which ataxia is the dominant symptom (e.g. cerebellar variant of multiple systems atrophy (MSA-C). Both sexes and age ≥ 18 years old. •Ability to understand and execute simple instructions.
• Exclusion Criteria: Concurrent neurologic disorder (e. g. Parkinson's disease) or major orthopedic problem (e. g. amputation) that hamper sitting balance, relevant psychiatric disorders that may prevent from following instructions, Other treatments that could influence the effects of the interventions, Contraindication to physical activity (e.g., heart failure).