Is physical exercise training beneficial for people with spinal muscular atrophy type 3?

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disease caused by a genetic mutation in the survival motor neuron 1 (SMN1) gene (5q11.2-q13.3). It is characterized by degeneration of spinal cord a-motor neurons, resulting in progressive proximal muscle weakness, fatigue, scoliosis, nutritional problems, respiratory complications, and severe functional limitations.

Guidelines recommend standardized training programs based on the FITT principle of ‘Frequency,’ ‘Intensity,’ ‘Time,’ and ‘Type,’ using an incremental exercise protocol.  
The aim of this study is to assess the effects of physical exercise training on functional performance in people with SMA type 3 and to identify any adverse effects. Specific aims were walking distance, cardiopulmonary exercise capacity, fatigue, quality of life, functional performance, and muscle strength. 
This Cochrane Systematic Review analysed data from 1 randomised controlled trial including 14 ambulatory SMA type 3 patients. Authors compared the effects of a 6-month, home-based program of combined muscle strength and recumbent cycle ergometry training versus usual care. 
Muscle strength training consisted of a three times per week regimen of three sets of 5-to-6 concentric, isometric, or gravity-eliminated exercises performed at an intensity of 60% to 80% of one repetition maximum. Recumbent cycle ergometry training was based on the FITT principle and was performed 5 times weekly for 30 minutes at an intensity level of a 5 to 7 on a maximum-10 perceived exertion scale, increasing the workload every 2 weeks.
Considering the scarcity and low to very low quality of the evidence, it is uncertain whether the proposed training is beneficial or harmful to people with SMA type 3. Further, high-quality research is needed.

Comment by María Soriano Micò