Before I give you my answer, I must advise you to speak with your doctor or a medical practitioner about spermidine supplementation and its effects on diseases on the peripheral nervous system. However, I can go a bit into detail regarding this topic. Multiple Sclerosis (MS) is a chronic autoimmune disease, characterized by chronic inflammation that leads to demyelination of nervous tissue and later to neurological dysfunction. Studies have shown that spermidine can lead to symptom relief in those with MS. It does this by regulating the migration of CD4+ cells and macrophages into the central nervous system. Studies show that spermidine administration can help alleviate disease progression by inhibiting the pro-inflammatory activity of macrophages. Without these macrophages, spermidine administration no longer has an impact on the progression of the disease. This shows that the impact spermidine has on the disease is directly tied to the regulation of macrophages.
As far as muscle weakness goes, muscle loss goes hand in hand with aging. This process can partly be prevented or at least delayed with regular exercise. However, regular exercise combined with spermidine shows increased improvement. When spermidine is taken in tandem with exercising the autophagy rate is increased.