Lack of activity destroys the good condition of every human being, while movement and methodical physical exercise save it and preserve it – Plato (cited in H. Dawes, p.867)
The “Exercise is Medicine” program was initiated by the American Medical Association due to the well studied, documented and widely recognised positive effects exercise has on the cardiovascular, metabolic and musculoskeletal systems . Of particular importance are the exercise induced benefits on brain health, relating to blood flow, trophic factors and immune system changes, which create an optimal environment for neuroplasticity . Neuroplasticity refers to the various structural and physiological mechanisms such as synaptogenesis, neurogenesis, neuronal sprouting and potentiating synaptic strength, which leads to the strengthening, repair and formation of neuronal circuitry, particularly beneficial for driving improvements in the injured brain .
Parkinson’s Disease (PD), is one of the most prevalent neurodegenerative conditions, characterised by specific decreases in motor function associated with progressive degeneration of nigrostriatal dopaminergic (DA) neurons . This leads to a reduction in overall neural activity of the motor cortex resulting in symptoms of bradykinesia , hypokinesia , rigidity , tremor , gait dysfunction , postural instability  and difficulty dual tasking . DA neurons are preferentially lost within the basal ganglia hence resulting in diminished automatic control of movement and subsequently increasing cognitive (frontal cortex) load when executing motor or cognitive tasks .
Literature reviews by The American Academy of Neurology and joint task force of the European Federation of Neurological Societies and European Movement Disorders Society suggest exercise based physiotherapy is a catalyst for positive neuroplasticity, which relates to improvements in movement, functional capacity and cognitive symptoms of those diagnosed with PD , this being especially true for those with mild to moderate presentations . However, despite the above evidence, studies suggest that those diagnosed with PD are likely to reduce their levels of physical activity .
Four specific exercise based PD treatments backed by level 2 evidence have been recommended :
Cuing strategies to improve gait
Cognitive movement strategies to improve transfers
Exercises to improve balance
Mobility and strength exercises to improve physical capacity
Laboratory studies have investigated the specific effects exercise has on the brain health of those diagnosed with PD. Effects include neuroprotection (slow, negate or reverse the neurodegenerative process) and neurorestoration (adaption of compromised neural pathways) .
In terms of neuro-protection and restoration, studies have shown regular exercise both triggers and maintains the production of glial cell line-derived neurotrophic factor (GDNF) producing cells in the substantial nigra where DA neurons are located and subsequently leading to an increase in dopamine release . This is particularly important finding from a pharmacological treatment stand point, especially for those with early PD, as can lead to a reduced reliance on levodopa going forwards . Levodopa is the most effective drug in reducing PD symptoms, however unwanted effects such as levodopa-induced dyskinesias can potentially be minimized or postponed with exercise intervention .
In terms of exercise intervention it is suggested that a combination of skilled and aerobic training is best to trigger and maintain multiple mechanisms of neurogenesis ; especially that which is forced (rate beyond what the participant would self-select)  and progressive in terms of intensity, duration, repetition and specific skill demand . The prefrontal cortex plays an important role in the early phases of motor development; hence to maximize motor learning, cognitive engagement is also necessary via verbal or proprioceptive feedback, cueing, dual tasking and motivation . Exercise and avoidance of a sedentary lifestyle also helps alleviate common secondary symptoms such as depression and constipation .
There are four important components of effective exercise based PD treatments:
Forced high intensity exercise with low variability and increased amplitude to increase cortical excitability and subsequent motor cortex output, improving symptoms of bradykinesia, hypokinesia and executive cognitive impairment 
Goal directed motor skill training to recruit cognitive circuitry important in skill acquisition 
Cognitive engagement with practice and learning of movements to enable volitional access to previously automatic motor patterns 
Further to the above, research shows that inactivity and/or stress can reverse the positive neuroplastic changes brought about through exercise (negative neuroplasticity). It can be said that a decrease in physical activity levels and an increase in stress is prodegenerative, thus increasing the rate of PD pathogenesis and associated symptoms .
Of all motor impairments affecting those with PD, balance impairments are of heightened concern as they lead to increased falls risk and subsequent morbidity . Exercise/movement practices reflective of Tai Chi, Dance and Boxing are backed by current evidence as being useful for PD patients due to their focus on multi-directional weight shift and postural control (balance) .
Interestingly the combination of skilled movements and cognitive engagement native to these varied movement practices has seen participants show transferrable improvements  in maximum exertion (eg. cardiovascular fitness and musculoskeletal strength) , movement amplitude (eg. stride length and speed) , postural control (balance) , dual tasking capability (eg. mobility plus cognitive-auditory attention)  and cognition (eg. visuospatial problem solving) . Randomised controlled trial paper discussions also bring to our attention the need to individualise training variables of cognitive movement modalities; if the difficulty level is too high or not high enough opportunities for improvements (positive neuroplasticity) are either limited or missed .
It can therefore be reasoned that regular exercise addressing multiple movement and cognitive elements specific to an individual’s PD presentation will be most effective, especially for those early in disease progression. At Inner Focus Physiotherapy we utilise a variety of cognitive movement practices, tailored to an individual’s needs to maximize physical capacity and quality of life for those with PD.
 Brauer, S.G., Morris, M.E. (2009). Can people with Parkinson’s disease improve dual tasking when walking? Gait & Posture. 31: 229-233.
 Farley, B.G., Koshland, G.F. (2005). Training BIG to move faster: the application of the speed-amplitude relation as a rehabilitation strategy for people with Parkinson’s disease. Experimental Brain Research.
 Frazzitta, M.D., et al. (2015). Intensive rehabilitation treatment in early Parkinson’s disease: A randomized pilot study with 2-year follow up. Neurorehabilitation and Neural Repair. 29(2): 123-131.
 Hirsch, M.A., Farley, B.G. (2009). Exercise and neuroplasticity in persons living with Parkinson’s disease. European Journal of Physical and Rehabilitation Medicine. 45: 215-229
 Petzinger, G.M., et al. (2013). Exercise-enhanced neuroplasticity targeting motor and cognitive circuitry in Parkinson’s Disease. Lancet Neurology. 12(7): 716-726.
 Ridgel, A.L., et al. (2009). Forced, not voluntary, exercise improves motor function in Parkinson’s disease patients. Neurorehabilitation and Neural Repair. 23 (6): 600-608.