The Role of Dopamine

Dopamine is a chemical substance that supports any physical activity in humans. In fact, it only takes a few seconds for a person to activate their dopamine production. For example, if you flex your elbow vigorously several times your brain will start producing dopamine. You may also choose to run on the treadmill for a mile whereby you would feel a high sense of accomplishment (especially if you went to the gym in March and daily workouts were your New Year’s resolution). The latter is related to the human reward system where activities that are rewarding increase dopamine levels. Exercise is a planned, structured physical activity which aims to improve one or more aspects of physical fitness. While we all know exercise can improve our cardiovascular fitness, prevent heart attack and stroke, and increase weight loss, many of us do not exercise regularly. However, getting regular exercise carries deeper implications for patients with Parkinson’s disease.

The Importance of Exercise and PD

Parkinson’s disease is a progressive disorder associated with the degeneration of dopamine producing neurons. By the time patients notice the symptoms or their physician suspects Parkinson’s disease there is about an 80 percent decrease in dopamine production. Because the diagnosis of PD is based in part on a patient’s clinical exam, it is safe to assume that any patient with early diagnosis of PD already has some degree of rigidity, slowness of movements, gait changes and possible balance troubles. Supplementation with dopamine is the basis of PD therapy, thus it could be appropriate to assume that even on day 1 of the diagnosis with PD a patient will benefit from increase of its dopamine production. And according to its physiology, exercise would increase dopamine production in patients with PD.

What does the Research show?

Intriguingly, there is a growing body of evidence regarding the benefits of exercise in terms of neuroplasticity and the ability of the brain to self repair. Studies with 6-hydroxydopamine animal models of PD have found that exercise has protective benefits against the onset of PD symptoms, possibly due to production of so called “trophic factors” and greater cerebral oxygenation, which together promotes new cell growth and cell survival[2, 3, 4]. The actual effect of slowing down the progression of PD has not been studied in patients, although there is significant evidence for symptomatic benefit of exercises for PD symptoms.

The early observations about improvement in PD patients following task specific physical exertion have contributed to the belief that exercise may be beneficial. Recently, a study utilizing high intensity exercise training on early and moderate stages of PD showed symptomatic benefit on motor performance, gait speed, step and stride length, sit and stand tasks [5]. Thacker and colleagues examined 143,325 healthy people, followed them for 8 years and identified a reduced relative risk of developing the disease for those individuals who had reported moderate to vigorous activity at baseline [6]. Although it is not yet clear whether exercise has a neuroprotective effect for people with PD, the message from all of these studies is that patients with mild to moderately severe PD can benefit from interventions that target flexibility, lower-extremity strength, and cardiovascular conditioning. These interventions may improve aspects of balance, gait, and overall functional ability, although further studies are needed to fully define the scope of benefits from each approach. Because PD is a chronic progressive disorder, it is probable that sustained exercise is necessary to maintain benefits. Indeed, follow-up data from a number of human exercise interventions have demonstrated a gradual return to baseline abilities after the supervised intervention is finished.

Cognitive changes in PD often are associated with impairment of the executive function and had been localized to the frontal lobe [7]. Although no studies exists on exercise as a prevention for cognitive changes in PD, evidence exists that regular walking prevents development of cognitive impairment in healthy elderly subjects and treadmill exercises could improve academic performance in young healthy adults [8, 9].

Summary

Taking all of the results together, it becomes clear that patients with PD should integrate regular physical activity into their daily lives. Furthermore, doctors and healthcare professionals working with patients with PD should advise that vigorous exercise begin immediately on diagnosis, if possible, and continue throughout the course of the disease for as long as the individual is able to exercise. As a physician, that treats people with PD everyday, it is common for me to tell my patients “to break a sweat” when they exercise. I also tell my patients to exercise at a speed in which they cannot carry on a conversation. Even at the latter stages of PD, when falls and postural instability becomes the main restriction for vigorous exercise, I advise my patients to focus on flexibility and lower-extremity strengthening exercises in a sitting position. In addition to suffering with changes in motor symptoms, PD patients often suffer from fatigue, sad mood and decrease in motivation and social isolation. Any exercise, whether it is done alone or in a group, at home or in community settings, whether it is Tai Chi [10], dancing [11], regular brisk walking or biking, may improve the patient’s feeling of self-worth and help prove to them that they have the ability to resist the symptoms of their disease.  And in the face of chronic illness, this empowerment of our patients, physically and emotionally, is what we can build our treatment upon.

Nina Browner, MD, is the Medical Director of the NPF Center of Excellence at the University of North Carolina at Chapel Hill in North Carolina.

References:

1.Morris ME, Martin CL, Schenkman ML. Striding out with Parkinson’s disease: evidence – based physical therapy for gait disorders. Physical Therapy 2010; 90 (2): 280 – 288

2. Smith AD, Zigmond MJ. Can the brain be protected through exercise? Lessons from an animal model of parkinsonism. Exp Neurol 2003;184:31-39.

3. Dishman RK, Berthoud HR, Booth FW, et al. Neurobiology of exercise. Obesity 2006;14:345-356.

4. Fox CM, Ramig LO, Ciucci MR, Sapir S, McFarland DH, Farley BG. The science and practice of LSVT/LOUD: neural plasticityprincipled approach to treating individuals with Parkinson’s disease and other neurological disorders. Semin Speech Lang 2006; 27:283-299.

5. Fisher BE, Wu AD, Salem GJ, Song J, Lin CH, Yip J, Cen S, Gordon J, Jakowec M, Petzinger G. The effect of exercise training in improving motor performance and corticomotor excitability in people with early Parkinson's disease. Arch Phys Med Rehabil. 2008 Jul;89(7):1221-9.

6. Thacker EL, Chen H, Patel AV, et al. Recreational physical activity and risk of Parkinson’s disease. Mov Disord. 2008;23: 69–74.

7. Brown RG, Marsden CD. Cognitive function in Parkinson’s disease: from description to theory. Trends Neurosci 1990; 13: 21–9.

8. Kamijo K, Hayashi Y, Sakai T, Yahiro T, Tanaka K, Nishihira Y. Acute effects of aerobic exercise on cognitive function in older adults. J Gerontol B Psychol Sci Soc Sci. 2009 May;64(3):356-63.

9. Hillman CH, Erickson KI, Kramer AF Be smart, exercise your heart: exercise effects on brain and cognition.Nat Rev Neurosci. 2008 Jan;9(1):58-65.

10. Hackney ME, Earhart GM. Tai Chi improves balance and mobility in people with Parkinson disease. Gait Posture. 2008;28:456–460.

11. Hackney ME, Earhart G. Effects of dance movement control in Parkinson’s disease: a comparison of Argentine tango and American ballroom. J Rehabil Med.2009; 41:475–481.

Posted: 3/8/2010 11:29:26 AM by Global Administrator


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