Active exercise is often recommended for PD patients, but the effect of exercise on Levodopa absorption and metabolism and on resultant PD disability has only been partially examined (Goetz et al., 1993). In order to guide physically active patients with PD, Goetz et al. conducted a study attempting to regulate Levodopa ingestion and exercise. Goetz et al. demonstrated that if patients ingest Levodopa 60 minutes prior to exercise, there is no deleterious or facilitory effect on the Levodopa levels. Based on their findings Goetz et al. recommend that patients ingest their Levodopa, rest quietly for 60 minutes, then proceed with their regular vigorous exercise.

Typically, people with PD have musculoskeletal impairments affecting both the axial and appendicular skeletons. Evidence indicates that in healthy adults, spinal flexibility is correlated with physical performance of tasks such as reaching, moving from a supine to a sitting position, and turning while standing. It has been suggested that losses of spinal flexibility may contribute to difficulty with balance control and physical limitations for people with PD (Schenkman et al., 1998). Current research done by Schenkman et al. studied an exercise program based on the concept that muscle length and improved coordination can be achieved when people are taught to move in a relaxed manner, with the participation of appropriate muscle groups only. This standardized program includes a series of exercises divided into seven graduated steps. The exercises begin in the supine position and progress to standing. The exercises learned in each stage are continued throughout the program with progressively higher-level activities added.

Schenkman et al. found baseline range of motion, spine configuration, and physical performance characteristics of the subjects showed significant improvements. It was suggested from this study that exercise designed to improve spinal flexibility and coordinated movement should also lead to improvements in balance and function, despite rigidity, bradykinesia and motor planning deficits that occur as a direct effect of PD. Furthermore, Schenkman et al. state that movement through relaxation, rather than specific stretching and strengthening, was incorporated into the program to counteract the effects of rigidity on axial motion and posture. Additionally, the exercises were designed to assist participants in overcoming the motor planning difficulties experienced by people with PD. Typically, people with PD revert to more primitive movement patterns lacking many of the autonomic postural adjustments and spinal movements that accompany simple activities, such as turning over in bed or getting up from a sitting position.

Additional functional results of this study are the subjective comments from the participants to the physical therapists, which were recorded during treatment. Comments included: "Now I'm able to turn over in bed myself;" "It's easier to stand up from a chair;" "I feel more stable on my feet;" and "I can scratch my back now."

Palmer et al. (1986) found improvements of general motor disability in people with PD through exercise therapy. This was a two-program study of slow stretching exercises recommended by the United Parkinson Foundation and upper-body karate training. Patients in both groups of the Palmer et al. (1986) study showed improvement in gait, arm tremor, grip strength and motor coordination tasks involving fine control after only 3 months of exercise therapy. This shows that a variety of modalities can be utilized in the enhancement of functionality of individuals with PD.

The findings of Palmer et al. (1986) were confirmed in a study by Reutter et al. (1999). They found significant improvement in PD-specific motor disability and of sport and specific motor disability as a result of a 14-week exercise program consisting of various standardized sports activities that were performed twice weekly for 1 hour.

Physicians tend to underestimate the importance of exercise for combating PD. Their first line of defense is often drug therapy, and not often is exercise added to that regimen. However, Formissano et al. (1992) found that in a comparison between patients with PD treated using drug therapy only and patients treated with drug therapy and exercise, there was a significantly lower level of disability in the latter group. Although the movement disorders associated with PD can cause considerable impairment and disability, the leading cause of death for those living with PD is respiratory complications such as pneumonia and cardiovascular disease (CVD) (Stanley et al., 1999). Some of the cardiovascular (CV) abnormalities often seen in PD subjects are orthostatic hypotension, cardiac arrhythmia, and less commonly, hypertension. It was further observed by Kuroda et al. (1992) that many patients with PD die from infection after a long period of general weakness. Considering this rationale as a cause of death, it can be concluded that continuing daily physical exercise influences the mortality of PD through an effect on prevention of the decline in physical function from disuse. It is important to keep in mind that these are often similar problems in the general older population to which subjects with PD belong. Thus, aerobic conditioning is very important for subjects with PD to help combat the influences the disease has on the respiratory system. Varied physiological changes or symptoms in individuals with PD influence the respiratory system directly or indirectly. The progressive muscular rigidity, which so frequently occurs, not only impacts the appendicular musculature, but the axial musculature as well.

Consequently, the rigidity in the vertebral and surrounding thoracic musculature, including the rib cage and the muscles of respiration, may have a direct or indirect effect on normal respiration. In addition, involvement of the facial and cervical muscles as well as throat and esophageal regions may also affect normal respiration (Stanley et al., 1999). This rigidity of muscles in both axial and appendicular musculature demonstrates the importance of flexibility in an exercise program for clients with PD. Finally, the importance of strength training is seen in the maintenance of enough strength to perform ADL.