Exercise as it relates to Disease/Improving strength and function in Parkinson's Disease through eccentric resistance training

Parkinson's Disease
Parkinson's disease (PD) is a progressive, degenerative disorder of the central neural system (CNS), causing a loss of mobility and difficulty controlling movements. The disease does not cause death, and can be lived with for a number of years, however, a person's quality of life is degraded. There is no definitive cause of PD, and there is no cure for the neurodegenerative process.

Prevalence
In Australia currently, approximately 80,000 people have PD, with the average age of diagnosis around 65. Worldwide, it is the second most common neurological disease. The incidence of the disease increases with age, and the ageing population is likely to cause an increased frequency of the disease.

Effects

 * Loss of or damage to dopamine secreting neurons in the substansia nigra, resulting in bradykinesia
 * Bradykinesia: One of the most recognisable and debilitating symptoms of Parkinson's, as it involves a slowing of movement and difficulty controlling movement.
 * Speech difficulties
 * Rapid eye movement disorders
 * Fatigue
 * Impaired memory
 * Sleep problems
 * Pain
 * Depression

Why resistance training?
There is currently no cure for PD, however there are treatments to help people deal with symptoms. Recently, research into the impact that high-intensity resistance training has on people with PD has shown positive evidence for its use as a method of treatment.
 * The goal of resistance training is to achieve muscle hypertrophy, which should aid in increasing functional strength in people with PD
 * Resistance training has the potential to slow the loss of strength due to bradykinesia through this hypertrophy, and therefore improve a person's quality of life
 * Bradykinesia is likely to amplify the effects of age induced sarcopenia, resulting in a positive feedback response which increases strength deficits. Resistance training can help to reduce these deficits.
 * There is a strong relationship between poor lower body strength, poor balance, and falls. Increasing lower body strength through resistance training can help to reduce the incidence of falls

Where is the research from?
The research, conducted by Dibble et al., was reviewed and approved by the University of Utah Health Services Centre Institutional Board. Funding was received from the University of Utah and the Foundation for Physical Therapy.

What kind of research was this?
Dibble et al.'s study was exploratory research, which is appropriate in this situation given how few studies had been conducted prior to this research on this particular topic.

What did the research involve?
Participants were recruited on a voluntary basis through local hospitals based on their involvement in movement disorder programs. Exclusion criteria included unpredictable motor fluctuations which were not being controlled by medicine, and existing conditions that were likely to limit participation in the exercise program. 20 people were initially recruited, however one person dropped out due to unrelated health problems. Participants were between 40 and 85 years of age and suffered from mild to moderate idiopathic PD.

Baseline information about muscle volume and mobility was gained through MRI scans and measures of mobility which have been proven to be appropriate by previous research (6 minute walk, stair ascent and descent). Participants were assigned to either the eccentric exercise group or the standard care control group. The two groups performed the same programs, including light stretching, walking on a treadmill, riding a standard cycle ergometer, and lifting weights with upper exptremities for 45–60 minutes 3 days a week for 12 weeks. The eccentric exercise group performed lower extremity resistance training in addition to this program.

Basic results
There were no significant differences between the groups before the intervention, however, both groups showed a significant difference in muscle volume in the quadriceps between the affect and non affected legs. The training returned several significant results:
 * An increase in muscle volume in both legs in the eccentric exercise group, greater than in the standard care group
 * Increased average torque in both legs in the eccentric exercise group, which exceeded the standard care group
 * Significant improvements in 6 minute walk and stair descent in eccentric exercise group

How did the researchers interpret the results?
Dibble et al. reported that their research demonstrates that quadriceps hypertrophy is clinically significant due to the association between muscle mass and strength and mobility limitations in older people. Further, their results are in line with previous studies which have demonstrated increases in muscle volume in older people who engage in strength training. The improvements in stair descent results indicate the functional benefit of eccentric training.

While the eccentric exercise group showed positive results, members of the standard care control group experienced minimal changes, and some worsened. This was of concern to the researchers because the exercise protocol used for the control group exceeded the guidelines recommend by various PD patient advocacy groups.

What conclusions should be taken away from this research?
Dibble et al. concluded that a 12 week eccentric resistance training program can produce hypertrophy, increase strength, and improve mobility in people with PD.

However, because this was an exploratory study, further research is needed before results of this research can be generalised beyond the sample population.

Further research needs to be conducted to determine the relative contribution of neural processes to muscle hypertrophy in people with PD. Dibble et al. acknowledge that the gains experienced by the eccentric group are still far smaller than those experienced by younger people with no neurological conditions undertaking a similar program. This is likely to be related to an altered neural drive to skeletal muscle, however more information is needed.

What are the implications of this research?
The results of this study imply that muscle volume and strength is important for elderly populations and those with PD. Therefore, if muscle hypertrophy can be achieved through a training program, their mobility is likely to be improved.

Dibble et al.'s research demonstrates that eccentric training may be a suitable form of treatment for people with PD, however further research involving larger groups is needed to validate their findings and overcome the issues with their study format.