Exercise as it relates to Disease/Does hand-based resistance training improve handwriting ability in patients with Parkinson's disease?

This is a critique of the article 'Bryant MS, Workman CD, Jamal F, Meng H, Jackson GR. Feasibility study: Effect of hand resistance exercise on handwriting in Parkinson’s disease and essential tremor. ''Journal of hand therapy. 2017 April 4;''31(1):29–34.'

What is the background of this research?
Parkinson’s disease (PD) is a neurodegenerative disease in which nerve cells (neurons) in the brain become damaged, weaken, or begin to die. The disease is characterized by a decline in motor control and noticeable shaking caused by a loss of dopaminergic neurons. As the disease progresses, symptoms worsen and begin to interfere with the sufferer’s ability to complete daily tasks. Primary symptoms of PD include tremor (shaking), rigidity (muscle stiffness), bradykinesia (the slowing down of automatic movement) and postural instability (impaired balance). Essential tremor (ET) is one of the most common types of tremors experienced in those with PD; with a difficulty in writing found to be a common complaint amongst those possessing the upper limb tremor. Decreased strength and reductions in writing size (a condition known as micrographia) and increased writing size (macrographia) have been reported in patients with PD and ET and are thought to contribute to the increased writing difficulty of PD sufferers. There is evidence to suggest that resistance training improves digit force steadiness as well as both intra- and inter-muscular coordination in neurologically impaired person’s. Hence, this research was conducted to examine the relationship between hand resistance training and hand movement control during handwriting. In particular, the research aimed to determine whether training would increase handwriting letter size in PD and decrease letter size in ET.

Where is the research from?
The study was conducted in the United States of America; with participants in the research, recruited from Parkinson’s Disease Research Education and Clinical Centre, Houston, Texas. The corresponding author of the study was Mon S Bryant, from the Michael E. DeBakey VA Medical Centre, Houston. The VA Medical Centre provides health care services across 12 locations in Texas and conducts research projects, with major research areas in gene therapy and traumatic brain injury. The Medical Centre is a teaching hospital with state-of-the-art technology, multiple awards and accreditation from multiple associations such as The Joint Commission, Rehabilitation Accreditation Commission and American Psychological Association.

Signed participant consent forms were approved by the institutional review boards of the Baylor College of Medicine and the Michael E. DeBakey VA Medical Centre, Houston, United States; whilst the study involved a home-based, resistance program that was carried out by participants in their homes in Houston.

What kind of research was this?
The research was conducted using an experimental, single group, repeated measures design. All participants completed resistance training and the results were measured after participants’ exposure to the ‘treatment.’ A comparison of subjects pre- and post- intervention test results was then conducted. An advantage of this research design is that fewer participants are required overall for the study which allowed the experiment to be conducted with greater ease and in a quicker manner. This research design, however, can also be disadvantageous due to the ‘order effect’. Factors such as fatigue can affect the performance of participants involved in the study and the level of reliability of results.

What did the research involve?
The study involved nine participants with PD and nine with ET. Participants were an average age of 65.3 years, and underwent a home-based, hand and arm resistance exercise program three times a week for six weeks. All participants had an average disease duration of 7.8 years, and an experienced tremor with difficulty writing. The aim of the study was to explore the influence of 6 weeks of home-based hand resistance exercise on handwriting letter size in individuals with PD and ET. Participants completed pre-intervention tests to assess grip strength and handwriting size. Two writing samples (a sentence and a set of three words) and a hand dynamometer were implemented for the conduction of these tests.

Following baseline testing, participants underwent a 6-week, home-based resistance exercise intervention which involved various upper limb exercises. Bicep curls, tricep extensions, wrist flexion and extension, hand and finger exercises were completed bilaterally for three sets of approximately 10-12 repetitions for the full six weeks. Throughout the study, a research staff member had weekly phone contact with participants to enhance adherence and to provide assistance if required. The study selected training duration based off previous studies to ensure that exercise volume demands were high enough for strength improvements to occur. Post training, participants underwent the same testing procedures as those conducted at baseline. A comparison between area of handwriting and maximal grip strength was then conducted between measurements pre- and post- six weeks of resistance exercise training.

The small number of participants involved in the study is a major limitation of the research. Small participant numbers provide a lack of normal distribution and an inability to confidently associate the results to the wider, neurologically impaired population. The study did attempt to overcome this limitation through the implementation of the Wilcoxon signed rank test, however, this does not completely resolve the existing limitation. The study also only consisted of male participants, which would further affect the ability to generalise results. Regarding the protocol that was followed throughout the exercise intervention, the study lacked the inclusion of important warm up and cool down procedures which increases the potential risk of injury for the participants involved within the study.

What were the basic results?
The results obtained from the research included participants’ maximum grip strength and handwriting size. 17 participants completed the study, with one participant dropping out due to unrelated injury. No significant differences were found in handwriting size between pre-post-test measures (for either words or the sentence) in participants with PD (p = 0.238 and p = 0.557, respectively) or ET (p = 0.282 and p = 0.160, respectively). Similarly, no significant increase in grip strength was found in participants with ET (p = 0.093). However, a significant increase in grip strength post-intervention was reported in those with PD (p = 0.031). The study hypothesized that the 6-week, home-based hand resistance exercise program would improve the size of handwriting in patients with a hand tremor related to PD or ET however the results confirm that the exercise program did not significantly change handwriting size for those with PD or ET. Although phone calls with participants for compliance checks were carried out weekly, a lack of participant adherence throughout the study could have negatively affected results due to the absence of supervision and motivation throughout training sessions.

What conclusion can we take from this research?
From the results of this research, it can be concluded that hand resistance training in patients with PD and ET had no positive effect on handwriting ability. Small improvements to strength and handwriting size were reported, however most data reported was insignificant. The variables explored (grip strength and letter size) may have lacked a strong correlation to handwriting ability, with other factors such as writing pressure, potentially more important.

Practical advice
Many factors need to be considered when aiming to improve one’s handwriting ability. Further research should be conducted to draw conclusions more confidently around the factors associated with handwriting ability in those with PD and ET, and how they are best to be managed. Additionally, a longer intervention duration would be useful to increase the magnitude and likelihood of achieving the desired result and or outcome.

Further information and resources
Understanding Parkinson's Disease

Strategies for those living with Parkinson's Disease

Managing Parkinson's Disease