People suffering from Parkinson’s disease (PD) experience less muscle control (Meg, Clarissa & Margaret, 2010). Symptoms include involuntary shaking of limbs when at rest and muscle rigidity. Patients also lose posture and become abnormally slow in performing certain life functions (Meg, Clarissa & Margaret, 2010). There has been very little success in terms of developing ideal intervention mechanisms for this problem (Meg, Clarissa& Margaret, 2010). To determine the extent of the problem, this paper analyses a study done by Cory et al. (2009).
Purpose of the Study
Cory et al. sought to establish the relationship between PD and walking economies (2009, 2). In neuroscience, ‘walking economy’ is defined as the amount of energy spent on walking (Cory et al. 2009). They also wanted to establish the effects of other factors such as gender, age and severity of the disease on walking economies (Cory et al., 2009, 5).
Study Design and Subjects
Cory et al. (2009) used quasi-experiment design to perform this study. Quasi-experiment design is used when there are at least two groups or waves of measurement (Baley, 2008, 18).
In this case, there is experiment group and comparison group. Unlike experimental design, quasi-experiment does not randomly assign subjects to groups. A study design is also considered to be quasi-experiment if the researcher actively manipulates the independent variable (Baley, 2008, 19). In the study by Cory et al. (2009), walking speed was the independent variable.
Cory et al. (2009) used human subjects. The experiment group comprised of people suffering from Parkinson’s disease while the control group comprised of healthy people. Volunteers gave a written consent and were screened for PD. Those in disease stages between1.5 to 3 were included. Members of the control group were picked from the community. Both groups comprised of men and women between the ages of 50-80 years.
Rate of oxygen intake was among measures used to determine energy consumption. Oxygen intake correlates with the amount of energy used in the body. The rates were measured when the participants were at rest and repeated while they were walking at different speeds. Walking speeds ranged from 0.8mph to 4mph. Increment from one speed to another was 0.5mph. Recording was done after every 30 seconds for each of the different speeds.
Other measures used include rate of carbon dioxide output as well as minute ventilation (Cory, 2009, 8). Respiratory exchange ratios were also determined and recorded (Cory et al., 2009, 10). Participants also had their heart rates recorded. All these measures are positively correlated to the amount of energy used in the body. Use of more than one response variable enhances reliability of the results by determining consistence.
On average, PD patients who participated had been sick for 4.8 years with a standard deviation of 4.1. The Hoehn &Yahr scores average was 2.3 with a standard deviation of 0.4 while disease severity average was 33.6 with a standard deviation of 14.4.
Cory et al. (2009) found that at rest, there were significant differences in heart rates, minute ventilations and respiratory exchange ratios for the two groups. Increase in speed translated into greater increase in oxygen intake by the PD group than the other group. The gradient of 3.32 with a standard deviation of 0.07 for PD patients was steeper than the gradient of 2.77 with a standard deviation of 0.09 for the control group.
T-test analysis with α = 0.05 produced a p-value of 0.001. Since 0.001 is less than 0.05, the differences were significant. The results showed no differences in oxygen intake between the two groups while at rest. As a show of consistence, the results also revealed significantly higher carbon dioxide output, respiratory exchange ratio, heart rate, and minute ventilation during walking in PD patients than the healthy participants.
Cory et al. (2009) also found that age and PD severity did not have significant effects on oxygen intake in PD patients. In the control group, women showed a lower oxygen intake of10.8 with a standard deviation of 0.7 than men who had 11.9 with a standard deviation of 1.6 and a p-value of 0.003 (Cory et al. 2009, 32).
These results show that PD patients use more energy in walking as compared to healthy people. Since walking involves movement, this study treated movement impairment. Movement impairment limits performance of basic life activities such as walking, turning in bed and getting out of seats (Mehta et al 2007). Patients are considered to be physically disabled if it reaches a point where they cannot perform such functions.
Cory et al (2009) concluded that PD people experience more stress in movement than normal people. However, they did not show the role of rigidity, shaking and reduced strides in the poor walking economy. Related studies by Baltadjieva et al. (2006) and Mehta et al. (2007) observed that reduction in walking strides causes poor walking economies in healthy people (2006, 812).
Another research by Dimitrova found that muscle activities in PD patients are more activated than in normal people when performing tasks that destabilize posture (2004, 490). However, there is need to perform a specific study to confirm the role of tremor, rigidity and reduced strides in poor walking economies among PD patients.
This paper finds that PD causes poor walking economy. Therefore, physical therapies should be designed to improve walking economies in PD patients. But there should be another research to explain the observed poor walking economies in these people.
Bailey, R.A. (2008). Design of Comparative Experiments. Cambridge: Cambridge University.
Baltadjieva, R, Giladi N, Gruendlinger L, Peretz C, Hausdorff JM. (2006). Marked Alterations in the Gait Timing and Rhythmicity of Patients with Parkinson’s disease. European Journal of Neuroscience. 24(6):1815–1820.
Cory, L. Christiansen, Margaret L. Schenkman, Kim McFann, Pamela Wolfe, and Wendy M. Kohrt, (2009). Walking Economy in People with Parkinson’s Disease, Movement Disorder. Denver: University of Colorado Denver.
Dimitrova, D. Horak FB & Nutt J. G. (2004). Postural Muscle Responses to Multidirectional Translations in Patients with Parkinson’s disease: Journal of Neurophysiology. 91(1): 489-501.
Mehta P, Kifley A, Wang J, Rochtchina E, Mitchell P & Sue C (2007). Population prevalence and incidence of Parkinson’s disease in an Australian community: Internal Medicine Journal 37: 812-814
Meg, E. Morris, Clarissa L. & Margaret L. (2010). Striding out with Parkinson Disease: Evidence-Based Physical Therapy for Gait Disorders. 90:280-288