LEVODOPA INFLUENCES THE REGULARITY OF THE ANKLE JOINT KINEMATICS IN INDIVIDUALS WITH PARKINSON'S DISEASE
Max J. Kurz1, Ashley Hickerson1, Chris Arellano1, J. G. Gabriel Hou2, and Eugene C. Lai2
1 Laboratory of Integrated Physiology, Department of Health and Human Performance,
University of Houston, Houston, TX, USA, firstname.lastname@example.org
2 Parkinson's Disease Research, Education & Clinical Center, Michael E. DeBakey VA Medical
Center, Baylor College of Medicine, Houston, TX, USA
Parkinson's disease (PD) is a progressive,
results mainly from a loss of dopaminergic
while "off" and then "on" their levodopa
therapy. Characteristics of the participants
nuclei, together with other related brain
are detailed in Table 1. All participants were
structures, compose the basal ganglia, which
initially assessed in the morning without
are largely attributed to controlling the
amplitude and timing of movement patterns.
functions appears to be the cause for the
larger amount of stride-to-stride variability
seen in PD patients (Schaafsma et al., 2003).
levodopa to be turned "on" before having
the participant repeat the walking bout.
including gait. It was demonstrated that
Hz) was used to collect the right leg's ankle,
levodopa therapy reduced the magnitude of
knee and hip joint sagittal plane kinematics.
the variations present in the stride time
interval dynamics (Schaafsma et al., 2003).
variations present in the respective joint's
improved regulation of the lower extremity
angle kinematics (Pincus, 1981; Equation 1).
joint kinematics. However, the influence of
levodopa on the regularity of the structural
variations found in the joint kinematics is
The purpose of this investigation was to
Table 1. Participants' characteristics.
regularity of the structural variations present
in the lower extremity joint kinematics. We
hypothesized that levodopa will reduce the
variations of the lower extremity kinematics
where Cm(r) is the number of data points of length m that are similar, Cm+1(r) is the number of data points of length m+1 that are similar, and r is the similarity criterion. For this investigation, m was 2 and r was 20% of the standard deviation of the time series (Pincus, 1991). A lower ApEn value indicates a greater regularity in the structural variations present in the joint kinematics. We used a two factor repeated measures
Figure 1. ApEn values for the respective
joints while "on" and "off" levodopa.
post-hoc to evaluate the effect of levodopa
on the regularity of the structural variations
the fact that our investigation was conducted
present in the joint kinematics. All statistical
on a treadmill. Potentially, the treadmill may
tests were performed at a 0.05 alpha level.
have acted as an external cueing device that
reduced the structural variations present in
RESULTS AND DISCUSSION
investigation that found that the magnitude
significant joint-medication interactive
of the stride-to-stride variations is reduced
effect (F(2,14) = 6.74; p = 0.009; Figure 1).
Our post-hoc analysis indicated that the
structural variations present in the ankle
joint kinematics were more regular while
being "on" levodopa (p < 0.0001). No
significant differences in the regularity of
Levodopa influences the regularity of the
the structural variations were found in the
structural variations present in the ankle
knee (p >0.05) and hip (p>0.05) joints'
joint kinematics of individuals with PD. We
suggest that an impaired ability to regulate
According to the above results, levodopa
abnormalities in PD. Future investigations
improves the Parkinsonian motor symptoms
the variations present in the Parkinsonian
by regulating the performance of the ankle
previously noted in the magnitude of the
stride-to-stride variations by levodopa may
be related to the ankle joint's ability to
regulate a consistent muscular performance
Frenkel-Toledo et al. (2005). Mov Disord,
(Schaafsma et al., 2003). This notion is
supported by a previous investigation that
demonstrated that individuals with PD have
a decreased amount of ankle power at push-
off if not taking levodopa (Morris et al.,
1999). The perceived resistance of the knee
Schaafsma JD et al. (2003). J Neuro Sci,
and hip joints to levodopa may be related to
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