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Chapter 5 – Discussion
Significant improvements in PPT performance such as that seen in the
study of Kornatz, et al. (2005) may also result in some reductions in
tremor. Héroux, et al. (2006) found a significant correlation (r = -0.61)
between changes in dexterity and tremor severity in a study of 31 ET
patients and 28 controls. Comparing PPT scores to a measure of tremor
severity, the authors found that for the non-dominant hand there was
an exponential relationship between tremor and PPT function, such that
an increase in tremor amplitude correlated to a lower PPT score. This
training- related reduction may be due to improvements in a number of
aspects of neuromuscular function. While no such measures were
obtained in the present study, previous exercise studies involving RT
protocols in neurologically normal and ET populations have
demonstrated significant reductions in motor unit firing rate variability
(Bilodeau, et al., 2000; Kornatz, et al., 2005) and co-activation (J W. L.
Keogh, et al., 2010). Furthermore these changes may also reflect
potential central adaptations, perhaps occurring at the cerebellum, or
inferior olive, due to their relation to ET and role in error correction of
force production (Llinás, 2009).
Quality of life
The SF-36 and QUEST questionnaires were used to measure possible
changes in QoL. The SF-36 is a general health-related QoL scale used in
many studies involving older adults and the QUEST is a recently
developed ET specific QoL scale. Disease specific QoL questionnaires,
such as the QUEST are important as they address concerns specific to a
group with a given disease (Louis & Rios, 2009), with a few being
developed for ET that include individual and clinical tremor ratings and
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