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Differences in Multiple Segment Tremor Dynamics Between Young and Elderly Persons

¹ School of Physiotherapy and Exercise Science, and² Applied Cognitive Neuroscience Research Centre, Griffith University, Queensland, Australia.
³ School of Human Movement and Exercise Science, University of Western Australia, Crawley.

Address correspondence to Steven Morrison, PhD, School of Physiotherapy and Exercise Science, Gold Coast Campus Griffith University, PMB 50 Gold Coast Mail Centre, Queensland 9276, Australia. E-mail: s.morrison{at}griffith.edu.au

Background. Physiological tremor is an intrinsic and highly variable motor output that is sensitive to alteration in both neuromuscular function and/or changing task demands. Given that any tremor increase can severely influence fine motor performance, there is a requirement to clarify what factors lead to increased tremor. Identification of those factors that alter tremor may be particularly pertinent for elderly persons, who often exhibit a decline in postural control and amplified tremor. The aim of this study was to examine the effect of whole body posture (seated vs standing) on multiple segment tremor and forearm electromyogram (EMG) activity of younger and older individuals.

Methods. Fourteen older and 12 young participants performed a bilateral pointing task. Tremor data were collected using accelerometers attached to the forearm, hand, and finger segments of each arm. Surface EMG data were also collected from the extensor digitorum muscle of each arm.

Results. Although the pattern of tremor was similar between age groups, older participants exhibited increased hand and finger tremor amplitude and increased EMG activity across all postural conditions. For older individuals, tremor increases were greatest when the participant performed the task in a standing position. All age-related increases in hand and/or finger tremor were confined to increases in peak power between 8 Hz and 12 Hz.

Conclusions. From a clinical perspective, these findings illustrate that using multiple segment tremor analyses can provide additional insight into potential age-related tremor differences. Additionally, the fact that postural position had a pronounced effect on tremor in older individuals suggests that body posture should be considered as a potential confounding factor when assessing tremor differences between population groups.