Laterality and Influence of Contraction Time during Low-intensity Isometric Contraction in the Case of Upper Limb Physiological Tremor

• Published in: Transactions of Japanese Society for Medical and Biological Engineering Vol. 47; no. 2; pp. 250 - 254
• Main Authors: OSHITA, Kazushige, YANO, Sumio
• Format: Journal Article
• Language: Japanese
• Published: Japanese Society for Medical and Biological Engineering 10.04.2009
• Subjects: Contraction time; Laterality; Physiological Tremor
• ISSN: 1347-443X; 1881-4379
• DOI: 10.11239/jsmbe.47.250

This study aimed to investigate the laterality and influence of contraction time during low-intensity isometric contraction (20% maximum voluntary contraction) in the case of upper limb physiological tremor (PT) . The PT signal was measured in 9 healthy and right-handed males by using an acceleration sensor. The maximum entropy method was used to compare the contraction time and laterality among these subjects. The amplitude of PT was found to increase with the contraction time. This increase was mainly influenced by components measuring < 12 Hz. Further, the amplitude of PT was greater in the left limb than in the right limb. During the first half of the contraction (0 to 30 sec), the standard deviation of amplitude (SD) significantly correlated with components measuring ranging from 8 to 12 Hz (r = 0.81 (right), r = 0.75 (left) ) ; however, in the latter half (30 to 60 sec) of the contraction, the SD significantly correlated with components measuring < 4 Hz (r = 0.91 (right), r = 0.71 (left) ) and those ranging from 8 to 12 Hz (r = 0.88 (right), r = 0.89 (left) ) . These results suggest that PT is influenced by a superspinal mechanism at the onset of contraction; however, with an increase in the contraction time, PT is influenced by both a superspinal mechanism and stretch reflex. Furthermore, PT is influenced by not only the contraction time but also laterality.