Mental set can modulate response onset in the lower limb muscles to falls in humans

• Published in: Neuroscience letters Vol. 321; no. 1; pp. 77 - 80
• Main Authors: Fu, S.N., Hui-Chan, C.W.Y.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 15.03.2002; Elsevier
• Subjects: Accidental Falls; Adult; Behavioral psychophysiology; Biological and medical sciences; Biomechanical Phenomena; Cognition - physiology; Electromyographic responses; Electromyography; Electrophysiology; Falls; Fundamental and applied biological sciences. Psychology; Humans; Impact force; Landing; Leg - physiology; Male; Mental set; Movement - physiology; Muscle Contraction - physiology; Muscle, Skeletal - physiology; Posture - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reaction Time - physiology; Reflex - physiology; Unexpected and self-initiated drops; Vestibule, Labyrinth - physiology; Visual Pathways - physiology; Volition - physiology; Falls; Mental set; Impact force; Unexpected and self-initiated drops; Landing; Electromyographic responses; Ankle; Human; Body movement; Electrophysiology; Cognition; Electromyography; Experimental study; Motricity
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/S0304-3940(02)00060-5

The objective of this study was to investigate the modulation of the ankle muscle electromyographic (EMG) response as a function of mental set. Thirteen young healthy subjects underwent 40 unexpected and self-initiated drops from 30 cm above two separate force-plates. Following unexpected drops, reflex activities were observed in the medial gastrocnemius (MG) and tibialis anterior (TA) at mean latencies (±SD) of 83.59±10.1 and 99.43±21.82 ms, respectively. Following self-initiated drops, the response latency of the MG was significantly shortened (to 71.98±10 ms, P<0.05), and the TA was significantly lengthened (to 183.33±45 ms, P<0.05) when compared with unexpected drops. Such a modulation was associated with a significant reduction of the impact force on landing as compared with unexpected drops (by 17%, P<0.05). Interestingly, a negative correlation was found between the onset of the TA EMG response and the magnitude of the impact force on landing during expected ( r=−0.66, P<0.05) but not unexpected drops.