Anticipatory scaling of grip forces when lifting objects of everyday life

• Published in: Experimental brain research Vol. 212; no. 1; pp. 19 - 31
• Main Authors: Hermsdörfer, Joachim, Li, Yong, Randerath, Jennifer, Goldenberg, Georg, Eidenmüller, Sandra
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.07.2011; Springer; Springer Nature B.V
• Subjects: Adult; Anticipation, Psychological - physiology; Applied physiology; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Brain research; Data processing; Female; Finger; Forecasting; Fundamental and applied biological sciences. Psychology; Grasping; Grip strength; Hand Strength - physiology; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Lifting; Male; Medical sciences; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Motor skill; Motor systems; Movement - physiology; Neurology; Neuropsychology; Neurosciences; Perceptual-motor processes; Physical properties; Physical training; Physiological aspects; Psychomotor Performance - physiology; Research Article; Scaling; Transports. Aerospace. Diving. Altitude; Vertebrates: nervous system and sense organs; Weight-Bearing - physiology; Young Adult; Germany; Sensorimotor control; Anticipation; Grip force; Internal model; Grasping and lifting; Gripping; Load; Force
• ISSN: 0014-4819; 1432-1106; 1432-1106
• DOI: 10.1007/s00221-011-2695-y

The ability to predict and anticipate the mechanical demands of the environment promotes smooth and skillful motor actions. Thus, the finger forces produced to grasp and lift an object are scaled to the physical properties such as weight. While grip force scaling is well established for neutral objects, only few studies analyzed objects known from daily routine and none studied grip forces. In the present study, eleven healthy subjects each lifted twelve objects of everyday life that encompassed a wide range of weights. The finger pads were covered with force sensors that enabled the measurement of grip force. A scale registered load forces. In a control experiment, the objects were wrapped into paper to prevent recognition by the subjects. Data from the first lift of each object confirmed that object weight was anticipated by adequately scaled forces. The maximum grip force rate during the force increase phase emerged as the most reliable measure to verify that weight was actually predicted and to characterize the precision of this prediction, while other force measures were scaled to object weight also when object identity was not known. Variability and linearity of the grip force–weight relationship improved for time points reached after liftoff, suggesting that sensory information refined the force adjustment. The same mechanism seemed to be involved with unrecognizable objects, though a lower precision was reached. Repeated lifting of the same object within a second and third presentation block did not improve the precision of the grip force scaling. Either practice was too variable or the motor system does not prioritize the optimization of the internal representation when objects are highly familiar.