Factors affecting grip strength testing

Neurotoxicology and Teratology 25 (2003) 543 – 553 www.elsevier.com/locate/neutera

Factors affecting grip strength testing
Jacques P.J. Maurissen*, Brian R. Marable, Amanda K. Andrus, Kenneth E. Stebbins
Toxicology & Environmental Research and Consulting, The Dow Chemical Company, 1803 Building, Midland, MI 48674, USA Received 17 February 2003; received in revised form 28 April 2003;accepted 1 May 2003

Abstract The rodent grip strength test was developed decades ago and is a putative measure of muscular strength. This test has been included in the functional observational battery (FOB) to screen for neurobehavioral toxicity, and changes in grip strength have been interpreted as evidence of motor neurotoxicity. Despite its widespread use, questions remain about what the gripstrength test actually measures. In this study, potential confounders of the grip strength test were identified and tested, including operational parameters, disruption of peripheral sensory function and changes in body weight. Operational parameters (sampling rate, system type and trial angle but not trial speed) had dramatic effects on grip strength data. Doxorubicin (DX, 10 mg/kg iv) was used tocause sensory impairment. It decreased forelimb and hindlimb grip strength (by 27% and 32%, respectively, compared with controls), an effect that was correlated with degeneration of peripheral and central sensory components (distal tibial and sural nerves, dorsal funiculus of the spinal cord and dorsal, but not ventral, spinal roots). Feed restriction-induced loss of body weight (26% compared withcontrols) and muscle mass (20% compared with controls) reversibly decreased both forelimb and hindlimb grip strength (18% and 17%, respectively, compared with controls). Ignoring these confounding factors could potentially lead to increased data variability and inconsistency within single studies, across studies and in historical control data sets. To assist in data interpretation and evaluation ofgrip strength results, it is suggested that exact conditions of application of the test be reported in greater detail. Furthermore, given that the grip strength test can be influenced by factors other than true muscular strength, use of the term grip performance is proposed to better reflect the apical nature of this test. D 2003 Elsevier Inc. All rights reserved.
Keywords: Grip strength; Loadcell; Sampling rate; Trial angle; Trial speed; Test system; Sensory effect; Doxorubicin; Body weight effect

1. Introduction A test for grip strength measurement in rodents was developed more than 20 years ago [2,14]. It is a behavioral test that was eventually introduced into regulatory test batteries to screen for neurobehavioral toxicity. It became a component of the functional observationalbattery (FOB) and typically fits under the motor test section [27]. Typically, the grip strength apparatus consists of a grasping device or platform (e.g., grid, ring, T-bar) that is connected to a strain gauge or load cell. In general, the test measurement is conducted by allowing the animal to grasp the device and then pulling it away until its grip is broken. A reading from the strain gauge isrecorded. Three such trials are performed and the measurements are usually averaged.

* Corresponding author. Tel.: +1-989-636-2541; fax: +1-989-6389863. E-mail address: jpjm@dow.com (J.P.J. Maurissen). 0892-0362/$ – see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/S0892-0362(03)00073-4

Often, no specific instructions are reported in the publications that indicate howpractically each test trial was performed. A potential source of differences in the results of grip strength tests arises from the fact that several types of grip strength devices are commercially available; some have been specially built. The systems that have been described in the literature potentially vary along several dimensions. The platforms the animals grasp can be unsupported or supported...