New assessment of forearm strength: reliability and validity.

OBJECTIVE The objective was to determine the reliability of a portable forearm strength hydraulic dynamometer with a doorknob handle and assess its validity compared with a Cybex 6000 (Cybex International, Inc., Medway, MA) isometric torque assessment. METHOD Eighteen volunteers (with a total of 30 forearms) participated in this one-session methodological study to determine the intra- and interrater reliability and criterion validity of a forearm dynamometer. RESULTS Intrarater reliability for both assessors for pronation was (intraclass correlation coefficient [ICC](3,1) = .937-.961) and for supination was (ICC(3,1) = .923-.968). Interrater reliability for pronation was ICC(3,2) = .927 and for supination was ICC(3,2) = .847. Criterion validity of the Baseline hydraulic dynamometer (Fabrication Enterprises Inc., White Plains, NY) compared with the Cybex 6000 was .574-.664 for pronation and .749-.750 for supination. CONCLUSION The Baseline hydraulic dynamometer with a more functional doorknob handle had good intra- and interrater reliability and demonstrated moderate validity compared with Cybex 6000 strength testing.