A comparison of isometric strength and dynamic lifting capability

Abstract

A laboruiory study was conducted to determine if job specific static strength can be used to predict dynamic lifting capability (maximum acceptable weight of lift) based on psychophysical methodology. Nine male college students were required to lift three different tote boxes (containers) from a 38 cm height to a 81 cm high table using a semi-squat body posture. For each tote boxsialic strength was measured in three different ways. These were (i) maximum voluntary isometric strength (MVIS) measured at the origin in a vertical direction, (ii) MVIS measured close to the body in a vertical direction, and (iii) maximum acceptable weight that a subject could hold for 3 s at the origin of the dynamic lift, MVIS al the origin of lift, MVIS close to the body and holding the tote box explained 24.32 and 62% variation, respectively, in dynamic lifting capability. On the average, MVIS al the origin of lift, MVIS close to the body and holding the tote box were 46. 120. 72%, respectively, of dynamic lifting strength. The findings of this study indicate the need to exercise extreme care in The use of static strength tests to determine dynamic lifting capability. Changes in MVIS measurement techniques are suggested to better determine dynamic lifting capability. Finally, effects of box size on dynamic and static strengths are discussed.