Date of Award


Document Type

Open Access Thesis

Degree Name

Master of Science (MS)



First Advisor

Peter M. McGinnis, Ph.D.

Second Advisor

Jeffrey Bauer, Ph.D.

Third Advisor

John Foley, Ph.D.


The purpose of the present study was to compare the peak resultant torque, shear, and compressive forces acting at the L3/L4 junction of the lumbar vertebrae and the peak power output during 40% one repetition maximum (1RM) and 80% 1RM attempts of the power clean. It was hypothesized that performance of a power clean at 80% 1RM will result in greater peak resultant compressive force, torque and shear force at the L3/L4 junction of the lumbar spine than that of a 40% 1RM attempt. Power cleans at 80% 1RM will also result in higher maximum instantaneous power outputs than that of the 40% attempts. The power clean attempts for each participant were performed on a force plate and video recorded. Kinetic data from the force plate and kinematic data derived from the videorecords were used in an inverse dynamic analysis to determine the peak resultant torque, shear force, and compressive force at the L3/L4 junction. Peak instantaneous power was calculated using data from the force platform. Statistical analysis revealed that the means for all four dependent variables were significantly greater during attempts at 80% 1RM than 40% 1RM. It was also found that from 40% to 80% attempts, peak torque increased by 52%, peak shear force increased by 64%, peak compressive force increased by 49% and power increased by 22%. Given the smaller percent increase in power relative to the forces experienced it is questionable whether or not increasing loads to 80% is worth the increase in torque and forces sustained at the L3/L4 junction.