Traditional Crate vs. XRTS Lever Arm Lift: Part 2 Maria McDonald, SPT, Grace Schwemmer, SPT, CSCS, and Dwayne Woldruff, SPT Faculty Mentor: Marcie C. Swift, PT, PhD, FAAOMPT and Janice Loudon, PT, Ph.D., SCS, ATC, CSCS
Purpose/Hypothesis: The purpose of this research study was to 1) compare the maximum lifting capacities and 2) determine the relationship of perceived exertion and 3) compare hip, knee, and ankle joint angles within subjects all between the two lifting modes.
Background: A total of 19 subjects between ages 20-40 with no upper or lower extremity injuries within the past 12 months and unable to lift more than 110 pounds were recruited to participate in this study.
Methods: Investigators established 1RM for each subject performing a lift using a traditional crate and XRTS Lever Arm. Subjects were randomly assigned 5 weights ranging from 10-100% of their determined 1RM and reported a rating of their perceived exertion (RPEs) after each lift. Peak hip flexion, knee flexion, and ankle joint angles during maximal lifts of two lifting modes were analyzed using Dartfish software.
Results: There was a statistically significant difference (p < 0.05) between maximal lift values for the two lifting modes. The % difference between the traditional crate lift and the XRTS Lever Arm was 20.5% +/- 11.7% with values ranging between .14%-42.6%. There was a positive correlation between the RPE on the two lifting modes (p=0.91). The peak joint angles between lifts was similar for the hip (p = 0.91), but statistically different between the knee (p < .05) and ankle (p < .05).
Conclusion: This validation study demonstrates that lift effort and RPE are not different between lifting modes. Although the actual maximal lift values for the modes of lifting were statistically different the two modes of lifting are equivalent within the standard 20% difference. The statistical difference found between peak knee and ankle angles may have been due to the fact that subjects were not cued on biomechanics per the protocol and subject unfamiliarity with lifting XRTS Lever Arm.