(C-114) Assessment of Variability in Hip Maximum Voluntary Isometric Contraction for Methodology Optimization

Friday, October 13, 2023

3:30 PM – 4:30 PM PDT

Location: Exhibit Hall - Row C - Poster # 114

Presenting Author(s)

Quentin Shin

Undergraduate Researcher
University of Virginia
Leesburg, Virginia, United States

Co-Author(s)

MG

Mario E. Garcia

PhD Candidate
University of Virginia, United States
EM

Emily McCain

Postdoctoral Researcher
University of Virginia, United States
SR

Shawn Russell

Associate Professor of Orthopedics
University of Virginia, United States

Primary Investigator(s)

SB

Silvia Blemker

Professor of Biomedical Engineering
University of Virginia, United States

Introduction::

Subtrack: Human Performance/Sports Biomechanics
Musculoskeletal models are increasingly used for simulations of lower limb movement. To ensure generic models match individuals, musculoskeletal models are scaled to subject specific anthropometry and experimentally measured joint torques are matched to model strength. Scaling hip strength can be challenging due to its multiple degrees of freedom and increased muscular redundancy caused by more muscles crossing the joint than degrees of freedom [1]. These scaling factors make measurement of experimental strength of the hip in any direction difficult [2]. There are currently two leading methodologies for collecting maximum voluntary isometric contraction (MVIC) of hip abduction/adduction and extension/flexion: standing or side lying [3]. The purpose of this work is to determine which method: 1) evokes greater maximum torque values, and 2) produces torque values with lower variability. We aim to establish a standardized practice for assessment of hip strength that returns the most consistent MVIC values for a broad range of subjects. We hypothesize that the side lying method will return significantly higher maximum torque values and significantly lower variance than the standing method for hip movement.

Materials and Methods:: For each methodology, three male subjects (height =1.77 ± 0.03 m, mass = 79.1 ± 16.74 kg) completed two repetitions of 5-second unilateral MVIC at three joint positions for hip abduction/adduction (θ = 0o, 10o, and 20o ) and hip extension/flexion (θ = 0o, 15o, and 30o ) using the Biodex System 4 Pro Dynamometer (Biodex Medical Systems Inc., Shirley, New York, USA). For the standing hip trials, subjects were placed in a custom-built standing hip rig. For the side lying trials, subjects laid on an examination table, placed adjacent to the dynamometer. A Donjoy T-ROM knee brace locked the knee at 0° for each method. Paired t-tests were used to determine differences in MVICs between methods at each joint position for each movement (abduction, adduction, flexion, extension). F-tests were used to compare variance between the two methods for each joint positions for each movement. The three subjects created a preliminary data set for our plan to increase the sample size in the future. The maximum torque data was normalized by body mass for each subject.

Results, Conclusions, and Discussions:: The MVICs were significantly greater (𝛼 < 0.05) across abduction 0o and 10o in the standing position (1.33 ± 0.14 Nm/kg and 1.16 ± 0.20 Nm/kg, respectively) than side lying (1.03 ± 0.19 Nm/kg and 0.83 ± 0.21 Nm/kg, respectively). For all other joint positions there were no significant differences. For hip abduction 20o, adduction 0o, 10o, and 20o, and flexion 20o, the side lying position had significantly less variance (𝛼 < 0.05) compared to standing.
Both positions produced similar MVICs values while the side lying method returned lower variance across these values in five of the joint positions tested compared to standing. Our pilot data suggest that the side lying method is the more consistent method for assessing hip strength and can be used to decrease variance in gathering maximum torque of the hip. Our future directions include expanding sample size for data collection and collecting data on females to determine the influence of sex as a variable. Additionally, we plan to incorporate a follow up testing session for each subject to assess reproducibility of the standing trial method. We intend to re-assess the information using the same statistical tests on the expanded data set to strengthen our results and determine if the conclusions from our pilot data are valid, and incorporate an ANOVA analysis.

Acknowledgements (Optional): :

References (Optional): :

Kutch, Jason, et al., Journal of Biomechanics (2011).

Arnold, E.M., et al., Ann Biomed Eng (2010).

de Castro, Marcelo P., et al., Journal of Bodywork and Movement Therapies (2022).