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B. Singh1, A. Sharma2, N. Fahoum3
1California State University, Department of Physical Therapy, Fresno Clovis, United States, 2Central Connecticut State University, New Britain, United States, 3California State University, Department of Physical Therapy, Fresno, United States
Background: Obesity rates have increased significantly in the United States over the years, with approximately 38% of adults now considered obese. Obese subjects tend to have lower normalized strength than their normal counterparts and it would be attributed to more fatty tissue infiltration in the muscle tissue. While many studies have been performed on functional tasks in obese adults, not many studies have looked at the muscle and fat tissue morphology using magnetic resonance imaging (MRI).
Purpose: The purpose of the study is to explore muscle differences, measured by moment arm and cross sectional areas in hip muscle MRI’s between obese and normal weight subjects.
Methods: The University’s Institutional Review Board approved the study. 6 subjects aged 21-65 participated were recruited for the study. Participants with lower limb pain, diabetes, and recent surgery were excluded from the study. The hip MRI images were obtained for analysis. The MRI images were imported, and scaled in the Image J software. The major muscles were manually identified by an experienced physical therapist. Gluteus Maximus (GMax), Gluteus Medius (GMed), Gluteus Minimus (GMin), Rectus Femoris (RF) and Gracillis (Gr) were used for final analysis. The anteroposterior (AP) and mediolateral (ML) distances from each muscle to the vertebral centroid were subsequently calculated as an estimate of the moment arm lengths of these muscles. Perpendicular distance from the Hip Joint center to the approximate line of action of the muscle. Boundaries of the muscle determined by manually observation to get estimate cross sectional area. Linear correlation coefficients were calculated to determine the relationship between BMI, cross sectional area, and moment arm lengths.
Results: The mean age of subjects was 47.3 ± 15.3 years, height 1.61± 0.1 m, weight 91.6± 27.1 kg with a BMI of 34.5 ± 9.47 kg/m2. The cross section area for 5 major muscle groups, Gluteus Maximus (GMax), Gluteus Medius (GMed), Gluteus Minimus (GMin), Rectus Femoris (RF) and Gracillis (Gr) was 0.75,0.37, 0.02, 0.28, 0.14 mm. R2 values obtained by regression analysis between moment arm and BMI Gluteus Maximus (GMax), Gluteus Medius (GMed), Gluteus Minimus (GMin), Rectus Femoris (RF) and Gracillis (Gr) was 0.82, 0.45, 0.02, 0.76, and 0.38.
Conclusion(s): Muscle moment lengths of major hip muscles and BMI showed significant strong relationships. Obese muscles are marbled, with more whiter spaces in between indicating longer moment arms. The normal weight muscles showed darker spaces with more intensities. The outer muscles like GMax and GMed Medius show more significant changes as compared to the deeper muscles.
Implications: Obese subjects tend to have sedentary behaviors that can be amplified due to current global pandemic of COVID19. More people are sitting on their chairs and gaining weight. As per the findings of the present study, clinicians may want to consider the implicaitons of weaker muscles in obese and sedentary adults.
Funding, acknowledgements: None
Keywords: Hip, MRI, Obesity
Topic: Musculoskeletal: lower limb
Did this work require ethics approval? Yes
Institution: California State University, Fresno
Committee: IRB Committee, College of Health and Human Services
Ethics number: 993
All authors, affiliations and abstracts have been published as submitted.
