Gluteus Maximus Volume And Fat Content As Predictors Of Low Levels Of Physical Activity

BELZUNCE, MARTIN A.; HENCKEL, JOHANN; DI LAURA, ANNA; HART, ALISTER

Conferencia; EFORT 2022; 2022

BackgroundMuscle wasting and an increase of intramuscular fat (IMF) are associated with loss of strength and mobility, making them important markers for muscle health. However, there is not enough quantitative data available to determine which variable and muscles are the most sensitive muscle health markers. We hypothesized that gluteus maximus (GMAX) is a muscle that is considerably affected by physical activity and therefore could be a good muscle to assess overall muscle health using magnetic resonance imaging (MRI).ObjectivesTo assess muscle atrophy and fat infiltration of GMAX as predictors of low levels of physical activity and as muscle health markers.Study Design & MethodsThis was a cross-sectional study involving 70 subjects that underwent Dixon MRI of the pelvis. The individuals were divided into four groups by levels of physical activity, from low to high: inactive patients due to hip pain (N=19); and Low (N=13), Medium (N=18) and High (N=20) physical activity groups of healthy subjects (HS) that did 0-4, 4-8 and more than 8 hours of exercise per week respectively. The patients had an MRI investigation requested after being assessed for hip pain by an orthopaedic surgeon.We estimated the GMAX size and IMF content for each subject using automated measurements of volume and fat fraction (FF) from Dixon MRI respectively. Volume measurements were normalized by the lean body mass.The volume and FF values were compared for the four groups of different levels of activity using a Kruskal-Wallis test. We then compared volume and FF metrics as predictors of physical activity using a multivariate logistic regression analysis. For this test, we grouped the study subjects into Not Active (hip pain and low level of physical activity groups) and Active (mid and high levels of physical activity). Gender, BMI and age were also included as independent variables.ResultsThe normalized volume of GMAX was larger for the High group than for the patient (p=0.03) and Low groups (p=0.004). There were not any statically significant differences between the patient, Low and Medium groups. The median volume values were 11.8, 10.7, 11.6 and 12.9 cm3/Kg for the patients, Low, Mid and High groups respectively.The GMAX FF was higher in the patient group than in the three groups of HS (p=0.002, p