Effect Of Exercise Habits On Intermuscular Adipose Tissue (IMAT) In Collegiate Young Healthy Women

AIM: It is well known that increment of intermuscular adipose tissue (IMAT) levels in the skeletal muscle mass are shown to experience increased levels of muscle weakness, decreased mobility function, and an increase in risk of future mobility limitation. This study aimed to investigate the association of the presence or absence of regular exercise habits with IMAT and muscle strength in collegiate healthy young women, focusing on IMAT using ultrasound tomography. METHODS: The participants included 20 collegiate young healthy women (age, 20.7 ± 1.0 years; body mass index, 23.0 ± 3.3 kg/m2; number of step counts, 7,706.9 ± 2,307.2 counts). Physical activity levels were measured using a uniaxial accelerometer. Lower limb muscle thickness and IMAT were measured using ultrasound tomography. The region of interest, which included as much muscle as possible but avoided visible bone and fascia, was determined using polygon selections to calculate echo intensity. Muscle strength was measured by maximal voluntary contraction force during isometric knee extension. RESULTS: Single correlation analysis showed number of step counts was positively associated with rectus femoris muscle thickness per thigh length, and muscle strength per thigh length in total participants (p < 0.001, respectively). The group without regular exercise habit had significantly lower values for rectus femoris muscle thickness per thigh length (p = 0.039), and muscle strength per thigh length (p < 0.0001), and trended to have higher echo intensity of rectus femoris (a.u.) (p = 0.056) than the group with regular exercise habits. CONCLUSIONS: The results of this study suggested that the presence or absence of an exercise habit can cause an increment of IMAT in collegiate healthy young women. Echo intensity in ultrasound tomography content is a major predictor explaining increased IMAT. Therefore, increased IMAT levels in collegiate healthy young women without regular exercise habits may be leads to decreased mobility function and an increased risk of future mobility limitation.