Muscle Quality Index Comparisons Between Hispanics and Non-hispanic Caucasians Using Dual Energy X-ray Absorptiometry and Handgrip Strength

Background & Aims: Muscle quality index (MQI) can be computed in various ways. Also, many studies have evaluated MQI in older adults and non-Hispanic populations. The aim of this study was to compare various muscle quality indexes between Hispanics and non-Hispanic Caucasians when stratifying grip strength and appendicular lean mass measurements. Methods: 235 participants (aged 25.5±9.5 for males and 26.4±9.9 for females) completed a DXA scan to assess appendicular lean mass (ALM). Handgrip strength (HGS) was assessed using a handheld dynamometer. MQI was computed using four different models: 1). MQI _RA : _{ALM and HGS of right arm and hand, respectively; 2). MQI LA : ALM and HGS of left arm and hand, respectively; 3). MQI ARMS : ALM and HGS of both arms and hands, respectively; and 4). MQI TOTAL : ALM of upper and lower-limbs and HGS of left and right hand. Results: Hispanic males and females exhibited lower HGS compared to Caucasians with effect sizes ranging from trivial ( d =0.17) to moderate ( d =0.80). Females demonstrated higher MQI values compared to males for MQI ARMS ( d =0.69), MQI RA ( d =0.75), and MQI LA ( d =0.57). However, MQI TOTAL yielded a small practical effect ( d =0.33) in favor of males (3.2±0.5 kg/kg vs. 3.1±0.5 kg/kg). After factoring by sex and ethnicity, Hispanic males and females, compared to non-Hispanic Caucasians males and females, showed trivial-to-small practical differences ( d values ranging from 0.03 to 0.39). Conclusions: These results demonstrate MQI models vary across sex, particularly when utilizing models that account for upper extremity strength and ALM (i.e., MQI ARMS , MQI RA , and MQI LA ). Lastly, to establish consistency in future research, the present study recommends using MQI models that account for ALM of upper- and lower-limbs (i.e., MQI TOTAL ). However, research measuring muscular strength via one upper-limb (e.g., left hand) might consider measuring ALM of the corresponding arm (e.g., left arm) when computing muscle quality (e.g., MQI LA ).}