Muscle quality (the ratio of strength to lean muscle mass) might be a better indicator of muscle function than strength alone. Differences in muscle quality index (MQI) between octogenarians and young older adults remain unclear. The aims of the present cross-sectional study were to compare (1) MQI between octogenarians and young older adults, (2) lab versus field-based MQI tools, and (3) determine possible confounding factors affecting MQI in older adults. Compiled data from two cross-sectional studies included 175 younger and older adults (31 men and 144 women) with a mean age of 75.93± 9.49 years. Participants with age ≥ 80 years old were defined as octogenarians (n= 79) and < 80 years was defined as young older adults (n= 96). Laboratory MQI was derived from the ratio of grip strength to arm muscle mass (in kg) measured by dual-energy x-ray absorptiometry. Field-based MQI was quantified from the ratio of grip strength to body mass index (BMI). Octogenarians displayed lower field (P= 0.003) and laboratory MQI (P< 0.001) as compared with young older adults. There was a strong correlation effect between field MQI and laboratory MQI (P= 0.001, R= 0.85). BMI (P= 0.001), and diabetes mellitus (P= 0.001) negatively affected MQI. Women presented lower MQI (P= 0.001) values than men. In light of this information, rehabilitation specialists should consider the use of fieldbased MQI as a tool for evaluation and follow-up of older population.

The muscle quality index (MQI) is associated with numerous health outcomes in adults; however, the effects of distinct MQI on functional capacity in obese older women have not yet been fully investigated. Thus, we investigated the contribution of different muscle quality indices on TUG performance prediction in obese older women. We secondarily evaluated the association between MQI, aerobic capacity performance (Treadmill performance and 6-minute walk test), and obesity indices (BMI, body fat percentage, and neck, waist, and hip circumference). Methods: Participants included 64 obese older women (mean age 67.05 ± 5.46 years, body fat ≥ 35%). General anthropometric, health history, body composition, treadmill exercise, and functional test (Time up and go) measures were collected. A hydraulic dynamometer was used to assess muscle strength, and Dual Energy X-ray Absorptiometry (DXA) to identify body fat percentage. The field MQI was defined as the highest reading divided by the subject's body mass index (BMI), while the laboratory MQI was obtained by the ratio of grip strength to the entire arm muscle in kilograms measured by DXA. A hierarchical multiple regression was performed to predict TUG-test performance. Results: An increase in field MQI of one unit is associated with a decrease of 2.59 seconds in the TUG test (β = −0.540; p = 0.004). There was no association between laboratory MQI and TUG performance (β = 0.067; p = 0.712). Furthermore, field MQI displays a positive correlation (p < 0.05) with aerobic capacity performance (6-minute walk test and peak O 2 consumption) and a negative correlation (p < 0.05) with diverse obesity indices (neck and waist circumference, body fat, and BMI). Conclusion: MQI displayed an important prediction with TUG-test, a positive correlation with aerobic capacity, and a negative correlation with obesity indices.

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