INTRAMUSCULAR ADIPOSE TISSUE ATTENUATES GAINS IN MUSCLE QUALITY IN OLDER ADULTS AT HIGH RISK FOR FALLING. A BRIEF REPORT

Objectives: To examine the influence of intramuscular adipose tissue (IMAT) on muscle quality (MQ) changes in older adults after 12 weeks of exercise training. Design: Prospective cohort design. Setting: Academic health science center clinical exercise facility. Participants: 70 older (mean age 73.4 + 6.3 years) adults with a history of falls. Intervention: Resistance, endurance and balance exercise three times weekly for 12 weeks. Measurements: Quadriceps strength was determined by maximum voluntary isometric contraction. An MRI of the thigh was used to determine cross-sectional area of lean tissue and IMAT. MQ was calculated as the force per unit area of lean tissue. Individuals were stratified into tertiles (Low IMAT, Middle IMAT, High IMAT) based on pre-IMAT levels. Changes in MQ, lean and IMAT were compared across groups. Results: No significant changes in lean or IMAT occurred in any group with training. MQ increased only in the Low IMAT group. The Middle and High IMAT groups did not demonstrate a significant change in MQ following 12 weeks of training. Low IMAT, pre = 2.7 [0.6] post= 3.0 [0.6]; Middle IMAT, pre =2.54 [0.8] post =2.75 [0.7]; High IMAT, pre =2.6 [0.6] to post =2.5 [0.6]. Conclusion: High levels of thigh IMAT appear to blunt the adaptive MQ response to training. High levels of thigh IMAT may be a potential reason why some older adults do not change their MQ following training. Future research should confirm these results and determine why IMAT impairs MQ and the adaptive response to training in older adults.