Resistance Training Muscle Adaptations Using D3-creatine Dilution In Older Adults: A Pilot Study

High intensity resistance training (RT) is well known to increase muscle mass in older adults. However, the degree to which is dependent on the measurement method. D3-creatine (D3Cr) dilution is a promising new method that provides a direct and accurate measurement of creatine pool size and whole-body skeletal muscle mass. There are a limited number of studies that compare intervention-based adaptations between D3Cr derived skeletal mass versus lean mass by dual energy x-ray absorptiometry (DXA) Purpose: To evaluate and compare D3Cr derived skeletal mass and DXA lean mass changes following whole body progressive RT in moderate to low functioning older adults. Methods: Twenty-four older adults who tested as moderate to low-functioning on a standardized performance battery were randomized to a whole-body RT or health education program. RT was performed 3 days per week for 14 weeks. It included upper and lower body exercises performed at ~70% of maximal strength in progressive manner. Health education workshops were conducted weekly as an attention "control". D3Cr dilution and whole body DXA scans were performed prior to randomization and shortly after completion of the programs. Results: D3Cr derived whole body skeletal mass increased more in participants randomized to the RT group compared to the health education group (3.5 ± 2.0 vs. 1.2 ± 1.7 kg, p = 0.03). Mean differences between groups was lower with DXA appendicular lean (RT: 0.81 ± 0.67 vs Education: -0.23 ± 0.70 kg, p = 0.008) and DXA total lean body mass (RT: 1.1 ± 1.4 vs Education: -0.19 ± 0.70 kg, p = 0.06). Pearson correlation coefficients showed weak relationships between changes in D3Cr muscle and DEXA appendicular (0.19, p = 0.48) and total lean mass measures (0.41, p = 0.13). Conclusions: This pilot study demonstrates that D3Cr dilution method is sufficiently sensitive to detect whole body changes in skeletal muscle mass of older adults. The unexpected discordance between D3Cr dilution and traditional DXA based measures of lean mass requires further study.