Downloaded from http://journals.lww.com/acsm-msse by BhDMf5ePHKbH4TTImqenVP9XFeJftgMxyyX86kkqc0k5AlQcf5sY1vTddvOh5nt7 on 03/19/2020 334 1278 Board #40 May 30 9:30 AM - 11:00 AM Effects Of Downhill Running On Muscle MRI T2 In Young mdx Mice Zahra Moslemi, Christopher Lopez, Abhinandan Batra, Andrew Rennick, Sean C. Forbes. University of Florida, Gainesville, FL. Email: zmoslemi@ufl.edu (No relationships reported) Previous studies have demonstrated that downhill treadmill running causes skeletal muscle damage that can be detected with magnetic resonance transverse relaxation time (T 2 ) in adult dystrophic mice (mdx). However, young mdx mice (under 12 weeks of age) are characterized by a peak inflammatory phase with greater heterogeneity among muscles, potentially making it more difficult to detect T 2 changes. PURPOSE: To determine whether muscle damage following downhill running can be detected in young mdx mice using proton magnetic resonance imaging (MRI) and spectroscopy (MRS). METHODS: C57BL/10ScSn-DMDmdx (mdx, n=5) and wild-type C57BL/10ScSn (controls, n=5) male mice of 6-9 weeks of age performed downhill running on a treadmill (14% grade at 8- 12m/min for 45-60 min). MRI/MRS was conducted prior to and 24 hours following running in the mice hindlimbs. T 2 -weighted, multiple-slice, single spin-echo MR axial images were acquired (TR 2s, TE 14/40 ms, 12 slices) from the hindlimbs. MRI T 2 values were calculated on a pixel-by-pixel basis for the anterior compartment (AC), posterior compartment (PC), and the deep medial region between the tibia and fibula (MC). In addition, single voxel 1 H-MRS data were acquired from the soleus and gastrocnemius using stimulated echo acquisition mode (STEAM; TR 9 s, 32 TE’s exponentially spaced: 5-288 ms, 4 phase cycles) with a 4.7 T Varian/Agilent MR system. RESULTS: At baseline, T 2 was elevated (p<0.05) in mdx mice (26.8±1.2ms) compared to controls (24.8±0.9 ms). Following downhill running, the mdx mice had elevated (p<0.05) T 2 values compared to baseline when a composite of the compartments were compared (Pre: 26.8±1.2ms; Post: 28.8±1.4 ms). The MC was typically (80%) the most affected hindlimb region in the mdx mice. Similarly, 1 H-MRS derived T 2 values were increased (p=0.05) in a composite measure of the soleus and gastrocnemius after downhill running (29.8±4.2ms) in mdx compared to before downhill running (26.4±2.8ms). There were no significant changes in T 2 in control mice after performing the downhill running protocol. CONCLUSIONS: Overall, our findings support the use of downhill running combined with MR T 2 measures as a valuable approach for testing potential therapeutic interventions in young dystrophic mice. Funding Source: NIH (NIAMS) R01 AR070101. 1279 Board #41 May 30 9:30 AM - 11:00 AM Interactions Among Age, Sex, and Scanning Location in the Assessment of Rectus Femoris Echo Intensity Adam Burton, Matthew Stock. University of Central Florida, Orlando, FL. Email: aburton426@gmail.com (No relationships reported) Echo intensity is an ultrasound-derived measurement of skeletal muscle quality believed to reflect both fibrous tissue content and adipocyte infiltration. Moderate correlations between echo intensity and measures of muscle function have been reported in older adults. But, it is less clear if the aging process results in comparable declines in muscle quality in men and women. Also, it has yet to be determined if age and sex discrepancies are uniform throughout a muscle. PURPOSE: The purpose of this investigation was to examine differences in echo intensity among younger and older men and women along the length of the rectus femoris. METHODS: Fifteen younger men (mean ± SD age = 23 ± 3 years), fifteen younger women (21 ± 2 years), eight older men (75 ± 6 years), and sixteen older women (70 ± 5 years) participated in this study. Participants were untrained, healthy, and had a body mass index ≤ 30 kg/m 2 . B-mode ultrasonography was used to acquire panoramic images of the dominant rectus femoris in the transverse plane at the one-third, one-half, and two-thirds distances along the length of the rectus femoris. ImageJ software was used to analyze the images. Echo intensity was corrected for subcutaneous tissue thickness using sex-specific equations. Analyses of variance and effect size statistics were used to analyze the data. RESULTS: When collapsed across scanning location, differences between men and women (marginal mean difference = 28.1 AU, p < .001) were greater in magnitude than those for younger versus older adults (marginal mean difference = 7.0 AU, p = .237). However, age had a strong influence on differences among scanning locations, with proximal echo intensity (107. 8 ± 14.5 AU) being significantly lower than the middle (127.6 ± 13.7 AU) and distal (130 ± 19.6 AU) values for older men (F = 7.4, p = .018, partial η 2 = .514), with a similar trend for older women (F = 2.9, p = .073, partial η 2 = .164). Within each sex, younger adults had very similar echo intensity values at the proximal, middle, and distal sites (greatest mean difference < 5.0 AU). CONCLUSION: The difference in corrected echo intensity is greater for men versus women compared to younger versus older adults. Furthermore, aging results in nonuniform changes in muscle quality throughout the belly of the rectus femoris, with greater deterioration at the middle and distal portions. 1280 Board #42 May 30 9:30 AM - 11:00 AM Can Changes In Echo-intensity Be Used To Detect The Presence Of Muscle Swelling? Noam Yitzchaki, Tayla E. Kuehne, Samuel L. Buckner. University of South Florida, Tampa, FL. (Sponsor: Marcus Kilpatrick, FACSM) Email: noamy@mail.usf.edu (No relationships reported) When examining skeletal muscle, it has been suggested that changes in echo-intensity (EI) measured with B-mode ultrasound can detect the presence of edema-induced muscle swelling. Specifically, if an increase in muscle size is accompanied by an increase in EI it is thought that true growth has not occurred. Interestingly, our research group has shown that small upward and downward tilting of the ultrasound probe can have a large influence on EI, while having minimal impact on muscle thickness (MT). This suggests that proposed changes in EI following resistance exercise may be artifact from probe tilt as opposed to swelling. PURPOSE: To examine the acute changes in biceps MT and EI, while accounting for probe tilt, following 4 sets of biceps curls. METHODS: 49 resistance-trained men and women were recruited. Individuals in the experimental group (n = 23) visited the laboratory twice. During the first visit, paperwork and one repetition maximum (1RM) strength were measured. During the second visit, individuals performed 4 sets of biceps curls to volitional failure using 70% of their 1RM. B-mode ultrasound images of the biceps were taken to examine changes in both MT and EI. The ultrasound probe was equipped with a standard spirit level to ensure that probe tilt would play a minimal role in all EI measurements. Ultrasound measurements were taken immediately before and following exercise. Individuals in the control group (n = 26) visited the lab on one occasion and served as a time-matched control for changes in both MT and EI. Results are presented as means (95% CI). RESULTS: For MT there was a group by time interaction (p < 0.001). MT increased in the experimental group [mean change = 0.44 (0.33-0.54) cm], but not in the control group [mean change = -0.015 (-0.03-0.01) cm]. For EI, there was no group x time interaction (p = 0.074). In addition, there were no main effects for group (p = 0.254) or time (p = 0.314). The mean difference in the change in EI between groups was -2.99 (-6.25-3.03) arbitrary units. CONCLUSIONS: Our results suggest that EI does not appreciably change in response to acute swelling when accounting for probe tilt. In addition, changes in EI were not different compared to a time matched non-exercise control. It seems unlikely that EI can provide meaningful information regarding the presence of muscle swelling following exercise. Copyright © 2019 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.