pQCT- and Ultrasound-based Muscle and Fat Estimate Errors after Resistance Exercise

Purpose Resistance exercise increases blood flow, induces osmotic and hydrostatic fluid shifts during and immediately after exercise, and may trigger inflammatory responses for several days in the working muscle. The resultant muscle swelling can subsequently affect muscle size and quality assessments. However, the effects of muscle swelling on x-ray attenuation of adipose estimate errors are unknown. Methods Peripheral quantitative computed tomography (pQCT) and ultrasonography were used to assess muscle and adipose tissue properties of both upper arms before, 24, 48 and 72 h after unilateral resistance exercise. Recreationally active participants (n=17) completed the exercise while their contralateral limb served as a control. Results Resistance exercise resulted in a significant increase in pQCT-derived muscle CSA (includes intermuscular adipose tissue [IMAT] area), muscle area (excludes IMAT area) and IMAT area, and ultrasound-derived muscle thickness at 24, 48, and 72 h. A significant decrease in pQCT-derived muscle density was also detected as well as an increase in ultrasound-derived echo intensity at 48 and 72 h. The changes in muscle area, IMAT area and muscle density were significantly correlated with changes in echo intensity, while the changes in muscle CSA and IMAT area were significantly correlated with changes in muscle thickness. Conclusion Unaccustomed resistance exercise can cause errors in pQCT- and ultrasound-based muscle and adipose estimates for at least 72 h. These errors are the result of muscle swelling likely caused by muscle blood flow and inflammation-dependent fluid shifts in muscle. These findings may have implications for measurements in other inflammatory conditions. Corresponding author: Grant S. Rowe, Centre for Exercise and Sports Science Research (CESSR), School of Medical and Health Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, Perth, Australia 6027. Email: g.rowe@ecu.edu.au Funding Sources: No funds were received to complete this work. Compliance with the ethical standards Conflict of Interest: The authors declare that they have no conflict of interest. Ethical approval: All procedures performed herein were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Declaration: The present study does not constitute endorsement by ACSM. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for publication: 7 December 2018. © 2018 American College of Sports Medicine

from Sports Medicine via xlomafota13 on Inoreader http://bit.ly/2SeG5xd
via IFTTT