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

Abstract

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 cross-sectional area (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, whereas the changes in muscle cross-sectional area 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.

Effects of velocity loss in the bench press exercise on strength gains, neuromuscular adaptations, and muscle hypertrophy

“…Lastly, it has recently been shown that unaccustomed resistance exercise can cause errors in ultrasound‐based measures 72 hours post‐exercise 48 . However, it should be noted that our participants were previously accustomed to the resistance exercise and we assessed a different muscle (pectoralis major) than the one assessed by Rowe et al 48 (biceps brachii), which likely limited the impact of this issue on our findings. Thus, whether a 72 hours post‐exercise ultrasound measure of the pectoralis major muscle can be affected by the acute effect of resistance exercise in previously accustomed subjects should be assessed in future studies.…”

“…Fourthly, it should be acknowledged that daily 1RM estimations may not be accurate 18 . Lastly, it has recently been shown that unaccustomed resistance exercise can cause errors in ultrasound‐based measures 72 hours post‐exercise 48 . However, it should be noted that our participants were previously accustomed to the resistance exercise and we assessed a different muscle (pectoralis major) than the one assessed by Rowe et al 48 (biceps brachii), which likely limited the impact of this issue on our findings.…”

Exercise induced changes in echo intensity within the muscle: a brief review

“…Although echo intensity is used as a marker for changes in muscle quality [7][8][9][10][20][21][22][23][24][25][26][27], studies using changes in echo intensity as a proxy have produced inconsistent results following resistance training (Table 1). Echo intensity has been reported to decrease [7, 20-24, 26, 27, 46], increase [25,27,57], or remain unchanged [8-10, 21, 27, 44-46, 64] following repeated bouts of resistance exercise. Using the traditional definition, a decrease in echo intensity should correspond to an increase in muscle strength per unit of muscle mass [9,20].…”

“…Echo intensity is determined by drawing a region of interest on the ultrasound image without including subcutaneous fat or bone. This region of interest may be a pre-specified sized box [3, 31, 33, 36, 40, 42, 48-51, 53, 54], a box containing as much of the muscle as possible [4,7,8,10,20,23,24,27,35,37,57,58], or free hand tracings between the adipose tissue and bone [9,15]. The majority of studies on echo intensity use a scale between 0 (black) and 255 (white) [4,20,24] or 0 (black) to 256 (white) [29,31,34].…”

Examination of the confounding effect of subcutaneous fat on muscle echo intensity utilizing exogenous fat

“…Acute and chronic changes in EI have been observed with exercise. However, further experimental work is needed to provide appropriate interpretations of these changes in physiological and clinical contexts (Routledge et al 2019;Rowe et al 2019;Wong et al 2020). The omission and/or inappropriate accounting of the effects of subcutaneous fat on EI might partly explain inconsistent results in skeletal muscle tissue quality following resistance training reported in a recent review (Wong et al 2020).…”