The amount of experience with ultrasonography may influence measurement outcomes while images are acquired or analyzed. The purpose of this study was to identify the interrater reliability of ultrasound image acquisition and image analysis between experienced and novice sonographers and image analysts, respectively. Following a brief hands-on training session (2 h), the experienced and novice sonographers and analysts independently performed image acquisition and analyses on the biceps brachii, vastus lateralis, and medial gastrocnemius in a sample of healthy participants (n = 17). Test–retest reliability statistics were computed for muscle thickness (transverse and sagittal planes), muscle cross-sectional area, echo intensity and subcutaneous adipose tissue thickness. The results show that image analysis experience generally has a greater impact on measurement outcomes than image acquisition experience. Interrater reliability for measurements of muscle size during image acquisition was generally good–excellent (ICC2,1: 0.82–0.98), but poor–moderate for echo intensity (ICC2,1: 0.43–0.77). For image analyses, interrater reliability for measurements of muscle size for the vastus lateralis and biceps brachii was poor–moderate (ICC2,1: 0.48–0.70), but excellent for echo intensity (ICC2,1: 0.90–0.98). Our findings have important implications for laboratories and clinics where members possess varying levels of ultrasound experience.

Succi, PJ, Dinyer-McNeely, TK, Voskuil, CC, Abel, MG, Clasey, JL, and Bergstrom, HC. Responses to exercise at the critical heart rate vs. the power output associated with the critical heart rate. J Strength Cond Res 37(12): 2362-2372, 2023-This study examined the physiological (volume of oxygen consumption [V Ȯ2 ], heart rate [HR], power output [PO], respiration rate [RR], muscle oxygen saturation [%SmO 2 ]), neuromuscular (electromyographic and mechanomyographic amplitude [EMG AMP and MMG AMP] and mean power frequency [EMG MPF and MMG MPF]), and perceptual (rating of perceived exertion [RPE]) responses during exercise anchored at the critical heart rate (CHR) vs. the PO associated with CHR (PCHR). Nine subjects (mean 6 SD; age 5 26 6 3 years) performed a graded exercise test and 4 constant PO trials to exhaustion at 85-100% of peak PO (PP) to derive CHR and PCHR on a cycle ergometer. Responses were recorded during trials at CHR (173 6 9 b•min 21 , time to exhaustion [T Lim ] 5 45.5 6 20.2 minutes) and PCHR (198 6 58 W, T Lim 5 21.0 6 17.8 minutes) and normalized to their respective values at PP in 10% intervals. There were significant (p # 0.05) mode (CHR vs. PCHR) 3 time (10%-100% T Lim ) interactions for all variables (p , 0.001-0.036) except MMG AMP (p . 0.05). Post hoc analyses indicated differences across time for CHR V Ȯ2 (%change 5 222 6 16%), PCHR

This study examines the relationships between ultrasonography measurements of skeletal muscle size and echo intensity (EI) with muscle strength and local muscle endurance in a habitually resistance-trained population. Twenty young, healthy participants underwent imaging of the biceps brachii in the sagittal and transverse planes and with the extended field of view (EFOV) technique. Linear regression was used to examine measures of muscle thickness (MT), muscle cross-sectional area (mCSA), EI, and corrected EI (cEI) in each scanning plane for their associations with strength (1RM biceps curl) and local muscle endurance (4x failure @ 50%1RM). The strongest predictor of 1RM strength and local muscle endurance was sagittal MT (adj. R2 = 0.682) and sagittal cEI (adj. R2 = 0.449), respectively. Strength and transverse MT (R2 = 0.661) and the EFOV mCSA (R2 = 0.643) demonstrated a positive relationship. Local muscle endurance and cEI in the transverse plane (R2 = 0.265) and the EFOV scan (R2 = 0.309) demonstrated a negative relationship. No associations were shown with uncorrected EI. While each scanning plane supports the muscle size-strength and echogenicity-endurance relationships, sagittal plane imaging demonstrated the strongest associations with muscle fitness. These findings provide important methodological insights regarding ultrasound imaging and muscle fitness relationships.

Succi, PJ, Dinyer, TK, Byrd, MT, Voskuil, CC, and Bergstrom, HC. Application of V Ȯ2 to the critical power model to derive the critical V Ȯ2 . J Strength Cond Res 36(12): 3374-3380, 2022-The purposes of this study were to (a) determine whether the critical power (CP) model could be applied to V Ȯ2 to estimate the critical V Ȯ2 (CV Ȯ2 ) and (b) to compare the CV Ȯ2 with the V Ȯ2 at CP (V Ȯ2 CP), the ventilatory threshold (VT), respiratory compensation point (RCP), and the CV Ȯ2 without the V Ȯ2 slow component (CV Ȯ2 slow). Nine subjects performed a graded exercise test to exhaustion to determine V Ȯ2 peak, VT, and RCP. The subjects performed 4 randomized, constant power output work bouts to exhaustion. The time to exhaustion (T Lim ), the total work (W Lim ), and the total volume of oxygen consumed with (TV Ȯ2 ) and without the slow component (TV Ȯ2 slow) were recorded during each trial. The linear regressions of the TV Ȯ2 vs. T Lim , TV Ȯ2 slow vs. T Lim , and W Lim vs. T Lim relationship were performed to derive the CV Ȯ2 , CV Ȯ2 slow, and CP, respectively. A 1-way repeated-measures analysis of variance (p # 0.05) with follow-up Sidak-Bonferroni corrected pairwise comparisons indicated that CV Ȯ2 (42.49 6 3.22 ml•kg 21 •min 21 ) was greater than VT (30.80 6 4.66 ml•kg 21 •min 21 ; p , 0.001), RCP (36.74 6 4.49 ml•kg 21 •min 21 ; p 5 0.001), V Ȯ2 CP (36.76 6 4.31 ml•kg 21 •min 21 ; p , 0.001), and CV Ȯ2 slow (38.26 6 2.43 ml•kg 21 •min 21 ; p , 0.001). However, CV Ȯ2 slow was not different than V Ȯ2 CP (p 5 0.140) or RCP (p 5 0.235). Thus, the CP model can be applied to V Ȯ2 to derive the CV Ȯ2 and theoretically is the highest metabolic steady state that can be maintained for an extended period without fatigue. Furthermore, the ability of the CV Ȯ2 to quantify the metabolic cost of exercise and the inefficiency associated with the V Ȯ2 slow component may provide a valuable tool for researchers and coaches to examine endurance exercise.

The study and application of the critical power (CP) concept has spanned many decades. The CP test provides estimates of two distinct parameters, CP and W′, that describe aerobic and anaerobic metabolic capacities, respectively. Various mathematical models have been used to estimate the CP and W′ parameters across exercise modalities. Recently, the CP model has been applied to dynamic constant external resistance (DCER) exercises. The same hyperbolic relationship that has been established across various continuous, whole-body, dynamic movements has also been demonstrated for upper-, lower-, and whole-body DCER exercises. The asymptote of the load versus repetition relationship is defined as the critical load (CL) and the curvature constant is L′. The CL and L′ can be estimated from the same linear and non-linear mathematical models used to derive the CP. The aims of this review are to (1) provide an overview of the CP concept across continuous, dynamic exercise modalities; (2) describe the recent applications of the model to DCER exercise; (3) demonstrate how the mathematical modeling of DCER exercise can be applied to further our understanding of fatigue and individual performance capabilities; and (4) make initial recommendations regarding the methodology for estimating the parameters of the CL test.