A-Mode Ultrasound Reliability in Fat and Muscle Thickness Measurement.

ABSTRACT: Ribeiro, G, de Aguiar, RA, Penteado, R, Lisbôa, FD, Raimundo, JAG, Loch, T, Meira, Â, Turnes, T, and Caputo, F. A-mode ultrasound reliability in fat and muscle thickness measurement. J Strength Cond Res 36(6): 1610-1617, 2022-This study aimed to verify the reliability of the BodyMetrix portable A-mode ultrasound in measuring fat and muscle tissue thickness. Thirty physically active men participated in daily body composition evaluations. The evaluations comprised 2 techniques: (a) graphic technique (GTBM), which measured the fat thickness at 9 body sites (abdomen, axillary, biceps brachii, calf, chest, subscapular, suprailiac, thigh, and triceps brachii), and (b) imaging technique (ITBM), which simultaneously measured the fat and muscle thickness of 6 body surfaces (abdomen, biceps brachii, chest, thigh, trapezius, and triceps brachii). Regarding GTBM, relative reliability was moderate to excellent (intraclass correlation coefficient [ICC]: 0.81-0.98), whereas absolute reliability was acceptable for abdomen, calf, chest, subscapular, suprailiac, and triceps brachii (coefficient of variation [CV]: 6.9-8.8%) but high for axillary, biceps brachii, and thigh (CV: 12.0-17.4%) in measuring fat thicknesses. Concerning ITBM, relative reliability was good to excellent (ICC: 0.93-0.99 and 0.90-0.98), whereas absolute reliability was acceptable (CV: 3.0-9.2% and 3.5-5.9%) in measuring fat and muscle thickness, respectively. These findings suggest that the, GTBM was only reliable in measuring fat thickness of abdomen, calf, chest, subscapular, suprailiac, and triceps brachii, whereas ITBM was reliable in measuring both fat and muscle thickness in all regions, but showed better reliability values in measuring muscle than fat thickness.

The effects of predictive trials on critical stroke rate and critical swimming speed.

BACKGROUND: Critical swimming speed (CSS) and critical stroke rate (CSR) have important practical applications in evaluating endurance capacity and stroke parameters. The CSS and CSR are determined from the linear regression between two or more performance times with the respective predictive distance or "number of stroke cycles," respectively. It is already known that CSS is dependent on the number and duration of the predictive trials chosen, and performance times ranging from 2 to 12 min have been recommended. However, the effects of predictive trials on the CSR have not been reported. It was hypothesized that CSS and CSR determined by different predictive trials lasting 2 to 12 min would elicit similar values. Therefore, the purpose of the present study was to determine the impact of different combinations of predictive trials lasting 2 to 12 min on both CSR and CSS. METHODS: Thirteen swimmers performed three fixed-distance (200, 400, and 800 m) performances. All possible combinations of CSR and CSS with two (CSR200-400/CSS200-400, CSR200-800/CSS200-800, CSR400-800/CSS400-800) and three (CSR200-400-800/CSS200-400-800) trials were determined. RESULTS: No significant differences were found between CSR and CSS determined with different predictive distance tests. In addition, CSR200-800 and CSS200-800 showed the lowest coefficient of variation and highest intraclass correlation coefficients with CSR200-400-800 and CSS200-400-800, respectively. CONCLUSIONS: This study demonstrated that CSR and CSS were not statistically different when determined with different predictive trials located within the recommended durations of 2-12 min. Nevertheless, CSR200-800 and CSS200-800 exhibited the best consistency with CSR200-400-800 and CSS200-400-800, respectively.

Association Between Deoxygenated Hemoglobin Breaking Point, Anaerobic Threshold, and Rowing Performance.

PURPOSE: To compare the intensity and physiological responses of deoxygenated hemoglobin breaking point ([HHb]BP) and anaerobic threshold (AnT) during an incremental test and to verify their association with 2000-m rowing-ergometer performance in well-trained rowers. METHODS: A total of 13 male rowers (mean [SD] age = 24 [11] y and V˙O2peak = 63.7 [6.1] mL·kg-1·min-1) performed a step incremental test. Gas exchange, vastus lateralis [HHb], and blood lactate concentration were measured. Power output, V˙O2, and heart rate of [HHb]BP and AnT were determined and compared with each other. A 2000-m test was performed in another visit. RESULTS: No differences were found between [HHb]BP and AnT in the power output (236 [31] vs 234 [31] W; Δ = 0.7%), 95% confidence interval [CI] 6.7%), V˙O2 (4.2 [0.5] vs 4.3 [0.4] L·min-1; Δ = -0.8%, 95% CI 4.0%), or heart rate (180 [16] vs 182 [12] beats·min-1; Δ = -1.6%, 95% CI 2.1%); however, there was high typical error of estimate (TEE) and wide 95% limits of agreement (LoA) for power output (TEE 10.7%, LoA 54.1-50.6 W), V˙O2 (TEE 5.9%, LoA -0.57 to 0.63 L·min-1), and heart rate (TEE 2.4%, LoA -9.6 to 14.7 beats·min-1). Significant correlations were observed between [HHb]BP (r = .70) and AnT (r = .89) with 2000-m mean power. CONCLUSIONS: These results demonstrate a breaking point in [HHb] of the vastus lateralis muscle during the incremental test that is capable of distinguishing rowers with different performance levels. However, the high random error would compromise the use of [HHb]BP for training and testing in rowing.

The Severe Exercise Domain Amplitude: A Comparison Between Endurance Runners and Cyclists.

PURPOSE: Metabolic perturbation and V˙O2 on-kinetics are potential modifiers of fatigue and vary in importance depending on the exercise task. Thus, performance fatigability during high-intensity exercise seems to be exercise mode dependent, affecting tolerance in the severe domain. However, the effects of exercise mode on severe domain amplitude are still unknown. The aims of this study were to compare the severe domain amplitude in endurance runners and cyclists and to verify its possible determinants. METHODS: Ten runners and eleven cyclists were tested to determine V˙O2 max, maximal velocity/power output of incremental test (v V˙O2 max/p V˙O2 max), critical velocity/power (CV/CP), distance/work above CV/CP (D'/W'), and the highest velocity/power output which V˙O2 max is attained during constant exercise (VHIGH/PHIGH). The severe domain amplitude was considered as VHIGH/PHIGH relative to CV/CP. RESULTS: When normalized by v V˙O2 max/p V˙O2 max, although VHIGH and PHIGH were similar, CV (89.0 ± 2.2% v V˙O2 max) was higher than CP (84.0 ± 4.1% p V˙O2 max; p < .05; ES = 1.51). Consequently, the severe domain amplitude was higher in cyclists (153.6 ± 14.4% CP vs. 137.2 ± 14.6% CV; p < .05; ES = 1.13). Runners presented faster V˙O2 on-kinetics than cyclists at VHIGH/PHIGH. The severe domain amplitude was correlated with D' (r = .65) and W' (r = .71), but not with V˙O2 on-kinetics. CONCLUSIONS: Cyclists have a lower CP (%p V˙O2 max) and a greater severe domain amplitude than runners, providing a greater range of intensities for attainment of V˙O2 max. Furthermore, the severe domain amplitude appears to be linked to finite energy reserves, but unrelated to V˙O2 on-kinetics.

Physiological responses to interval endurance exercise at different levels of blood flow restriction.

PURPOSE: We aimed to identify a blood flow restriction (BFR) endurance exercise protocol that would both maximize cardiopulmonary and metabolic strain, and minimize the perception of effort. METHODS: Twelve healthy males (23 ± 2 years, 75 ± 7 kg) performed five different exercise protocols in randomized order: HI, high-intensity exercise starting at 105% of the incremental peak power (P peak); I-BFR30, intermittent BFR at 30% P peak; C-BFR30, continuous BFR at 30% P peak; CON30, control exercise without BFR at 30% P peak; I-BFR0, intermittent BFR during unloaded exercise. Cardiopulmonary, gastrocnemius oxygenation (StO2), capillary lactate ([La]), and perceived exertion (RPE) were measured. RESULTS: V̇O2, ventilation (V̇ E), heart rate (HR), [La] and RPE were greater in HI than all other protocols. However, muscle StO2 was not different between HI (set1-57.8 ± 5.8; set2-58.1 ± 7.2%) and I-BRF30 (set1-59.4 ± 4.1; set2-60.5 ± 6.6%, p < 0.05). While physiologic responses were mostly similar between I-BFR30 and C-BFR30, [La] was greater in I-BFR30 (4.2 ± 1.1 vs. 2.6 ± 1.1 mmol L-1, p = 0.014) and RPE was less (5.6 ± 2.1 and 7.4 ± 2.6; p = 0.014). I-BFR30 showed similar reduced muscle StO2 compared with HI, and increased blood lactate compared to C-BFR30 exercise. CONCLUSION: Therefore, this study demonstrate that endurance cycling with intermittent BFR promotes muscle deoxygenation and metabolic strain, which may translate into increased endurance training adaptations while minimizing power output and RPE.