An Assessment of the Potential for Standardizing Various Measures of Arterial Stiffness

Arterial stiffness is an independent risk factor for cardiovascular disease. Different measures of arterial stiffness have been used to assess the impacts of exercise training interventions. One of the primary problems faced by investigators conducting systematic reviews and meta-analyses is the lack of standardized methodology to evaluate and compare efficacies of the existing and newly conducted exercise interventions on arterial stiffness. The reference standard measure of arterial stiffness is pulse wave velocity (PWV) while other commonly-used methodologies are ultrasound-derived arterial compliance and distensibility. PURPOSE: To describe standardized equations to convert common ultrasound-based measures of arterial stiffness (arterial compliance, distensibility, ß-stiffness index, elastic modulus) to local PWV. METHODS: We first conducted a literature search to derive conversion equations. For measures of arterial stiffness that conversion equations cannot be used, we generated regression equations using the accumulated dataset available in the laboratory. Subsequently, these equations were cross-validated in a well-controlled laboratory-based study, in which all measures of arterial stiffness were collected in 49 apparently healthy participants. RESULTS: The literature search revealed that some measures of arterial stiffness such as distensibility coefficient (DC) can be converted to local PWV using the Bramwell-Hill model (PWV = [p.DC]1/2) with an assumption of p=1059 kg/m3. Ultrasound-based measures of arterial stiffness were strongly and significantly associated with local PWV with Pearson r ranging from 0.74 to 0.99 (p \u3c 0.01). Converted local PWV using regression models were correlated with each other (r=0.73 to 0.97, pCONCLUSION: Our findings indicate that commonly-used measures of ultrasound-based arterial stiffness can be converted to local PWV and can be compared with a reference standard measure. These conversions can be used in systematic reviews and meta-analyses to synthesize evidence across studies to detect effects

Effects of Blood Flow Restriction Training on Vascular Function: Impacts of Different Types of Cuffs

Blood flow restriction (BFR) training is becoming a very popular form of resistance training in inducing muscular adaptations. Narrow-elastic bands (NE) and wide-rigid cuffs (WR) are two types of cuffs that are frequently used in BFR. Because these different types of BFR cuffs produce markedly different hemodynamic responses, vascular adaptations resulting from BFR training might differ depending upon what cuffs are used. PURPOSE: To examine the hypothesis that BFR with NE would improve vascular function while the use of WR would decrease vascular function. METHODS: Ten apparently healthy participants (7 females, 23±5 years) completed supervised BFR training 3 times a week for 2 weeks. During the BFR training, the WR cuff was placed on one arm and the NE band on the other arm in a randomized order. Vascular function was evaluated by brachial artery flow-mediated dilation (FMD), and a 1-repetition maximum (1-RM) test was conducted for biceps curl on both arms. To explore possible mechanisms underlying vascular adaptations, acute blood flow responses (levels of ischemia and retrograde shear rate) to three different conditions (no cuff, WR occlusion, NE occlusion) were measured by Doppler ultrasound. RESULTS: Maximal strength of biceps curl increased in both NE arm (20.6±3.5 to 22.6±3.7 kg, p=0.006) and WR arm (19.0±3.5 to 21.6±3.7 kg, p=0.001). Brachial FMD increased in the NE arm (7.7±0.9 to 10.4±0.8%, p=0.015) but did not change in the WR arm (8.1±0.9 to 6.6±0.8%, p=0.163). For the possible mechanisms related to the vascular adaptation, blood flow velocity was lower under WR occlusion compared with no cuff (78±7 vs. 93±6 cm/s, p=0.049) but was not different between NE occlusion and no cuff (90±6 vs. 93±6 cm/s, p=0.357). Retrograde shear rate was highest under WR occlusion (45±5 s-1), higher under NE occlusion (31±3 s-1), and lowest under no cuff (27±3 s-1, all p=0.001). CONCLUSIONS: Both types of cuffs were effective in gaining muscle strength. However, endothelium-dependent vasodilation was significantly improved with 2 weeks of BFR with NE, but not with WR. The difference in the vascular adaptation between two different cuffs might be explained by a higher level of ischemia (lower blood flow velocity) and greater retrograde shear stress under WR occlusion

Sex differences in post-exercise hypotension, ambulatory blood pressure variability, and endothelial function after a power training session in older adults

Background: The efficacy of power training (PT) to acutely reduce blood pressure (BP) in participants with hypertension is controversial, and no studies have assessed the influence of sex on post-exercise hypotension and its mechanisms in older adults. Purpose: The aims of this secondary, exploratory analysis were to compare the effects of a single bout of PT on post-exercise hypotension, BP variability, and endothelial function between older men and women with hypertension. Methods: Twenty-four participants with hypertension (12 men and 12 women aged to >60 years old) took part in this crossover study and randomly performed two experimental sessions: power exercise training (PT) and non-exercising control session (Con). The PT protocol was composed of 3 sets of 8–10 repetitions of five exercises performed in the following order: leg press, bench press, knee extension, upright row, and knee flexion, using an intensity corresponding to 50% of one repetition maximal test (1RM) and 2-min intervals between sets and exercises. The concentric phase of exercises during each repetition was performed “as fast as possible,” while the eccentric phase lasted 1 to 2 s. During Con, the participants remained at seated rest on the same exercise machines, but without any exercise. Each protocol lasted 40 min. Office BP, flow-mediated dilatation (FMD), 24-h ambulatory BP, and the average real variability (ARV) of systolic and diastolic BP were assessed before and after experimental sessions. Results: Comparing PT with Con, a reduced office BP after exercise was found in men (systolic BP—average post 1 h: −14 mmHg, p < 0.001; diastolic BP—average post 1 h: −8 mmHg, p < 0.001) and only a reduced systolic BP in women (average post 1 h: −7 mmHg, p = 0.04). Comparing men and women, a reduced systolic BP (post 60': −15 mmHg, p = 0.048; average post 1 h: −7 mmHg, p = 0.046) and diastolic BP (post 60': −9 mmHg, p = 0.049) after the first hour were found in men. In relation to 24-h ambulatory BP, ARV, and FMD, no statistically significant differences were found between men and women. Conclusion: In older adults with hypertension, the office BP response after the experimental sessions was different in men and women, showing that the PT protocol is more effective to acutely reduce BP in men. Additionally, the mechanisms behind this reduction remain unclear. This finding suggests that sex cannot be combined to analyze post-exercise hypotension

A Chest‐Conformable, Wireless Electro‐Mechanical E‐Tattoo for Measuring Multiple Cardiac Time Intervals

Abstract Cardiovascular diseases are the leading cause of death globally. Noninvasive, accurate, and continuous cardiovascular monitoring can enable the preemptive detection of heart diseases and timely intervention to prevent serious cardiac complications. However, unobtrusive, ambulatory, and comprehensive cardiac monitoring is still a challenge as conventional electronics are rigid, heavy, or consume too much power for long‐term measurement. This work presents a thin (200 µm), stretchable (20%), lightweight (2.5 g), wireless, and low‐power (<3 mW) cardiac monitoring device that conforms to the human chest like a temporary tattoo sticker, correspondingly known as an e‐tattoo. This chest e‐tattoo features dual‐mode electro‐mechanical sensing—bio‐electric cardiac signals via electrocardiography and mechanical cardiac rhythm via seismocardiography. A unique peripheral synchronization strategy between the two sensors enables the measurement of systolic time intervals like the pre‐ejection period and the left ventricular ejection time with high accuracy (error = −0.44 ± 8.74 ms) while consuming very low power. The e‐tattoo is validated against clinically approved gold‐standard instruments on five human subjects. The good wearability and low power consumption of this e‐tattoo permit 24‐h continuous ambulatory monitoring