Changes in vascular and cardiac function after prolonged strenuous exercise in humans

Association of vitamin D deficiency with post-exercise hypotension and arterial stiffness following prolonged endurance exercise in healthy young men

BACKGROUND

Vitamin D is associated with vascular function; however, the impact of different vitamin D levels on vascular elasticity following prolonged exercise remains uncertain. The primary objective of this study was to investigate the association of vitamin D levels with changes in peripheral pulse wave velocity (pPWV) and the magnitude of acute post-exercise hypotension (PEH) following prolonged endurance exercise in healthy young men.

METHODS

All the participants were divided into two groups: the 25-hydroxyvitamin D (25(OH)D) sufficiency group (25(OH)D ≧50 nmol/L) and the deficiency group (25(OH)D < 50 nmol/L). A cardiopulmonary exercise test for maximal oxygen uptake (V . O2max) was performed on the graded cycling. The prolonged exercise was set at 60% V . O2max for 120 min of continuous riding on a stationary bicycle. The pPWV and blood pressure were measured at baseline and 0, 15, 30, 45, 60 min after prolonged endurance exercise.

RESULTS

Post hoc analysis revealed that the vitamin D sufficient group had a greater magnitude of PEH than the deficiency group at post-45 min. Multiple linear regression analyses showed a significant correlation between 25(OH)D and both pPWV (p = 0.036) and PEH (p = 0.007), after adjusting for V . O2max, weight, height, and physical activity. In addition, the 25(OH)D deficiency group also had higher pPWV at post-15 min (5.41 ± 0.93 vs 4.84 ± 0.75 m/s), post-30 min (5.30 ± 0.77 vs 4.87 ± 0.50 m/s), post-45 min (5.56 ± 0.93 vs 5.05 ± 0.68 m/s) than the sufficiency group.

CONCLUSIONS

There was a positive correlation between 25(OH)D levels and systolic PEH following prolonged endurance exercise. Individuals with sufficient 25(OH)D status may have better vascular elasticity and more efficient blood pressure regulation during exercise.

Arterial function in response to a 50 km ultramarathon in recreational athletes

This study was performed to determine whether prolonged endurance running results in acute endothelial dysfunction and wave-reflection, as endothelial dysfunction and arterial stiffness are cardiovascular risk factors. Vascular function (conduit artery/macrovascular and resistance artery/microvascular) was assessed in 11 experienced runners (8 males, 3 females) before, during and after a 50 km ultramarathon. Blood pressure (BP), heart rate (HR), wave reflection, augmentation index (AIx) and AIx corrected for HR (AIx75) were taken at all time points-Baseline (BL), following 10, 20, 30 and 40 km, 1 h post-completion (1HP) and 24 h post-completion (24HP). Flow-mediated dilatation (FMD) and inflammatory biomarkers were examined at BL, 1HP and 24HP. Reactive hyperaemia area under the curve (AUC) and shear rate AUC to peak dilatation were lower (∼75%) at 1HP compared with BL (P < 0.001 for both) and reactive hyperaemia was higher at 24HP (∼27%) compared with BL (P = 0.018). Compared to BL, both mean central systolic BP and mean central diastolic BP were 7% and 10% higher, respectively, following 10 km and 6% and 9% higher, respectively, following 20 km, and then decreased by 5% and 8%, respectively, at 24HP (P < 0.05 for all). AIx (%) decreased following 20 km and following 40 km compared with BL (P < 0.05 for both) but increased following 40 km when corrected for HR (AIx75) compared with BL (P = 0.02). Forward wave amplitude significantly increased at 10 km (15%) compared with BL (P = 0.049), whereas backward wave reflection and reflected magnitude were similar at all time points. FMD and baseline diameter remained similar. These data indicate preservation of macrovascular (endothelial) function, but not microvascular function resulting from the 50 km ultramarathon.

Preexercise intermittent passive stretching and vascular function after treadmill exercise

Acute aerobic exercise stress is associated with decreased endothelial function that may increase the likelihood of an acute cardiovascular event. Passive stretch (PS) elicits improvements in vascular function, but whether PS can be performed before exercise to prevent declines in vascular function remains unknown. This strategy could be directly applicable in populations that may not be able to perform dynamic exercise. We hypothesized that preexercise PS would provide better vascular resilience after treadmill exercise. Sixteen healthy college-aged males and females participated in a single laboratory visit and underwent testing to assess micro- and macrovascular function. Participants were randomized into either PS group or sham control group. Intermittent calf PS was performed by having the foot in a splinting device for a 5-min stretch and 5-min relaxation, repeated four times. Then, a staged V̇o2 peak test was performed and 65% V̇o2 peak calculated for subjects to run at for 30 min. Near-infrared spectroscopy-derived microvascular responsiveness was preserved with the PS group [(pre: 0.53 ± 0.009%/s) (post: 0.56 ± 0.012%/s; P = 0.55)]. However, there was a significant reduction in the sham control group [(pre: 0.67 ± 0.010%/s) (post: 0.51 ± 0.007%/s; P = 0.05)] after treadmill exercise. Flow-mediated vasodilation (FMD) of the popliteal artery showed similar responses. In the PS group, FMD [(pre: 7.23 ± 0.74%) (post: 5.86 ± 1.01%; P = 0.27)] did not significantly decline after exercise. In the sham control group, FMD [(pre: 8.69 ± 0.72%) (post: 5.24 ± 1.24%; P < 0.001)] was significantly reduced after treadmill exercise. Vascular function may be more resilient if intermittent PS is performed before moderate-intensity exercise and, importantly, can be performed by most individuals.NEW & NOTEWORTHY We demonstrate for the first time that popliteal artery and gastrocnemius microvascular responsiveness after acute aerobic exercise are reduced. The decline in vascular function was mitigated in those who performed intermittent passive stretching before the exercise bouts. Collectively, these findings suggest that intermittent passive stretching is a novel method to increase vascular resiliency before aerobic activity.

Intermittent versus continuous handgrip exercise and peripheral endothelial function: impact of shear rate fluctuations

Sustained exercise-induced elevations in shear rate (SR) have been well established as beneficial for improving endothelial function. However, the impact of intermittent fluctuations in SR is not understood. We investigated the effect of intermittent SR elevations compared with sustained elevations on peripheral endothelial function. Brachial artery flow-mediated dilation (FMD) was assessed in 13 adults (9 M/4 F; 22 ± 4 yr) before and after 30 min of handgrip exercise. Three different rhythmic forearm exercise interventions were performed at a rate of 20 contractions/min. Intermittent exercises (6 × 3 min exercise interspersed by 2 min of rest) were performed at 25% (INT-25%) and 15% (INT-15%) maximum voluntary contraction (MVC), and continuous exercise was completed at 15% MVC. Brachial artery diameter and velocity were measured using Doppler ultrasound. The total increase in SR above baseline throughout exercise was greater during INT-25% (4,441 ± 516 s-1) and continuous (4,070 ± 407 s-1) compared with INT-15% (2,811 ± 342 s-1, P < 0.05). The %FMD increased following all exercises (INT-25%: 5.7 ± 1.2% to 8.1 ± 1.2%; INT-15%: 5.2 ± 1.2% to 7.0 ± 1.1%; continuous: 5.5 ± 1.3% to 6.8 ± 1.3%, P < 0.05 for all). The increase following INT-25% was significantly greater than INT-15% and continuous (P < 0.05 for both). Normalized FMD to shear rate area under the curve increased with intermittent exercise (INT-25%: 2.2 ± 0.2% to 3.4 ± 0.3%; INT-15%: 2.1 ± 0.2% to 3.2 ± 0.2%, P < 0.05 for both) but did not following continuous (2.1 ± 0.2% to 2.5 ± 0.1%, P = 0.06). The increase in normalized FMD with intermittent exercises were greater than continuous (P < 0.05 for both). These findings suggest intermittent fluctuations in SR during handgrip exercise may be more beneficial than sustained elevations on improving peripheral endothelial function.NEW & NOTEWORTHY Exercise-induced increases in shear rate is a well-established stimulus for improving peripheral endothelial function. This study presents novel findings that intermittent elevations in shear rate may be more effective at acutely improving endothelial function compared with continuous elevations. Despite similar increases in total shear rate during handgrip exercise intermittent elevations produced a significantly greater increase in endothelial function when compared with continuous elevations potentially indicating intermittent elevations as a more effective stimulus for acute improvements.

Impact of Oxygen Supplementation on Brachial Artery Hemodynamics and Vascular Function During Ascent to 5,050 m

Vizcardo-Galindo, Gustavo A., Connor A. Howe, Ryan L. Hoiland, Howard H. Carter, Christopher K. Willie, Philip N. Ainslie, and Joshua C. Tremblay. Impact of oxygen supplementation on brachial artery hemodynamics and vascular function during ascent to 5,050 m. High Alt Med Biol. 24:27-36, 2023.-High-altitude trekking alters upper limb hemodynamics and reduces brachial artery vascular function in lowlanders. Whether these changes are reversible with the removal of hypoxia is unknown. We investigated the impact of 20 minutes of oxygen supplementation (O₂) on brachial artery hemodynamics, reactive hyperemia (RH; microvascular function), and flow-mediated dilation (FMD; endothelial function). Participants (aged 21-42 years) were examined before and with O₂ at 3,440 m (n = 7), 4,371 m (n = 7), and 5,050 m (n = 12) using Duplex ultrasound (days 4, 7, and 10 respectively). At 3,440 m, O₂ decreased brachial artery diameter (-5% ± 5%; p = 0.04), baseline blood flow (-44% ± 15%; p < 0.001), oxygen delivery (-39 ± 16; p < 0.001), and peak RH (-8% ± 8%; p = 0.02), but not RH normalized for baseline blood flow. Elevated FMD (p = 0.04) with O₂ at 3,440 m was attributed to the reduction in baseline diameter. At 5,050 m, a reduction in brachial artery blood flow (-17% ± 22%; p = 0.03), but not oxygen delivery, diameter, RH, or FMD occurred with O₂. These findings suggest that during early trekking at high altitude, O₂ causes vasoconstriction in the upper limb along the arterial tree (conduit and resistance arteries). With incremental high-altitude exposure, O₂ reduces blood flow without compromising oxygen delivery, RH, or FMD, suggesting a differential impact on vascular function modulated by the duration and severity of high-altitude exposure.

Post-exercise endothelial function is not associated with extracellular vesicle release in healthy young males

Acute exercise can result in temporary decrease in endothelial functions, which may represent a transient period of risk. Numerous mechanisms underpinning these responses included release of extracellular vesicles (EVs) derived from apoptotic or activated endothelial cells and platelets. This study aims to compare the time course of endothelial responses to moderate-intensity continuous exercise (MICE) and high-intensity interval exercise (HIIE) and the associations with EV release. Eighteen young healthy males (age: 22.6 ± 3.7 years, BMI: 25.6 ± 2.5 m²/kg, and VO_2peak: 38.6 ± 6.5 mL/kg/min) completed two randomly assigned exercises: HIIE (10 × 1 min-@-90% heart rate reserve (HRR) and 1 min passive recovery) and MICE (30 min-@-70% HRR) on a cycle ergometer. Flow-mediated dilation (FMD) was used to assess endothelial function and blood samples were collected to evaluate endothelial cell-derived EV (CD62E⁺) and platelet-derived EV (CD41a⁺), 10, 60, and 120 min before and after exercise. There were similar increases but different time courses (P = 0.017) in FMD (increased 10 min post-HIIE, P < 0.0001 and 60 min post-MICE, P = 0.038). CD62E⁺ remained unchanged (P = 0.530), whereas overall CD41a⁺ release was reduced 60 min post-exercise (P = 0.040). FMD was not associated with EV absolute release or change (P > 0.05). Acute exercise resulted in similar improvements, but different time course in FMD following either exercise. Whilst EVs were not associated with FMD, the reduction in platelet-derived EVs may represent a protective mechanism following acute exercise.

Sex-Specific Impacts of Exercise on Cardiovascular Remodeling

Cardiovascular diseases (CVD) remain the leading cause of death in men and women. Biological sex plays a major role in cardiovascular physiology and pathological cardiovascular remodeling. Traditionally, pathological remodeling of cardiovascular system refers to the molecular, cellular, and morphological changes that result from insults, such as myocardial infarction or hypertension. Regular exercise training is known to induce physiological cardiovascular remodeling and beneficial functional adaptation of the cardiovascular apparatus. However, impact of exercise-induced cardiovascular remodeling and functional adaptation varies between males and females. This review aims to compare and contrast sex-specific manifestations of exercise-induced cardiovascular remodeling and functional adaptation. Specifically, we review (1) sex disparities in cardiovascular function, (2) influence of biological sex on exercise-induced cardiovascular remodeling and functional adaptation, and (3) sex-specific impacts of various types, intensities, and durations of exercise training on cardiovascular apparatus. The review highlights both animal and human studies in order to give an all-encompassing view of the exercise-induced sex differences in cardiovascular system and addresses the gaps in knowledge in the field.

Marathon-Induced Cardiac Fatigue: A Review over the Last Decade for the Preservation of the Athletes' Health

AIM

To provide a state-of-the-art review of the last 10 years focusing on cardiac fatigue following a marathon.

METHODS

The PubMed, Bookshelf and Medline databases were queried during a time span of 10 years to identify studies that met the inclusion criteria. Twenty-four studies focusing only on the impact of marathons on the cardiac function and factors involved in cardiac fatigue were included in this review.

RESULTS

Sixteen studies focused on the impact of marathons on several biomarkers (e.g., C-reactive protein, cardiac troponin T). Seven studies focused on the left (LV) or right (RV) ventricular function following a marathon and employed cardiac magnetic resonance, echocardiography, myocardial speckle tracking and heart rate variability to analyze global and regional LV or RV mechanics and the impact of the autonomic nervous system on cardiac function. One study focused on serum profiling and its association with cardiac changes after a marathon.

CONCLUSIONS

This review reported a negligible impact of marathons on LV and RV systolic and contractile function but a negative impact on LV diastolic function in recreational runners. These impairments are often associated with acute damage to the myocardium. Thus, the advice of the present review to athletes is to adapt their training and have a regular medical monitoring to continue to run marathons while preserving their cardiac health.

Transient Reduction of FMD-Response and L-Arginine Accompanied by Increased Levels of E-Selectin, VCAM, and ICAM after Prolonged Strenuous Exercise

We assessed endothelial function by flow-mediated dilatation (FMD), levels of the NO-precursor L-arginine, and markers of endothelial inflammation before, at the finish line, and one week after the Norseman Xtreme triathlon. The race is an Ironman distance triathlon with a total elevation of 5200 m. Nine male participants were included. They completed the race in 14.5 (13.4–15.3) h. FMD was significantly reduced to 3.1 (2.1–5.0)% dilatation compared to 8.7 (8.2–9.3)% dilatation before the race (p < 0.05) and was normalized one week after the race. L-arginine showed significantly reduced levels at the finish line (p < 0.05) but was normalized one week after the race. Markers of endothelial inflammation E-Selectin, VCAM-1, and ICAM-1 all showed a pattern with increased values at the finish line compared to before the race (all p < 0.05), with normalization one week after the race. In conclusion, we found acutely reduced FMD with reduced L-arginine levels and increased E-Selectin, VCAM-1, and ICAM-1 immediately after the Norseman Xtreme triathlon. Our findings indicate a transient reduced endothelial function, measured by the FMD-response, after prolonged strenuous exercise that could be explained by reduced NO-precursor L-arginine levels and increased endothelial inflammation.

Exercise modality, but not exercise training, alters the acute effect of exercise on endothelial function in healthy men

We used a within-subject crossover design to examine the impact of exercise modality, i.e., resistance (RT) and endurance (END), on the acute impact of exercise on endothelial function. Then, we examined whether a 4-wk period of chronic exercise training altered the acute exercise-induced change in endothelial function in healthy individuals. Thirty-four healthy, young men (21 ± 2 yr) reported to our laboratory and completed assessment of endothelial function [using the brachial artery flow-mediated dilation test (FMD)] before and immediately after a single bout of RT (leg-extension) or END (cycling). Subsequently, participants completed a 4-wk period of training (12 sessions), followed by evaluation of the FMD before and after a single bout of exercise. Following a 3-wk washout, participants repeated these experiments with the different exercise modality (in a balanced crossover design). An exercise × modality interaction effect was found (P < 0.001). Post hoc pairwise analyses revealed a decrease in FMD after END (P < 0.001) but not after RT (P = 0.06). Four weeks of exercise training improved resting FMD after END and RT (P = 0.04) but did not alter the acute effect of exercise on FMD (exercise × modality × training effect: P = 0.63), an effect independent of the modality of exercise (exercise × training interaction: P = 0.46 and P = 0.11 in RT and END, respectively). These distinct changes in FMD following acute exercise may relate to the different prolonged physiological responses induced by endurance versus resistance exercise. Specifically, endurance exercise, but not resistance exercise, causes a decrease in brachial artery endothelial function, which was unaffected by 4 wk of chronic exercise training.NEW & NOTEWORTHY We found that resistance and endurance exercise modalities lead to different endothelial function responses after a single bout of exercise. Endothelial function increased after an acute bout of resistance exercise, whereas it decreased after an acute bout of endurance exercise. Four weeks of chronic exercise training did not affect the acute endothelial function response.

Exercise alters cardiac function independent of acute systemic inflammation in healthy men

Acute elevations in inflammatory cytokines have been demonstrated to increase aortic and left ventricular stiffness and reduce endothelial function in healthy subjects. As vascular and cardiac functions are often transiently reduced following prolonged exercise, it is possible that cytokines released during exercise may contribute to these alterations. The a priori aims of this study were to determine whether vaccine-induced increases in inflammatory cytokines would reduce vascular and left ventricular function, whether vascular alterations would drive cardiac impairments, and whether this would be potentiated by moderate exercise. In a randomized crossover fashion, 16 male participants were tested under control (CON) and inflammatory (INF) conditions, wherein INF testing occurred 8 h following administration of an influenza vaccine. On both days, participants underwent measures of echocardiography performed during light cycling (stress-echocardiography), carotid-femoral pulse wave velocity (cf-PWV), and superficial femoral flow-mediated dilation (FMD) before and after cycling for 90 min at ∼85% of their first ventilatory threshold. IL-6 increased significantly (Δ1.9 ± 1.3 pg/mL, P < 0.001), whereas TNFα was nonsignificantly augmented (Δ0.05 ± 0.11 pg/mL, P = 0.09), 8 h following vaccination. Vascular function was unaltered following cycling or inflammation (all P > 0.05). The use of echocardiography during light cycling revealed cardiac alterations traditionally expected to occur only with greater exercise loads, with reduced systolic (e.g., longitudinal strain CON: Δ3.3 ± 4.4%, INF: Δ1.7 ± 2.7%, P = 0.002) and diastolic function (e.g., E/A ratio CON: Δ-0.32 ± 0.34 a.u., INF:Δ-0.25 ± 0.27 a.u., P = 0.002) following cycling, independent of inflammation. The vaccine reduced stroke volume (SV) (main effect of condition P = 0.009) before-and-after cycling. These findings indicate that reduced cardiac function following exercise occurs largely independent of additional inflammatory load.NEW & NOTEWORHTHY This experimental investigation sought to determine the role of inflammation on the occurrence of cardiovascular alterations following exercise. Despite successfully stimulating systemic inflammation via vaccination, vascular and cardiac functions were largely unaltered. Prolonged exercise itself reduced cardiac function assessed via echocardiography performed during light exercise stress. This demonstrates a potential advantage to using stress-echocardiography for measuring exercise-induced cardiac fatigue, as typical resting measures following similar exercise exposures commonly suggest no effect.

Endothelial Vasodilation After a High-Volume Training Load and Tapered Training in Collegiate Female Swimmers

ABSTRACT

Weihl, FM and Van Guilder, GP. Endothelial vasodilation after a high-volume training load and tapered training in collegiate female swimmers. J Strength Cond Res 35(3): 811-818, 2021-High-volume endurance training loads have been linked to adverse remodeling of the heart and large arteries; yet, data on the vascular endothelial function are unclear. Moreover, although collegiate-level endurance athletes often perform high-volumes of vigorous endurance training and resistance training as part of their strength and conditioning programs, it is unknown whether they also experience vascular abnormalities, particularly changes in endothelial function. The aim of this study was to verify the impact of a high-volume training load phase followed by low-volume tapered training on endothelial vasodilator function in National Collegiate Athletic Association (NCAA) Division I competitive female swimmers. Microvascular endothelial vasodilation was assessed by pulse arterial tonometry that provides a reactive hyperemia index in 10 female NCAA Division 1 swimmers after 4 weeks of a high-volume training load, and subsequently, after 3 weeks of low-volume tapered training as part of preparation for annual conference championships. The reactive hyperemia index was calculated as the ratio of the pulse volume amplitude after 5 minutes of left-arm brachial artery ischemia to the baseline amplitude, divided by same ratio in the contralateral arm. The high-volume training load included a 4-week block of dual-day sessions (120 minutes per practice) consisting of vigorous intensity endurance and high-intensity interval/sprint swim training, coupled with 5K running, resistance training, and Olympic weightlifting. Tapered training consisted of 3 weeks of 3-5 swims per week at ∼50% V̇o2max for 60 minutes per practice (∼4,000 minutes per practice). The reactive hyperemia index (1.73 ± 0.50) was low in athletes after the high-volume training load with 8 athletes demonstrating endothelial dysfunction. However, after tapered training, the reactive hyperemia index was ∼33% higher (2.29 ± 0.43; 95% confidence interval [CI]: 1.98-2.60, p = 0.0223 vs. the high-volume training load). Effect size, as expressed by the partial eta2 (0.46) and Cohen's dz (1.1923; 95% CI: 0.1687-2.4643) with tapered training, was large. These results demonstrate distinct differences in endothelial vasodilation after 4 weeks of a high-volume training load compared with a 3-week taper in NCAA Division I female swimmers.

Vascular Function Is Differentially Altered by Distance after Prolonged Running

PURPOSE

Ultraendurance exercise is steadily growing in popularity; however, the effect of increasingly prolonged durations of exercise on the vascular endothelium is unknown. The aim of this study was to characterize the effect of various ultramarathon running distances on vascular form and function.

METHODS

We evaluated vascular endothelial function via flow-mediated dilation (FMD) in the superficial femoral artery, as well as microvascular function, inflammatory factors, and central artery stiffness, before and after participants completed 25-km (7M:2F), 50-km (11M:10F), 80-km (9M:4F), or 160-km (9M:2F) trail races all run on the same day and course.

RESULTS

Completion required 149 ± 20, 386 ± 111, 704 ± 130, and 1470 ± 235 min, with corresponding average paces of 6.0 ± 0.8, 7.7 ± 2.2, 8.6 ± 1.3, and 9.6 ± 1.3 min·km-1, respectively. At baseline, there were no differences in participant characteristics across race distance groups. Shear rate stimulus trended toward an increase after the race (P = 0.07), but resting postrace artery diameter (P < 0.001) was elevated to a similar extent in all conditions. There was a reduction in FMD after the 50-km race (Δ -1.9% ± 2.2%, P < 0.01), but not the 25-km (Δ +0.3% ± 2.9%, P = 0.8), the 80-km (Δ -1.5% ± 3.2%, P = 0.1), or the 160-km (Δ +0.5% ± 2.5%, P = 0.5) race. Inflammatory markers increased most after 160 km, but arterial stiffness and microvascular function were not differently affected by race distance.

CONCLUSIONS

Although the superficial femoral artery baseline diameter was larger postexercise regardless of race distance, only the 50-km race reduced FMD, whereas a short-duration higher-intensity race (25 km) and longer-duration lower-intensity races (160 km) did not. Therefore, a 50-km ultramarathon may represent the intersection between higher-intensity exercise over a prolonged duration, causing reduced endothelial function not seen in shorter or longer distances.

The influence of habitual endurance exercise on carotid artery strain and strain rate in young and middle-aged men

NEW FINDINGS

What is the central question of this study? Carotid artery peak circumferential strain (PCS) and strain rate attenuate with age, but appear to be modulated by cardiorespiratory fitness status in young males. However, the relationship between habitual endurance exercise (running) and these parameters has not been studied in young and middle-aged men. What is the main finding and its importance? Young and middle-aged runners exhibited elevated PCS and systolic strain rate (S-SR) compared with non-runners, but habitual running did not influence diastolic strain rate (D-SR). Habitual exercise is associated with comparable improvements in carotid strain parameters in young and middle-aged men, but the age-related decline in PCS and S-SR might be more amenable to habitual endurance exercise than D-SR.

ABSTRACT

Central arterial stiffness is an independent predictor of cardiovascular risk that can be modified by exercise training. However, conventional local measures of carotid artery stiffness display conflicting responses to habitual endurance exercise in young and older adults. Two-dimensional (2D)-Strain imaging of the common carotid artery (CCA) quantifies circumferential deformation (strain) of the arterial wall across the cardiac cycle, which is more sensitive at detecting age-related alterations in CCA stiffness than conventional methods. Therefore, the study was designed to examine the relationship between habitual endurance exercise (running) and CCA 2D-Strain parameters in young and middle-aged men. Short-axis ultrasound images of the CCA were obtained from 13 young non-runners [23 years of age (95% confidence interval: 21, 26 years of age)], 19 young runners [24 (22, 26) years of age], 13 middle-aged non-runners [54 (52, 56) years of age] and 19 middle-aged runners [56 (54, 58) years of age]. Images were analysed for peak circumferential strain (PCS; magnitude of deformation) and systolic and diastolic strain rates (S-SR and D-SR; deformation velocity), and group differences were examined via two-way ANOVA. PCS, S-SR and D-SR were attenuated in middle-aged men compared with young men (all P ≤ 0.001). PCS and S-SR were elevated in young and middle-aged runners when compared with non-runners (P = 0.002 and P = 0.009, respectively), but no age × training status interaction was observed. In contrast, there was no influence of habitual running on D-SR. Habitual exercise is associated with comparable improvements in CCA 2D-Strain parameters in young and middle-aged men, but the age-related decline in PCS and S-SR might be more amenable to habitual endurance exercise than D-SR.

Can strenuous exercise harm the heart? Insights from a study of cardiovascular neural regulation in amateur triathletes

Regular exercise is recommended to improve the cardiovascular risk profile. However, there is growing evidence that extreme volumes and intensity of long-term exertion may increase the risk of acute cardiac events. The aim of this study is to investigate the after-effects of regular, strenuous physical training on the cardiovascular neural regulation in a group of amateur triathletes compared to age-matched sedentary controls. We enrolled 11 non-elite triathletes (4 women, age 24±4 years), who had refrained from exercise for 72 hours, and 11 age-matched healthy non-athletes (3 women, age 25±2 years). Comprehensive echocardiographic and cardiopulmonary exercise tests were performed at baseline. Electrocardiogram, non-invasive blood pressure, respiratory activity, and muscle sympathetic nerve activity (MSNA) were continuously recorded in a supine position (REST) and during an incremental 15° step-wise head-up tilt test up to 75° (TILT). Blood samples were collected for determination of stress mediators. Autoregressive spectral analysis provided the indices of the cardiac sympathetic (LF_RR) and vagal (HF_RR) activity, the vascular sympathetic control (LF_SAP), and the cardiac sympatho-vagal modulation (LF/HF). Compared to controls, triathletes were characterized by greater LF_RR, LF/HF ratio, LF_SAP, MSNA, and lower HF_RR at REST and during TILT, i.e. greater overall cardiovascular sympathetic modulation together with lower cardiac vagal activity. Cortisol and adrenocorticotropic hormone concentrations were also higher in triathletes. In conclusion, triathletes were characterized by signs of sustained cardiovascular sympathetic overactivity. This might represent a risk factor for future cardiovascular events, given the known association between chronic excessive sympathetic activity and increased cardiovascular risk.

Effects of Catheterization on Artery Function and Health: When Should Patients Start Exercising Following Their Coronary Intervention?

Coronary artery disease (CAD) is a leading cause of death worldwide, and percutaneous transluminal coronary angiography (PTCA) and/or percutaneous coronary intervention (PCI; angioplasty) are commonly used to diagnose and/or treat the obstructed coronaries. Exercise-based rehabilitation is recommended for all CAD patients; however, most guidelines do not specify when exercise training should commence following PTCA and/or PCI. Catheterization can result in arterial dysfunction and acute injury, and given the fact that exercise, particularly at higher intensities, is associated with elevated inflammatory and oxidative stress, endothelial dysfunction and a pro-thrombotic milieu, performing exercise post-PTCA/PCI may transiently elevate the risk of cardiac events. This review aims to summarize extant literature relating to the impacts of coronary interventions on arterial function, including the time-course of recovery and the potential deleterious and/or beneficial impacts of acute versus long-term exercise. The current literature suggests that arterial dysfunction induced by catheterization recovers 4-12 weeks following catheterization. This review proposes that a period of relative arterial vulnerability may exist and exercise during this period may contribute to elevated event susceptibility. We therefore suggest that CAD patients start an exercise training programme between 2 and 4 weeks post-PCI, recognizing that the literature suggest there is a 'grey area' for functional recovery between 2 and 12 weeks post-catheterization. The timing of exercise onset should take into consideration the individual characteristics of patients (age, severity of disease, comorbidities) and the intensity, frequency and duration of the exercise prescription.

Left ventricular function and mechanics following prolonged endurance exercise: an update and meta-analysis with insights from novel techniques

Background

The cardiac consequences of undertaking endurance exercise are the topic of recent debate. The purpose of this review is to provide an update on a growing body of literature, focusing on left ventricular (LV) function following prolonged endurance exercise over 2 h in duration which have employed novel techniques, including myocardial speckle tracking, to provide a more comprehensive global and regional assessment of LV mechanics.

Methods

Prospective studies were filtered independently following a pre-set criteria, resulting in the inclusion of 27 studies in the analyses. A random-effects meta-analysis was used to determine the weighted mean difference and 95% confidence intervals (CI) of LV functional and mechanical data from pre-to-post-exercise. Narrative commentary was also provided where volume of available evidence precluded meta-analysis.

Results

A significant overall reduction in LV longitudinal strain (Ɛ) n = 22 (− 18 ± 1 to − 17 ± 1%; effect size (d) − 9: − 1 to − 0.5%), strain rate n = 10 (SR;d − 0.9: − 0.1.3 to − 0.5 l/s) and twistn = 5 (11.9 ± 2.2 to 8.7 ± 2.2°,d − 1: − 1.6 to − 0.3°) was observed following strenuous endurance exercise (range 120–1740 min) (P < 0.01). A smaller number of studies (n = 4) also reported a non-significant reduction in global circumferential and radial Ɛ (P > 0.05).

Conclusion

The meta-analysis and narrative commentary demonstrated that a reduction in LV function and mechanics is evident following prolonged endurance exercise. The mechanism(s) responsible for these changes are complex and likely multi-factorial in nature and may be linked to right and left ventricular interaction.

High-Intensity Exercise Enhances Conduit Artery Vascular Function in Older Adults

PURPOSE

Modulation of vascular function follows an exercise intensity-dependent pattern in young adults. This study aimed to investigate the potential intensity-dependent effects of an acute bout of exercise on conduit and resistance artery function in healthy older adults.

METHODS

Eleven healthy older adults (five males/six females, 66 ± 1 yr) completed 30 min of recumbent cycling at 50%-55% (low intensity) and 75%-80% (high intensity) of their age-predicted HRmax on two separate study visits. Doppler ultrasound measures of brachial artery flow-mediated dilation (FMD) and reactive hyperemia were taken at baseline, 10 min postexercise, and 1 h postexercise. In addition, cardiovascular hemodynamics and brachial shear rate were measured every 5 min during exercise.

RESULTS

Brachial artery FMD was enhanced 10 min after high-intensity exercise (4.8% ± 0.2% to 9.1% ± 0.3%, P < 0.01), but not low-intensity (4.7% ± 0.2% to 6.2% ± 0.3%, P = 0.54) exercise. Peak and total (area under the curve) blood flow during reactive hyperemia (measures of resistance artery function) were enhanced 10 min postexercise for both intensities (peak low intensity, 372 ± 31 to 444 ± 37 mL·min; peak high intensity, 391 ± 30 to 455 ± 28 mL·min; total low intensity, 142 ± 16 to 205 ± 20 mL; total high intensity, 158 ± 14 to 240 ± 25 mL; main effect of time for both, P < 0.05). However, the magnitude of change in peak and the total blood flow were not different between exercise intensities (interaction effect; P = 0.56 and P = 0.97, respectively). Independent of exercise intensity, FMD returned to baseline 1 h after exercise (high, 5.9% ± 0.3%; low, 5.1% ± 0.1%; both P > 0.05).

CONCLUSION

Our data indicate that high-intensity exercise acutely enhances conduit artery function in healthy older adults. In addition, an acute bout of exercise enhances resistance artery function independent of intensity.

UBC-Nepal Expedition: acute alterations in sympathetic nervous activity do not influence brachial artery endothelial function at sea level and high altitude

Evidence indicates that increases in sympathetic nervous activity (SNA), and acclimatization to high altitude (HA), may reduce endothelial function as assessed by brachial artery flow-mediated dilatation (FMD); however, it is unclear whether such changes in FMD are due to direct vascular constraint, or consequential altered hemodynamics (e.g., shear stress) associated with increased SNA as a consequence of exposure to HA. We hypothesized that 1) at rest, SNA would be elevated and FMD would be reduced at HA compared with sea-level (SL); and 2) at SL and HA, FMD would be reduced when SNA was acutely increased, and elevated when SNA was acutely decreased. Using a novel, randomized experimental design, brachial artery FMD was assessed at SL (344 m) and HA (5,050 m) in 14 participants during mild lower-body negative pressure (LBNP; -10 mmHg) and lower-body positive pressure (LBPP; +10 mmHg). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (Duplex ultrasound) were recorded during LBNP, control, and LBPP trials. Muscle SNA was recorded (via microneurography) in a subset of participants (n = 5). Our findings were 1) at rest, SNA was elevated (P < 0.01), and absolute FMD was reduced (P = 0.024), but relative FMD remained unaltered (P = 0.061), at HA compared with SL; and 2) despite significantly altering SNA with LBNP (+60.3 ± 25.5%) and LBPP (-37.2 ± 12.7%) (P < 0.01), FMD was unaltered at SL (P = 0.448) and HA (P = 0.537). These data indicate that acute and mild changes in SNA do not directly influence brachial artery FMD at SL or HA.NEW & NOTEWORTHY The role of the sympathetic nervous system on endothelial function remains unclear. We used lower-body negative and positive pressure to manipulate sympathetic nervous activity at sea level and high altitude and measured brachial endothelial function via flow-mediated dilation. We found that acutely altering sympathetic nervous activity had no effect on endothelial function.

Brief Myocardial Ischemia Produces Cardiac Troponin I Release and Focal Myocyte Apoptosis in the Absence of Pathological Infarction in Swine

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High-sensitivity cTnI assays have increasingly identified a rise and fall in situations not typically thought to be associated with infarction, such as exercise stress in patients with coronary disease and prolonged exercise in apparently healthy marathon runners.

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Using a porcine model of brief ischemia leading to myocardial stunning following a 10-min coronary occlusion, the authors demonstrate a delayed release of cTnI after what had previously been felt to be completely reversible ischemia.

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Although tissue necrosis, sarcolemmal disruption, and infarction are absent after brief ischemia, TUNEL staining demonstrates rare single myocytes undergoing irreversible injury from apoptosis.

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These studies demonstrate that significant cTnI release can occur after a brief duration of ischemia that could be compatible with angina.

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In the absence of an acute coronary syndrome or a prolonged myocardial supply/demand imbalance, it may be more appropriate to ascribe significant cTnI elevations after brief ischemia to myocardial injury rather than infarction.

In a porcine model of brief ischemia leading to reversible stunning in the absence of tissue necrosis, we demonstrated delayed release of cardiac troponin I (cTnI) that exceeded the 99th percentile for normal animals 60 min after reperfusion and rose to readily detectable levels 24 h later. Although tissue analysis at 60 min showed no evidence of infarction, TUNEL staining demonstrated isolated myocytes undergoing apoptosis, which was absent after 24 h. These results demonstrate that cTnI elevations occur after ischemia of a duration that is insufficient to produce myocyte necrosis and reflect myocyte injury associated with apoptosis in the absence of pathological evidence of infarction.

Sex impacts the flow-mediated dilation response to acute aerobic exercise in older adults

There is growing evidence of sex differences in the chronic effect of aerobic exercise on endothelial function (flow-mediated dilation; FMD) in older adults, but whether there are sex differences also in the acute effect of aerobic exercise on FMD in older adults is unknown. The purpose of this study was to test the hypothesis that sex modulates the FMD response to acute aerobic exercise in older adults. Thirteen older men and fifteen postmenopausal women (67±1 vs. 65±2years, means±SE, P=0.6), non-smokers, free of major clinical disease, participated in this randomized crossover study. Brachial artery FMD was measured: 1) prior to exercise; 2) 20min after a single bout of high-intensity interval training (HIIT; 40min; 4×4 intervals 90% peak heart rate (HRpeak)), moderate-intensity continuous training (MICT; 47min 70% HRpeak) and low-intensity continuous training (LICT; 47min 50% HRpeak) on treadmill; and 3) following 60-min recovery from exercise. In older men, FMD was attenuated by 45% following HIIT (5.95±0.85 vs. 3.27±0.52%, P=0.003) and by 37% following MICT (5.97±0.87 vs. 3.73±0.47%, P=0.03; P=0.9 for FMD response to HIIT vs. MICT) and was normalized following 60-min recovery (P=0.99). In postmenopausal women, FMD did not significantly change in response to HIIT (4.93±0.55 vs. 6.31±0.57%, P=0.14) and MICT (5.32±0.62 vs. 5.60±0.68%, P=0.99). In response to LICT, FMD did not change in postmenopausal women nor older men (5.21±0.64 vs. 6.02±0.73%, P=0.7 and 5.70±0.80 vs. 5.55±0.67%, P=0.99). In conclusion, sex and exercise intensity influence the FMD response to acute aerobic exercise in older adults.

Similar pattern of change in V̇o2 kinetics, vascular function, and tissue oxygen provision following an endurance training stimulus in older and young adults

The purpose of this study was to examine the time course of changes in the oxygen uptake (V̇o₂) kinetics response subsequent to short-term exercise training (i.e., 24, 48, 72, and 120 h posttraining) and examine the relationship with the time course of changes in microvascular [deoxygenated hemoglobin concentration ([HHb])-to-V̇o₂ ratio ([HHb])/V̇o₂)] and macrovascular [flow-mediated dilation (FMD)] O₂ delivery to the active tissues/limbs. Seven healthy older [OA; 74 ± 6 (SD) yr] and young men (YA; 25 ± 3 yr) completed three endurance cycling exercise training sessions at 70% V̇o_2peak Moderate-intensity exercise on-transient V̇o₂ (measured breath by breath) and [HHb] (measured by near-infrared spectroscopy) were modeled with a monoexponential and normalized (0-100% of response), and the [HHb])/V̇o₂ was calculated. Ultrasound-derived FMD of the popliteal artery was assessed after 5 min of cuff occlusion. %FMD was calculated as the greatest percent change in diameter from baseline. Time constant of V̇o₂ (τV̇o₂) was significantly reduced in both OA (~18%) and YA (~23%) at 24 h (P < 0.001) posttraining and remained decreased at 48 h before returning toward pretraining (PRE) values. Both groups showed a significant decrease in the [HHb])/V̇o₂ at 24, 48, and 72 h (P = 0.001, 0.01, and 0.03, respectively) posttraining before returning toward PRE values at 120 h. %FMD followed a similar time course to that of changes in the [HHb])/V̇o₂, being significantly greater in both OA (by ~64%) and YA (by ~26%) at 24 h (P < 0.001), remaining increased at 48 and 72 h (P = 0.02 and 0.03, respectively), and returning toward PRE values at 120 h. These data suggest the rate of adjustment of V̇o₂ may be constrained by O₂ availability in the active tissues.

The effect of α1 -adrenergic blockade on post-exercise brachial artery flow-mediated dilatation at sea level and high altitude

KEY POINTS

Our objective was to quantify endothelial function (via brachial artery flow-mediated dilatation) at sea level (344 m) and high altitude (3800 m) at rest and following both maximal exercise and 30 min of moderate-intensity cycling exercise with and without administration of an α₁ -adrenergic blockade. Brachial endothelial function did not differ between sea level and high altitude at rest, nor following maximal exercise. At sea level, endothelial function decreased following 30 min of moderate-intensity exercise, and this decrease was abolished with α₁ -adrenergic blockade. At high altitude, endothelial function did not decrease immediately after 30 min of moderate-intensity exercise, and administration of α₁ -adrenergic blockade resulted in an increase in flow-mediated dilatation. Our data indicate that post-exercise endothelial function is modified at high altitude (i.e. prolonged hypoxaemia). The current study helps to elucidate the physiological mechanisms associated with high-altitude acclimatization, and provides insight into the relationship between sympathetic nervous activity and vascular endothelial function.

ABSTRACT

We examined the hypotheses that (1) at rest, endothelial function would be impaired at high altitude compared to sea level, (2) endothelial function would be reduced to a greater extent at sea level compared to high altitude after maximal exercise, and (3) reductions in endothelial function following moderate-intensity exercise at both sea level and high altitude are mediated via an α₁ -adrenergic pathway. In a double-blinded, counterbalanced, randomized and placebo-controlled design, nine healthy participants performed a maximal-exercise test, and two 30 min sessions of semi-recumbent cycling exercise at 50% peak output following either placebo or α₁ -adrenergic blockade (prazosin; 0.05 mg kg ^-1 ). These experiments were completed at both sea-level (344 m) and high altitude (3800 m). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (ultrasound) were recorded before, during and following exercise. Endothelial function assessed by brachial artery flow-mediated dilatation (FMD) was measured before, immediately following and 60 min after exercise. Our findings were: (1) at rest, FMD remained unchanged between sea level and high altitude (placebo P = 0.287; prazosin: P = 0.110); (2) FMD remained unchanged after maximal exercise at sea level and high altitude (P = 0.244); and (3) the 2.9 ± 0.8% (P = 0.043) reduction in FMD immediately after moderate-intensity exercise at sea level was abolished via α₁ -adrenergic blockade. Conversely, at high altitude, FMD was unaltered following moderate-intensity exercise, and administration of α₁ -adrenergic blockade elevated FMD (P = 0.032). Our results suggest endothelial function is differentially affected by exercise when exposed to hypobaric hypoxia. These findings have implications for understanding the chronic impacts of hypoxaemia on exercise, and the interactions between the α₁ -adrenergic pathway and endothelial function.

Cardiorespiratory Fitness and Atherosclerosis: Recent Data and Future Directions

Historically, the relationship between exercise and the cardiovascular system was viewed as unidirectional, with a disease resulting in exercise limitation and hazard. This article reviews and explores the bidirectional nature, delineating the effects, generally positive, on the cardiovascular system and atherosclerosis. Exercise augments eNOS, affects redox potential, and favorably affects mediators of atherosclerosis including lipids, glucose homeostasis, and inflammation. There are direct effects on the vasculature as well as indirect benefits related to exercise-induced changes in body composition and skeletal muscle. Application of aerobic exercise to specific populations is described, with the hope that this knowledge will move the science forward and improve individual patient outcome.

Troponin and exercise

Cardiac troponins are the preferred biomarkers in diagnostic of myocardial infarction, but these markers also can rise in response to exercise. Multiple studies have assessed troponins post-exercise, but the results have varied and there have been disagreements about the mechanism of troponin release. The aim of this paper was to review the literature, and to consider factors and mechanisms regarding exercise-induced increase of troponin. 145 studies were found after a search in pubmed and inclusion of additional articles found in the reference list of the first articles. Results showed that troponin rises in 0-100% of subjects after prolonged heavy exercise like marathon, but also after short-term and intermittent exercise like 30min of running and basketball. The variation can be due to factors like intensity, age, training experience, variation in sample size, blood sample timing and troponin assay. The pattern of troponin level post-exercise corresponds to release from the cytosolic compartment of cardiomyocytes. Increased membrane permeability might be caused by production of reactive oxygen species or alterations in calcium, pH, glucose/fat metabolism or in communication between integrins. Other suggested mechanisms are increased cardiovascular stress, inflammation, vasculitis, release of troponin degradation products in "blebs", dehydration, impaired renal clearance and expression of cardiac troponin in skeletal muscle. It can be concluded that both heavy and light exercise may cause elevated troponin, which have to be considered when patient are suspected to have a myocardial infarction. Several factors probably influence post-exercise levels of troponin, but the mechanism of release is most likely physiologic.

Left Ventricular Function After Prolonged Exercise in Equine Endurance Athletes

BACKGROUND

Prolonged exercise in human athletes is associated with transient impairment of left ventricular (LV) function, known as cardiac fatigue. Cardiac effects of prolonged exercise in horses remain unknown.

OBJECTIVES

To investigate the effects of prolonged exercise on LV systolic and diastolic function in horses.

ANIMALS

Twenty-six horses competing in 120-160 km endurance rides.

METHODS

Cross-sectional field study. Echocardiography was performed before and after rides, and the following morning, and included two-dimensional echocardiography, anatomical M-mode, pulsed-wave tissue Doppler imaging, and two-dimensional speckle tracking. Correlation between echocardiographic variables and cardiac troponin I was evaluated.

RESULTS

Early diastolic myocardial velocities decreased significantly in longitudinal (baseline: -17.4 ± 2.4cm/s; end of ride: -15.8 ± 3.2cm/s (P = .013); morning after: -15.4 ± 3.0cm/s (P = .0033)) and radial directions (-32.8 ± 3.4cm/s; -28.1 ± 5.8cm/s (P < .001); -26.4 ± 5.5cm/s (P < .001)). Early diastolic strain rates decreased significantly in longitudinal (1.58 ± 0.27s(-1) ; 1.45 ± 0.26s(-1) (P = .036); 1.41 ± 0.25s(-1) (P = .013)) and circumferential directions (2.43 ± 0.29s(-1) ; 1.96 ± 0.46s(-1) (P < .001); 2.11 ± 0.32s(-1) (P < .001)). Systolic variables showed ambiguous results. No correlations with serum cardiac troponin I concentrations were evident.

CONCLUSIONS AND CLINICAL IMPORTANCE

Prolonged exercise in horses is associated with impaired LV diastolic function. Reduced ventricular filling persisted for 7-21 hours despite normalization of biochemical indicators of hydration status, indicating that the observed changes were not entirely related to altered preload conditions. The clinical relevance of cardiac fatigue in horses remains uncertain.

Low-Volume Intense Exercise Elicits Post-exercise Hypotension and Subsequent Hypervolemia, Irrespective of Which Limbs Are Exercised

Introduction: Exercise reduces arterial and central venous blood pressures during recovery, which contributes to its valuable anti-hypertensive effects and to facilitating hypervolemia. Repeated sprint exercise potently improves metabolic function, but its cardiovascular effects (esp. hematological) are less well-characterized, as are effects of exercising upper versus lower limbs. The purposes of this study were to identify the acute (<24 h) profiles of arterial blood pressure and blood volume for (i) sprint intervals versus endurance exercise, and (ii) sprint intervals using arms versus legs.

Methods: Twelve untrained males completed three cycling exercise trials; 50-min endurance (legs), and 5^*30-s intervals using legs or arms, in randomized and counterbalanced sequence, at a standardized time of day with at least 8 days between trials. Arterial pressure, hemoglobin concentration and hematocrit were measured before, during and across 22 h after exercise, the first 3 h of which were seated rest.

Results: The post-exercise hypotensive response was larger after leg intervals than endurance (AUC: 7540 ± 3853 vs. 3897 ± 2757 mm Hg·min, p = 0.049, 95% CI: 20 to 6764), whereas exercising different limbs elicited similar hypotension (arms: 6420 ± 3947 mm Hg·min, p = 0.48, CI: −1261 to 3896). In contrast, arterial pressure at 22 h was reduced after endurance but not after leg intervals (−8 ± 8 vs. 0 ± 7 mm Hg, p = 0.04, CI: 7 ± 7) or reliably after arm intervals (−4 ± 8 mm Hg, p = 0.18 vs. leg intervals). Regardless, plasma volume expansion at 22 h was similar between leg intervals and endurance (both +5 ± 5%; CI: −5 to 5%) and between leg and arm intervals (arms: +5 ± 7%, CI: −8 to 5%).

Conclusions: These results emphasize the relative importance of central and/or systemic factors in post-exercise hypotension, and indicate that markedly diverse exercise profiles can induce substantive hypotension and subsequent hypervolemia. At least for endurance exercise, this hypervolemia may not depend on the volume of post-exercise hypotension. Finally, endurance exercise led to reduced blood pressure the following day, but sprint interval exercise did not.

Left Ventricular Function and Physiological Performance in Female Ironman Athletes and Female Police Officers

Data about physiological performance of female ironman triathletes are rare. However, some studies have reported this endurance sport may cause damage to the right or left ventricles, even in females. The goal of this study was to assess prospectively the right/left ventricular function and physiological performance in female athletes (middle- and long ironman distance) and to compare the findings to female federal police officers. A total of 33 female triathletes and 37 female police officers were examined using spiro-ergometry and echocardiography. Female triathletes achieved VO2max 52.8 ± 5.7 ml/kg−1·min−1, and police officers 35.3 ± 6.5 ml/kg−1·min−1. In athletes, left ventricular end-diastolic diameter was 4.4 ± 0.3 cm and in police officers 4.5 ± 0.4 cm, and the left ventricular muscle mass index was 85.8 g/m2 ± 18.7 in athletes and in police officers 72.0 g/m2 ± 9.1. Right ventricular area change among athletes was 49.4 ± 8.5%, and in police officers 46.0 ± 6.9%. The performance date of female triathletes can be used as training prescription for leisure female triathletes, when middle or long distances in triathlon competitions are planned. No right or left ventricular dysfunction was found despite long training and finishing of long distance competitions: non-elite athletes, 5.4 ± 2.8 years of triathlon competitions; elite athletes, 7.6 ± 5.8 years.

Assessing the perceived quality of brachial artery Flow Mediated Dilation studies for inclusion in meta-analyses and systematic reviews: Description of data employed in the development of a scoring ;tool based on currently accepted guidelines

Brachial artery Flow Mediated Dilation (FMD) is widely used as a non-invasive measure of endothelial function. Adherence to expert consensus guidelines on FMD measurement has been found to be of vital importance to obtain reproducible data. This article lists the literature data which was considered in the development of a tool to aid in the objective judgement of the extent to which published studies adhered to expert guidelines for FMD measurement. Application of this tool in a systematic review of FMD studies (http://dx.doi.org/10.1016/j.atherosclerosis.2016.03.011) (Greyling et al., 2016 [1]) indicated that adherence to expert consensus guidelines is strongly correlated to the reproducibility of FMD data.

Neurovascular coupling in humans: Physiology, methodological advances and clinical implications

Neurovascular coupling reflects the close temporal and regional linkage between neural activity and cerebral blood flow. Although providing mechanistic insight, our understanding of neurovascular coupling is largely limited to non-physiologicalex vivopreparations and non-human models using sedatives/anesthetics with confounding cerebrovascular implications. Herein, with particular focus on humans, we review the present mechanistic understanding of neurovascular coupling and highlight current approaches to assess these responses and the application in health and disease. Moreover, we present new guidelines for standardizing the assessment of neurovascular coupling in humans. To improve the reliability of measurement and related interpretation, the utility of new automated software for neurovascular coupling is demonstrated, which provides the capacity for coalescing repetitive trials and time intervals into single contours and extracting numerous metrics (e.g., conductance and pulsatility, critical closing pressure, etc.) according to patterns of interest (e.g., peak/minimum response, time of response, etc.). This versatile software also permits the normalization of neurovascular coupling metrics to dynamic changes in arterial blood gases, potentially influencing the hyperemic response. It is hoped that these guidelines, combined with the newly developed and openly available software, will help to propel the understanding of neurovascular coupling in humans and also lead to improved clinical management of this critical physiological function.

Substantive hemodynamic and thermal strain upon completing lower-limb hot-water immersion; comparisons with treadmill running

Exercise induces arterial flow patterns that promote functional and structural adaptations, improving functional capacity and reducing cardiovascular risk. While heat is produced by exercise, local and whole-body passive heating have recently been shown to generate favorable flow profiles and associated vascular adaptations in the upper limb. Flow responses to acute heating in the lower limbs have not yet been assessed, or directly compared to exercise, and other cardiovascular effects of lower-limb heating have not been fully characterized. Lower-limb heating by hot-water immersion (30 min at 42°C, to the waist) was compared to matched-duration treadmill running (65-75% age-predicted heart rate maximum) in 10 healthy, young adult volunteers. Superficial femoral artery shear rate assessed immediately upon completion was increased to a greater extent following immersion (mean ± SD: immersion +252 ± 137% vs. exercise +155 ± 69%, interaction: p = 0.032), while superficial femoral artery flow-mediated dilation was unchanged in either intervention. Immersion increased heart rate to a lower peak than during exercise (immersion +38 ± 3 beats·min^-1 vs. exercise +87 ± 3 beats·min^-1, interaction: p < 0.001), whereas only immersion reduced mean arterial pressure after exposure (−8 ± 3 mmHg, p = 0.012). Core temperature increased twice as much during immersion as exercise (+1.3 ± 0.4°C vs. +0.6 ± 0.4°C, p < 0.001). These data indicate that acute lower-limb hot-water immersion has potential to induce favorable shear stress patterns and cardiovascular responses within vessels prone to atherosclerosis. Whether repetition of lower-limb heating has long-term beneficial effects in such vasculature remains unexplored.

Acute Changes in Inflammatory Biomarker Levels in Recreational Runners Participating in a Marathon or Half-Marathon

Background

Strenuous physical activity activates the participant’s immune responses; however, few studies exist, observing exercise-induced simultaneous changes in mediators of inflammation.

Methods

We examined individual responses in soluble urokinase-type plasminogen activator receptor (suPAR), a marker of immune activation, soluble endocytic receptor for haptoglobin-hemoglobin complexes (CD163), a marker of monocyte-macrophage activation, C-reactive protein (CRP), and pro- and anti-inflammatory cytokines from blood samples drawn at baseline, at 3- and 48-h post-races from recreational runners who successfully completed the marathon (199 ± 8 min, n = 4) or half-marathon (132 ± 4 min, n = 4) run. For comparisons, biomarkers reflecting muscle, heart, kidney, and liver functions were measured.

Results

Significant 3-h post-race increases occurred in levels of suPAR (p < 0.01), CD163 (p < 0.05), white blood cells (p < 0.001), pro-inflammatory cytokines, interleukin-6 (IL-6) (p < 0.001), IL-8 (p < 0.05), and anti-inflammatory cytokine IL-10 (p < 0.05), whereas tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β) remained relatively stable. Full-marathon running lead to more pronounced increases in suPAR, CD163, IL-8, and IL-10 than half-marathon running. In addition, 3-h post-race increases of all these parameters correlated significantly with changes in serum TNF-α and cortisol. The 48-h levels of serum suPAR and both pro- and anti-inflammatory cytokines had decreased to baseline levels, whereas CRP, a marker of acute phase response, increased in those with the most prominent IL-6 and IL-10 elevations in their preceding samples. The highest suPAR, CRP, IL-6, TNF-α, IL-10, and cortisol levels were noted in the individual with the most severe post-race fatigue.

Conclusions

Prolonged running increases mediators of inflammation in an exercise-dose-dependent manner which should be considered in the assessment of health status of physically active individuals after recent acute bouts of strenuous exercise.

Impact of sympathetic nervous system activity on post-exercise flow-mediated dilatation in humans

Transient reduction in vascular function following systemic large muscle group exercise has previously been reported in humans. The mechanisms responsible are currently unknown. We hypothesised that sympathetic nervous system activation, induced by cycle ergometer exercise, would contribute to post-exercise reductions in flow-mediated dilatation (FMD). Ten healthy male subjects (28 ± 5 years) undertook two 30 min sessions of cycle exercise at 75% HR(max). Prior to exercise, individuals ingested either a placebo or an α1-adrenoreceptor blocker (prazosin; 0.05 mg kg(-1)). Central haemodynamics, brachial artery shear rate (SR) and blood flow profiles were assessed throughout each exercise bout and in response to brachial artery FMD, measured prior to, immediately after and 60 min after exercise. Cycle exercise increased both mean and antegrade SR (P < 0.001) with retrograde SR also elevated under both conditions (P < 0.001). Pre-exercise FMD was similar on both occasions, and was significantly reduced (27%) immediately following exercise in the placebo condition (t-test, P = 0.03). In contrast, FMD increased (37%) immediately following exercise in the prazosin condition (t-test, P = 0.004, interaction effect P = 0.01). Post-exercise FMD remained different between conditions after correction for baseline diameters preceding cuff deflation and also post-deflation SR. No differences in FMD or other variables were evident 60 min following recovery. Our results indicate that sympathetic vasoconstriction competes with endothelium-dependent dilator activity to determine post-exercise arterial function. These findings have implications for understanding the chronic impacts of interventions, such as exercise training, which affect both sympathetic activity and arterial shear stress.

Technical recommendations for the use of carotid duplex ultrasound for the assessment of extracranial blood flow

Duplex ultrasound is an evolving technology that allows the assessment of volumetric blood flow in the carotid and vertebral arteries during a range of interventions along the spectrum of health and chronic disease. Duplex ultrasound can provide high-resolution diameter and velocity information in real-time and is noninvasive with minimal risks or contraindications. However, this ultrasound approach is a specialized technique requiring intensive training and stringent control of multiple complex settings; results are highly operator-dependent, and analysis approaches are inconsistent. Importantly, therefore, methodological differences can invalidate comparisons between different imaging modalities and studies; such methodological errors have potential to discredit study findings completely. The task of this review is to provide the first comprehensive, user-friendly technical guideline for the application of duplex ultrasound in measuring extracranial blood flow in human research. An update on recent developments in the use of edge-detection software for offline analysis is highlighted, and suggestions for future directions in this field are provided. These recommendations are presented in an attempt to standardize measurements across research groups and, hence, ultimately to improve the accuracy and reproducibility of measuring extracranial blood flow both within subjects and between groups.

Intermittent cardiac overload results in adaptive hypertrophy and provides protection against left ventricular acute pressure overload insult

The present study aimed to test whether a chronic intermittent workload could induce an adaptive cardiac phenotype Chronic intermittent workload induced features of adaptive hypertrophy This was paralleled by protection against acute pressure overload insult The heart may adapt favourably to balanced demands, regardless of the nature of the stimuli. The present study aimed to test whether submitting the healthy heart to intermittent and tolerable amounts of workload, independently of its nature, could result in an adaptive cardiac phenotype. Male Wistar rats were subjected to treadmill running (Ex) (n = 20), intermittent cardiac overload with dobutamine (ITO) (2 mg kg(-1) , s.c.; n = 20) or placebo administration (Cont) (n = 20) for 5 days week(-1) for 8 weeks. Animals were then killed for histological and biochemical analysis or subjected to left ventricular haemodynamic evaluation under baseline conditions, in response to isovolumetric contractions and to sustained LV acute pressure overload (35% increase in peak systolic pressure maintained for 2 h). Baseline cardiac function was enhanced only in Ex, whereas the response to isovolumetric heartbeats was improved in both ITO and Ex. By contrast to the Cont group, in which rats developed diastolic dysfunction with sustained acute pressure overload, ITO and Ex showed increased tolerance to this stress test. Both ITO and Ex developed cardiomyocyte hypertrophy without fibrosis, no overexpression of osteopontin-1 or β-myosin heavy chain, and increased expression of sarcoplasmic reticulum Ca(2+) protein. Regarding hypertrophic pathways, ITO and Ex showed activation of the protein kinase B/mammalian target of rapamycin pathway but not calcineurin. Mitochondrial complex IV and V activities were also increased in ITO and Ex. Chronic submission to controlled intermittent cardiac overload, independently of its nature, results in an adaptive cardiac phenotype. Features of the cardiac overload, such as the duration and magnitude of the stimuli, may play a role in the development of an adaptive or maladaptive phenotype.

Flow mediated dilation with photoplethysmography as a substitute for ultrasonic imaging

Flow mediated dilation (FMD) is a non-invasive method for endothelial function assessment providing an index extracted from ultrasonic B-mode images. Although utilized in the research community, the difficulty of its application and high cost of ultrasonic devices prevent it from being widely used in clinical settings. In this study we show that substituting the ultrasonic device with more easily handled and low cost photoplethysmography and electrocardiography is possible. We introduce new indices based on the photoplethysmogram (PPG) and electrocardiogram (ECG) and show that they are correlated with the ultrasound-based FMD Index. To this end, a conventional ultrasound FMD test was carried out whereas PPG and ECG were simultaneously recorded from 20 healthy volunteers (13 M, 7 F) in the age range of 23-32 years. Our results show a significant correlation between our proposed index and ultrasound FMD when using the ECG in conjunction with the PPG (R = 0.77, p < 0.000 01). Using the PPG alone produces a lower correlation (R = 0.72, p < 0.0001). Compared to conventional FMD, the proposed method is low cost and does not require any special operator skills. Hence it may be easily utilized as a screening tool in locations deprived of high-end ultrasound imaging devices.

Lower limb conduit artery endothelial responses to acute upper limb exercise in spinal cord injured and able-bodied men

Vascular improvements in the nonactive regions during exercise are likely primarily mediated by increased shear rate (SR). Individuals with spinal cord injury (SCI) experience sublesional vascular deconditioning and could potentially benefit from upper body exercise-induced increases in lower body SR. The present study utilized a single bout of incremental arm-crank exercise to generate exercise-induced SR changes in the superficial femoral artery in an effort to evaluate the acute postexercise impact on superficial femoral artery endothelial function via flow-mediated dilation (FMD), and determine regulatory factors in the nonactive legs of individuals with and without SCI. Eight individuals with SCI and eight age, sex, and waist-circumference-matched able-bodied (AB) controls participated. Nine minutes of incremental arm-crank exercise increased superficial femoral artery anterograde SR (P = 0.02 and P < 0.01), retrograde SR (P < 0.01 and P < 0.01), and oscillatory shear index (OSI) (P < 0.001 and P < 0.001) in both SCI and AB, respectively. However, these SR alterations resulted in acute postexercise increases in FMD in the AB group only (SCI 6.0 ± 1.2% to 6.3 ± 2.7%, P = 0.74; AB 7.5 ± 1.4% to 11.2 ± 1.4%, P = 0.03). While arm exercise has many cardiovascular benefits and results in changes in SR patterns in the nonactive legs, these changes are not sufficient to induce acute changes in FMD among individuals with SCI, and therefore are less likely to stimulate exercise training-associated improvements in nonactive limb endothelial function. Understanding the role of SR patterns on FMD brings us closer to designing effective strategies to combat impaired vascular function in both healthy and clinical populations.

Exercise intensity and the protection from postprandial vascular dysfunction in adolescents

Acute exercise transiently improves endothelial function and protects the vasculature from the deleterious effects of a high-fat meal (HFM). We sought to identify whether this response is dependent on exercise intensity in adolescents. Twenty adolescents (10 male, 14.3 ± 0.3 yr) completed three 1-day trials: 1) rest (CON); 2) 8 × 1 min cycling at 90% peak power with 75 s recovery [high-intensity interval exercise (HIIE)]; and 3) cycling at 90% of the gas exchange threshold [moderate-intensity exercise (MIE)] 1 h before consuming a HFM (1.50 g/kg fat). Macrovascular and microvascular endothelial function was assessed before and immediately after exercise and 3 h after the HFM by flow-mediated dilation (FMD) and laser Doppler imaging [peak reactive hyperemia (PRH)]. FMD and PRH increased 1 h after HIIE [P < 0.001, effect size (ES) = 1.20 and P = 0.048, ES = 0.56] but were unchanged after MIE. FMD and PRH were attenuated 3 h after the HFM in CON (P < 0.001, ES = 1.78 and P = 0.02, ES = 0.59). FMD remained greater 3 h after the HFM in HIIE compared with MIE (P < 0.001, ES = 1.47) and CON (P < 0.001, ES = 2.54), and in MIE compared with CON (P < 0.001, ES = 1.40). Compared with CON, PRH was greater 3 h after the HFM in HIIE (P = 0.02, ES = 0.71) and MIE (P = 0.02, ES = 0.84), with no differences between HIIE and MIE (P = 0.72, ES = 0.16). Plasma triacylglycerol concentration and total antioxidant status concentration were not different between trials. We conclude that exercise intensity plays an important role in protecting the vasculature from the deleterious effects of a HFM. Performing HIIE may provide superior vascular benefits than MIE in adolescent groups.

Impact of handgrip exercise intensity on brachial artery flow-mediated dilation

PURPOSE

Previous studies that have examined the impact of exercise intensity on conduit artery endothelial function have involved large muscle group exercise which induces local and systemic effects. The aim of this study was to examine flow-mediated dilation (FMD) before and after incremental intensities of handgrip exercise (HE), to assess the role of local factors such as blood flow and shear rate on post-exercise brachial artery function.

METHODS

Eleven healthy men attended the laboratory on three occasions. Subjects undertook 30 min of handgrip exercise at three intensities (5, 10 or 15 % MVC). Brachial artery FMD, shear and blood flow patterns were examined before, immediately after and 60 min post exercise.

RESULTS

Handgrip exercise increased mean and antegrade shear rate (SR) and blood flow (BF) and reduced retrograde SR and BF (all P < 0.01). Exercise intensity was associated with a dose-dependent increase in both mean and antegrade BF and SR (interaction, P < 0.01). Post-hoc tests revealed that, whilst handgrip exercise did not immediately induce post-exercise changes, FMD was significantly higher 60 min post-exercise following the highest exercise intensity (5.9 ± 2.8-10.4 ± 5.8 %, P = 0.01).

CONCLUSIONS

Handgrip exercise leads to intensity-and time-dependent changes in conduit artery function, possibly mediated by local increases in shear, with improvement in function evident at 1 h post-exercise when performed at a higher intensity.

Regional and global left ventricular function following a simulated 5 km race in sports-trained adolescents

The effects of a short, high-intensity bout of exercise on cardiac systolic and diastolic function are not well understood in adolescent athletes. Consequently, the aims of the study were to evaluate global left ventricular (LV) systolic and diastolic function, as well as segmental wall motion responses (cardiac strain), prior to as well as 45 and 225 min following a simulated 5 km cross-country race. Twenty trained, adolescent males (age: 15.2 ± 0.7 years) volunteered for exercise testing. LV fractional shortening and the ratio of early (E) and late (A) peak flow velocities reflected global systolic and diastolic function, respectively. Peak longitudinal mitral annular septal tissue velocities were also determined during systole and diastole. Longitudinal strain (ε) and strain rates were determined across the LV. LV fractional shortening was significantly (P < 0.05) higher at 225 min post-race (37.6 ± 5.8%) compared to pre-race (34.5 ± 4.7%) and 45 min post-race (34.9 ± 5.4 %). This difference was abolished after adjusting for post-race heart rates. There was a significant (P < 0.05) decrease in the E:A ratio at both 45 min (2.04 ± 0.57) and 225 min post-race (2.20 ± 0.66) compared to the pre-race value (2.80 ± 0.68). When these data were adjusted for post-race heart rates, these pre-post-race differences in E:A ratio were abolished. There were no significant alterations in either tissue Doppler velocities or longitudinal ε. The evidence suggests that a 5 km race does not lead to any significant post-exercise attenuation in global or regional LV systolic and diastolic function in trained adolescents.