Endurance-trained Individuals Research Articles

Long-Term Incidence of Bradycardia and Pacemaker Implantations Among Cross-Country Skiers: A Cohort Study.

Bradycardia is more common among well-trained athletes than in the general population, but the association with pacemaker implantations is less known. We investigated associations of endurance training with incidence of bradycardia and pacemaker implantations, including sex differences and long-term outcome, in a cohort of endurance trained individuals. All Swedish skiers who completed >1 race in the cross-country skiing event Vasaloppet between 1989 and 2011 (n=209 108) and a sample of 532 290 nonskiers were followed until first event of bradycardia, pacemaker implantation, or death, depending on end point. The Swedish National Patient Register was used to obtain diagnoses. Cox regression was used to investigate associations of number of completed races and finishing time in Vasaloppet with incidence of bradycardia and pacemaker implantations. In addition, Cox regression was used to investigate associations of pacemaker implantations with death in skiers and nonskiers. Male skiers had a higher incidence of bradycardia (adjusted hazard ratio [aHR], 1.19 [95% CI, 1.05-1.34]) and pacemaker implantations (aHR, 1.17 [95% CI, 1.04-1.31]) compared with male nonskiers. Those who completed the most races and had the best performances exhibited the highest incidence. For female skiers in Vasaloppet, the incidence of bradycardia (aHR, 0.98 [95% CI, 0.75-1.30]) and pacemaker implantations (aHR, 0.98 [95% CI, 0.75-1.29]) was not different from that of female nonskiers. The indication for pacemaker differed between skiers and nonskiers, with sick sinus syndrome more common in the former and third-degree atrioventricular block in the latter. Skiers had lower overall mortality rates than nonskiers (aHR, 0.16 [95% CI, 0.15-0.17]). There were no differences in mortality rates by pacemaker status among skiers. In this study, male endurance skiers had a higher incidence of bradycardia and pacemaker implantations compared with nonskiers, a pattern not seen in women. Among male skiers, those who completed the most races and had the fastest finishing times had the highest incidence of bradycardia and pacemaker implantations. Within each group, mortality rates did not differ in relation to pacemaker status. These findings suggest that bradycardia associated with training leads to a higher risk for pacemaker implantation without a detrimental effect on mortality risk.

Remodeling of the Human Skeletal Muscle Proteome Found After Long-Term Endurance Training but Not After Strength Training

Regular exercise training has tremendous systemic tissue-specific health benefits, but the molecular adaptations to long-term exercise training are not completely understood. The aim of the current study was to investigate the skeletal muscle proteome of highly endurance-trained, strength-trained and untrained individuals and performed exercise- and sex-specific analyses. As a previous investigation from our lab showed limited baseline differences at the gene expression level between highly strength-trained males and untrained males, we hypothesized that the that long-term resistance training results in baseline differences in protein abundances. Additionally, we hypothesized that endurance-trained individuals would have a greater abundance of mitochondrial proteins compared with the untrained and the strength-trained individuals. Liquid-chromatography followed by mass-spectrometry (LC-MS/MS) was performed on skeletal muscle tissue from all individuals. A total of 6713 proteins were detected, with 4269 proteins being expressed in at least 50% of the samples. Over 650 proteins were differentially expressed in the skeletal muscle of endurance-trained individuals compared with controls. Strikingly, 92% of the shared proteins with higher expression in both the male and female endurance groups were known mitochondrial proteins. In contrast to the findings in endurance trained individuals, minimal differences were found in strength-trained individuals and between females and males. Lastly, to determine the preventive-medicine capabilities of long-term training, a co-expression network and comparative literature analysis revealed key proteins and pathways related to the health benefits of exercise, which were primarily related to differences in mitochondrial protein abundance. This network is available as an interactive database resource ( https://inetmodels.com ) where investigators can correlate clinical data with global gene and protein expression data for hypothesis generation. In conclusion, we suggest that long-term endurance training but not strength training results in a r emodeling of the skeletal muscle proteome in humans. This work was financially supported by grants from the Swedish Research Council (2018-02932), the Swedish Center for Sports Research (2020-D0007, P2022-0082), the National Science Foundation (Award Number: 1951792), the Whitaker International Program and the Karolinska Institute. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Exploring the Relationship between Ultrasonographic Measures of the Quadriceps and Knee Extensor Muscle Fitness in Endurance-Trained Individuals.

B-mode ultrasonography is an accessible and cost-effective method to assess muscle size and quality through muscle thickness (MT) and echo intensity (EI), respectively. Muscle thickness and EI have demonstrated relationships with maximal strength and local muscle endurance, providing a noninvasive and efficient modality to examine muscle fitness. However, these relationships have not been quantified in the individual quadriceps muscles of habitually endurance-trained populations, which may provide information to practitioners regarding rehabilitation and performance. Twenty-three participants (males: N = 10; females: N = 13) underwent B-mode ultrasonography to assess MT, EI, and adipose tissue thickness-corrected echo intensity (cEI) in the vastus intermedius (VI), vastus lateralis (VL), and rectus femoris (RF). Muscle fitness was evaluated through maximal strength (1RM) and local muscle endurance (4 sets to failure at 50% 1RM) during dynamic knee extension. Relationships between ultrasonography outcomes and muscle fitness were examined through stepwise multiple linear regression. The results indicate that VI cEI is the strongest predictor of 1RM strength (r = -0.643), while no ultrasonography-derived measures significantly predicted local muscle endurance. The study demonstrates that ultrasonography, specifically measures of cEI in the VI, has the greatest association with maximal strength in endurance-trained individuals. These findings suggest monitoring VI muscle size and quality may benefit practitioners who aim to improve knee extension strength for performance or following injury. In addition, the findings support the use of EI examinations in trained populations.

Muscle fibre size and myonuclear positioning in trained and aged humans.

Changes in myonuclear architecture and positioning are associated with exercise adaptations and ageing. However, data on the positioning and number of myonuclei following exercise are inconsistent. Additionally, whether myonuclear domains (MNDs; i.e., the theoretical volume of cytoplasm within which a myonucleus is responsible for transcribing DNA) and myonuclear positioning are altered with age remains unclear. The aim of this investigation was to investigate relationships between age and activity status and myonuclear domains and positioning. Vastus lateralis muscle biopsies from younger endurance-trained (YT) and older endurance-trained (OT) individuals were compared with age-matched untrained counterparts (YU and OU; OU samples were acquired during surgical operation). Serial, optical z-slices were acquired throughout isolated muscle fibres and analysed to give three-dimensional coordinates for myonuclei and muscle fibre dimensions. The mean cross-sectional area (CSA) of muscle fibres from OU individuals was 33%-53% smaller compared with the other groups. The number of nuclei relative to fibre CSA was 90% greater in OU compared with YU muscle fibres. Additionally, scaling of MND volume with fibre size was altered in older untrained individuals. The myonuclear arrangement, in contrast, was similar across groups. Fibre CSA and most myonuclear parameters were significantly associated with age in untrained individuals, but not in trained individuals. These data indicate that regular endurance exercise throughout the lifespan might better preserve the size of muscle fibres in older age and maintain the relationship between fibre size and MND volumes. Inactivity, however, might result in reduced muscle fibre size and altered myonuclear parameters.

The Improvement in Exercise Performance during Reduced Muscle Mass Exercise is Associated with an Increase in Femoral Blood Flow in Older and Younger Endurance-Trained Athletes.

This study investigated whether the improved performance observed with maximal self-paced single-leg (SL), compared with double-leg (DL) cycling, is associated with enhanced femoral blood flow and/or altered tissue oxygenation. The hyperaemic response to exercise was assessed in younger and older athletes. Power output was measured in 12 older (65 ± 4 y) and 12 younger (35 ± 5 y) endurance-trained individuals performing 2 x 3 min maximal self-paced exercise using SL and DL cycling. Blood flow (BF) in the femoral artery was assessed using Doppler ultrasound and muscle oxygenation was measured using near-infrared spectroscopy on the vastus lateralis. SL cycling elicited a greater power output (295 ± 83 vs 265 ± 70 W, P < 0.001) and peak femoral BF (1749.1 ± 533.3 vs 1329.7 ± 391.7 ml/min, P < 0.001) compared with DL cycling. Older individuals had a lower peak BF in response to exercise (1355.4 ± 385.8 vs 1765.2 ± 559.6 ml/min, P = 0.019) compared with younger individuals. Peak BF in response to exercise was correlated with power output during SL (r = 0.655, P = 0.002) and DL (r = 0.666, P = 0.001) cycling. The greater exercise performance during SL compared with DL cycling may be partly explained by a greater hyperaemic response when reducing active muscle mass. Despite regular endurance training, older athletes had a lower femoral BF in response to maximal self-paced exercise compared with younger athletes.

The increase in core body temperature in response to exertional-heat stress can predict exercise-induced gastrointestinal syndrome

ABSTRACT Utilizing metadata from existing exertional and exertional-heat stress studies, the study aimed to determine if the exercise-associated increase in core body temperature can predict the change in exercise-induced gastrointestinal syndrome (EIGS) biomarkers and exercise-associated gastrointestinal symptoms (Ex-GIS). Endurance-trained individuals completed 2 h of running exercise in temperate (21.2-30.0°C) to hot (35.0-37.2°C) ambient conditions (n = 132 trials). Blood samples were collected pre- and post-exercise to determine the change in gastrointestinal integrity biomarkers and systemic inflammatory cytokines. Physiological and thermoregulatory strain variables were assessed every 10–15 min during exercise. The strength of the linear relationship between maximal (M-Tre) and change (Δ Tre) in rectal temperature and EIGS variables was determined via Spearman’s rank correlation coefficients. While the strength of prediction was determined via simple and multiple linear regression analyses dependent on screened EIGS and Ex-GIS confounding factors. Significant positive correlations between Tre maximum (M-Tre) and change (Δ Tre) with I-FABP (rs = 0.434, p < 0.001; and rs = 0.305, p < 0.001; respectively), sCD14 (rs = 0.358, p < 0.001; and rs = 0.362, p < 0.001), systemic inflammatory response profile (SIR-Profile) (p < 0.001), and total Ex-GIS (p < 0.05) were observed. M-Tre and Δ Tre significantly predicted (adjusted R2) magnitude of change in I-FABP (R2(2,123)=0.164, p < 0.001; and R2(2,119)=0.058, p = 0.011; respectively), sCD14 (R2(2,81)=0.249, p < 0.001; and R2(2,77)=0.214, p < 0.001), SIR-Profile (p < 0.001), and total Ex-GIS (p < 0.05). Strong to weak correlations were observed between M-Tre and Δ Tre with plasma concentrations of I-FABP, sCD14, SIR-Profile, and Ex-GIS in response to exercise. M-Tre and Δ Tre can predict the magnitude of these EIGS variables and Ex-GIS in response to exercise.

Effects of detraining on left ventricular mass in endurance-trained individuals: a systematic review and meta-analysis.

Detraining refers to a loss of training adaptations resulting from reductions in training stimulus due to illness, injury, or active recovery breaks in a training cycle and is associated with a reduction in left ventricular mass (LVM). The purpose of this study was to conduct a systematic review and meta-analysis to determine the influence of detraining on LVM in endurance-trained, healthy individuals. Using electronic databases (e.g. EMBASE and MEDLINE), a literature search was performed looking for prospective detraining studies in humans. Inclusion criteria were adults, endurance-trained individuals with no known chronic disease, detraining intervention >1 week, and pre- and post-detraining LVM reported. A pooled statistic for random effects was used to assess changes in LVM with detraining. Fifteen investigations (19 analyses) with a total of 196 participants (ages 18-55 years, 15% female) met inclusion criteria, with detraining ranging between 1.4 and 15 weeks. The meta-analysis revealed a significant reduction in LVM with detraining (standardized mean difference = -0.586; 95% confidence interval = -0.817, -0.355; P < 0.001). Independently, length of detraining was not correlated with the change in LVM. However, a meta-regression model revealed length of the detraining, when training status was accounted for, was associated with the reduction of LVM (Q = 15.20, df = 3, P = 0.0017). Highly trained/elite athletes had greater reductions in LVM compared with recreational and newly trained individuals (P < 0.01). Limitations included relatively few female participants and inconsistent reporting of intervention details. In summary, LVM is reduced following detraining of one week or more. Further research may provide a greater understanding of the effects of sex, age, and type of detraining on changes in LVM in endurance-trained individuals.

Postexercise cardiovascular hemodynamics assessment before and after a 30-minute standing still recovery.

Although postexercise syncope usually occurs shortly after physical exercise conclusion, athletes commonly reveal symptoms of postexercise hypotension several tens of minutes after exercise completion. Currently, no studies have investigated central hemodynamic regulation during posture changes occurring several tens of minutes after exercise compared to immediately after cessation. This study examined changes in mean arterial pressure (MAP), heart rate (HR), systemic vascular conductance (SVC), cardiac output, and stroke volume during two sets of tilt tests performed before vs. after a 30-minute standing still recovery, respectively. Tilt tests were performed after a short-lasting supramaximal test (WNG) and long-lasting maximal incremental test (INC) in 12 young endurance-trained individuals. The key findings were that, regardless of the exercise type, the 30-minute recovery augmented (P<0.01) the increase in HR and the drop in SVC during the transition from supine to upright, although the MAP drop was similar (P=0.99) after vs. before recovery. INC led to greater increases (P<0.01) in HR and drops (P<0.01) in SVC compared to WNG during postural transitions both before and after the recovery. These findings suggest that, in a population that tolerates postexercise hypotension, MAP neural control is more challenged after a 30-minute standing still recovery than before, as evidenced by an augmented vasodilation capacity along with an increased HR buffering response during posture changes. Moreover, our data suggest that effective MAP control is resulting from an equally effective HR buffering response on MAP. Therefore, exercises that induce greater systemic vasodilation lead to greater HR buffering responses.

In-vivo Estimation of Intramuscular and Diffusive Limitations to O2 Flow Limitations in Resistance and Endurance Trained Individuals by Near Infra-red Spectroscopy

Introduction: Compared with resistance training (RT), endurance training (ET) induces structural changes within skeletal muscles that include increased capillary density and increased oxidative enzyme activity. The adaptations in ET of oxidative capacity are thought to be greater than those of capillary density, causing the location of O2 flow limitation to move from the intramuscular (O2 utilization limited) to the extramuscular (O2supply limited) compartment. We recently proposed a new approach to estimate oxidative capacity and O2diffusion limitation in vivo by near-infrared spectroscopy (NIRS), using the premise that diffusion limitation is exposed by an experimentally-imposed reduction in O2 supply. We therefore evaluated whether this technique could distinguish muscular adaptations between ET and RT individuals. We hypothesized that both muscle oxidative capacity and diffusion limitation would be greater in ET than RT. Methods: Twenty-one young male resistance (RT, n=9, 26±4 yrs) and endurance (ET, n=12, 27±7 yrs) trained individuals volunteered. RT or ET status was characterized using: maximal isometric voluntary torque (MVT) of knee extensors; incremental cycle-ergometry to the limit of tolerance for peak oxygen uptake (V̇O2peak); vastus lateralis fractional O2extraction at V̇O2peak (ΔHHbMbpeak), expressed as percentage of ΔHHbMb during sustained occlusion; and by V̇O2 kinetics (τV̇O2) during moderate intensity constant work-rate exercise. Vastus lateralis muscle V̇O2recovery rate constant ( k) following brief knee extensor exercise was assessed using NIRS and repeated transient arterial occlusions. k was assessed twice, with arterial occlusions manipulated to maintain tissue saturation index within a 10% range in either LOW or HIGH conditions. Results: MVT was greater in RT than ET (328±43 vs. 255±40N, P&lt;0.001). V̇O2peak was lower in RT than ET (38.8±4.6 vs. 55.6±3.8ml∙kg-1∙min-1, P&lt;0.001). ΔHHbMbpeak was lower in RT than ET (57±11 vs. 91±6%, P&lt;0.001). τV̇O2 was lower in RT than ET (39.8±7.6 vs. 24.0±4.4s, P&lt;0.001). kHIGH was lower in RT than ET (1.49±0.25 vs. 3.04±0.71min-1, P=0.001) and the difference in k (Δ k = kHIGH – kLOW) was less in RT than ET (0.29±0.16 vs 0.80±0.69 min-1, P=0.045). Conclusions: As hypothesized, non-invasive assessment of muscle functional indices of oxidative and diffusive O2 flow in vivo revealed significantly greater oxidative capacity (greater kHIGH) and a greater diffusion limitation (greater Δ k) in ET individuals compared with RT. The new NIRS method allows independent assessment of limitations in muscle oxidative and diffusive O2 flow in resistance and endurance trained individuals. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Inhaled formoterol impairs aerobic exercise capacity in endurance-trained individuals: a randomised controlled trial.

The 2022 Global Initiative for Asthma guidelines emphasise the inhaled long-acting β2-agonist formoterol as part of the first treatment step, and therefore formoterol use among athletes will probably increase. However, prolonged supratherapeutic use of inhaled β2-agonists impairs training outcomes in moderately trained men. We investigated whether inhaled formoterol, at therapeutic doses, imposes detrimental effects in endurance-trained individuals of both sexes. 51 endurance-trained participants (31 male, 20 female; mean±sd maximal oxygen consumption (V̇ O2 max) 62±6 mL·min-1·kg bw-1 and 52±5 mL·min-1·kg bw-1, respectively) inhaled formoterol (24 µg; n=26) or placebo (n=25) twice daily for 6 weeks. At baseline and follow-up, we assessed V̇ O2 max and incremental exercise performance during a bike-ergometer ramp-test; body composition by dual-energy X-ray absorptiometry; muscle oxidative capacity by high-resolution mitochondrial respirometry, enzymatic activity assays and immunoblotting; intravascular volumes by carbon monoxide rebreathing; and cardiac left ventricle mass and function by echocardiography. Compared to placebo, formoterol increased lean body mass by 0.7 kg (95% CI 0.2-1.2 kg; treatment×trial p=0.022), but decreased V̇ O2 max by 5% (treatment×trial p=0.013) and incremental exercise performance by 3% (treatment×trial p<0.001). In addition, formoterol lowered muscle citrate synthase activity by 15% (treatment×trial p=0.063), mitochondrial complex II and III content (treatment×trial p=0.028 and p=0.007, respectively), and maximal mitochondrial respiration through complexes I and I+II by 14% and 16% (treatment×trial p=0.044 and p=0.017, respectively). No apparent changes were observed in cardiac parameters and intravascular blood volumes. All effects were sex-independent. Our findings demonstrate that inhaled therapeutic doses of formoterol impair aerobic exercise capacity in endurance-trained individuals, which is in part related to impaired muscle mitochondrial oxidative capacity. Thus, if low-dose formoterol fails to control respiratory symptoms in asthmatic athletes, physicians may consider alternative treatment options.

Left Ventricular Mass Following Detraining In Endurance Trained Individuals: Systematic Review And Meta-analysis

Exercise training has been shown to cause unique cardiac adaptations, such as increases in left ventricular (LV) mass. Detraining or cessation of training reportedly decreases LV mass, however this has not been systematically evaluated. Furthermore, the dose-response relationship between cardiac dimensions and detraining is unknown. Purpose: This investigation aimed to systematically review the literature and conduct a meta-analysis to assess the impact of detraining on LV mass in endurance trained individuals. Methods: A literature search of prospective detraining studies was conducted using electronic databases (eg. EMBASE & MEDLINE). Inclusion criteria comprised those who were adults, endurance trained, detrained for at least one week, and findings that reported changes in LV mass. In studies that assessed LV mass at multiple time points, we used final time points in the meta-analysis. The association between the changes in LV mass and detraining was calculated using a pooled statistic for random effects; statistical significance was set at p < 0.05. Study quality was assessed by two reviewers using a modified version of the National Institute of Health (NIH) quality assessment tool. Results: Thirteen studies with a total of 189 participants (ages 18-55, 15% female) satisfied the inclusion criteria, each with various detraining programs lasting from 1.42-15 weeks. The meta-analysis revealed a significant decrease in LV mass following detraining (standardized mean difference = -0.710, 95%CI = -.874 - -0.546, p > 0.001). Changes in LV mass were not associated with length of the detraining period which appears to stabilize over detraining blocks longer than 2 weeks. Mean change in LV mass did not differ according to training level. Study quality was rated poor to fair, with inconsistent participant details and varying workloads during detraining (i.e., reduced frequency of training vs. no exercise). Conclusion: LV mass decreases as a result of detraining in healthy, endurance-trained individuals, and appears to be unaffected by length of the detraining period or training history /athlete status. Study findings are limited due to poor to fair study quality and lack of female participants. Further investigations are warranted to understand the impact of detraining on cardiac structure in healthy individuals.

Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis.

Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (CT) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat. To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and CT in the heat. Systematic review with meta-analysis. Four databases and cross-referencing. Weighted mean effect summaries using robust variance random-effects models for EP and CT, as well as robust variance meta-regressions to explore confounders. Placebo-controlled, randomized studies in adults (≥ 18years old) with caffeine intake at least 30min before endurance exercise ≥ 30min, performed in ambient conditions ≥ 27°C. Respectively six and 12 studies examined caffeine's impact on EP and CT, representing 52 and 205 endurance-trained individuals. On average, 6mg/kg body mass of caffeine were taken 1h before exercises of ~ 70min conducted at 34°C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in CT by 0.10 ± 0.03°C/h (95% CI 0.02to 0.19), compared with the ingestion of a placebo. Caffeine ingestion of 6mg/kg body mass ~ 1h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in CT.

Directional sensitivity of the cerebral pressure-flow relationship in young healthy individuals trained in endurance and resistance exercise.

What is the central question of this study? Does habitual exercise modality affect the directionality of the cerebral pressure-flow relationship? What is the main finding and its importance? These data suggest the hysteresis-like pattern of dynamic cerebral autoregulation appears present in long-term sedentary and endurance-trained individuals, but absent in resistance-trained individuals. This is the first study to expand knowledge on the directional sensitivity of the cerebral pressure-flow relationship to trained populations. Evidence suggests the cerebrovasculature may be more efficient at dampening cerebral blood flow (CBF) variations when mean arterial pressure (MAP) transiently increases, compared to when it decreases. Despite divergent MAP and CBF responses to acute endurance and resistance training, the long-term impact of habitual exercise modality on the directionality of dynamic cerebral autoregulation (dCA) is currently unknown. Thirty-six young healthy participants (sedentary (n=12), endurance-trained (n=12), and resistance-trained (n=12)) undertook a 5-min repeated squat-stand protocol at two forced MAP oscillation frequencies (0.05 and 0.10Hz). Middle cerebral artery mean blood velocity (MCAv) and MAP were continuously monitored. We calculated absolute (ΔMCAvT /ΔMAPT ) and relative (%MCAvT /%MAPT ) changes in MCAv and MAP with respect to the transition time intervals of both variables to compute a time-adjusted ratio in each MAP direction, averaged over the 5-min repeated squat-stand protocols. At 0.10Hz repeated squat-stands, ΔMCAvT /ΔMAPT and %MCAvT /%MAPT were lower when MAP increased compared with when MAP decreased for sedentary (ΔMCAvT /ΔMAPT : P=0.032; %MCAvT /%MAPT : P=0.040) and endurance-trained individuals (ΔMCAvT /ΔMAPT : P=0.012; %MCAvT /%MAPT P=0.007), but not in the resistance-trained individuals (ΔMCAvT /ΔMAPT : P=0.512; %MCAvT /%MAPT P=0.666). At 0.05Hz repeated squat-stands, time-adjusted ratios were similar for all groups (all P>0.605). These findings suggest exercise training modality does influence the directionality of the cerebral pressure-flow relationship and support the presence of a hysteresis-like pattern during 0.10Hz repeated squat-stands in sedentary and endurance-trained participants, but not in resistance-trained individuals. In future studies, assessment of elite endurance and resistance training habits may further elucidate modality-dependent discrepancies on directional dCA measurements.

Evidence of region-specific right ventricular functional adaptation in endurance-trained men in response to an acute volume infusion.

What is the central question of this study? Endurance athletes demonstrate altered regional right ventricular (RV) wall mechanics, characterized by lower basal deformation, in comparison to non-athletic control subjects at rest. We hypothesized that regional adaptations at the RV base reflect an enhanced functional reserve capacity in response to haemodynamic volume loading. What is the main finding and its importance? Free wall RV longitudinal strain is elevated in response to acute volume loading in both endurance athletes and control subjects. However, the RV basal segment longitudinal strain response to acute volume infusion is greater in endurance athletes. Our findings suggest that training-induced cardiac remodelling might involve region-specific adaptation in the RV functional response to volume manipulation. Eccentric remodelling of the right ventricle (RV) in response to increased blood volume and repetitive haemodynamic load during endurance exercise is well established. Structural remodelling is accompanied by decreased deformation at the base of the RV free wall, which might reflect an enhanced functional reserve capacity in response to haemodynamic perturbation. Therefore, in this study we examined the impact of acute blood volume expansion on RV wall mechanics in 16 young endurance-trained men (aged 24±3years) and 13 non-athletic male control subjects (aged 27±5years). Conventional echocardiographic parameters and the longitudinal strain and strain rate were quantified at the basal and apical levels of the RV free wall. Measurements were obtained at rest and after 7ml/kg i.v. Gelofusine infusion, with and without a passive leg raise. After infusion, blood volume increased by 12±4 and 14±5% in endurance-trained individuals versus control subjects, respectively (P=0.264). Both endurance-trained individuals (8±10%) and control subjects (7±9%) experienced an increase in free wall strain from baseline, which was also similar following leg raise (7±10 and 6±10%, respectively; P=0.464). However, infusion evoked a greater increase in basal longitudinal strain in endurance-trained versus control subjects (16±14 vs. 6±11%; P=0.048), which persisted after leg raise (16±18 vs. 3±11%; P=0.032). Apical longitudinal strain and RV free wall strain rates were not different between groups and remained unchanged after infusion across all segments. Endurance training results in a greater contribution of longitudinal myocardial deformation at the base of the RV in response to a haemodynamic volume challenge, which might reflect a greater region-specific functional reserve capacity.

Acute Exercise Regulates Htert Alternative Splicing In Contractile Tissues Of Htert-bac Mice

Full length human telomerase reverse transcriptase (FL hTERT) is the rate-limiting, catalytic component necessary for telomerase enzyme activity and telomere length maintenance. Unlike rodents, humans evolved elongated introns with cis-elements that when bound by specific RNA binding proteins (RNAbp) splice hTERT to FL transcripts or produce inactive variants through alternative splicing (AS). Our working hypothesis is that hTERT AS regulates the amount of active telomerase. Evidence from human studies have shown that aerobic exercise maintains telomere length through increased hTERT expression and telomerase enzyme activity, however the impact of acute exercise on hTERT AS is unknown. PURPOSE: To examine hTERT AS regulation in response to acute treadmill running. METHODS: A bacterial artificial chromosome mouse model containing the full hTERT gene (5' and 3' regulatory elements; 16 exons and 15 introns) inserted into its genome (hTERT-BAC) was utilized. Gastrocnemius (Gas.) and heart (Hrt.) were excised from 10-week old hTERT-BAC mice prior to (PRE), upon cessation (POST), and during recovery (1, 24, 48, and 72H; n = 5/time point) from 30 min. of treadmill running (60% max. speed). Primers specific to hTERT were utilized to measure FL and the most common AS variant minus beta (-β, which skips exons 7 and 8) by two different RT-PCR methods - gel based and droplet digital PCR. Gene expression of the RNAbp PTBP1 was also measured. RESULTS: The expected human patterns of hTERT AS was recapitulated across all tissues examined. Compared to PRE, FL hTERT gene expression increased at POST before decreasing in the Gas. (48 and 72H; p ≤ 0.001) and Hrt. (24H; p = 0.004). Acute exercise also increased the percentage of FL hTERT in the Gas. at 1 and 72H (p ≤ 0.017), whereas a decrease was observed in the Hrt. at 1, 24, and 48H (p ≤ 0.041). Finally, Ptbp1 decreased at POST (Gas.) and at 1, 24, 48, and 72H (Gas. and Hrt.; p ≤ 0.05). CONCLUSIONS: Evolutionarily conserved mouse splicing machinery (RNAbp) recognize hTERT cis-elements to recapitulate human AS patterns and highlight the importance of the intronic elements in regulating hTERT splicing choice in humans. The hTERT-BAC mouse is a valuable resource to study the exercise-induced adaptive mechanisms that maintain telomere lengths in endurance trained individuals across the lifespan.

Ventilatory efficiency in athletes, asthma and obesity.

During submaximal exercise, minute ventilation (V' E) increases in proportion to metabolic rate (i.e. carbon dioxide production (V' CO2 )) to maintain arterial blood gas homeostasis. The ratio V' E/V' CO2 , commonly termed ventilatory efficiency, is a useful tool to evaluate exercise responses in healthy individuals and patients with chronic disease. Emerging research has shown abnormal ventilatory responses to exercise (either elevated or blunted V' E/V' CO2 ) in some chronic respiratory and cardiovascular conditions. This review will briefly provide an overview of the physiology of ventilatory efficiency, before describing the ventilatory responses to exercise in healthy trained endurance athletes, patients with asthma, and patients with obesity. During submaximal exercise, the V' E/V' CO2 response is generally normal in endurance-trained individuals, patients with asthma and patients with obesity. However, in endurance-trained individuals, asthmatics who demonstrate exercise induced-bronchoconstriction, and morbidly obese individuals, the V' E/V' CO2 can be blunted at maximal exercise, likely because of mechanical ventilatory constraint.

The Comparison of Eight Weeks of HIIT and BFR on Mitochondrial Biogenesis and Angiogenesis Markers in Vastus Lateralis Muscle of Amateur Male Runners

Background and Aims Post-exercise Blood Flow Restriction (BFR) is a novel training method that, through alterations to the haemodynamic, metabolic, and hypoxic stimulus, could augment skeletal muscle adaptation in endurance-trained individuals. This study aimed to compare the effect of eight weeks of High-Intensity Interval Training (HIIT) and BFR on PGC-1α and Vascular Endothelial Growth Factor (VEGF) as mitochondrial biogenesis and angiogenesis biomarkers, respectively, in amateur male runners. Methods In the current study, 15 runners (Meas±SD of age: 23±3 years; height: 172±5 cm; weight: 73±4 kg: BMI: 23±1.7 kg/m2) voluntarily participating in this study were divided into three groups: 1-Control 2-HIIT and 3-HIIT+BFR or BFR. The experimental groups performed three sessions a week (six trials each session) for eight weeks. The biopsy samples were collected from the vastus lateralis muscle at the first and end of eight weeks. The protein expression levels of the PGC-1α and VEGF were studied by immunohistochemical method. Data analysis was performed using the one-way Analysis of Covariance (ANCOVA), and a significance level of P&lt;0.05 was considered. Results The findings showed that PGC-1α values were significantly increased in the HIIT and BFR groups (54.9% and 60.85%, respectively) compared to the control group, as well as VEGF levels were 51.31% and 57.52%, respectively (P&lt;0.05). There were also significant differences between experimental groups in the protein expressions (P&lt;0.05). Conclusion Given that activation of VEGF from the PGC-1 pathway is part of cellular-molecular mechanisms of high-intensity interval training, It seems that the combination of intense interval training and BFR can effectively affect the process of angiogenesis in the vastus lateralis muscle of amateur runners.

The fit-active profile to better reflect the benefits of a lifelong vigorous physical activity participation: mini-review of literature and population data.

Physical activity is favourably considered for its effect on metabolic fitness and body composition. This observation is generally supported by observational studies and is concordant with endurance-trained individuals' metabolic and morphological profiles. However, in some contexts, the measurement of physical activity habits may not provide an adequate representation of its benefits. In this paper, we review relevant literature on the respective effects of fitness and physical activity on anthropometric and metabolic variables and the informative potential of a classification based on aerobic fitness and activity indicators. The relevance to defining a profile based on both fitness and activity is reinforced by data from the Quebec Family Study showing that, in both men and women, "fit-active" individuals displayed a much more favourable morphological and metabolic profile than "unfit-inactive" individuals. Moreover, these benefits seemed to be more related to variations in fitness than in physical activity. In summary, evidence suggests that a profile combining information on aerobic fitness and physical activity may better reflect the lifelong impact of physical activity on body composition and health. Novelty: The fit-active profile better reflects the long-term benefits of vigorous physical activity participation on health. The reported benefits seem to be more related to variations in aerobic fitness than to those in physical activity.

Blood-flow-restricted exercise: Strategies for enhancing muscle adaptation and performance in the endurance-trained athlete.

What is the topic of this review? Blood-flow-restricted (BFR) exercise represents a potential approach to augment the adaptive response to training and improve performance in endurance-trained individuals. What advances does it highlight? When combined with low-load resistance exercise, low- and moderate-intensity endurance exercise and sprint interval exercise, BFR can provide an augmented acute stimulus for angiogenesis and mitochondrial biogenesis. These augmented acute responses can translate into enhanced capillary supply and mitochondrial function, and subsequent endurance-type performance, although this might depend on the nature of the exercise stimulus. There is a requirement to clarify whether BFR training interventions can be used by high-performance endurance athletes within their structured training programme. A key objective of the training programme for an endurance athlete is to optimize the underlying physiological determinants of performance. Training-induced adaptations are governed by physiological and metabolic stressors, which initiate transcriptional and translational signalling cascades to increase the abundance and/or function of proteins to improve physiological function. One important consideration is that training adaptations are reduced as training status increases, which is reflected at the molecular level as a blunting of the acute signalling response to exercise. This review examines blood-flow-restricted (BFR) exercise as a strategy for augmenting exercise-induced stressors and subsequent molecular signalling responses to enhance the physiological characteristics of the endurance athlete. Focus is placed on the processes of capillary growth and mitochondrial biogenesis. Recent evidence supports that BFR exercise presents an intensified training stimulus beyond that of performing the same exercise alone. We suggest that this has the potential to induce enhanced physiological adaptations, including increases in capillary supply and mitochondrial function, which can contribute to an improvement in performance of endurance exercise. There is, however, a lack of consensus regarding the potency of BFR training, which is invariably attributable to the different modes, intensities and durations of exercise and BFR methods. Further studies are needed to confirm its potential in the endurance-trained athlete.

Elevated peak systolic blood pressure in endurance-trained athletes: Physiology or pathology?

Blood pressure is a function of cardiac output and peripheral vascular resistance. During graded exercise testing (GXT), systolic blood pressure (SBP) is expected to increase gradually along with work rate, oxygen consumption, heart rate, and cardiac output. Individuals exposed to chronic endurance training attain a greater exercise SBP than in their untrained state and sedentary counterparts, but it is currently unknown what is considered a safe upper limit. This review discusses key studies examining blood pressure response in sedentary individuals and athletes. We highlight the physiological characteristics of highly fit individuals in terms of cardiovascular physiology and exercise blood pressure and review the state of the current literature regarding the safety of high SBP during exercise in this particular subgroup. Findings from this review indicate that a consensus on what is a normal SBP response to exercise in highly fit subjects and direct causation linking high GXT SBP to pathology is lacking. Consequently, applying GXT SBP guidelines developed for a "normal" population to endurance-trained individuals appears unsupported at this time. Lack of evidence for poor outcomes leads us to infer that elevated peak SBP in this subgroup could more likely reflect an adaptive response to training, rather than a pathological outcome. Future studies should track clinical outcomes of those achieving elevated SBP and develop athlete-specific guidelines.