The Influence of Ultra-Endurance Exercise on the Cardiovascular and Related Physiological Systems

INTRODUCTION: There is currently limited longitudinal data investigating the performance and health-related influence of ultra-endurance training and participation. Cross-sectional investigations have highlighted a potential for those performing most exercise to be at an increased risk of cardiovascular events. If such risks occur, they are likely to be due to a combination of the stress provided through training and events together. PURPOSE: To assess the development of several physiological factors associated with exercise training and to gain a greater insight regarding the changes in cardiac electrical conductance from endurance training. A sub-study sought to investigate the short and longer-term influence of an iron-distance triathlon on indirect measures of arterial stiffness. METHOD: Part 1: Seventy-six previously recreationally active participants underwent a 6 month endurance training programme in preparation for an iron-distance triathlon, consisting of a 3.86km swim, 180.25km cycle, and a 42.2km run. Multiple assessments were performed at months 0, 2, 4 and 6; including submaximal and exhaustive cycling tests, anthropometric measurements and 12-lead ECG’s. Part 2: Eleven athletes from part 1 (TRI) and 10 recreational control participants (NOTRI) were assessed on 4 occasions with identical time intervals. Arterial stiffness and cardiovascular functional parameters were obtained 7 days prior (T1) to an iron-distance triathlon, 12–18 hours post-event, 7 days post-event, and 28 days post-event. RESULTS: Part 1: Cardiorespiratory fitness and performance parameters increased over the training period, irrespective of age, with greatest improvements from month 0–2 and the least improvements from month 4–6. Additionally, a progressive increase was observed in the frequency of both training-related and training-unrelated ECG findings. Part 2: A significant difference in central arterial stiffness was found between TRI and NOTRI 12–18 hours post-event and 7 days post-event but not prior to or 28 days post-event. No differences were observed between groups for peripheral stiffness at any time-point. Additionally, no time effect was observed when the TRI group were treated separately. CONCLUSION: Training caused significant improvements to fitness related physiological factors. In a minority of individuals, endurance training induced bioelectrical patterns of what is currently referred to as abnormal criteria, which may reflect a normal change to what was previously thought of as abnormal findings or, alternatively, be pathological manifestations in previously healthy individuals. Part 2 of this study showed a delayed central arterial stiffening may occur one day and one week following a single day ultra-endurance event. Importantly, all measurements were found to be similar one month post-event; implying only a transient exercise-induced elevation to arterial stiffness

The effect of long term physical training on the development of mental toughness in recreationally active participants

This study investigated the effect of long-term training on the development of mental toughness (MT). Thirty recreationally active participants (age: 33.53±6.83years; height: 177.41±7.11cm; weight: 78.40±11.94kg; maximal oxygen uptake (VO2max): 47.00±6.48 ml.kg-1.min-1) undertook 6-months of training prior to completing an iron-distance triathlon. Mental toughness questionnaires (MTQ48) were completed at 0,2,4,6 months of training and 1-month post-race. Repeated measures ANOVAs were performed for each MTQ48 variable with consideration to faster v slower finishers. No significant differences (p>0.05) were found between fast and slow finishers on any of the MT criteria. There was an effect for time with overall mental toughness (OMT) improving from baseline-post race (cohens d = 0.52; p<0.01) and month 2-post race (d = 0.39; p<0.01), commitment improving from baseline-post race (d = 0.60; p<0.05) and confidence increasing from month 2 post-race (d = 0.39; p<0.05). MT was not associated with race time. The findings indicate that longitudinal training culminating with competitive experience may favourably impact MT

The effect of long term physical training in the development of mental toughness in recreationally active participants

This study investigated the effect of a long-term training program on the development of mental toughness (MT). Thirty (2 female and 28 male) recreationally active participants (age: 33.53±6.83years; height: 177.41±7.11cm; weight: 78.40±11.94kg; maximal oxygen uptake (VO2max): 47.00±6.48 ml.kg-1.min-1; mean±SD) undertook 6 months of training prior to completing a long-distance triathlon. Participants completed mental toughness questionnaires (MTQ48) at 0, 2, 4, and 6 months of training and 1-month post-race. Data analysis included repeated measures ANOVAs for each MTQ48 variable with consideration to faster and slower finishers. Faster and slower finishers demonstrated non-significant differences (p>0.05) on all MT criteria. There was an effect for time with overall mental toughness (OMT) improving from baseline-post race (cohens d = 0.52; p<0.01) and month 2 post race (d = 0.39; p<0.01), commitment improving from baseline-post race (d = 0.60; p<0.05) and confidence increasing from month 2 post race (d = 0.39; p<0.05). The findings indicate that long term training culminating with competitive experience favourably impacts MT

Aortic haemodynamics: the effects of habitual endurance exercise, age and muscle sympathetic vasomotor outflow in healthy men

PURPOSE: We determined the effect of habitual endurance exercise and age on aortic pulse wave velocity (aPWV), augmentation pressure (AP) and systolic blood pressure (aSBP), with statistical adjustments of aPWV and AP for heart rate and aortic mean arterial pressure, when appropriate. Furthermore, we assessed whether muscle sympathetic nerve activity (MSNA) correlates with AP in young and middle-aged men. METHODS: Aortic PWV, AP, aortic blood pressure (applanation tonometry; SphygmoCor) and MSNA (peroneal microneurography) were recorded in 46 normotensive men who were either young or middle-aged and endurance-trained runners or recreationally active nonrunners (10 nonrunners and 13 runners within each age-group). Between-group differences and relationships between variables were assessed via ANOVA/ANCOVA and Pearson product-moment correlation coefficients, respectively. RESULTS: Adjusted aPWV and adjusted AP were similar between runners and nonrunners in both age groups (all, P > 0.05), but higher with age (all, P < 0.001), with a greater effect size for the age-related difference in AP in runners (Hedges’ g, 3.6 vs 2.6). aSBP was lower in young (P = 0.009; g = 2.6), but not middle-aged (P = 0.341; g = 1.1), runners compared to nonrunners. MSNA burst frequency did not correlate with AP in either age group (young: r = 0.00, P = 0.994; middle-aged: r = − 0.11, P = 0.604). CONCLUSION: There is an age-dependent effect of habitual exercise on aortic haemodynamics, with lower aSBP in young runners compared to nonrunners only. Statistical adjustment of aPWV and AP markedly influenced the outcomes of this study, highlighting the importance of performing these analyses. Further, peripheral sympathetic vasomotor outflow and AP were not correlated in young or middle-aged normotensive men

The overlooked significance of plasma volume for successful adaptation to high altitude in Sherpa and Andean natives

In contrast to Andean natives, high altitude Tibetans present with a lower hemoglobin concentration that correlates with reproductive success and exercise capacity. Decades of physiological and genomic research have assumed that the lower hemoglobin concentration in Himalayan natives results from a blunted erythropoietic response to hypoxia (i.e. no increase in total hemoglobin mass). In contrast, herein we test the hypothesis that the lower hemoglobin concentration is the result of greater plasma volume, rather than an absence of increased hemoglobin production. We assessed hemoglobin mass, plasma volume and blood volume in lowlanders at sea level, lowlanders acclimatized to high altitude, Himalayan Sherpa and Andean Quechua, and explored the functional relevance of volumetric hematological measures to exercise capacity. Hemoglobin mass was highest in Andeans, but also elevated in Sherpa compared to lowlanders. Sherpa demonstrated a larger plasma volume than Andeans, resulting in a comparable total blood volume at a lower hemoglobin concentration. Hemoglobin mass was positively related to exercise capacity in lowlanders at sea level and Sherpa at high altitude, but not in Andean natives. Collectively, our findings demonstrate a unique adaptation in Sherpa that reorientates attention away from hemoglobin concentration and towards a paradigm where hemoglobin mass and plasma volume may represent phenotypes with adaptive significance at high altitude

An exploratory investigation of endotoxin levels in novice long distance triathletes, and the effects of a multi-strain probiotic/prebiotic, antioxidant intervention.

Abstract: Gastrointestinal (GI) ischemia during exercise is associated with luminal permeability and increased systemic lipopolysaccharides (LPS). This study aimed to assess the impact of a multistrain pro/prebiotic/ antioxidant intervention on endotoxin unit levels and GI permeability in recreational athletes. Thirty healthy participants (25 males, 5 females) were randomly assigned either a multistrain pro/prebiotic/ antioxidant (LAB4ANTI; 30 billion CFU.d-1 containing 10 billion CFU.d-1 Lactobacillus acidophilus CUL-60 [NCIMB 30157], 10 billion CFU.d-1 Lactobacillus acidophillus CUL-21 [NCIMB 30156], 9.5 billion CFU.d-1 Bifidobacterium bifidum CUL-20 [NCIMB 30172] and 0.5 billion CFU.d-1 Bifidobacterium animalis subspecies lactis CUL-34 [NCIMB 30153]/ 55.8 mg.d-1 fructooligosaccharides/ 400 mg.d-1 α-lipoic acid, 600 mg.d-1 N-acetyl-carnitine); matched pro/prebiotic (LAB4) or placebo (PL) for 12 weeks preceding a long-distance triathlon. Plasma endotoxin units (via Limulus amebocyte lysate chromogenic quantification) and GI permeability (via 5 hour urinary lactulose (L): mannitol (M) recovery) were assessed at baseline, pre-race and 6 days post-race. Endotoxin unit levels were not significantly different between groups at baseline (LAB4ANTI: 8.20±1.60 pg.ml-1; LAB4: 8.92±1.20 pg.ml-1; PL: 9.72± 2.42 pg.ml-1). The use of a 12 week LAB4ANTI intervention significantly reduced endotoxin units both pre-race (4.37± 0.51 pg.ml-1) and 6 days post-race (5.18±0.57 pg.ml-1; p=0.03, ηp2 = 0.35), but only 6 days post-race with LAB4 (5.01± 0.28 pg.ml-1; p=0.01, ηp2 = 0.43). In contrast, endotoxin units remained unchanged with PL. L:M significantly increased from 0.01±0.01 at baseline to 0.06± 0.01 with PL only (p=0.004, ηp2 = 0.51). Mean race times (hr:min:sec) were not statistically different between groups despite faster times with both pro/prebiotoic groups (LAB4ANTI:13:17:07±34:48; LAB4: 12:47:13±25:06; PL: 14:12:51±29:54; p>0.05). Combined multistrain pro/prebiotic use may reduce endotoxin unit levels, with LAB4ANTI potentially conferring an additive effect via combined GI modulation and antioxidant protection

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

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. 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 nonrunners (23 years [95% CI: 21-26]), 19 young runners (24 [22-26]), 13 middle-aged nonrunners (54 [52-56]) and 19 middle-aged runners (56 [54-58]). Images were analysed for peak circumferential strain (PCS; magnitude of deformation) as well as systolic and diastolic strain-rate (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 males when compared to young men (all P ≤ 0.001). PCS and S-SR were elevated in young and middle-aged runners when compared to nonrunners (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 may be more amenable to habitual endurance exercise than D-SR

The influence of barosensory vessel mechanics on the vascular sympathetic baroreflex: Insights into ageing and blood pressure homeostasis

Changes in the arterial baroreflex arc contribute to elevated sympathetic outflow and altered reflex control of blood pressure with human ageing. Utilizing ultrasound and sympathetic microneurography (muscle sympathetic nerve activity; MSNA) we investigated the relationships between aortic and carotid artery wall tension (indices of baroreceptor activation) and the vascular sympathetic baroreflex operating point (OP; MSNA burst incidence) in healthy, normotensive young (n = 27, 23 ± 3 years) and middle-aged men (n = 22, 55 ± 4 years). In young men, the OP was positively related to the magnitude and rate of unloading and time spent unloaded in the aortic artery (r = 0.56, 0.65 and 0.51, P = 0.02, 0.003 and 0.03), but not related to the magnitude or rate of unloading or time spent unloaded in the carotid artery (r = -0.32, -0.07 and 0.06, P = 0.25, 0.81 and 0.85). In contrast, in middle-aged men, the OP was not related to either the magnitude or rate of unloading or time spent unloaded in the aortic (r = 0.22, 0.21 and 0.27, P = 0.41, 0.43 and 031) or carotid artery (r = 0.48, 0.28 and -0.01, P = 0.06, 0.25 and 0.98). In conclusion, in young men, aortic unloading mechanics may play a role in determining the vascular sympathetic baroreflex OP. In contrast, in middle-aged men, barosensory vessel unloading mechanics do not appear to determine the vascular sympathetic baroreflex OP, and therefore do not contribute to age-related arterial baroreflex resetting and increased resting MSNA. KEYWORDS: muscle sympathetic nerve activity; barosensory vessel unloading mechanics; healthy ageing; sympathetic nervous system; baroreflex Page Break NEW AND NOTEWORTHY We assessed the influence of barosensory vessel mechanics (magnitude and rate of unloading and time spent unloaded) as a surrogate for baroreceptor unloading. In young men, aortic unloading mechanics are important in regulating the operating point of the vascular sympathetic baroreflex, whereas in middle-aged men, these arterial mechanics do not influence this operating point. The age-related increase in resting muscle sympathetic nerve activity does not appear to be driven by altered baroreceptor input from stiffer barosensory vessels