The Effect of Different Training Loads on the Lung Health of Competitive Youth Swimmers

International Journal of Exercise Science 11(6): 999-1018, 2018. Airway hyperresponsiveness (AHR), airway inflammation, and respiratory symptoms are common in competitive swimmers, however it is unclear how volume and intensity of training exacerbate these problems. Thus, our purpose was to measure AHR, inflammation, and respiratory symptoms after low, moderate, and high training loads in swimmers. Competitive youth swimmers (n=8) completed nine weeks of training split into three blocks (Low, Moderate, and High intensity). Spirometry at rest and post-bronchial provocation [Eucapnic Voluntary Hyperpnea (EVH)] and Fractional Exhaled Nitric Oxide (FeNO) were completed at the end of each training block. A weekly self-report questionnaire determined respiratory symptoms. Session Rating of Perceived Exertion (sRPE) quantified internal training loads. Internal load was significantly lower after Moderate training (4840 ± 971 AU) than after High training (5852 ± 737 AU) (p= 0.02, d= 1.17). Pre-EVH FEV1was significantly decreased after Moderate (4.52 ± 0.69 L) compared to Low (4.74 ± 0.63 L) (p= 0.025, d= 0.326), but not different from High load. Post-EVH FeNO after Moderate training was significantly decreased (9.4 ± 4.9 ppb) compared to Low training (15.4 ± 3.6 ppb) (p= 0.012, r= 0.884).Respiratory symptom frequency was significantly correlated with percent decrease in FEV120 minutes post-EVH after Low and Moderate loads (both ρ= -0.71, sig = 0.05), and after High load was significantly correlated with percent decrease in FEV1at 10 (ρ= -0.74, sig = 0.03), 15 (ρ= -0.91, sig = 0.00), and 20 minutes post (ρ= -0.75, sig = 0.03). In conclusion, Moderate load training resulted in the worst lung health results, suggesting there may be factors other than the total amount of stress within training blocks that influence lung health. Further research is needed to determine the effect of manipulating specific acute training load variables on the lung health of swimmers

The Effect of Different Training Loads on the Lung Health of Competitive Youth Swimmers

International Journal of Exercise Science 11(6): 999-1018, 2018. Airway hyperresponsiveness (AHR), airway inflammation, and respiratory symptoms are common in competitive swimmers, however it is unclear how volume and intensity of training exacerbate these problems. Thus, our purpose was to measure AHR, inflammation, and respiratory symptoms after low, moderate, and high training loads in swimmers. Competitive youth swimmers (n=8) completed nine weeks of training split into three blocks (Low, Moderate, and High intensity). Spirometry at rest and post-bronchial provocation [Eucapnic Voluntary Hyperpnea (EVH)] and Fractional Exhaled Nitric Oxide (FeNO) were completed at the end of each training block. A weekly self-report questionnaire determined respiratory symptoms. Session Rating of Perceived Exertion (sRPE) quantified internal training loads. Internal load was significantly lower after Moderate training (4840 ± 971 AU) than after High training (5852 ± 737 AU) (p= 0.02, d= 1.17). Pre-EVH FEV1was significantly decreased after Moderate (4.52 ± 0.69 L) compared to Low (4.74 ± 0.63 L) (p= 0.025, d= 0.326), but not different from High load. Post-EVH FeNO after Moderate training was significantly decreased (9.4 ± 4.9 ppb) compared to Low training (15.4 ± 3.6 ppb) (p= 0.012, r= 0.884).Respiratory symptom frequency was significantly correlated with percent decrease in FEV120 minutes post-EVH after Low and Moderate loads (both ρ= -0.71, sig = 0.05), and after High load was significantly correlated with percent decrease in FEV1at 10 (ρ= -0.74, sig = 0.03), 15 (ρ= -0.91, sig = 0.00), and 20 minutes post (ρ= -0.75, sig = 0.03). In conclusion, Moderate load training resulted in the worst lung health results, suggesting there may be factors other than the total amount of stress within training blocks that influence lung health. Further research is needed to determine the effect of manipulating specific acute training load variables on the lung health of swimmers

Sympathetic neural activation: An ordered affair

Is there an ordered pattern in the recruitment of postganglionic sympathetic neurones? Using new multi-unit action potential detection and analysis techniques we sought to determine whether the activation of sympathetic vasomotor neurones during stress is governed by the size principle of recruitment. Multi-unit postganglionic sympathetic activity (fibular nerve) was collected from five male subjects at rest and during periods of elevated sympathetic stress (end-inspiratory apnoeas; 178 ± 37 s(mean ± S.D.)). Compared to baseline (0.24 ± 0.04 V), periods of elevated stress resulted in augmented sympathetic burst size (1.34 ± 0.38 V, P \u3c 0.05). Increased burst size was directly related to both the number of action potentials within a multi-unit burst of postganglionic sympathetic activity (r= 0.88 ± 0.04, P \u3c 0.001 in all subjects), and the amplitude of detected action potentials (r= 0.88 ± 0.06, P \u3c 0.001 in all subjects). The recruitment of larger, otherwise silent, neurons accounted for approximately 74% of the increase in detected action potentials across burst sizes. Further, action potential conduction velocities (inverse of latencies) were increased as a function of action potential size (R2= 0.936, P= 0.001). As axon diameter is positively correlated with action potential size and conduction velocity, these data suggest that the principle of ordered recruitment based on neuronal size applies to postganglionic sympathetic vasomotor neurones. This information may be pertinent to our understanding of reflex-specific recruitment strategies in postganglionic sympathetic nerves, patterns of vasomotor control during stress, and the malleability of sympathetic neuronal properties and recruitment in health and disease.The sympathetic nervous system is an important controller of blood pressure and blood flow to critical tissues and organs. In other neural systems (e.g. the skeletal motor system) there is a well understood pattern of neural recruitment during activation. Alternatively, our understanding of how sympathetic neurones are coordinated during stress is limited. We demonstrate that during stress otherwise silent sympathetic neurones are activated in an order based on neuronal size (from smallest to largest). This recruitment pattern is similar to what is known in other neural systems. This information has important implications for how blood pressure and blood flow are controlled, and the malleability of sympathetic activation in health and disease. © 2010 The Authors. Journal compilation © 2010 The Physiological Society

A sympathetic view of blood pressure control at high altitude: new insights from microneurographic studies

High altitude (HA) hypoxia is a potent activator of the sympathetic nervous system, eliciting increases in sympathetic vasomotor activity. Microneurographic evidence of HA sympathoexcitation dates back to the late 20thcentury, yet only recently have the characteristics and underpinning mechanisms been explored in detail. This review summarises recent findings and highlightstheimportance of HA sympathoexcitation for theregulation of blood pressure in lowlanders and indigenous highlanders. In addition, this review will identify gaps in our knowledge and corresponding avenues for future study

Leisure-Time Physical Activity before and during Pregnancy Is Associated with Improved Insulin Resistance in Late Pregnancy

A total of 83 third trimester pregnant women were recruited to examine the role of pre-pregnancy versus late-pregnancy physical activity on maternal insulin resistance. Principal component analysis plots demonstrated a distinction between the high and low Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) groups. The variation was driven primarily by exercise prior to and during pregnancy. Specifically, higher levels of physical activity prior to pregnancy was associated with a lower HOMA-IR and is not modified by other variables. Women who were active prior to pregnancy were more active during pregnancy. These results suggest that being active before pregnancy may be a good strategy for mitigating the risk of insulin resistance during late pregnancy

Global REACH 2018: Renal oxygen delivery is maintained during early acclimatization to 4330 m

Early acclimatization to high-altitude is characterized by various respiratory, hematological, and cardiovascular adaptations that serve to restore oxygen delivery to tissue. However, less is understood about renal function and the role of renal oxygen delivery (RDO2) during high altitude acclimatization. We hypothesized that: 1) RDO2 would be reduced after 12-hours of high-altitude exposure (high-altitude day1) but restored to sea-level values after one-week (high altitude day7); and 2) RDO2 would be associated with renal reactivity (RR), an index of acid base compensation at high-altitude. Twenty-four healthy lowlander participants were tested at sea-level (344m; Kelowna, Canada), on day1 and day7 at high-altitude (4330m; Cerro de Pasco, Peru). Cardiac output, renal blood flow, arterial and venous blood sampling for renin angiotensin-aldosterone-system hormones and NT pro-B type natriuretic peptides were collected at each time point. RR was calculated as: (Δ arterial bicarbonate)/(Δ partial pressure of arterial carbon dioxide) between sea-level and high-altitude day1, and sea-level and high-altitude day7. The main findings were: 1) RDO2 was initially decreased at high-altitude compared to sea-level (ΔRDO2: -22±17%, P<0.001), but was restored to sea-level values on high-altitude day7 (ΔRDO2: -6±14%, P=0.36). The observed improvements in RDO2 resulted from both changes in renal blood flow (Δ from high-altitude day1: +12±11%; P=0.008), and arterial oxygen content (Δ from high-altitude day1 +44.8±17.7%; P=0.006); and 2) RR was positively correlated with RDO2 on high-altitude day7 (r=0.70; P<0.001), but not high-altitude day1 (r=0.26; P=0.29). These findings characterize the temporal responses of renal function during early high-altitude acclimatization, and the influence of RDO2 in the regulation of acid-base

Highs and Lows of Sympathetic Neuro-cardiovascular Transduction: Influence of Altitude Acclimatization and Adaptation

High-altitude (>2500m) exposure results in increased muscle sympathetic nervous activity (MSNA) in acclimatizing lowlanders. However, little is known about how altitude affects MSNA in 66 indigenous high-altitude populations. Additionally, the relationship between MSNA and blood 67 pressure regulation (i.e., neurovascular transduction) at high-altitude is unclear. We sought to 68 determine 1) how high-altitude effects neuro-cardiovascular transduction and 2) whether 69 differences exist in neuro-cardiovascular transduction between low and high-altitude 70 populations. Measurements of MSNA (microneurography), mean arterial blood pressure (MAP; 71 finger photoplethysmography), and heart rate (electrocardiogram) were collected in: I) 72 lowlanders (n=14) at low (344m) and high-altitude (5050m), II) Sherpa highlanders (n=8; 73 5050m), and III) Andean (with and without excessive erythrocytosis) highlanders (n=15; 74 4300m). Cardiovascular responses to MSNA burst sequences (i.e. singlet, couplet, triplet, and 75 quadruplets) were quantified using custom software (coded in MATLAB, v2015b). Slopes were 76 generated for each individual based on peak responses and normalized total MSNA. High 77 altitude reduced neuro-cardiovascular transduction in lowlanders (MAP slope: high-altitude, 78 0.0075±0.0060 vs low-altitude, 0.0134±0.080; p=0.03). Transduction was elevated in Sherpa 79 (MAP slope, 0.012±0.007) compared to Andeans (0.003±0.002; p=0.001). MAP transduction 80 was not statistically different between acclimatizing lowlanders and Sherpa (MAP slope, p=0.08) 81 or Andeans (MAP slope, p=0.07). When accounting for resting MSNA (ANCOVA), transduction 82 was inversely related to basal MSNA (bursts/min) independent of population (RRI, r= 0.578 83 p<0.001; MAP, r= -0.627 p<0.0001). Our results demonstrate transduction is blunted in 84 individuals with higher basal MSNA, suggesting blunted neuro-cardiovascular transduction is a 85 physiological adaptation to elevated MSNA rather than an effect or adaptation specific to 86 chronic hypoxic exposure

Global REACH 2018: Andean Highlanders, Chronic Mountain Sickness and the Integrative Regulation of Resting Blood Pressure

High‐altitude maladaptation syndrome chronic mountain sickness (CMS) is characterised by excessive erythrocytosis and frequently accompanied by accentuated arterial hypoxaemia. Whether altered autonomic cardiovascular regulation is apparent in CMS is unclear. Therefore, we assessed integrative control of blood pressure (BP) and determined basal sympathetic vasomotor outflow and arterial baroreflex function in 8 Andean natives with CMS ([Hb] 22.6 ± 0.9 g/dL) and 7 healthy highlanders ([Hb] 19.3 ± 0.8 g/dL) at their resident altitude (Cerro de Pasco, Peru; 4383 m). R‐R interval (RRI, electrocardiogram), beat‐by‐beat BP (photoplethysmography) and muscle sympathetic nerve activity (MSNA; microneurography) were recorded at rest and during pharmacologically‐induced changes in BP (modified Oxford test). Although [Hb] and blood viscosity (7.8 ± 0.7 vs 6.6 ± 0.7cP; d = 1.7, P = 0.01) were elevated in CMS compared to healthy highlanders, cardiac output, total peripheral resistance and mean BP were similar between groups. The vascular sympathetic baroreflex MSNA set‐point (i.e. MSNA burst incidence) and reflex gain (i.e. responsiveness) were also similar between groups (MSNA set‐point; d = 0.75, P = 0.16, gain; d = 0.2, P = 0.69). In contrast, in CMS the cardiovagal baroreflex operated around a longer RRI (960 ± 159 vs 817 ± 50msec; d = 1.4, P = 0.04) with a greater reflex gain (17.2 ± 6.8 vs 8.8 ± 2.6msec·mmHg−1; d = 1.8, P = 0.01) versus healthy highlanders. Basal sympathetic vasomotor activity was also lower compared to healthy highlanders (33 ± 11 vs 45 ± 13bursts·min−1; d = 1.0, P = 0.08). In conclusion, our findings indicate adaptive differences in basal sympathetic vasomotor activity and heart rate compensate for the haemodynamic consequences of excessive erythrocyte volume and contribute to integrative blood pressure regulation in Andean highlanders with mild CMS

The 2018 Global Research Expedition on Altitude-related Chronic Health (REACH) to Cerro de Pasco, Peru: An Experimental Overview

In 2016, the international research team - Global Research Expedition onAltitude-related Chronic Health (REACH) - was established and executed a high altituderesearch expedition to Nepal. The team consists of ~45 students, principal investigatorsand physicians with the common objective of conducting experiments focused on highaltitude adaptation in lowlanders, and highlanders with lifelong exposure to high altitude.In 2018, Global REACH traveled to Peru where we performed a series of experiments inthe Andean highlanders. The experimental objectives, organization and characteristics,and key cohort data from Global REACH's latest research expedition are outlined herein.Herein, fifteen major studies are described that aimed to elucidate the physiologicaldifferences in high altitude acclimatization between lowlanders (n=30) and Andean bornhighlanders with (n=22) and without (n=45) Excessive Erythrocytosis (EE). Afterbaseline testing in Kelowna, BC, Canada (344m), Global REACH travelled to Lima, Peru(~80 m), and then ascended by automobile to Cerro de Pasco, Peru (~4300m) whereexperiments were conducted over 25 days. The core studies focused on elucidating themechanism(s) governing cerebral and peripheral vascular function, cardiopulmonaryregulation, exercise performance, and autonomic control. Despite encountering seriouslogistical challenges, each of the proposed studies were completed at both sea level andhigh altitude amounting to ~780 study sessions and >3000 hrs of experimental testing.Participant demographics and data related to acid-base balance and exercise capacityare presented. The collective findings will contribute to our understanding of howlowlanders and Andean highlanders have adapted under high altitude stress