Loading of trained inspiratory muscles speeds lactate recovery kinetics

Purpose: To investigate the effects of inspiratory muscle loading (ITL) and inspiratory muscle training (IMT) upon blood lactate concentration ([lacj]B)and acid-base balance following maximal incremental cycling. Methods: 18 subjects were divided into a control (n = 9) or IMT group (n = 9). Prior to and following a 6 wk intervention subjects completed two maximal incremental cycling tests followed by 20 min of recovery with (ITL) or without (passive recovery; PR) a constant inspiratory resistance (15 cmH2O). The IMT group performed 6 wk pressure threshold IMT at 50% maximal inspiratory mouth pressure (MIP). Throughout recovery, acid-base balance was quantified using the physicochemical approach by measuring the strong ion difference ([SID])=[Na+]+[K+]-[ Clj]+[ lacj]), the total concentration of weak acids ([Atot j]) and the partial pressure of carbon dioxide (PCO2). Results: Following the intervention MIP increased in the IMT group only (+34%). No differences in lactate clearance were observed between PR and ITL before the intervention in both groups and following the intervention in the control group. Following IMT, relative to PR, [lacj]B was reduced throughout ITL (min 2 to 20) by 0.66 ± 1.28 mmol·L-1 (P<0.05) and both the fast (lactate exchange) and slow (lactate clearance) velocity constants of the lactate recovery kinetics were increased (P<0.05). Relative to pre-IMT, ITL reduced plasma [H+] which was accounted for by an IMT-mediated increase in [SID] due almost exclusively to a 1.7 mmol·L-1 reduction in [lacj]B. Conclusions: Following maximal exercise ITL affected lactate recovery kinetics only after IMT. Our data support the notion that the inspiratory muscles are capable of lactate clearance which increases [SID] and reduces [H+]. These effects may facilitate subsequent bouts of high-intensity exercise

Determinants of inspiratory muscle strength in healthy humans

We investigated 1) the relationship between the baseline and inspiratory muscle training (IMT) induced increase in maximal inspiratory pressure (PI,max) and 2) the relative contributions of the inspiratory chest wall muscles and the diaphragm (Poes/Pdi) to PI,max prior to and following-IMT. Experiment 1: PI,max was assessed during a Müeller manoeuvre before and after 4-wk IMT (n=30). Experiment 2: PI,max and the relative contribution of the inspiratory chest wall muscles to the diaphragm (Poes/Pdi) were assessed during a Müeller manoeuvre before and after 4-wk IMT (n=20). Experiment 1: PI,max increased 19% (P<0.01) post-IMT and was correlated with baseline PI,max (r=−0.373, P<0.05). Experiment 2: baseline PI,max was correlated with Poe/Pdi (r=0.582, P<0.05) and after IMT PI,max increased 22% and Poe/Pdi increased 5% (P<0.05). In conclusion, baseline PI,max and the contribution of the chest wall inspiratory muscles relative to the diaphragm affect, in part, baseline and IMT-induced ΔPI,max. Great care should be taken when designing future IMT studies to ensure parity in the between-subject baseline PI,max

Inspiratory muscle training abolishes the blood lactate increase associated with volitional hyperpnoea superimposed on exercise and accelerates lactate and oxygen uptake kinetics at the onset of exercise

We examined the effects of inspiratory muscle training (IMT) upon volitional hyperpnoea-mediated increases in blood lactate ([lac−]B) during cycling at maximal lactate steady state (MLSS) power, and blood lactate and oxygen uptake kinetics at the onset of exercise. Twenty males formed either an IMT (n=10) or control group (n=10). Before and after a 6-wk intervention two 30 min trials were performed at MLSS (207 ± 28 W), which was determined using repeated 30 min constant power trials. The first was a reference trial, whereas during the second trial from 20-28 min participants mimicked the breathing pattern commensurate with 90% of the maximal minute ventilation (V ˙ E) measured during maximal incremental exercise. Before the intervention the MLSS [lac−]B was 3.7 ± 1.8 and 3.9 ± 1.6 mmol·L-1 in the IMT and control group, respectively

Prior upper body exercise reduces cycling work capacity but not critical power

Purpose: This study examined whether metabolite accumulation, induced by prior upper body exercise, affected the power–duration relationship for leg cycle ergometry

Response [letter to Editor-in-Chief in response to Chiappa et al.]

We thank Chiappa et al. (4,5) for commending our work (2,3,7), which we reciprocate in light of their thought provoking research that sparked the ensuing trans-Atlantic debate on the effects of inspiratory muscle loading on lactate clearance after exercise. Specifically, despite using similar methodologies, Chiappa et al. (4,5) have twice shown accelerated lactate clearance with inspiratory loading, whereas we have twice shown no effect (2,7). We hypothesized that these discrepancies may be due to interstudy differences in participant endurance training status, as evidenced by higher V˙O2peak and faster blood lactate recovery kinetics in our participants. We were thus intrigued by the authors’ unpublished data showing, in sedentary individuals, no effect of inspiratory loading on lactate clearance. In their accompanying figure, the authors also present novel data showing a significant correlation between maximal inspiratory pressure (MIP) and changes in the area under the blood [Laj] curve with inspiratory loading. This observation informed their hypothesis that the efficacy of inspiratory loading is influenced by inspiratory muscle mass rather than training status

Impact of Weekly Swimming Training Distance on the Ergogenicity of Inspiratory Muscle Training in Well-Trained Youth Swimmers

The aim of this study was to examine the impact of weekly swimming training distance upon the ergogenicity of inspiratory muscle training (IMT). Thirty-three youth swimmers were recruited and separated into a LOW and HIGH group based on weekly training distance ( 41 km.wk-1, respectively). The LOW and HIGH groups were further subdivided into control and IMT groups for a 6-week IMT intervention giving a total of four groups: LOWcon, LOWIMT, HIGHcon, HIGHIMT. Before and after the intervention period, swimmers completed maximal effort 100 m and 200 m front crawl swims, with maximal inspiratory and expiratory mouth pressures (PImax and PEmax, respectively) assessed before and after each swim. IMT increased PImax (but not PEmax) by 36% in LOWIMT and HIGHIMT groups (P < 0.05) but 100 m and 200 m swims were faster only in the LOWIMT group (3% and 7% respectively, P < 0.05). Performance benefits only occurred in those training up to 31 km.wk-1 and indicate that the ergogenicity of IMT is affected by weekly training distance. Consequently, training distances are important considerations, among others, when deciding whether or not to supplement swimming training with IMT

Quantizing Majorana Fermions in a Superconductor

A Dirac-type matrix equation governs surface excitations in a topological insulator in contact with an s-wave superconductor. The order parameter can be homogenous or vortex valued. In the homogenous case a winding number can be defined whose non-vanishing value signals topological effects. A vortex leads to a static, isolated, zero energy solution. Its mode function is real, and has been called "Majorana." Here we demonstrate that the reality/Majorana feature is not confined to the zero energy mode, but characterizes the full quantum field. In a four-component description a change of basis for the relevant matrices renders the Hamiltonian imaginary and the full, space-time dependent field is real, as is the case for the relativistic Majorana equation in the Majorana matrix representation. More broadly, we show that the Majorana quantization procedure is generic to superconductors, with or without the Dirac structure, and follows from the constraints of fermionic statistics on the symmetries of Bogoliubov-de Gennes Hamiltonians. The Hamiltonian can always be brought to an imaginary form, leading to equations of motion that are real with quantized real field solutions. Also we examine the Fock space realization of the zero mode algebra for the Dirac-type systems. We show that a two-dimensional representation is natural, in which fermion parity is preserved.Comment: 26 pages, no figure

The influence of ocean acidification on nitrogen regeneration and nitrous oxide production in the North-West European shelf sea

The assimilation and regeneration of dissolved inorganic nitrogen, and the concentration of N2O, was investigated at stations located in the NW European shelf sea during June/July 2011. These observational measurements within the photic zone demonstrated the simultaneous regeneration and assimilation of NH4+, NO2− and NO3−. NH4+ was assimilated at 1.82–49.12 nmol N L−1 h−1 and regenerated at 3.46–14.60 nmol N L−1 h−1; NO2− was assimilated at 0–2.08 nmol N L−1 h−1 and regenerated at 0.01–1.85 nmol N L−1 h−1; NO3− was assimilated at 0.67–18.75 nmol N L−1 h−1 and regenerated at 0.05–28.97 nmol N L−1 h−1. Observations implied that these processes were closely coupled at the regional scale and nitrogen recycling played an important role in sustaining phytoplankton growth during the summer. The [N2O], measured in water column profiles, was 10.13 ± 1.11 nmol L−1 and did not strongly diverge from atmospheric equilibrium indicating that sampled marine regions where neither a strong source nor sink of N2O to the atmosphere. Multivariate analysis of data describing water column biogeochemistry and its links to N-cycling activity failed to explain the observed variance in rates of N-regeneration and N-assimilation, possibly due to the limited number of process rate observations. In the surface waters of 5 further stations, Ocean Acidification (OA) bioassay experiments were conducted to investigate the response of NH4+ oxidising and regenerating organisms to simulated OA conditions, including the implications for [N2O]. Multivariate analysis was undertaken which considered the complete bioassay dataset of measured variables describing changes in N-regeneration rate, [N2O] and the biogeochemical composition of seawater. While anticipating biogeochemical differences between locations, we aimed to test the hypothesis that the underlying mechanism through which pelagic N-regeneration responded to simulated OA conditions was independent of location and that a mechanistic understanding of how NH4+ oxidation, NH4+ regeneration and N2O production responded to OA could be developed. Results indicated that N-regeneration process responses to OA treatments were location specific; no mechanistic understanding of how N-regeneration processes respond to OA in the surface ocean of the NW European shelf sea could be developed

Employees’ perceptions of corporate social responsibility and ethical leadership: Are they uniquely related to turnover intention?

© 2020, Emerald Publishing Limited. Purpose: The purpose of this study is to investigate the simultaneous effect of ethical leadership (EL) and corporate social responsibility (CSR) on employees’ turnover intention and examine the mediating mechanism in these relationships. Design/methodology/approach: The authors conducted a field study of 851 employees across a variety of industries. This study applied partial least squares structural equation modelling for hypothesis testing. Findings: The results show that employees’ perceptions of CSR as well as EL are both uniquely and negatively related to turnover intention. The authors also found that employees’ job satisfaction but not commitment, mediates these relationships. Research limitations/implications: This study answers the recent call (Schminke and Sheridan, 2017) for ethics researchers to put competing explanations to the test to determine their relative importance. Research limitations have been discussed in the paper. Social implications: Through providing empirical support for the positive impact of CSR and EL on employee-related outcomes and creating a decent and empowering work environment, this study provides further support for CSR and EL. As CSR and EL require accountability, responsible management and addressing societal well-being of stakeholders, this study can contribute to the United Nations sustainable development goals. Originality/value: Previous research has found that both employees’ perceptions of supervisory EL and CSR are negatively related to employees’ turnover intentions. Yet, the authors know little about their relative importance because these relationships have not been adequately examined simultaneously

Influence of oxidative stress, diaphragm fatigue, and inspiratory muscle training on the plasma cytokine response to maximum sustainable voluntary ventilation

The influence of oxidative stress, diaphragm fatigue, and inspiratory muscle training (IMT) on the cytokine response to maximum sustainable voluntary ventilation (MSVV) is unknown. Twelve healthy males were divided equally into an IMT or placebo (PLA) group, and before and after a 6-wk intervention they undertook, on separate days, 1h of (1) passive rest and (2) MSVV, whereby participants undertook volitional hyperpnea at rest that mimicked the breathing and respiratory muscle recruitment patterns commensurate with heavy cycling exercise. Plasma cytokines remained unchanged during passive rest. There was a main effect of time (P < 0.01) for plasma interleukin-1 (IL-1) and interleukin-6 (IL-6) concentrations and a strong trend (P = 0.067) for plasma interleukin-1 receptor antagonist concentration during MSVV. Plasma IL-6 concentration was reduced after IMT by 27 + 18% (main effect of intervention, P = 0.029), whereas there was no change after PLA (P = 0.753). There was no increase in a systemic marker of oxidative stress [DNA damage in peripheral blood mononuclear cells (PBMC)], and diaphragm fatigue was not related to the increases in plasma IL-1 and IL-6 concentrations. A dose-response relationship was observed between respiratory muscle work and minute ventilation and increases in plasma IL-6 concentration. In conclusion, increases in plasma IL-1 and IL-6 concentrations during MSVV were not due to diaphragm fatigue or DNA damage in PBMC. Increases in plasma IL-6 concentration during MSVV are attenuated following IMT, and the plasma IL-6 response is dependent upon the level of respiratory muscle work and minute ventilation