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

Reproducibility of the bronchoconstrictive response to eucapnic voluntary hyperpnoea

Background: Eucapnic voluntary hyperpnoea (EVH) is considered an effective bronchoprovocation challenge for identifying exercise-induced bronchoconstriction (EIB). However, the reproducibility of the hyperpnoea-induced bronchoconstriction (HIB) response elicited by EVH remains unknown and was therefore the focus of this study. Methods: Two cohorts of 16 physically active males (each cohort comprised 8 controls and 8 with physician diagnosis of asthma) participated in two studies of the short- and long-term reproducibility of the bronchoconstrictive response to an EVH test with dry air. EVH was performed on days 0, 7, 14, and 21 (short-term study), and 0, 35, and 70 (long-term study). HIB was diagnosed by a ≥10% fall in forced expiratory volume in 1 s (FEV1) after EVH. Results: On day 0 of the short-term study, FEV1 fell by 2 ± 1% (P < 0.05) and 27 ± 18% (P < 0.01) from pre-to post-EVH in control and HIB-positive groups respectively. The post-EVH fall in FEV1 did not differ across the short-term study test days. In the HIB-positive group, the day-to-day coefficient of variation, reproducibility, and smallest meaningful change for the fall in FEV1 were 12%, 328 mL, and 164 mL, respectively. On day 0 of the long-term study, FEV1 fell by 2 ± 2% and 25 ± 18% (P < 0.01) after EVH in control and HIB-positive groups respectively. The post-EVH fall in FEV1 did not differ across the long-term study test days. In the HIB-positive group, the day-to-day coefficient of variation, reproducibility, and smallest meaningful change for the fall in FEV1 were 10%, 196 mL, and 98 mL respectively. Conclusion: The EVH test elicits a reproducible bronchoconstrictive response in physically active males with physician diagnosed asthma. These data thus support the clinical utility of the EVH test for EIB screening and monitoring

Effects of protocol design on lactate minimum power

The aim of this investigation was to use a validated lactate minimum test protocol and evaluate whether blood lactate responses and the lactate minimum power are influenced by the starting power (study 1) and 1 min inter-stage rest intervals (study 2) during the incremental phase. Study 1: 8 subjects performed a lactate minimum test comprising a lactate elevation phase, recovery phase, and incremental phase comprising 5 continuous 4 min stages with starting power being 40% or 45% of the maximum power achieved during the lactate elevation phase, and with power increments of 5% maximum power. Study 2: 8 subjects performed 2 identical lactate minimum tests except that during one of the tests the incremental phase included 1 min inter-stage rest intervals. The lactate minimum power was lower when the incremental phase commenced at 40% (175±29 W) compared to 45% (184±30 W) maximum power (p<0.01), and was increased when 1 min inter-stage rest intervals were included during the incremental phase (192±25 vs. 200±26 W, p<0.01). In conclusion, changes in lactate minimum power were small and thus unlikely to compromise test validity and therefore training status evaluation and exercise prescription

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

Machine learning analysis for quantitative discrimination of dried blood droplets

One of the most interesting and everyday natural phenomenon is the formation of different patterns after the evaporation of liquid droplets on a solid surface. The analysis of dried patterns from blood droplets has recently gained a lot of attention, experimentally and theoretically, due to its potential application in diagnostic medicine and forensic science. This paper presents evidence that images of dried blood droplets have a signature revealing the exhaustion level of the person, and discloses an entirely novel approach to studying human dried blood droplet patterns. We took blood samples from 30 healthy young male volunteers before and after exhaustive exercise, which is well known to cause large changes to blood chemistry. We objectively and quantitatively analysed 1800 images of dried blood droplets, developing sophisticated image processing analysis routines and optimising a multivariate statistical machine learning algorithm. We looked for statistically relevant correlations between the patterns in the dried blood droplets and exercise-induced changes in blood chemistry. An analysis of the various measured physiological parameters was also investigated. We found that when our machine learning algorithm, which optimises a statistical model combining Principal Component Analysis (PCA) as an unsupervised learning method and Linear Discriminant Analysis (LDA) as a supervised learning method, is applied on the logarithmic power spectrum of the images, it can provide up to 95% prediction accuracy, in discriminating the physiological conditions, i.e., before or after physical exercise. This correlation is strongest when all ten images taken per volunteer per condition are averaged, rather than treated individually. Having demonstrated proof-of-principle, this method can be applied to identify diseases

Effects of prior voluntary hyperventilation on the 3-min all-out cycling test in men

Introduction: The ergogenic effects of respiratory alkalosis induced by prior voluntary hyperventilation (VH) are controversial. This study examined the effects of prior VH on derived parameters from the 3-min all-out cycling test (3MT). Methods: Eleven men V̇O2max = 46 ± 8 mL⋅kg-1⋅min-1) performed a 3MT preceded by 15-min of rest (CONT) or voluntary hyperventilation (V˙E = 38 ± 5 L⋅min-1) with PETCO2 reduced to 21 ± 1 mmHg (HYP). End-test power (EP; synonymous with critical power) was calculated as the mean power output over the last 30-s of the 3MT, and the work done above EP (WEP; synonymous with W') was calculated as the power-time integral above EP. Results: At the start of the 3MT, capillary blood PCO2 and [H+] were lower in HYP (25.2 ± 3.0 mmHg, 27.1 ± 2.6 nmol⋅L-1) than CONT (43.2 ± 2.0 mmHg, 40.0 ± 1.5 nmol⋅L-1) (P < 0.001). At the end of the 3MT, blood PCO2 was still lower in HYP (35.7 ± 5.4 mmHg) than CONT (40.6 ± 5.0 mmHg) (P < 0.001). WEP was 10% higher in HYP (19.4 ± 7.0 kJ) than CONT (17.6 ± 6.4 kJ) (P = 0.006), whereas EP was 5% lower in HYP (246 ± 69 W) than CONT (260 ± 74 W) (P = 0.007). The ΔWEP (J·kg-1) between CONT and HYP correlated positively with the PCO2 immediately before the 3MT in HYP (r = 0.77, P = 0.006). Conclusion: These findings suggest that acid-base changes elicited by prior voluntary hyperventilation increase WEP but decrease EP during the all-out 3MT