Inflection points of cardiovascular responses and oxygenation are correlated in the distal but not the proximal portions of muscle during incremental exercise

To test whether there is a regional difference in the exercise pressor reflex within a given muscle, we investigated the relationship between the inflection points of cardiovascular responses and muscle oxygenation during exercise. Seven subjects performed incremental exercise, which consisted of incremental 30-s static knee extensions, each separated by 30 s of recovery. The workload started at 5% maximal voluntary contraction (MVC) and increased by 5% MVC for each increment until exhaustion. Changes (Δ) in the concentrations (denoted by brackets) of oxygenated Hb (O2Hb) and deoxygenated Hb (HHb) were monitored in proximal and distal portions of the vastus lateralis by near-infrared spectroscopy. The inflection points of mean arterial pressure (MAP), calf vascular resistance (CVR), and muscle deoxygenation index (Δ[O2Hb − HHb]) were calculated as the intersection point of two regression equations obtained at lower and higher workloads. The inflection point of Δ[O2Hb − HHb] differed significantly between proximal and distal portions (28.5 ± 3.0 vs. 39.5 ± 3.0%MVC, P < 0.05). Linear regression analysis showed significant correlations between the inflection point of Δ[O2Hb − HHb] in the distal portion and MAP ( r = 0.89; P < 0.01) and CVR ( r = 0.89; P < 0.05), but no significant relationship between the inflection point in the proximal portion and MAP or CVR. These data show that the inflection point of muscle deoxygenation differs between proximal and distal portions within the vastus lateralis during incremental exercise and suggest that the distal portion of the vastus lateralis contributes more to the pressor response than does the proximal portion.

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Time-course of V̇O2 kinetics responses during moderate-intensity exercise subsequent to HIIT vs moderate-intensity continuous training in type 2 diabetes.

Journal of Applied Physiology ◽

10.1152/japplphysiol.00952.2020 ◽

2021 ◽

Author(s):

Norita Gildea ◽

Adam McDermott ◽

Joel Rocha ◽

Donal O'Shea ◽

Simon Green ◽

...

Keyword(s):

Type 2 Diabetes ◽

Time Course ◽

Near Infrared ◽

Vastus Lateralis ◽

Moderate Intensity ◽

Vastus Lateralis Muscle ◽

Maximal Heart Rate ◽

Continuous Training ◽

Muscle Deoxygenation

We assessed the time course of changes in oxygen uptake (V̇O2) and muscle deoxygenation (i.e., deoxygenated haemoglobin and myoglobin, [HHb+Mb]) kinetics during transitions to moderate-intensity cycling following 12-weeks of low-volume high-intensity interval training (HIIT) vs. moderate-intensity continuous training (MICT) in adults with type 2 diabetes (T2D). Participants were randomly assigned to MICT (n=10, 50 min of moderate-intensity cycling), HIIT (n=9, 10x1 min at ~90% maximal heart rate) or non-exercising control (n=9) groups. Exercising groups trained 3 times per week and measurements were taken every 3 weeks. [HHb+Mb] kinetics were measured by near-infrared spectroscopy at the vastus lateralis muscle. The local matching of O2 delivery to O2 utilization was assessed by the Δ[HHb+Mb]/ΔV̇O2ratio. The pretraining time constant of the primary phase of V̇O2 (τV̇O2p ) decreased (P<0.05) at wk 3 of training in both MICT (from 44±12 to 32±5 s) and HIIT (from 42±8 to 32 ± 4 s) with no further changes thereafter; while no changes were reported in controls. The pretraining overall dynamic response of muscle deoxygenation (τ'[HHb+Mb]) was faster than τV̇O2p in all groups, resulting in Δ[HHb+Mb]/V̇O2p showing a transient "overshoot" relative to the subsequent steady-state level. After 3 wks, the Δ[HHb+Mb]/V̇O2p overshoot was eliminated only in the training groups, so that τ'[HHb+Mb] was not different to τV̇O2p in MICT and HIIT. The enhanced V̇O2 kinetics response consequent to both MICT and HIIT in T2D was likely attributed to a training-induced improvement in matching of O2 delivery to utilization.

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Resistance behaviour of carbon fibre-reinforced polymers subjected to lightning strikes: Experimental investigation and application

Advanced Composites Letters ◽

10.1177/2633366x19892272 ◽

2019 ◽

Vol 28 ◽

pp. 2633366X1989227 ◽

Cited By ~ 1

Author(s):

Jian Chen ◽

Zhengcai Fu ◽

Yang Zhao

Keyword(s):

Carbon Fibre ◽

Surface Resistance ◽

Inflection Point ◽

Front Surface ◽

Resistance Change ◽

Reinforced Polymers ◽

Change Rate ◽

Lightning Strikes ◽

Inflection Points ◽

Carbon Fibre Reinforced Polymers

It is difficult to monitor lightning damage to carbon fibre-reinforced polymers (CFRPs) online. This work experimentally investigates the changes associated with the electrical resistance of CFRPs subjected to lightning strikes. Two kinds of simulated lightning currents with different amplitudes in the range of 10–80 kA were injected into the CFRP samples. By measuring and comparing the changes in the struck-side (front) surface resistance, the surface resistance of the side opposite to the struck-side (back) and the oblique resistance of each sample before and after the lightning strike, it was observed that inflection points exist in the curve of the resistance change rate. The resistance decreases with increasing peak currents before the inflection point and increases when the peak current goes beyond the inflection point. The change rate of the front surface resistance is more sensitive to the lightning damage than are those of the back surface resistance and the oblique resistance. Different simulated lightning currents have approximately the same action integrals at the inflection points of resistance change rate. The characteristics indicate that resistance change detection could be a possible method for the online monitoring of CFRP lightning damage.

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Effect of regular voluntary exercise on resting cardiovascular responses in SHR and WKY pregnant rats

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.2.713 ◽

1992 ◽

Vol 73 (2) ◽

pp. 713-720 ◽

Cited By ~ 1

Author(s):

M. T. Jones ◽

K. I. Norton ◽

D. M. Black ◽

R. E. Graham ◽

R. B. Armstrong

Keyword(s):

Blood Flow ◽

Mean Arterial Pressure ◽

Cytochrome C ◽

Arterial Pressure ◽

Vastus Lateralis ◽

Cardiovascular Responses ◽

Voluntary Exercise ◽

Uterine Blood Flow ◽

Pregnant Rats ◽

Significant Difference

The purpose of this study was to assess the influence of regular voluntary exercise in pregnant normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats on 1) uteroplacental perfusion and mean arterial pressure in the resting conscious condition and 2) fetal number, fetal weight, and number of fetal resorptions. WKYs and SHRs were randomly assigned to standard cages [CWKY (n = 10); CSHR (n = 6)] or cages with activity wheels [EWKY (n = 7); ESHR (n = 8)]. EWKYs and ESHRs exercised for 12 wk, and then all rats were bred and experiments were conducted on gestational day 17. Resting blood flow (microspheres), heart rate (HR), and mean arterial pressure (Pa) were measured. No significant difference was found in Pa, HR, uterine blood flow (ESHRs 52 +/- 8 ml.min-1.100 g-1; CSHRs 28 +/- 6 ml.min-1.100 g-1), or maternal placental blood flow (ESHRs, 122 +/- 31 ml.min-1.100 g-1; CSHRs 78 +/- 21 ml.min-1.100 g-1) among the groups. Exercise altered the relationship between maternal placental and uterine blood flow and Pa in the SHR; SHRs with lower Pa maintained higher placental and uterine blood flow after training. Before gestation ESHRs ran on average more kilometers per week than EWKYs (43 +/- 3 vs. 34 +/- 4), but during gestation ESHRs averaged fewer kilometers per week than EWKYs (16 +/- 4 vs. 22 +/- 4). Succinate dehydrogenase activity was higher in the white vastus lateralis (1.02 +/- 0.2 mumol cytochrome c reduced.min-1.g wet wt-1) and vastus intermedius (3.1 +/- 0.5 mumol cytochrome c reduced.min-1.g wet wt-1) muscles of ESHRs.(ABSTRACT TRUNCATED AT 250 WORDS)

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PENGARUH LINGKUNGAN KERJA DAN KOMPENSASI TERHADAP KINERJA PEGAWAI PADA DINAS PENDIDIKAN, PEMUDA DAN OLAHRAGA KABUPATEN MAJENE

JURNAL LENTERA BISNIS ◽

10.34127/jrlab.v9i2.385 ◽

2020 ◽

Vol 9 (2) ◽

pp. 121

Author(s):

Sri Indira Hartawati ◽

Meutia A Sahur

Keyword(s):

Linear Regression ◽

Multiple Linear Regression ◽

Work Environment ◽

Employee Performance ◽

Linear Regression Analysis ◽

Youth Sports ◽

Multiple Linear Regression Analysis ◽

Department Of Education ◽

Test Reliability ◽

Regression Equations

This research was conducted at the Department of Education, Youth and Sports of Majene Regency with the title The Effect of Work Environment and Compensation on Employee Performance. The formulation of the problem used by researchers is How the influence of the Work Environment on Employee Performance at the Education and Youth Sports Office of Majene Regency, How the influence of Compensation on Employee Performance at the Education and Youth Sports Office of Majene Regency, which variables have more influence on Employee Performance at the Education and Youth Office Majene District Sports. The research method, namely the population and sample used in this study were all employees of the Department of Education and Youth Sports of Majene Regency, which amounted to about 50 people, while the analysis method used the Validity Test, Reliability Test, Multiple Linear Regression Analysis This analysis was used to determine how much influence it had. independent variables, namely: compensation (X1), and work environment (X2) on the dependent variable, namely Employee Performance (Y). Multiple linear regression equations, Partial Significance Test (t test) and Simultaneous Test (F test). The results obtained from this study are the work environment has a significant effect on employee performance at the Department of Education and Youth Sports of Majene Regency, compensation has an effect on employee performance at the Education and Youth Sports Office of Majene Regency. and the work environment has a more dominant influence on employee performance at the Department of Education and Youth Sport, Majene Regency.Keywords: Work Environment, Compensation, Employee Performance

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A GROWTH STUDY OF BEEF CATTLE

Canadian Journal of Animal Science ◽

10.4141/cjas81-128 ◽

1981 ◽

Vol 61 (4) ◽

pp. 1041-1048 ◽

Cited By ~ 28

Author(s):

L. A. GOONEWARDENE ◽

R. T. BERG ◽

R. T. HARDIN

Keyword(s):

Birth Weight ◽

Beef Cattle ◽

Inflection Point ◽

Prediction Errors ◽

Von Bertalanffy ◽

University Of Alberta ◽

Inflection Points ◽

Richards Function ◽

Residual Variances ◽

The University

Four growth equations (Richards, Brody, Von Bertalanffy and Logistic) were fitted to data from two breed groups of female beef cattle, purebred Hereford (HE) and synthetic of Charolais, Angus and Galloway (SY), which were maintained at the University of Alberta beef breeding research ranch at Kinsella, Alberta. All functions fitted three common parameters (an asymptote, an integration constant and a maturing rate parameter). Two functions (Von Bertalanffy and Logistic) had fixed inflection points while the Richards function fitted the inflection point as a fourth parameter. The Brody function had no inflection point. Based on the R2, mean prediction errors (MPE) and residual variances, the Richards function, with a variable inflection point, provided the best overall and the most consistent fit to both sets of data, followed by the Brody function with no inflection point. The Richards was the only function that could predict birth weight with any degree of accuracy. The Logistic and Von Bertalanffy functions, with fixed inflection points, provided poor estimates of actual weights at each end of the growth curve, overestimating birth weight and converging too early leading to underestimation of adult weight or the asymptote. Intermediate weights were reasonably well estimated by these functions. The HE group showed a 28% greater maturing rate compared with the SY based on the Richards function.

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Muscle Deoxygenation during Incremental Exercise is Delayed in Children Compared to Young Adults

Medicine & Science in Sports & Exercise ◽

10.1249/01.mss.0000518685.60359.4f ◽

2017 ◽

Vol 49 (5S) ◽

pp. 640-641 ◽

Cited By ~ 1

Author(s):

Abraham S. Chiu ◽

Harry B. Rossiter ◽

Shlomit Radom-Aizik ◽

Ronen Bar-Yoseph ◽

Robert V. Warren ◽

...

Keyword(s):

Young Adults ◽

Incremental Exercise ◽

Muscle Deoxygenation

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The receptor mechanisms for histamine actions in proximal portion differ from those in distal portion in human coronary artery.

The Tohoku Journal of Experimental Medicine ◽

10.1620/tjem.154.415 ◽

1988 ◽

Vol 154 (4) ◽

pp. 415-416 ◽

Cited By ~ 3

Author(s):

MITSUMASA KEITOKU ◽

YUKIO MARUYAMA ◽

TAMOTSU TAKISHIMA

Keyword(s):

Coronary Artery ◽

Distal Portion ◽

Proximal Portion ◽

Human Coronary Artery

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Evaluation of the Electromyography Test for the Analysis of the Aerobic-Anaerobic Transition in Elite Cyclists during Incremental Exercise

Applied Sciences ◽

10.3390/app9030589 ◽

2019 ◽

Vol 9 (3) ◽

pp. 589

Author(s):

Iban Latasa ◽

Alfredo Cordova ◽

Gregorio Quintana-Ortí ◽

Ana Lavilla-Oiz ◽

Javier Navallas ◽

...

Keyword(s):

Linear Regression ◽

Vastus Lateralis ◽

Gluteus Maximus ◽

Biceps Femoris ◽

Incremental Exercise ◽

Linear Regression Method ◽

Validity And Reliability ◽

Time Curve ◽

Invasive Method ◽

Elite Cyclists

(1) Background: The aim of this study was to investigate the validity and reliability of surface electromyography (EMG) for automatic detection of the aerobic and anaerobic thresholds during an incremental continuous cycling test using 1 min exercise periods in elite cyclists. (2) Methods: Sixteen well-trained cyclists completed an incremental exercise test (25 W/1 min) to exhaustion. Surface bipolar EMG signals were recorded from the vastus lateralis, vastus medialis, biceps femoris, and gluteus maximus, and the root mean square (RMS) were assessed. The multi-segment linear regression method was used to calculate the first and second EMG thresholds (EMGT1 and EMGT2). During the test, gas exchange data were collected to determine the first and second ventilatory thresholds (VT1 and VT2). (3) Results: Two breakpoints (thresholds) were identified in the RMS EMG vs. time curve for all muscles in 75% of participants. The two breakpoints, EMGT1 and EMGT2, were detected at around 70%–80% and 90%–95% of VO2MAX, respectively. No significant differences were found between the means of VT1 and EMGT1 for the vastii and biceps femoris muscles (p > 0.05). There were no significant differences between means of EMGT2 and VT2 (p > 0.05). (4) Conclusions: It is concluded that the multi-segment linear regression algorithm is a valid non-invasive method for analyzing the aerobic-anaerobic transition during incremental tests with 1 min stage durations.

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