The Effects of Creatine Supplementation on Cardiovascular, Metabolic, and Thermoregulatory Responses during Exercise in the Heat in Endurance-Trained Humans

2004 ◽  
Vol 14 (4) ◽  
pp. 443-460 ◽  
Author(s):  
L.P. Kilduff ◽  
E. Georgiades ◽  
N. James ◽  
R.H. Minnion ◽  
M. Mitchell ◽  
...  
Keyword(s):  
Prolonged Exercise ◽  
Sweat Rate ◽  
Creatine Supplementation ◽  
Cardiovascular Responses ◽  
Constant Load ◽  
Time To Exhaustion ◽  
Exercise Tests ◽  
Thermoregulatory Responses ◽  
Before And After ◽  
Constant Load Exercise

The effects of creatine (Cr) supplementation on cardiovascular, metabolic, and thermoregulatory responses, and on the capacity of trained humans to perform prolonged exercise in the heat was examined. Endurance-trained males (n = 21) performed 2 constant-load exercise tests to exhaustion at 63 ± 5 % VO2max in the heat (ambient temperature: 30.3 ± 0.5 °C) before and after 7 d of Cr (20 g · d–1 ’ Cr + 140 g • d–1 glucose polymer) or placebo. Cr increased intraccl-lular water and reduced thermoregulatory and cardiovascular responses (e.g., heart rate, rectal temperature, sweat rate) but did not significantly increase time to exhaustion (47.0 ± 4.7 min vs. 49.7 ± 7.5 min, P = 0.095). Time to exhaustion was increased significantly in subjects whose estimated intramuscular Cr levels were substantially increased (“responders”: 47.3 ± 4.9 min vs. 51.7 ± 7.4 min, P = 0.031). Cr-induced hyperhydration can result in a more efficient thermoregulatory response during prolonged exercise in the heat.

Influence of endurance training on muscle [PCr] kinetics during high-intensity exercise

2007 ◽  
Vol 293 (1) ◽  
pp. R392-R401 ◽  
Author(s):  
Andrew M. Jones ◽  
Daryl P. Wilkerson ◽  
Nicolas J. Berger ◽  
Jonathan Fulford
Keyword(s):  
Endurance Training ◽  
High Intensity ◽  
Slow Component ◽  
Knee Extension ◽  
High Intensity Exercise ◽  
Whole Body ◽  
Time To Exhaustion ◽  
Exercise Tests ◽  
Before And After ◽  
Knee Extension Exercise

We hypothesized that a period of endurance training would result in a speeding of muscle phosphocreatine concentration ([PCr]) kinetics over the fundamental phase of the response and a reduction in the amplitude of the [PCr] slow component during high-intensity exercise. Six male subjects (age 26 ± 5 yr) completed 5 wk of single-legged knee-extension exercise training with the alternate leg serving as a control. Before and after the intervention period, the subjects completed incremental and high-intensity step exercise tests of 6-min duration with both legs separately inside the bore of a whole-body magnetic resonance spectrometer. The time-to-exhaustion during incremental exercise was not changed in the control leg [preintervention group (PRE): 19.4 ± 2.3 min vs. postintervention group (POST): 19.4 ± 1.9 min] but was significantly increased in the trained leg (PRE: 19.6 ± 1.6 min vs. POST: 22.0 ± 2.2 min; P < 0.05). During step exercise, there were no significant changes in the control leg, but end-exercise pH and [PCr] were higher after vs. before training. The time constant for the [PCr] kinetics over the fundamental exponential region of the response was not significantly altered in either the control leg (PRE: 40 ± 13 s vs. POST: 43 ± 10 s) or the trained leg (PRE: 38 ± 8 s vs. POST: 40 ± 12 s). However, the amplitude of the [PCr] slow component was significantly reduced in the trained leg (PRE: 15 ± 7 vs. POST: 7 ± 7% change in [PCr]; P < 0.05) with there being no change in the control leg (PRE: 13 ± 8 vs. POST: 12 ± 10% change in [PCr]). The attenuation of the [PCr] slow component might be mechanistically linked with enhanced exercise tolerance following endurance training.

Effects of sustained exercise on pulmonary clearance of aerosolized 99mTc-DTPA

1989 ◽  
Vol 67 (5) ◽  
pp. 2055-2059 ◽  
Author(s):  
A. M. Lorino ◽  
M. Meignan ◽  
P. Bouissou ◽  
G. Atlan
Keyword(s):  
Tidal Volume ◽  
Clearance Rate ◽  
Constant Load ◽  
Pulmonary Mechanics ◽  
Epithelial Permeability ◽  
Alveolar Epithelial ◽  
Pulmonary Clearance ◽  
Before And After ◽  
Pulmonary Volumes ◽  
Constant Load Exercise

The effects of intensive prolonged exercise on the pulmonary clearance rate of aerosolized 99mTc-labeled diethylenetriaminepentaacetate (99mTc-DTPA) and pulmonary mechanics were studied in seven healthy nonsmoking volunteers. 99mTc-DTPA clearance and pulmonary mechanics (lung volumes and compliance) were assessed before and after 75 min of constant-load exercise performed on a treadmill, corresponding to 75% of maximal O2 uptake. Because both clearance measurements were made in similar conditions of pulmonary blood flow, respiratory rate, and tidal volume, changes in clearance rate can be assumed to represent changes of alveolar epithelial permeability. After exercise, total, apical, and basal clearance were significantly increased (P less than 0.01, 0.05, and 0.05, respectively) and the increases in total clearance and tidal volume observed during exercise were significantly correlated (P less than 0.05). In contrast, no significant change was found in pulmonary mechanics. These results show that prolonged intensive exercise induces an increase in epithelial permeability, which appears to be related to the mechanical effects of sustained increased ventilation. Because no change was evidenced in pulmonary volumes or in lung elasticity, our results suggest that this increase may result from alteration of the intercellular tight junctions rather than from a surfactant deficiency.

Cardiovascular responses of heart transplant patients to exercise training

1991 ◽  
Vol 70 (6) ◽  
pp. 2627-2631 ◽  
Author(s):  
S. Keteyian ◽  
R. Shepard ◽  
J. Ehrman ◽  
F. Fedel ◽  
C. Glick ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Exercise Training ◽  
Comparison Group ◽  
Cardiovascular Responses ◽  
Orthotopic Heart Transplantation ◽  
O2 Consumption ◽  
Peak Heart Rate ◽  
Exercise Tests ◽  
Before And After

Orthotopic heart transplantation (OHT) represents an effective alternative for individuals with end-stage heart disease. The current literature reports only the responses of OHT patients to greater than or equal to 4 mo of exercise training (ET) and frequently lacks adequate controls. Most programs currently treating OHT patients usually provide 6-12 wk of ET. This study describes the effects of a 10-wk supervised ET program in 12 male OHT patients and 5 other male OHT patients who served as a comparison group. Graded exercise tests were performed before and after ET. After ET, maximal O2 consumption was significantly greater for the ET group than the comparison group (P less than 0.05) and the mean increase in peak heart rate was 18 +/- 4 and 6 +/- 4 (SE) min-1 for ET and comparison groups, respectively (P less than 0.05). Maximal ventilation was also significantly greater for the ET group at after ET, while resting heart rate and blood pressure and peak blood pressure, O2 pulse, respiratory rate, and ventilatory equivalents for O2 and CO2 were not significantly changed. We conclude that after OHT a 10-wk ET program improves maximal O2 consumption and, by improving peak heart rate, improves O2 delivery.

scholarly journals Intensity Thresholds and Maximal Lactate Steady State in Small Muscle Group Exercise

Sports ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 77
Author(s):  
Florian Spendier ◽  
Alexander Müller ◽  
Markus Korinek ◽  
Peter Hofmann
Keyword(s):  
Steady State ◽  
Peak Load ◽  
Constant Load ◽  
Muscle Group ◽  
Group Exercise ◽  
Exercise Tests ◽  
Three Phase ◽  
Load Tests ◽  
Small Muscle ◽  
Constant Load Exercise

The aim of our study is to determine the first (LTP1) and the second (LTP2) lactate turn points during an incremental bicep curl test and to verify these turn points by ventilatory turn points (VT1 and VT2) and constant-load exercise tests. Twelve subjects performed a one-arm incremental bicep curl exercise (IET) after a one repetition maximum (1RM) test to calculate the step rate for the incremental exercise (1RM/45). Workload was increased every min at a rate of 30 reps/min until maximum. To verify LTPs, VT1 and VT2 were determined from spirometric data, and 30 min constant-load tests (CL) were performed at 5% Pmax below and above turn points. Peak load in IET was 5.3 ± 0.9 kg (Lamax: 2.20 ± 0.40 mmol·L−1; HRmax: 135 ± 15 b·min−1; VO2max: 1.15 ± 0.30 L·min−1). LTP1 was detected at 1.9 ± 0.6 kg (La: 0.86 ± 0.36 mmol·L−1; HR 90 ± 13 b·min−1; VO2: 0.50 ± 0.05 L·min−1) and LTP2 at 3.8 ± 0.7 kg (La: 1.38 ± 0.37 mmol·L−1; 106 ± 10 b·min−1; VO2: 0.62 ± 0.11 L·min−1). Constant-load tests showed a lactate steady-state in all tests except above LTP2, with early termination after 16.5 ± 9.1 min. LTP1 and LTP2 could be determined in IET, which were not significantly different from VT1/VT2. Constant-load exercise validated the three-phase concept, and a steady-state was found at resting values below VT1 and in all other tests except above LTP2. It is suggested that the three-phase model is also applicable to small muscle group exercise.

Effect of Creatine Supplementation on Aerobic Performance and Anaerobic Capacity in Elite Rowers in the Course of Endurance Training

2003 ◽  
Vol 13 (2) ◽  
pp. 173-183 ◽  
Author(s):  
Jolanta Chwalbiñska-Moneta
Keyword(s):  
Endurance Training ◽  
Lactate Threshold ◽  
Anaerobic Capacity ◽  
Creatine Supplementation ◽  
Anaerobic Exercise ◽  
Aerobic Performance ◽  
Anaerobic Performance ◽  
Exercise Tests ◽  
Before And After ◽  
Elite Rowers

The effect of oral creatine supplementation on aerobic and anaerobic performance was investigated in 16 elite male rowers during 7-day endurance training. Before and after the daily ingestion of 20 g creatine monohydrate for 5 days (Cr-Group, n = 8) or placebo (Pl-Group, n = 8), subjects performed two exercise tests on a rowing ergometer: (a) incremental exercise consisting of 3-min stage durations and increased by 50 W until volitional exhaustion; (b) an all-out anaerobic exercise performed against a constant load of 7 W/kg. Heart rate and blood lactate concentrations were determined during exercise and recovery. Maximal power output did not significantly differ after the treatment in either group. The mean individual lactate threshold rose significantly after Cr treatment from 314.3 ± 5.0 W to 335.6 ± 7.1 W (p < .01), as compared with 305.0 ± 6.9 W and 308.9 ± 5.9 W (ns), before and after placebo ingestion, respectively. During the anaerobic test, the athletes supplemented with creatine were able to continue rowing longer (mean increase, 12.1 ± 4.5 s; p < .01) than Pl-Group (2.4 ± 8.2 s; ns). No significant differences were found between groups in blood LA after the all-out exercise. The results indicate that in elite rowers, creatine supplementation improves endurance (expressed by the individual lactate threshold) and anaerobic performance, independent of the effect of intensive endurance training.

Hypnotic manipulation of effort sense during dynamic exercise: cardiovascular responses and brain activation

2001 ◽  
Vol 90 (4) ◽  
pp. 1392-1399 ◽  
Author(s):  
J. W. Williamson ◽  
R. McColl ◽  
D. Mathews ◽  
J. H. Mitchell ◽  
P. B. Raven ◽  
...  
Keyword(s):  
Perceived Exertion ◽  
Insular Cortex ◽  
Cardiovascular Responses ◽  
Constant Load ◽  
Dynamic Exercise ◽  
Anterior Cingulate ◽  
Regional Cerebral Blood ◽  
Ratings Of Perceived Exertion ◽  
Effort Sense ◽  
Constant Load Exercise

The purpose of this investigation was to hypnotically manipulate effort sense during dynamic exercise and determine whether cerebral cortical structures previously implicated in the central modulation of cardiovascular responses were activated. Six healthy volunteers (4 women, 2 men) screened for high hypnotizability were studied on 3 separate days during constant-load exercise under three hypnotic conditions involving cycling on a 1) perceived level grade, 2) perceived downhill grade, and 3) perceived uphill grade. Ratings of perceived exertion (RPE), heart rate (HR), blood pressure (BP), and regional cerebral blood flow (rCBF) distributions for several sites were compared across conditions using an analysis of variance. The suggestion of downhill cycling decreased both the RPE [from 13 ± 2 to 11 ± 2 (SD) units; P< 0.05] and rCBF in the left insular cortex and anterior cingulate cortex, but it did not alter exercise HR or BP responses. Perceived uphill cycling elicited significant increases in RPE (from 13 ± 2 to 14 ± 1 units), HR (+16 beats/min), mean BP (+7 mmHg), right insular activation (+7.7 ± 4%), and right thalamus activation (+9.2 ± 5%). There were no differences in rCBF for leg sensorimotor regions across conditions. These findings show that an increase in effort sense during constant-load exercise can activate both insular and thalamic regions and elevate cardiovascular responses but that decreases in effort sense do not reduce cardiovascular responses below the level required to sustain metabolic needs.

Assessment of Critical Power with Children

2002 ◽  
Vol 14 (3) ◽  
pp. 259-268 ◽  
Author(s):  
Samantha G. Fawkner ◽  
Neil Armstrong
Keyword(s):  
Regression Analysis ◽  
Linear Regression ◽  
Power Output ◽  
Critical Power ◽  
Linear Regression Analysis ◽  
Constant Load ◽  
Time To Exhaustion ◽  
Limits Of Agreement ◽  
Constant Load Exercise ◽  
Constant Power Output

The purpose of this study was to examine methods of assessing Critical Power (CP) with children. Eight boys and 9 girls (10.3 – 0.4 yrs) completed 3 cycle tests in one day, each at a different constant power output predicted to induce fatigue in 2 to 15 min. Time to exhaustion was recorded, and order of the tests was randomized, with 3 hours recovery between tests. The children repeated these tests and 2 additional tests with at least 24 hr recovery between each test. CP was determined using least squares linear regression analysis of the power — t−1 relationship, for the single day (CP1), the 5 tests from different days (CP2), and the repeated 3 tests from different days (CP3). The 95% limits of agreement (range of percentage differences) were −15.4 to 13.1% (CP1 v CP2), −16.8 to 13.5% (CP1 v CP3), and −8.4 to 6.7% (CP2 v CP3). CP is a robust measure even when only 3 tests are completed in a single day and may be used to provide a simple and useful parameter of exercise intensity for constant load exercise with children.

Exercise throughout 6° head-down tilt bed rest preserves thermoregulatory responses

2003 ◽  
Vol 95 (5) ◽  
pp. 1817-1823 ◽  
Author(s):  
Manabu Shibasaki ◽  
Thad E. Wilson ◽  
Jian Cui ◽  
Benjamin D. Levine ◽  
Craig G. Crandall
Keyword(s):  
Sweat Rate ◽  
Local Heating ◽  
Bed Rest ◽  
Peak Oxygen Uptake ◽  
Dynamic Exercise ◽  
Cutaneous Vasodilation ◽  
Thermoregulatory Responses ◽  
Short Period ◽  
Before And After ◽  
The Relationship

Spaceflight and its bed rest analog [6° head-down tilt (HDT)] decrease plasma and blood volume and aerobic capacity. These responses may be associated with impaired thermoregulatory responses observed during exercise and passive heating after HDT exposure. This project tested the hypothesis that dynamic exercise during 13 days of HDT bed rest preserves thermoregulatory responses. Throughout HDT bed rest, 10 subjects exercised for 90 min/day (75% of pre-HDT maximum heart rate; supine). Before and after HDT bed rest, each subject exercised in the supine position at the same workload in a 28°C room. The internal temperature (Tcore) threshold for the onset of sweating and cutaneous vasodilation, as well as the slope of the relationship between the elevation in Tcore relative to the elevation in sweat rate (SR) and cutaneous vascular conductance (CVC; normalized to local heating maximum), were quantified pre- and post-HDT. Tcore thresholds for the onset of cutaneous vasodilation on the chest and forearm (chest: 36.79 ± 0.12 to 36.94 ± 0.13°C, P = 0.28; forearm: 36.76 ± 0.12 to 36.91 ± 0.11°C, P = 0.16) and slope of the elevation in CVC relative to Tcore (chest: 77.9 ± 14.2 to 80.6 ± 17.2%max/°C; P = 0.75; forearm: 76.3 ± 11.8 to 67.5 ± 14.3%max/°C, P = 0.39) were preserved post-HDT. Moreover, the Tcore threshold for the onset of SR (36.66 ± 0.12 to 36.74 ± 0.10°C; P = 0.36) and the slope of the relationship between the elevation in SR and the elevation in Tcore (1.23 ± 0.19 to 1.01 ± 0.14 mg · cm-2 · min-1 · °C-1; P = 0.16) were also maintained. Finally, after HDT bed rest, peak oxygen uptake and plasma and blood volumes were not different relative to pre-HDT bed rest values. These data suggest that dynamic exercise during this short period of HDT bed rest preserves thermoregulatory responses.

scholarly journals Exercise Heat Acclimation With Dehydration Does Not Affect Vascular and Cardiac Volumes or Systemic Hemodynamics During Endurance Exercise

2021 ◽  
Vol 12 ◽  
Author(s):  
Gavin Travers ◽  
José González-Alonso ◽  
Nathan Riding ◽  
David Nichols ◽  
Anthony Shaw ◽  
...  
Keyword(s):  
Endurance Exercise ◽  
Sweat Rate ◽  
Cardiovascular Responses ◽  
Heat Acclimation ◽  
Left Ventricular ◽  
Systemic Hemodynamics ◽  
Thermal Stimulus ◽  
Before And After ◽  
Cardiac Volumes ◽  
Experimental Trials

Permissive dehydration during exercise heat acclimation (HA) may enhance hematological and cardiovascular adaptations and thus acute responses to prolonged exercise. However, the independent role of permissive dehydration on vascular and cardiac volumes, ventricular-arterial (VA) coupling and systemic hemodynamics has not been systematically investigated. Seven males completed two 10-day exercise HA interventions with controlled heart rate (HR) where euhydration was maintained or permissive dehydration (-2.9 ± 0.5% body mass) occurred. Two experimental trials were conducted before and after each HA intervention where euhydration was maintained (-0.5 ± 0.4%) or dehydration was induced (-3.6 ± 0.6%) via prescribed fluid intakes. Rectal (Tre) and skin temperatures, HR, blood (BV) and left ventricular (LV) volumes, and systemic hemodynamics were measured at rest and during bouts of semi-recumbent cycling (55% V̇O2peak) in 33°C at 20, 100, and 180 min. Throughout HA sweat rate (12 ± 9%) and power output (18 ± 7 W) increased (P &lt; 0.05), whereas Tre was 38.4 ± 0.2°C during the 75 min of HR controlled exercise (P = 1.00). Neither HA intervention altered resting and euhydrated exercising Tre, BV, LV diastolic and systolic volumes, systemic hemodynamics, and VA coupling (P &gt; 0.05). Furthermore, the thermal and cardiovascular strain during exercise with acute dehydration post-HA was not influenced by HA hydration strategy. Instead, elevations in Tre and HR and reductions in BV and cardiac output matched pre-HA levels (P &gt; 0.05). These findings indicate that permissive dehydration during exercise HA with controlled HR and maintained thermal stimulus does not affect hematological or cardiovascular responses during acute endurance exercise under moderate heat stress with maintained euhydration or moderate dehydration.

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