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Creatine supplementation improves performance above critical power but does not influence the magnitude of neuromuscular fatigue at task failure.
Schäfer, LU, Hayes, M, Dekerle, J
Experimental physiology. 2019;(12):1881-1891
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NEW FINDINGS What is the central question of this study? Does the magnitude of neuromuscular fatigue depend on the amount of work done (W') at task failure when cycling above critical power (CP)? What is the main finding and its importance? Creatine supplementation increases W' and enhances supra-CP performance, but induces similar magnitudes of neuromuscular fatigue at task failure compared to placebo. Increased W' does not lead to higher levels of neuromuscular fatigue. This supports the notion of a critical level of neuromuscular fatigue at task failure and challenges a direct causative link between W' depletion and neuromuscular fatigue. ABSTRACT The present study examined the effect of creatine supplementation on neuromuscular fatigue and exercise tolerance when cycling above critical power (CP). Eleven males performed an incremental cycling test with four to five constant-load trials to task failure (TTF) to obtain asymptote (CP) and curvature constant (W') of the power-duration relationship, followed by three constant-load supra-CP trials: (1) one TTF following placebo supplementation (PLA); (2) one TTF following creatine supplementation (CRE); and (3) one trial of equal duration to PLA following creatine supplementation (ISO). Neuromuscular assessment of the right knee extensors was performed pre- and post-exercise to measure maximal voluntary contraction (MVC), twitch forces evoked by single (Qpot ) and paired high- (PS100) and low- (PS10) frequency stimulations and voluntary activation. Creatine supplementation increased TTF in CRE vs. PLA by ∼11% (P = 0.017) and work done above CP by ∼10% (P = 0.015), with no difference (P > 0.05) in reductions in MVC (-24 ± 8% vs. -20 ± 9%), Qpot (-39 ± 13% vs. -32 ± 14%), PS10 (-42 ± 14% vs. -36 ± 13%), PS100 (-25 ± 10% vs. -18 ± 12%) and voluntary activation (-7 ± 8% vs. -5 ± 7%). No significant difference was found between ISO and either PLA or CRE (P > 0.05). These findings suggest similar levels of neuromuscular fatigue can be found following supra-CP cycling despite increases in performance time and amount of work done above CP, supporting the notion of a critical level of neuromuscular fatigue and challenging a direct causative link between W' depletion and neuromuscular fatigue.
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The effects of upper and lower limb exercise on the microvascular reactivity in limited cutaneous systemic sclerosis patients.
Mitropoulos, A, Gumber, A, Crank, H, Akil, M, Klonizakis, M
Arthritis research & therapy. 2018;(1):112
Abstract
BACKGROUND Aerobic exercise in general and high-intensity interval training (HIIT) specifically is known to improve vascular function in a range of clinical conditions. HIIT in particular has demonstrated improvements in clinical outcomes, in conditions that have a strong macroangiopathic component. Nevertheless, the effect of HIIT on microcirculation in systemic sclerosis (SSc) patients is yet to be investigated. Therefore, the purpose of the study was to compare the effects of two HIIT protocols (cycle and arm cranking) on the microcirculation of the digital area in SSc patients. METHODS Thirty-four limited cutaneous SSc patients (65.3 ± 11.6 years old) were randomly allocated in three groups (cycling, arm cranking and control group). The exercise groups underwent a 12- week exercise program twice per week. All patients performed the baseline and post-exercise intervention measurements where physical fitness, functional ability, transcutaneous oxygen tension (ΔTcpO2), body composition and quality of life were assessed. Endothelial-dependent as well as -independent vasodilation were assessed in the middle and index fingers using LDF and incremental doses of acetylcholine (ACh) and sodium nitroprusside (SNP). Cutaneous flux data were expressed as cutaneous vascular conductance (CVC). RESULTS Peak oxygen uptake increased in both exercise groups (p < 0.01, d = 1.36). ΔTcpO2 demonstrated an increase in the arm-cranking group only, with a large effect, but not found statistically significant,(p = 0.59, d = 0.93). Endothelial-dependent vasodilation improvement was greater in the arm-cranking (p < 0.05, d = 1.07) in comparison to other groups. Both exercise groups improved life satisfaction (p < 0.001) as well as reduced discomfort and pain due to Raynaud's phenomenon (p < 0.05). Arm cranking seems to be the preferred mode of exercise for study participants as compared to cycling (p < 0.05). No changes were observed in the body composition or the functional ability in both exercise groups. CONCLUSIONS Our results suggest that arm cranking has the potential to improve the microvascular endothelial function in SSc patients. Also notably, our recommended training dose (e.g., a 12-week HIIT program, twice per week), appeared to be sufficient and tolerable for this population. Future research should focus on exploring the feasibility of a combined exercise such as aerobic and resistance training by assessing individual's experience and the quality of life in SSc patients. TRIAL REGISTRATION ClinicalTrials.gov (NCT number): NCT03058887 , February 23, 2017.
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Addition of vitamin B12 to exercise training improves cycle ergometer endurance in advanced COPD patients: A randomized and controlled study.
Paulin, FV, Zagatto, AM, Chiappa, GR, Müller, PT
Respiratory medicine. 2017;:23-29
Abstract
Vitamin B12 is essential in the homocysteine, mitochondrial, muscle and hematopoietic metabolisms, and its effects on exercise tolerance and kinetics adjustments of oxygen consumption (V'O2p) in rest-to-exercise transition in COPD patients are unknown. This randomized, double-blind, controlled study aimed to verify a possible interaction between vitamin B12 supplementation and these outcomes. After recruiting 69 patients, 35 subjects with moderate-to-severe COPD were eligible and 32 patients concluded the study, divided into four groups (n = 8 for each group): 1. rehabilitation group; 2. rehabilitation plus B12 group; 3. B12 group; and 4. placebo group. The primary endpoint was cycle ergometry endurance before and after 8 weeks and the secondary endpoints were oxygen uptake kinetics parameters (time constant). The prevalence of vitamin B12 deficiency was high (34.4%) and there was a statistically significant interaction (p < 0.05), favoring a global effect of supplementation on exercise tolerance in the supplemented groups compared to the non-supplemented groups, even after adjusting for confounding variables (p < 0.05). The same was not found for the kinetics adjustment variables (τV'O2p and MRTV'O2p, p > 0.05 for both). Supplementation with vitamin B12 appears to lead to discrete positive effects on exercise tolerance in groups of subjects with more advanced COPD and further studies are needed to establish indications for long-term supplementation.
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Effects of time-of-day on oxidative stress, cardiovascular parameters, biochemical markers, and hormonal response following level-1 Yo-Yo intermittent recovery test.
Aloui, K, Abedelmalek, S, Chtourou, H, Wong, DP, Boussetta, N, Souissi, N
Physiology international. 2017;(1):77-90
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The aim of this study was to investigate the effect of time-of-day on oxidative stress, cardiovascular parameters, muscle damage parameters, and hormonal responses following the level-1 Yo-Yo intermittent recovery test (YYIRT). A total of 11 healthy subjects performed an intermittent test (YYIRT) at two times-of-day (i.e., 07:00 h and 17:00 h), with a recovery period of ≥36 h in-between, in a randomized order. Blood samples were taken at the rest (baseline) and immediately (post-YYIRT) after the YYIRT for measuring oxidative stress, biochemical markers, and hormonal response. Data were statistically analyzed using one-way and two-way repeated measures ANOVA and Bonferroni test at p < 0.05. Observed power (α = 0.05) and partial eta-squared were used. Our results showed that oxygen uptake (VO2max), maximal aerobic speed, and the total distance covered tended to be higher in the evening (17:00 h). There was also a main effect of time-of-day for cortisol and testosterone concentration, which were higher after the YYIRT in the morning (p < 0.05). The heart rate peak and the rating of perceived exertion scales were lower in the morning (p < 0.05). However, the plasma glucose (p < 0.01), malondialdehyde, creatine kinase (p < 0.01), lactate dehydrogenase (p < 0.05), high-density lipoprotein (p < 0.01), total cholesterol (p < 0.01), and triglycerides (p < 0.05) were higher after the YYIRT in the evening. Low-density lipoprotein, systolic blood pressure, diastolic blood pressure, and lactate levels (p > 0.05) were similar for the morning and evening test. In conclusion, our findings suggest that aerobic performance presents diurnal variation with great result observed in the evening accompanied by an improvement of hormonal, metabolic, and oxidative responses. These data may help to guide athletes and coaches and contribute to public health recommendations on exercise and muscle damage particularly in the competitive periods.
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Acute effects of exercise on appetite, ad libitum energy intake and appetite-regulatory hormones in lean and overweight/obese men and women.
Douglas, JA, King, JA, Clayton, DJ, Jackson, AP, Sargeant, JA, Thackray, AE, Davies, MJ, Stensel, DJ
International journal of obesity (2005). 2017;(12):1737-1744
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BACKGROUND Acute exercise does not elicit compensatory changes in appetite parameters in lean individuals; however, less is known about responses in overweight individuals. This study compared the acute effects of moderate-intensity exercise on appetite, energy intake and appetite-regulatory hormones in lean and overweight/obese individuals. METHODS Forty-seven healthy lean (n=22, 11 females; mean (s.d.) 37.5 (15.2) years; 22.4 (1.5) kg m-2) and overweight/obese (n=25, 11 females; 45.0 (12.4) years, 29.2 (2.9) kg m-2) individuals completed two, 8 h trials (exercise and control). In the exercise trial, participants completed 60 min treadmill exercise (59 (4)% peak oxygen uptake) at 0-1 h and rested thereafter while participants rested throughout the control trial. Appetite ratings and concentrations of acylated ghrelin, peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) were measured at predetermined intervals. Standardised meals were consumed at 1.5 and 4 h and an ad libitum buffet meal was provided at 7 h. RESULTS Exercise suppressed appetite (95% confidence interval (CI) -3.1 to -0.5 mm, P=0.01), and elevated delta PYY (95% CI 10 to 17 pg ml-1, P<0.001) and GLP-1 (95% CI 7 to 10 pmol l-1, P<0.001) concentrations. Delta acylated ghrelin concentrations (95% CI -5 to 3 pg ml-1, P=0.76) and ad libitum energy intake (95% CI -391 to 346 kJ, P=0.90) were similar between trials. Subjective and hormonal appetite parameters and ad libitum energy intake were similar between lean and overweight/obese individuals (P⩾0.27). The exercise-induced elevation in delta GLP-1 was greater in overweight/obese individuals (trial-by-group interaction P=0.01), whereas lean individuals exhibited a greater exercise-induced increase in delta PYY (trial-by-group interaction P<0.001). CONCLUSIONS Acute moderate-intensity exercise transiently suppressed appetite and increased PYY and GLP-1 in the hours after exercise without stimulating compensatory changes in appetite in lean or overweight/obese individuals. These findings underscore the ability of exercise to induce a short-term energy deficit without any compensatory effects on appetite regardless of weight status.
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The effects of dietary nitrate supplementation on the adaptations to sprint interval training in previously untrained males.
Muggeridge, DJ, Sculthorpe, N, James, PE, Easton, C
Journal of science and medicine in sport. 2017;(1):92-97
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OBJECTIVES Dietary nitrate can improve repeated high-intensity and supramaximal exercise performance, although the effect on adaptations to training has received limited attention. The purpose of this study was to investigate the effects of dietary nitrate on the response to 3-weeks of sprint interval training (SIT). DESIGN Randomized control trial. METHODS Twenty-seven untrained males (Age: 28±7 y, V⋅O2Max: 42±7mlkg-1min-1) completed an incremental exercise test at the beginning and end of the study. Participants were matched for V⋅O2Max and randomly assigned to a control group (CON; n=8), SIT+placebo group (PLA; n=10), or SIT+nitrate group (NIT; n=9). The SIT comprised 4-6 repeated 15 s all out sprints on a cycle ergometer, interspersed with 4min active recovery, 3-times per week. Approximately 2.5h prior to exercise, participants consumed gels containing ∼0.1mmol (PLA) or ∼8mmol nitrate (NIT). RESULTS Following SIT, V⋅O2Max (PLA: 5%, p=0.057, d=0.34; NIT: 6.3%, p=0.041, d=0.34) and ventilatory threshold (VT) increased to a similar extent in both SIT groups. Maximum work rate tended to increase to a greater extent in NIT (8.7%, d=0.55) compared to PLA (4.7%, d=0.31, p=0.073). Fatigue index, calculated by the change in mean power from the first to the last sprint, tended to be reduced following SIT in NIT compared to PLA (PLA: 7.3±7.4%, NIT: 0.5±7.1%, p=0.058). CONCLUSIONS While dietary nitrate supplementation does not augment improvements to V⋅O2Max and VT following SIT, it may improve WRmax and indices of repeated high-intensity exercise.
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The effect of acute magnesium loading on the maximal exercise performance of stable chronic obstructive pulmonary disease patients.
Amaral, AF, Gallo, L, Vannucchi, H, Crescêncio, JC, Vianna, EO, Martinez, JA
Clinics (Sao Paulo, Brazil). 2012;(6):615-22
Abstract
OBJECTIVE The potential influence of magnesium on exercise performance is a subject of increasing interest. Magnesium has been shown to have bronchodilatatory properties in asthma and chronic obstructive pulmonary disease patients. The aim of this study was to investigate the effects of acute magnesium IV loading on the aerobic exercise performance of stable chronic obstructive pulmonary disease patients. METHODS Twenty male chronic obstructive pulmonary disease patients (66.2 + 8.3 years old, FEV1: 49.3+19.8%) received an IV infusion of 2 g of either magnesium sulfate or saline on two randomly assigned occasions approximately two days apart. Spirometry was performed both before and 45 minutes after the infusions. A symptom-limited incremental maximal cardiopulmonary test was performed on a cycle ergometer at approximately 100 minutes after the end of the infusion. RESULTS Magnesium infusion was associated with significant reductions in the functional residual capacity (-0.41 l) and residual volume (-0.47 l), the mean arterial blood pressure (-5.6 mmHg) and the cardiac double product (734.8 mmHg.bpm) at rest. Magnesium treatment led to significant increases in the maximal load reached (+8 w) and the respiratory exchange ratio (0.06) at peak exercise. The subgroup of patients who showed increases in the work load equal to or greater than 5 w also exhibited significantly greater improvements in inspiratory capacity (0.29 l). CONCLUSIONS The acute IV loading of magnesium promotes a reduction in static lung hyperinflation and improves the exercise performance in stable chronic obstructive pulmonary disease patients. Improvements in respiratory mechanics appear to be responsible for the latter finding.
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Effect of caffeine on adenosine-induced reversible perfusion defects assessed by automated analysis.
Lee, JC, Fraser, JF, Barnett, AG, Johnson, LP, Wilson, MG, McHenry, CM, Walters, DL, Warnholtz, CR, Khafagi, FA
Journal of nuclear cardiology : official publication of the American Society of Nuclear Cardiology. 2012;(3):474-81
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OBJECTIVES This prospective study investigated the effects of caffeine ingestion on the extent of adenosine-induced perfusion abnormalities during myocardial perfusion imaging (MPI). METHODS Thirty patients with inducible perfusion abnormalities on standard (caffeineabstinent) adenosine MPI underwent repeat testing with supplementary coffee intake. Baseline and test MPIs were assessed for stress percent defect, rest percent defect, and percent defect reversibility. Plasma levels of caffeine and metabolites were assessed on both occasions and correlated with MPI findings. RESULTS Despite significant increases in caffeine [mean difference 3,106 μg/L (95% CI 2,460 to 3,752 μg/L; P < .001)] and metabolite concentrations over a wide range, there was no statistically significant change in stress percent defect and percent defect reversibility between the baseline and test scans. The increase in caffeine concentration between the baseline and the test phases did not affect percent defect reversibility (average change -0.003 for every 100 μg/L increase; 95% CI -0.17 to 0.16; P = .97). CONCLUSION There was no significant relationship between the extent of adenosine-induced coronary flow heterogeneity and the serum concentration of caffeine or its principal metabolites. Hence, the stringent requirements for prolonged abstinence from caffeine before adenosine MPI - based on limited studies - appear ill-founded.
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Blood pressure reduction in hyper-reactive individuals after aerobic exercise.
Richter, CM, Panigas, TF, Bündchen, DC, Dipp, T, Belli, KC, Viecili, PR
Arquivos brasileiros de cardiologia. 2010;(2):251-7
Abstract
BACKGROUND Some normotensive sedentary individuals have an exaggerated increase in blood pressure (BP) during physical activity, which is a behavior that is called blood pressure hyper-reactivity. OBJECTIVE To investigate the effect of an aerobic exercise program (AEP) on blood pressure in individuals with blood pressure hyper-reactivity (BPH). METHODS Ten male volunteers with BPH, aged 45 ± 10 years, referred to as the experimental group (EG), took part in an AEP on a treadmill, 3 times a week for two months. They were compared to 14 men with BPH, aged 48 ± 8 years, referred to as the control group (CG), who remained sedentary. The subjects were evaluated before and after the AEP by stress test for comparison purposes. We evaluated the initial, peak and test-end heart rates (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP). RESULTS There a significant decrease in the initial SBP (-5%; p=0.01), initial DBP (-4.6%; p=0.01), peak SBP (-12.4%; p=0.001), peak DBP (-14.7%; p=0.03), final SBP (-4.6%, p=0.03) in the EG. The CG continued with its hyper-reactive behavior, which evolved to more exaggerated levels when the results before and after the study were compared (p<0.04). In the HR, there was an increase only in the final HR, of 11.3 bpm, after training (p=0.02). The test-peak VO2 increased by 4.4 ml.kg(-1) x min(-1) in the EG (p=0.01) and remained similar in the CG. CONCLUSION The AEP normalized the behavior of the blood pressure hyper-reactivity in sedentary men.
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Cardiopulmonary responses to treadmill and cycle ergometry exercise in patients with peripheral vascular disease.
Tuner, SL, Easton, C, Wilson, J, Byrne, DS, Rogers, P, Kilduff, LP, Kingsmore, DB, Pitsiladis, YP
Journal of vascular surgery. 2008;(1):123-30
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BACKGROUND Peripheral arterial disease (PAD) presenting as intermittent claudication (IC) is routinely assessed as the distance or time walked to the onset of pain, which often occurs before significant cardiopulmonary stress and is subject to confounding factors such as increased body mass and altered gait. Thus, where exercise-induced cardiovascular stress is desirable, such as in cardiac stress testing or clinical trials, an alternative modality of exercise is required. Cycling will circumvent several of the associated problems of treadmill walking and may provide an alternative preferable method of exercise, although there is limited information on the physiologic response of patients with PAD to cycling. This study compared the peak cardiorespiratory responses and the repeatability of cycling and treadmill exercise in patients with PAD. METHODS Ten men (mean age, 54 +/- 10 years) with stable IC completed two incremental exercise tests to the limit of tolerance on a treadmill and a cycle ergometer after familiarization with the outcome measures of exercise duration, work performed, respiratory gas exchange variables using continuous breath-by-breath measurement, heart rate, and ratings of perceived pain. RESULTS Both methods of exercise assessment revealed high reproducibility in terms of absolute claudication time (treadmill, r = 0.95; cycle, r = 0.91), time to volitional fatigue (treadmill, r = 0.96; cycle, r = 0.91), and cardiopulmonary exercise responses such as the lactate threshold (treadmill, r = 0.95; cycle, r = 0.94), peak heart rate (treadmill, r = 0.94; cycle, r = 0.96), and peak oxygen uptake (treadmill, r = 0.98; cycle, r = 0.87). Cycling induced significantly higher cardiopulmonary responses (peak heart rate, peak carbon dioxide output, peak minute ventilation, and respiratory exchange ratio) than treadmill exercise. There was no difference in time to volitional fatigue or in absolute claudication time between exercise modalities. CONCLUSION These results demonstrate that exercise testing using cycling offers an alternative method of cardiopulmonary testing for patients with IC that is equally reliable and reproducible to treadmill walking. Cycling may be preferable to treadmill exercise because it induces greater cardiopulmonary and metabolic responses and is better tolerated by patients.