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1.
Am J Physiol Heart Circ Physiol ; 321(3): H532-H541, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34328346

RESUMO

Adverse childhood experiences (ACEs) are psychosocial stressors that occur during sensitive developmental windows and are associated with increased lifetime cardiovascular disease (CVD) risk in a dose-dependent manner. Vascular endothelial dysfunction is a pathophysiological mechanism that promotes hypertension and CVD and may be a mechanism by which ACEs contribute to lifetime CVD risk. We examined whether exposure to ACEs is associated with reduced vascular endothelial function (VEF) in otherwise healthy, young adult women (20.7 ± 3 yr) with (ACE+) versus without (ACE-) ACEs, explored whether differences in circulating sirtuin 1 (SIRT1) or systemic oxidative stress could explain ACEs-related differences in VEF, and examined the ability of a pilot, 8-wk exercise intervention to augment VEF and SIRT1 or reduce oxidized LDL cholesterol (oxLDL) in ACE+ young adult women. Forty-two otherwise healthy young adults completed this study. Prior to the intervention, VEF (P = 0.002) and SIRT1 (P = 0.004) were lower in the ACE+ than ACE- group, but oxLDL concentrations were not different (P = 0.77). There were also significant relationships (P ≤ 0.04) among flow-mediated dilation (FMD), SIRT1, and oxLDL in the ACE+, but not ACE- group. Adjusting for circulating SIRT1 and oxLDL reduced the differences in FMD observed between groups (P = 0.10), but only SIRT1 was a significant adjuster of the means (P < 0.05). Finally, the exercise intervention employed was unable to enhance VEF or SIRT1 in the ACE+ exercise group. Our data suggest that ACEs likely increase susceptibility to hypertension and CVD by causing endothelial dysfunction, perhaps through a SIRT1 pathway-related mechanism.NEW & NOTEWORTHY Our study provides novel evidence that young adult women with moderate-to-severe adverse childhood experience (ACE) exposure present impaired endothelial function and lower circulating sirtuin 1 (SIRT1) concentrations than age-matched controls. However, an 8-wk exercise intervention was unable to augment endothelial function or SIRT1 concentrations in a subset of those with ACEs. Our data suggest that ACEs-related impairments in endothelial function may be secondary to decreased NO bioavailability via SIRT1 and/or oxidative stress-related mechanisms.


Assuntos
Experiências Adversas da Infância , Endotélio Vascular/metabolismo , Estresse Oxidativo , Sirtuína 1/genética , Estresse Psicológico/metabolismo , Adolescente , Adulto , Idoso , Endotélio Vascular/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Sirtuína 1/metabolismo , Estresse Psicológico/etiologia , Estresse Psicológico/fisiopatologia
2.
J Hum Kinet ; 67: 133-142, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31523312

RESUMO

Sensing carbohydrates via the oral cavity benefits performance outcomes during brief high intensity bouts of exercise. However, the extent to which carbohydrates need to be present in the oral cavity to influence sprint performance is less understood. The purpose of this study was to determine if serial increases in carbohydrate rinse time across sprint sets attenuates increases in sprint time compared to no serial increases in carbohydrate rinse time across sprint sets. Fifteen sprint trained participants completed three repeated anaerobic sprint tests (RAST), 3 sets of 6 x 35-m sprints, under two different carbohydrate mouth rinsing (CMR) conditions; (1) rinsing for only 5 seconds (s), and (2) rinsing for 5 s, 10 s and 15 s (serial rinse). Prior to a RAST, participants provided perceived recovery status (PRS) and perceived feeling of arousal (FAS). Upon completion of each individual sprint, participants gave a rating of perceived exertion (RPE). A lactate sample was taken upon completion of each individual sprint set and after all 3 RASTs a session rating of perceived exertion (S-RPE) was measured. There were no significant differences in peak (p = 0.18) and average sprint time (p = 0.41). There were no significant differences in perceptual measures: RPE, PRS, FAS, S-RPE or for blood lactate concentration between CMR conditions. Overall, serial rinsing resulted in changes that were most likely trivial, but showed a 50% chance in perceiving a sprint session as less difficult. Rinsing carbohydrates in a serial manner between repeated sprint sets produces trivial changes of sprint speed and perceptual measures from sprint performance.

3.
J Electromyogr Kinesiol ; 48: 121-127, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31344640

RESUMO

OBJECTIVE: The purpose was two-fold: (1) to examine differences in maximal voluntary isometric torque (MVIT) production, and electromyographic signal amplitude (EMGAMP) and mean power frequency (EMGMPF) values obtained during traditional (MVICTRAD), rapid (MVICRAPID), and ramp (MVICRAMP) maximal voluntary isometric contractions, and (2) to determine if there were differences in the reliability of MVIT, EMGAMP and EMGMPF among the three MVIC types. APPROACH: Twenty-two young males and females completed MVICTRAD, MVICRAPID, and MVICRAMP muscle actions on two separate visits separated by 48 h. During all MVICs, MVIT and EMGAMP and EMGMPF of the vastus lateralis (VL) and rectus femoris (RF) were quantified. MAIN RESULTS: MVIT was greater during MVICTRAD and MVICRAPID than during MVITRAMP (both p < 0.001). VL and RF EMGAMP were greater during MVICRAMP than during MVICRAPID (p = 0.02 and 0.004). For EMGMPF, there were no significant differences among MVIC types. Although all MVIC types generally resulted in reliable measurements of MVIT and EMGAMP, reliability was stronger for EMGMPF quantified during the MVICRAMP. SIGNIFICANCE: Investigators may choose MVIC type based on preference or equipment availability. However, investigators should note that MVICRAMP contractions will likely yield the greatest EMGAMP values and more reliable measurements of VL and RF EMGMPF.


Assuntos
Eletromiografia/métodos , Contração Isométrica , Adulto , Eletromiografia/normas , Feminino , Humanos , Masculino , Músculo Esquelético/fisiologia , Valores de Referência , Reprodutibilidade dos Testes , Torque
4.
Nutrients ; 11(5)2019 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-31100881

RESUMO

BACKGROUND: Postprandial lipemia (PPL) is a cardiovascular disease risk factor. However, the effects of different fat sources on PPL remain unclear. We aimed to determine the postprandial response in triglycerides (TG) to four dietary fat sources in adults. METHODS: Participants completed four randomized meal trials. For each meal trial, participants (n = 10; 5M/5F) consumed a high-fat meal (HFM) (13 kcal/kg; 61% of total kcal from fat) with the fat source derived from butter, coconut oil, olive oil, or canola oil. Blood was drawn hourly for 6 h post-meal to quantify PPL. RESULTS: Two-way ANOVA of TG revealed a time effect (p < 0.0001), but no time-meal interaction (p = 0.56), or meal effect (p = 0.35). Meal trials did not differ with regard to TG total (p = 0.33) or incremental (p = 0.14) area-under-the-curve. When stratified by sex and the TG response was averaged across meals, two-way ANOVA revealed a time effect (p < 0.0001), time-group interaction (p = 0.0001), and group effect (p = 0.048), with men exhibiting a greater response than women, although this difference could be attributed to the pronounced difference in BMI between men and women within the sample. CONCLUSION: In our sample of young adults, postprandial TG responses to a single HFM comprised of different fat sources did not differ.


Assuntos
Gorduras na Dieta/metabolismo , Ácidos Graxos Monoinsaturados/administração & dosagem , Ácidos Graxos/administração & dosagem , Lipídeos/sangue , Período Pós-Prandial , Adolescente , Adulto , Peso Corporal , Exercício Físico , Feminino , Análise de Alimentos , Humanos , Masculino , Adulto Jovem
5.
J Strength Cond Res ; 33(4): 1007-1019, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30789573

RESUMO

Muddle, TWD, Magrini, MA, Colquhoun, RJ, Luera, MJ, Tomko, PM, and Jenkins, NDM. Impact of fatiguing, submaximal high- vs. low-torque isometric exercise on acute muscle swelling, and echo intensity in resistance-trained men. J Strength Cond Res 33(4): 1007-1019, 2019-To evaluate the effects of repeated, fatiguing isometric knee extension contractions performed at high-torque (HT) vs. low-torque (LT) maximal voluntary isometric contraction (MVIC) on acute muscle swelling, and echo intensity (EI) of the rectus femoris (RF) and vastus lateralis (VL) muscles in resistance-trained males. Twenty-two resistance-trained men performed either HT (70% MVIC) or LT (30% MVIC) isometric contractions to fatigue on separate days. Before and after exercise, muscle cross-sectional area (mCSA) and EI of the RF and VL were assessed through ultrasound. Muscle cross-sectional area and EI (collapsed across muscle) increased similarly after HT (mean ± 95% confidence interval: mCSAΔ: 3.52 ± 0.52 cm; EIΔ: 4.58 ± 1.65 au) and LT (mCSAΔ: 3.61 ± 0.59 cm; EIΔ: 3.30 ± 1.36 au) exercise. No relationships between mCSAΔ and time to task failure (TTF), normalized MVIC, or the tension-time integral were observed during either HT or LT exercise. During both conditions, EIΔ was related to TTF (HT: r = 0.44; LT: r = 0.66) and normalized MVIC (HT: r = -0.60; LT: r = -0.57). These results suggest that acute muscle swelling and increased EI observed in response to intermittent, submaximal, fatiguing isometric exercise are similar for the RF and VL and are not dependent on the torque-level or tension-time integral when exercise is performed to failure. Factors such as the duration of time performing exercise and relative muscle strength may influence the magnitude of change in EI, but not acute muscle swelling, during intermittent fatiguing isometric exercise.


Assuntos
Edema/etiologia , Exercício Físico/fisiologia , Contração Isométrica/fisiologia , Fadiga Muscular/fisiologia , Músculo Quadríceps/fisiologia , Adulto , Humanos , Masculino , Esforço Físico/fisiologia , Músculo Quadríceps/diagnóstico por imagem , Distribuição Aleatória , Treinamento de Força , Torque , Ultrassonografia , Adulto Jovem
6.
Ultrasound ; 26(4): 214-221, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30479636

RESUMO

Introduction: The purpose of this investigation was to: (1) to determine the reliability of rectus femoris muscle cross-sectional area and echo intensity obtained using panoramic ultrasound imaging during seated and supine lying positions before and after a 5-minute rest period and (2) to determine the influence of body position and rest period on the magnitude of rectus femoris muscle cross-sectional area and echo intensity measurements. Methods: A total of 23 males and females (age = 21.5 ± 1.9 years) visited the laboratory on two separate occasions. During each visit, panoramic ultrasound images of the rectus femoris were obtained in both a seated and a supine position before (T1) and after a 5-minute (T2) rest period to quantify any potential changes in either muscle cross-sectional area and/or echo intensity. Results: None of the muscle cross-sectional area or echo intensity measurements exhibited systematic variability, and the ICCs were 0.98-0.99 and 0.88-0.91, and the coefficients of variation were ≤ 3.9% and ≤ 8.2% for muscle cross-sectional area and echo intensity, respectively. Our results indicated that muscle cross-sectional area was greater in the seated than supine position, whereas echo intensity was greater in the supine position. Further, echo intensity increased in the seated position from T1 to T2. Conclusion: Both rectus femoris muscle cross-sectional area and echo intensity may be reliably measured in either a seated or supine lying position before or after a 5-minute rest period. Aside from echo intensity in the seated position, rest period had no influence on the magnitude of muscle cross-sectional area or echo intensity. Comparison of muscle cross-sectional area values that are obtained in different body positions is ill-advised.

7.
J Neurophysiol ; 120(6): 3131-3139, 2018 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-30355024

RESUMO

Decomposition of the surface electromyographic (sEMG) signal is commonly used to examine motor unit (MU) firing behavior. However, the intra- and inter-day reliability of these measurements has yet to be quantified or reported. This investigation 1) examined the effect of input excitation on the mean firing rate (MFR) vs. recruitment threshold (RT) relationship and 2) determined the inter- and intra-day reliability of the MFR vs. RT relationship at 30%, 50%, and 70% of maximum voluntary isometric strength (MVIC). Twenty-eight healthy males (23 ± 3 yr) completed two experimental visits, during which they performed MVIC testing and isometric ramp contractions at 30%, 50%, and 70% MVIC. sEMG signals were recorded from the vastus lateralis during the ramp contractions and decomposed to establish the MFR vs. RT relationship for the detected MUs. Intra- and inter-day reliability was then established for the slopes and y-intercepts of the MFR vs. RT relationship at each contraction intensity. All participants displayed significant MFR vs. RT relationships ( r range: -0.662 to -0.999; P ≤ 0.001-0.006). Intra- and inter-day intraclass correlation coefficients (ICCs) ranged from 0.766-0.824 and 0.867-0.919 for the slopes and from 0.780-0.915 and 0.804-0.927 for the y-intercepts, respectively. Furthermore, the slope coefficient was significantly greater at 70% than at 30% MVIC, and the y-intercepts increased with increasing contraction intensities. Changes in input excitation to the MU pool alter the magnitude, but not the reliability, of the slopes and y-intercepts of the MFR vs. RT relationship. NEW & NOTEWORTHY The firing behavior of the motor unit (MU) pool is often characterized using the mean firing rate vs. recruitment threshold relationship of the active MUs. Although this relationship has been widely used, this is the first study to report the effects of input excitation (contraction intensity) on the intra- and inter-day reliability of this relationship. The criteria used for MU analysis and the model utilized in this study allow for generalization to outside investigators and laboratories.


Assuntos
Músculo Esquelético/fisiologia , Recrutamento Neurofisiológico , Adulto , Eletromiografia/normas , Potencial Evocado Motor , Humanos , Masculino , Músculo Esquelético/inervação
8.
Exp Physiol ; 103(12): 1645-1655, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30267546

RESUMO

NEW FINDINGS: What is the central question of this study? Does a common genetic variant in the ß2 -adrenergic receptor (ß2 -AR) have effects on skeletal muscle function in young, healthy men? What is the main finding and its importance? This study provides preliminary evidence that ß2 -AR Arg16Gly genotype has a significant effect on fat-free mass, muscle strength and motor unit behaviour in recreationally trained men. These data might have important clinical and exercise-related implications. For example, ß2 -AR (rs1042713) genotype might influence the responsiveness of skeletal muscle to clinical or exercise-based interventions or ß-AR agonist treatment. ABSTRACT: This study explored whether the ß2 -adrenergic receptor (ß2 -AR) single nucleotide polymorphism at amino acid 16 (Arg16Gly) has functional effects on skeletal muscle mass, torque production and motor unit behaviour in young, healthy men. Twenty-eight recreationally active men (mean ± SD 23.1 ± 1.3 years of age) were genotyped for Arg16Gly polymorphisms of ß2 -AR as arginine homozygous (ArgArg; n = 5), glycine homozygous (GlyGly; n = 11) or arginine-glycine heterozygous (ArgGly; n = 12). The participants then completed body composition testing, assessments of leg extensor size and echo intensity, and evoked and voluntary isometric leg-extension muscle actions. During the evoked muscle actions, peak twitch torque, peak rate of torque development and peak relaxation rate were assessed. During the voluntary muscle actions, maximal voluntary isometric (MVIC) strength was assessed, and surface EMG signals were obtained during submaximal isometric muscle actions and later decomposed to examine motor unit firing behaviour. Fat-free mass and MVIC strength were greater (P = 0.004, d = 1.74 and P = 0.026, d = 1.10, respectively) in those expressing the GlyGly versus ArgArg allele. The slope of the mean firing rate versus recruitment threshold relationship was more negative in the GlyGly than the ArgArg allele carriers (P = 0.012, d = 1.68) at 50% MVIC, but was less negative in GlyGly and ArgGly versus ArgArg allele carriers (P = 0.013 and 0.016, respectively; d = 1.34 and 1.20, respectively) at 70% MVIC. These data provide preliminary evidence that ß2 -AR Arg16Gly genotype has a significant effect on fat-free mass, muscle strength and motor unit behaviour in humans.


Assuntos
Arginina/genética , Glicina/genética , Neurônios Motores/fisiologia , Força Muscular/genética , Músculo Esquelético/fisiologia , Polimorfismo Genético/genética , Receptores Adrenérgicos beta 2/genética , Adulto , Alelos , Eletromiografia/métodos , Genótipo , Humanos , Masculino , Neurônios Motores/metabolismo , Força Muscular/fisiologia , Músculo Esquelético/metabolismo , Torque , Adulto Jovem
9.
J Electromyogr Kinesiol ; 42: 111-116, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30015134

RESUMO

OBJECTIVE: To determine if maximal isometric contraction (MVIC) method (i.e., ramp (MVICRAMP) versus traditional MVIC) influences (1) maximal voluntary isometric torque (MVIT) production of the knee extensors, (2) electromyographic signal amplitude (EMGAMP), and (3) EMG mean power frequency (EMGMPF) of the rectus femoris and vastus lateralis in moderately-to highly-activated subjects. We hypothesized that EMGAMP would be greater during the MVICRAMP than MVIC muscle contractions, but that there would be no difference in MVIT. APPROACH: Twenty-five males (23.4 ±â€¯3.4 y; % voluntary activation = 93.9 ±â€¯5.1%) visited the laboratory and completed MVICRAMPs and MVICs. During all contractions, leg extensor torque and sEMG signals from the vastus lateralis (VL) and rectus femoris (RF) were recorded. MAIN RESULTS: There was no significant difference in the MVIT produced (p = 0.65) or in EMGMPF (p = 0.052) during MVICRAMP versus MVIC. However, EMGAMP was 18.1% higher during the MVICRAMP than MVIC (p = 0.004). SIGNIFICANCE: Maximal isometric muscle contraction method significantly influenced EMGAMP, and had a moderate effect on EMGMPF (d = 0.49). Investigators who utilize MVICs to determine maximal EMG signal amplitude and frequency to normalize their EMG signals should be aware of these differences.


Assuntos
Eletromiografia/métodos , Contração Isométrica , Joelho/fisiologia , Adulto , Eletromiografia/normas , Humanos , Masculino , Músculo Esquelético/fisiologia , Valores de Referência , Torque
10.
Physiol Rep ; 6(5)2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29527830

RESUMO

Previous investigations have reported a relationship between skeletal muscle phenotype and motor unit (MU) firing parameters during submaximal contractions. The purpose of the current investigation, however, was to examine the relationships between motor unit firing behavior during a maximal voluntary contraction, Myosin Heavy Chain (MHC) isoform content, and various molecular neuromuscular targets of the vastus lateralis (VL) muscle in resistance-trained men. Ten resistance-trained males completed a trapezoidal ramp contraction up to 100% of their maximal voluntary isometric strength (MVIC). Surface electromyography was recorded from the VL using a multichannel electrode array and decomposed to examine the firing characteristics of individual MUs. A skeletal muscle biopsy of the VL was also collected from each subject. Regression analyses were performed to identify relationships between type II fiber area and the slopes and/or intercepts of the mean firing rate (FRMEAN ) versus recruitment threshold (RT), max firing rate (FRMAX ) versus RT, and RT versus MU action potential amplitude (MUAPPP ) relationships. There were significant inverse relationships between type II fiber area and the y-intercept of the FR versus RT relationship (P < 0.05). Additionally, strong relationships (r > 0.5) were found between type II fiber area and FRMEAN versus RT slope and RT versus MUAPPP slope and intercept. These data further support the hypothesis that skeletal muscle phenotype is related to MU behavior during isometric contraction. However, our data, in concert with previous investigations, may suggest that these relationships are influenced by the intensity of the contraction.


Assuntos
Contração Isométrica , Músculo Esquelético/fisiologia , Recrutamento Neurofisiológico , Potencial Evocado Motor , Humanos , Masculino , Músculo Esquelético/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Fenótipo , Adulto Jovem
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