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1.
J Dairy Sci ; 88(7): 2295-301, 2005 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-15956292

RESUMEN

We conducted 2 studies to determine the effect of vitamin D-fortified cheese on vitamin D status and the bioavailability of vitamin D in cheese. The first study was designed to determine the effect of 2 mo of daily consumption of vitamin D3-fortified (600 IU/d) process cheese on serum 25-hydroxyvitamin D (25-OHD), parathyroid hormone (PTH), and osteocalcin (OC) concentrations among 100 older (> or =60 yr) men and women. Participants were randomized to receive vitamin D-fortified cheese, nonfortified cheese, or no cheese. Serum levels of 25-OHD, PTH, and OC were measured at the beginning and end of the study. There were no differences in 25-OHD, PTH, or OC after 2 mo of fortified cheese intake. The vitamin D-fortified cheese group had a greater decrease in 25-OHD than other groups, due to higher baseline 25-OHD. A second study was conducted to determine whether the bioavailability of vitamin D2 in cheese (delivering 5880 IU of vitamin D2/56.7-g serving) and water (delivering 32,750 IU/250 mL) is similar and whether absorption differs between younger and older adults. The second study was a crossover trial involving 2 groups of 4 participants each (younger and older group) that received single acute feedings of either vitamin D2-fortified cheese or water. Serial blood measurements were taken over 24 h following the acute feeding. Peak serum vitamin D and area under the curve were similar between younger (23 to 50 yr) and older (72 to 84 yr) adults, and vitamin D2 was absorbed more efficiently from cheese than from water. These studies demonstrated that vitamin D in fortified process cheese is bioavailable, and that young and older adults have similar absorption. Among older individuals, consuming 600 IU of vitamin D3 daily from cheese for 2 mo was insufficient to increase serum 25-OHD during limited sunlight exposure.


Asunto(s)
Envejecimiento , Queso/análisis , Alimentos Fortificados/análisis , Estado Nutricional , Vitamina D/farmacocinética , Absorción , Anciano , Disponibilidad Biológica , Calcifediol/sangre , Colecalciferol/administración & dosificación , Colecalciferol/farmacocinética , Estudios Cruzados , Método Doble Ciego , Ergocalciferoles/administración & dosificación , Ergocalciferoles/farmacocinética , Femenino , Humanos , Masculino , Persona de Mediana Edad , Osteocalcina/sangre , Hormona Paratiroidea/sangre , Luz Solar
2.
Int J Vitam Nutr Res ; 71(5): 293-301, 2001 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-11725694

RESUMEN

The effectiveness of a nutritional supplement designed to enhance serum testosterone concentrations and prevent the formation of dihydrotestosterone and estrogens from the ingested androgens was investigated in healthy 30- to 59-year old men. Subjects were randomly assigned to consume DION (300 mg androstenedione, 150 mg dehydroepiandrosterone, 540 mg saw palmetto, 300 mg indole-3-carbinol, 625 mg chrysin, and 750 mg Tribulus terrestris per day; n = 28) or placebo (n = 27) for 28 days. Serum free testosterone, total testosterone, androstenedione, dihydrotestosterone, estradiol, prostate-specific antigen (PSA), and lipid concentrations were measured before and throughout the 4-week supplementation period. Serum concentrations of total testosterone and PSA were unchanged by supplementation. DION increased (p < 0.05) serum androstenedione (342%), free testosterone (38%), dihydrotestosterone (71%), and estradiol (103%) concentrations. Serum HDL-C concentrations were reduced by 5.0 mg/dL in DION (p < 0.05). Increases in serum free testosterone (r2 = 0.01), androstenedione (r2 = 0.01), dihydrotestosterone (r2 = 0.03), or estradiol (r2 = 0.07) concentrations in DION were not related to age. While the ingestion of androstenedione combined with herbal products increased serum free testosterone concentrations in older men, these herbal products did not prevent the conversion of ingested androstenedione to estradiol and dihydrotestosterone.


Asunto(s)
Adyuvantes Inmunológicos/uso terapéutico , Androstenodiona/uso terapéutico , Deshidroepiandrosterona/uso terapéutico , Suplementos Dietéticos , Hormonas Esteroides Gonadales/sangre , Fitoterapia , Preparaciones de Plantas/uso terapéutico , Adulto , Factores de Edad , Análisis de Varianza , Método Doble Ciego , Humanos , Masculino , Persona de Mediana Edad , Testosterona/sangre
3.
J Strength Cond Res ; 15(4): 491-7, 2001 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-11726262

RESUMEN

The purpose of this study was to determine the effect of beta-hydroxy beta-methylbutyrate (HMB) supplementation on maximal oxygen consumption (.V(O)(2)peak) and the onset of blood lactate accumulation (OBLA) in endurance-trained cyclists. Eight cyclists randomly (double blind) completed 3 2-week supplementation periods (HMB, 3g.day(-1); leucine [LEU], 3g.day(-1); placebo [CON], 3g.day(-1)) followed by a 2-week washout period. Testing consisted of a graded cycle ergometry test to measure .V(O)(2)peak and OBLA, the .V(O)(2) at 2 mM blood lactate. .V(O)(2)peak was unaffected by HMB (4.0 +/- 1.4%), LEU (-1.9 +/- 1.3%), and CON (-2.6 +/- 2.6%). HMB resulted in a greater time to reach .V(O)(2)peak, whereas LEU and CON did not affect this time (HMB, 3.6 +/- 1.5 min, LEU, -1.2 +/- 1.5 min; CON, -3.6 +/- 3.5 min). Lactate accumulation peak was unaffected by supplementation (HMB, 8.1 +/- 1.1 mM; LEU, 6.2 +/- 0.8 mM; CON, 7.5 +/- 1.3 mM). OBLA increased with HMB (9.1 +/- 2.4%) and LEU (2.1 +/- 1.5%), but not in the CON trial (0.75 +/- 2.1%). Blood glucose was significantly greater during the HMB trial compared with the LEU trial. It is concluded that HMB supplementation may have positive affects on performance by increasing the onset of blood lactate accumulation; however, the mechanism is unknown.


Asunto(s)
Ciclismo/fisiología , Lactatos/sangre , Consumo de Oxígeno/efectos de los fármacos , Resistencia Física/efectos de los fármacos , Valeratos/farmacología , Adulto , Umbral Anaerobio/efectos de los fármacos , Análisis de Varianza , Glucemia/efectos de los fármacos , Estudios Cruzados , Suplementos Dietéticos , Método Doble Ciego , Ejercicio Físico/fisiología , Hematócrito , Hemoglobinas/efectos de los fármacos , Humanos , Leucina/administración & dosificación , Masculino , Educación y Entrenamiento Físico/métodos , Factores de Tiempo , Valeratos/sangre
4.
Int J Sport Nutr Exerc Metab ; 11(3): 384-96, 2001 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-11599506

RESUMEN

This investigation evaluated the effects of oral beta-hydroxy-beta-methylbutyrate (HMB) supplementation on training responses in resistance-trained male athletes who were randomly administered HMB in standard encapsulation (SH), HMB in time release capsule (TRH), or placebo (P) in a double-blind fashion. Subjects ingested 3 g x day(-1) of HMB or placebo for 6 weeks. Tests were conducted pre-supplementation and following 3 and 6 weeks of supplementation. The testing battery assessed body mass, body composition (using dual energy x-ray absorptiometry), and 3-repetition maximum isoinertial strength, plus biochemical parameters, including markers of muscle damage and muscle protein turnover. While the training and dietary intervention of the investigation resulted in significant strength gains (p < .001) and an increase in total lean mass (p = .01), HMB administration had no influence on these variables. Likewise, biochemical markers of muscle protein turnover and muscle damage were also unaffected by HMB supplementation. The data indicate that 6 weeks of HMB supplementation in either SH or TRH form does not influence changes in strength and body composition in response to resistance training in strength-trained athletes.


Asunto(s)
Composición Corporal/efectos de los fármacos , Suplementos Dietéticos , Ejercicio Físico , Contracción Muscular/efectos de los fármacos , Valeratos/uso terapéutico , Adulto , Análisis de Varianza , Método Doble Ciego , Metabolismo Energético/efectos de los fármacos , Humanos , Masculino , Educación y Entrenamiento Físico
5.
J Am Coll Nutr ; 20(5): 520-8, 2001 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-11601567

RESUMEN

OBJECTIVE: The effectiveness of an androgenic nutritional supplement designed to enhance serum testosterone concentrations and prevent the formation of dihydrotestosterone and estrogen was investigated in healthy 3 to 58 year old men. DESIGN: Subjects were randomly assigned to consume a nutritional supplement (AND-HB) containing 300-mg androstenediol, 480-mg saw palmetto, 450-mg indole-3-carbinol, 300-mg chrysin, 1,500 mg gamma-linolenic acid and 1.350-mg Tribulus terrestris per day (n = 28), or placebo (n = 27) for 28 days. Subjects were stratified into age groups to represent the fourth (30 year olds, n = 20), fifth (40 year olds, n = 20) and sixth (50 year olds, n = 16) decades of life. MEASUREMENTS: Serum free testosterone, total testosterone, androstenedione, dihydrotestosterone, estradiol, prostate specific antigen and lipid concentrations were measured before supplementation and weekly for four weeks. RESULTS: Basal serum total testosterone, estradiol, and prostate specific antigen (PSA) concentrations were not different between age groups. Basal serum free testosterone concentrations were higher (p < 0.05) in the 30- (70.5 +/- 3.6 pmol/L) than in the 50 year olds (50.8 +/- 4.5 pmol/L). Basal serum androstenedione and dihydrotestosterone (DHT) concentrations were significantly higher in the 30- (for androstenedione and DHT, respectively, 10.4 +/- 0.6 nmol/L and 2198.2 +/- 166.5 pmol/L) than in the 40- (6.8 +/- 0.5 nmol/L and 1736.8 +/- 152.0 pmol/L) or 50 year olds (6.0 +/- 0.7 nmol/L and 1983.7 +/- 147.8 pmol/L). Basal serum hormone concentrations did not differ between the treatment groups. Serum concentrations of total testosterone and PSA were unchanged by supplementation. Ingestion of AND-HB resulted in increased (p < 0.05) serum androstenedione (174%), free testosterone (37%), DHT (57%) and estradiol (86%) throughout the four weeks. There was no relationship between the increases in serum free testosterone, androstenedione, DHT, or estradiol and age (r2 = 0.08, 0.03, 0.05 and 0.02, respectively). Serum HDL-C concentrations were reduced (p < 0.05) by 0.14 mmol/L in AND-HB. CONCLUSIONS: These data indicate that ingestion of androstenediol combined with herbal products does not prevent the formation of estradiol and dihydrotestosterone.


Asunto(s)
Anabolizantes/administración & dosificación , Androstenodiol/administración & dosificación , Suplementos Dietéticos , Estradiol/sangre , Testosterona/sangre , Administración Oral , Adulto , Factores de Edad , Androstenodiona/sangre , HDL-Colesterol/sangre , LDL-Colesterol/sangre , Método Doble Ciego , Humanos , Masculino , Persona de Mediana Edad , Placebos , Antígeno Prostático Específico/sangre , Factores de Tiempo
6.
J Nutr ; 131(7): 2049-52, 2001 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-11435528

RESUMEN

Studies in young adults have demonstrated that beta-hydroxy-beta-methylbutyrate (HMB) can increase gains in strength and fat-free mass during a progressive resistance-training program. The purpose of this study was to determine whether HMB would similarly benefit 70-y-old adults undergoing a 5 d/wk exercise program. Thirty-one men (n = 15) and women (n = 16) (70 +/- 1 y) were randomly assigned in a double-blind study to receive either capsules containing a placebo or Ca-HMB (3 g/d) for the 8-wk study. Skin fold estimations of body composition as well as computerized tomography (CT) and dual X-ray absorptiometry (DXA) scans were measured before the study and immediately after the 8-wk training program. HMB supplementation tended to increase fat-free mass gain (HMB, 0.8 +/- 0.4 kg; placebo, -0.2 +/- 0.3 kg; treatment x time, P = 0.08). Furthermore, HMB supplementation increased the percentage of body fat loss (skin fold: HMB, -0.66 +/- 0.23%; placebo, -0.03 +/- 0.21%; P = 0.05) compared with the placebo group. CT scans also indicated a greater decrease in the percentage of body fat with HMB supplementation (P < 0.05). In conclusion, changes in body composition can be accomplished in 70-y-old adults participating in a strength training program, as previously demonstrated in young adults, when HMB is supplemented daily.


Asunto(s)
Envejecimiento/fisiología , Composición Corporal/efectos de los fármacos , Músculo Esquelético/efectos de los fármacos , Valeratos/farmacología , Levantamiento de Peso , Absorciometría de Fotón , Tejido Adiposo , Anciano , Suplementos Dietéticos , Método Doble Ciego , Femenino , Humanos , Masculino , Placebos , Grosor de los Pliegues Cutáneos , Tomografía Computarizada por Rayos X
7.
J Clin Endocrinol Metab ; 85(11): 4074-80, 2000 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-11095435

RESUMEN

In young men, chronic ingestion of 100 mg androstenedione (ASD), three times per day, does not increase serum total testosterone but does increase serum estrogen and ASD concentrations. We investigated the effects of ASD ingestion in healthy 30- to 56-yr-old men. In a double-blind, randomly assigned manner, subjects consumed 100 mg ASD three times daily (n = 28), or placebo (n = 27) for 28 days. Serum ASD, dihydrotestosterone (DHT), free and total testosterone, estradiol, prostate-specific antigen (PSA), and lipid concentrations were measured at week 0 and each week throughout the supplementation period. Serum total testosterone and PSA concentrations did not change with supplementation. Elevated serum concentrations of ASD (300%), free testosterone (45%), DHT (83%), and estradiol (68%) were observed during weeks 1-4 in ASD (P < 0.05). There was no relationship between age and changes in serum ASD (r2 = 0.024), free testosterone (r2 = 0.00), or estradiol (r2 = 0.029) concentrations with ASD, whereas the serum DHT response to ASD ingestion was related to age (r2 = 0.244; P < 0.05). Serum concentrations of high-density lipoprotein cholesterol were decreased by 10% during the supplementation period (P < 0.05). These results suggest that the ingestion of 100 mg ASD, three times per day, does not increase serum total testosterone or PSA concentrations but does elicit increases in ASD, free testosterone, estradiol, and DHT and decreases serum high-density lipoprotein cholesterol concentrations.


Asunto(s)
Afecto , Androstenodiona/sangre , Androstenodiona/farmacología , Testosterona/sangre , Administración Oral , Adulto , Factores de Edad , Androstenodiona/administración & dosificación , Colesterol/sangre , HDL-Colesterol/sangre , LDL-Colesterol/sangre , Método Doble Ciego , Estradiol/sangre , Humanos , Masculino , Persona de Mediana Edad , Placebos , Antígeno Prostático Específico/sangre , Factores de Tiempo
8.
Int J Sport Nutr Exerc Metab ; 10(3): 340-59, 2000 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-10997957

RESUMEN

The effects of androgen precursors, combined with herbal extracts designed to enhance testosterone formation and reduce conversion of androgens to estrogens was studied in young men. Subjects performed 3 days of resistance training per week for 8 weeks. Each day during Weeks 1, 2, 4, 5, 7, and 8, subjects consumed either placebo (PL; n = 10) or a supplement (ANDRO-6; n = 10), which contained daily doses of 300 mg androstenedione, 150 mg DHEA, 750 mg Tribulus terrestris, 625 mg Chrysin, 300 mg Indole-3-carbinol, and 540 mg Saw palmetto. Serum androstenedione concentrations were higher in ANDRO-6 after 2, 5, and 8 weeks (p <.05), while serum concentrations of free and total testosterone were unchanged in both groups. Serum estradiol was elevated at Weeks 2, 5, and 8 in ANDRO-6 (p <.05), and serum estrone was elevated at Weeks 5 and 8 (p <.05). Muscle strength increased (p <.05) similarly from Weeks 0 to 4, and again from Weeks 4 to 8 in both treatment groups. The acute effect of one third of the daily dose of ANDRO-6 and PL was studied in 10 men (23 +/- 4 years). Serum androstenedione concentrations were elevated (p <.05) in ANDRO-6 from 150 to 360 min after ingestion, while serum free or total testosterone concentrations were unchanged. These data provide evidence that the addition of these herbal extracts to androstenedione does not result in increased serum testosterone concentrations, reduce the estrogenic effect of androstenedione, and does not augment the adaptations to resistance training.


Asunto(s)
Adaptación Fisiológica/efectos de los fármacos , Androstenodiona/farmacología , Deshidroepiandrosterona/farmacología , Fitoterapia , Testosterona/sangre , Adulto , Andrógenos , Androstenodiona/administración & dosificación , Antropometría , Antioxidantes/administración & dosificación , Antioxidantes/farmacología , HDL-Colesterol/efectos de los fármacos , Deshidroepiandrosterona/administración & dosificación , Método Doble Ciego , Antagonistas de Estrógenos/administración & dosificación , Antagonistas de Estrógenos/farmacología , Flavonoides/administración & dosificación , Flavonoides/farmacología , Humanos , Indoles/administración & dosificación , Indoles/farmacología , Masculino , Músculo Esquelético/fisiología , Extractos Vegetales/administración & dosificación , Extractos Vegetales/farmacología , Rosales , Serenoa , Levantamiento de Peso
9.
J Nutr ; 130(8): 1937-45, 2000 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10917905

RESUMEN

The leucine metabolite, beta-hydroxy-beta-methylbutyrate (HMB) enhances the effects of exercise on muscle size and strength. Although several reports in animals and humans indicate that HMB is safe, quantitative safety data in humans have not been reported definitively. The objective of this work was to summarize safety data collected in nine studies in which humans were fed 3 g HMB/d. The studies were from 3 to 8 wk in duration, included both males and females, young and old, exercising or nonexercising. Organ and tissue function was assessed by blood chemistry and hematology; subtle effects on emotional perception were measured with an emotional profile test (Circumplex), and tolerance of HMB was assessed with a battery of 32 health-related questions. HMB did not adversely affect any surrogate marker of tissue health and function. The Circumplex emotion profile indicated that HMB significantly decreased (improved) one indicator of negative mood (Unactivated Unpleasant Affect category, P < 0.05). No untoward effects of HMB were indicated. Compared with the placebo, HMB supplementation resulted in a net decrease in total cholesterol (5.8%, P < 0.03), a decrease in LDL cholesterol (7.3%, P < 0.01) and a decrease in systolic blood pressure (4.4 mm Hg, P < 0.05). These effects of HMB on surrogate markers of cardiovascular health could result in a decrease in the risk of heart attack and stroke. In conclusion, the objective data collected across nine experiments indicate that HMB can be taken safely as an ergogenic aid for exercise and that objective measures of health and perception of well-being are generally enhanced.


Asunto(s)
Enfermedades Cardiovasculares/prevención & control , Suplementos Dietéticos , Valeratos/farmacología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores , Suplementos Dietéticos/efectos adversos , Evaluación de Medicamentos , Emociones/efectos de los fármacos , Ejercicio Físico , Femenino , Humanos , Pruebas de Función Hepática , Masculino , Persona de Mediana Edad , Cooperación del Paciente , Distribución Aleatoria , Factores de Riesgo , Valeratos/efectos adversos
10.
J Appl Physiol (1985) ; 87(6): 2274-83, 1999 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-10601178

RESUMEN

This study examined the effects of acute dehydroepiandrosterone (DHEA) ingestion on serum steroid hormones and the effect of chronic DHEA intake on the adaptations to resistance training. In 10 young men (23 +/- 4 yr old), ingestion of 50 mg of DHEA increased serum androstenedione concentrations 150% within 60 min (P < 0.05) but did not affect serum testosterone and estrogen concentrations. An additional 19 men (23 +/- 1 yr old) participated in an 8-wk whole body resistance-training program and ingested DHEA (150 mg/day, n = 9) or placebo (n = 10) during weeks 1, 2, 4, 5, 7, and 8. Serum androstenedione concentrations were significantly (P < 0.05) increased in the DHEA-treated group after 2 and 5 wk. Serum concentrations of free and total testosterone, estrone, estradiol, estriol, lipids, and liver transaminases were unaffected by supplementation and training, while strength and lean body mass increased significantly and similarly (P < 0.05) in the men treated with placebo and DHEA. These results suggest that DHEA ingestion does not enhance serum testosterone concentrations or adaptations associated with resistance training in young men.


Asunto(s)
Adaptación Fisiológica/efectos de los fármacos , Deshidroepiandrosterona/farmacología , Educación y Entrenamiento Físico , Testosterona/sangre , Levantamiento de Peso/fisiología , Administración Oral , Adulto , Antropometría , Dieta , Método Doble Ciego , Prueba de Tolerancia a la Glucosa , Histocitoquímica , Hormonas/sangre , Humanos , Insulina/sangre , Masculino , Músculo Esquelético/enzimología , Músculo Esquelético/fisiología
11.
JAMA ; 281(21): 2020-8, 1999 Jun 02.
Artículo en Inglés | MEDLINE | ID: mdl-10359391

RESUMEN

CONTEXT: Androstenedione, a precursor to testosterone, is marketed to increase blood testosterone concentrations as a natural alternative to anabolic steroid use. However, whether androstenedione actually increases blood testosterone levels or produces anabolic androgenic effects is not known. OBJECTIVES: To determine if short- and long-term oral androstenedione supplementation in men increases serum testosterone levels and skeletal muscle fiber size and strength and to examine its effect on blood lipids and markers of liver function. DESIGN AND SETTING: Eight-week randomized controlled trial conducted between February and June 1998. PARTICIPANTS: Thirty healthy, normotestosterogenic men (aged 19-29 years) not taking any nutritional supplements or androgenic-anabolic steroids or engaged in resistance training. INTERVENTIONS: Twenty subjects performed 8 weeks of whole-body resistance training. During weeks 1, 2, 4, 5, 7, and 8, the men were randomized to either androstenedione, 300 mg/d (n = 10), or placebo (n = 10). The effect of a single 100-mg androstenedione dose on serum testosterone and estrogen concentrations was determined in 10 men. MAIN OUTCOME MEASURES: Changes in serum testosterone and estrogen concentrations, muscle strength, muscle fiber cross-sectional area, body composition, blood lipids, and liver transaminase activities based on assessments before and after short- and long-term androstenedione administration. RESULTS: Serum free and total testosterone concentrations were not affected by short- or long-term androstenedione administration. Serum estradiol concentration (mean [SEM]) was higher (P<.05) in the androstenedione group after 2 (310 [20] pmol/L), 5 (300 [30] pmol/L), and 8 (280 [20] pmol/L) weeks compared with presupplementation values (220 [20] pmol/L). The serum estrone concentration was significantly higher (P<.05) after 2 (153 [12] pmol/L) and 5 (142 [15] pmol/L) weeks of androstenedione supplementation compared with baseline (106 [11] pmol/L). Knee extension strength increased significantly (P<.05) and similarly in the placebo (770 [55] N vs 1095 [52] N) and androstenedione (717 [46] N vs 1024 [57] N) groups. The increase of the mean cross-sectional area of type 2 muscle fibers was also similar in androstenedione (4703 [471] vs 5307 [604] mm2; P<.05) and placebo (5271 [485] vs 5728 [451] mm2; P<.05) groups. The significant (P<.05) increases in lean body mass and decreases in fat mass were also not different in the androstenedione and placebo groups. In the androstenedione group, the serum high-density lipoprotein cholesterol concentration was reduced after 2 weeks (1.09 [0.08] mmol/L [42 (3) mg/dL] vs 0.96 [0.08] mmol/L [37 (3) mg/dL]; P<.05) and remained low after 5 and 8 weeks of training and supplementation. CONCLUSIONS: Androstenedione supplementation does not increase serum testosterone concentrations or enhance skeletal muscle adaptations to resistance training in normotestosterogenic young men and may result in adverse health consequences.


Asunto(s)
Androstenodiona/farmacología , Ejercicio Físico/fisiología , Músculo Esquelético/efectos de los fármacos , Testosterona/sangre , Administración Oral , Adulto , Análisis de Varianza , Androstenodiona/administración & dosificación , Androstenodiona/metabolismo , Biopsia con Aguja , Composición Corporal , Suplementos Dietéticos , Método Doble Ciego , Estrógenos/sangre , Humanos , Lípidos/sangre , Pruebas de Función Hepática , Masculino , Fibras Musculares Esqueléticas/patología , Músculo Esquelético/patología , Evaluación Nutricional , Transaminasas/metabolismo
12.
Int J Sport Nutr ; 7(4): 298-309, 1997 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-9407256

RESUMEN

The purpose of this study was to determine if amino acid supplementation influences blood and muscle lactate response to exercise and the time course of the metabolic adaptations to training. Two groups of untrained males (n = 7 each) were given (double-blind) a daily supplement (2.9 g.day-1) containing a mixture of leucine, isoleucine, valine, glutamine, and carnitine (EXP) or 3 g.day-1 of lactose (CON). Following 7 days of supplementation there was no significant change in VO2peak, time to exhaustion (TTX) at 120% VO2peak, or muscle and blood lactate in either EXP or CON. Subjects then initiated 6 weeks of combined aerobic and anaerobic training on a Monark cycle ergometer. It was found that amino acid supplementation had no effect on either blood or muscle lactate accumulation during exercise, while supplementation resulted in a faster adaptation in buffer capacity. Performance during intense exercise was not improved with amino acid supplementation.


Asunto(s)
Adaptación Fisiológica , Aminoácidos/administración & dosificación , Ciclismo , Ejercicio Físico/fisiología , Resistencia Física , Adulto , Humanos , Concentración de Iones de Hidrógeno , Cinética , Ácido Láctico/sangre , Ácido Láctico/metabolismo , Lactosa/administración & dosificación , Masculino , Músculo Esquelético/metabolismo , Consumo de Oxígeno , Factores de Tiempo
13.
Int J Sport Nutr ; 4(3): 280-8, 1994 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-7987362

RESUMEN

This study examined the effects of 14 days of L-carnitine supplementation on muscle and blood carnitine fractions, and muscle and blood lactate concentrations, during high-intensity sprint cycling exercise. Eight subjects performed three experimental trials: control I (CON I, Day 0), control II (CON II, Day 14), and L-carnitine (L-CN, Day 28). Each trial consisted of a 4-min ride at 90% VO2max, followed by a rest period of 20 min, and then five repeated 1-min rides at 115% VO2max (2 min rest between each). Following CON II, all subjects began dietary supplementation of L-carnitine for a period of 14 days (4 g/day). Plasma total acid soluble and free carnitine concentrations were significantly higher (p < .05) at all time points following supplementation. L-carnitine supplementation had no significant effect on muscle carnitine content and thus could not alter lactate accumulation during exercise.


Asunto(s)
Ciclismo/fisiología , Carnitina/análisis , Carnitina/farmacología , Lactatos/análisis , Lactatos/sangre , Músculo Esquelético/química , Músculo Esquelético/efectos de los fármacos , Equilibrio Ácido-Base/efectos de los fármacos , Adulto , Alcalosis/sangre , Alcalosis/fisiopatología , Carnitina/administración & dosificación , Carnitina/sangre , Prueba de Esfuerzo , Humanos , Concentración de Iones de Hidrógeno , Masculino , Consumo de Oxígeno/fisiología , Descanso/fisiología , Factores de Tiempo
14.
Med Sci Sports Exerc ; 26(9): 1122-9, 1994 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-7808246

RESUMEN

This study investigated the effects of L-carnitine supplementation on muscle carnitine and glycogen content during submaximal exercise (EX). Triglycerides were evaluated by a fat feeding (90 g fat) and 3 h later subjects cycled for 60 min at 70% VO2max (CON). Muscle biopsies were obtained preexercise and after 30 and 60 min of EX. Blood samples were taken prior to and every 15 min of exercise. Subjects randomly completed two additional trials following 7 and 14 d of carnitine supplementation (6 g.d-1). During one of the two trials, subjects received 2000 units of heparin 15 min prior to EX to elevate FFA (CNhep); no heparin was administered during the other trial (CN). There were no differences in VO2, respiratory exchange ratio, heart rate, or g.min-1 of CHO and fat oxidized among the three trials. At rest serum total acid soluble (TASC) and free (FC) carnitine increased with supplementation (TASC; CON, 71.3 +/- 2.9; CN, 92.8 +/- 5.4; CNhep, 109.8 +/- 3.5 mumol.l-1) (FC; CON, 44.1 +/- 2.7; CN, 66.1 +/- 5.3; CNhep, 77.1 +/- 4.1 mumol.l-1). During EX, TASC remained stable, while FC decreased and short-chain acylcarnitine (SCAC) increased (P < 0.05). Muscle carnitine concentration at rest was unaffected by supplementation. During EX, muscle TASC did not change, FC decreased, and SCAC increased significantly in all three trials. Pre-EX and post-EX muscle glycogens were not different. Increased availability of serum carnitine does not result in an increase in muscle carnitine content nor does it alter lipid oxidation. It appears that there is an adequate amount of carnitine present within the mitochondria to support lipid oxidation.


Asunto(s)
Carnitina/administración & dosificación , Ejercicio Físico/fisiología , Glucógeno/metabolismo , Músculo Esquelético/metabolismo , Adulto , Carnitina/metabolismo , Carnitina/farmacocinética , Metabolismo Energético , Humanos , Metabolismo de los Lípidos , Masculino , Mitocondrias Musculares/metabolismo , Consumo de Oxígeno
15.
Int J Sports Med ; 15(4): 181-5, 1994 May.
Artículo en Inglés | MEDLINE | ID: mdl-8063466

RESUMEN

To examine the effects of L-carnitine supplementation on short high-intensity exercise, twenty male collegiate swimmers completed two trials separated by seven days. Each trial consisted of five 91.4 m (100 yd) swims with a two minute rest interval between each bout. Following the first trial subjects were evenly and randomly assigned to either an L-carnitine (LC) group or a placebo (PL) group. The LC group ingested 2 grams L-carnitine in a citrus drink twice daily for 7 days, while the PL group received only the citrus drink during the same time period. Performance times were recorded for each repeat during both trials. Blood samples (5 ml) were obtained from an antecubital vein 1 minute following the interval set. Blood pH, base excess (BE), lactate (LA), carnitine and carnitine fractions were measured. Total serum carnitine was significantly (p < 0.05) elevated (75.9 +/- 2.0 vs. 106.4 +/- 3.5 mumol.l-1) in the LC group following treatment, while the PL group was unchanged (79.5 +/- 2.8 vs. 77.6 +/- 5.3 mumol.l-1). Free and short-chain serum carnitine fractions were also increased (p < 0.05) in the LC group, but were not altered in the PL group. No differences in performance times were observed between trials or between groups. Blood pH, LA and BE revealed a similar response in both groups during each trial. Despite the elevation in serum L-carnitine and carnitine fractions, these results indicate that L-carnitine supplementation does not provide an ergogenic benefit during repeated bouts of high-intensity anaerobic exercise in highly trained swimmers.


Asunto(s)
Carnitina/farmacología , Ejercicio Físico/fisiología , Natación/fisiología , Adulto , Análisis Químico de la Sangre , Carnitina/sangre , Humanos , Concentración de Iones de Hidrógeno , Lactatos/sangre , Ácido Láctico , Masculino
16.
J Appl Physiol (1985) ; 75(4): 1513-8, 1993 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-8282597

RESUMEN

Elevated plasma fatty acids have been shown to spare muscle glycogen during exercise. However, on the basis of recent findings, the saturation of fatty acids may influence this response. The purpose of this study was to determine whether saturated or unsaturated fatty acids affected muscle glycogenolysis to varying degrees during cycle exercise. Five healthy men completed three 60-min cycle ergometer trials (EX) at approximately 70% maximal O2 uptake (VO2max). Triglyceride levels were elevated by a fat feeding (FF) composed of 90% saturated fatty acids (heavy whipping cream, 90 g) or by the infusion of Intralipid (IL; Clintec Nutrition; 45 ml/h of 20% IL, 9.0 g), which was 85% unsaturated. A control trial (CON) consisted of a light breakfast (43 g carbohydrate and 1 g fat). Heparin (2,000 U) was administered 15 min before EX in FF and IL trials, resulting in one- and threefold increases in free fatty acid (FFA) levels in IL and FF, respectively. Pre-EX muscle glycogen did not differ. The utilization of muscle glycogen during 60 min of EX was less (P < 0.05) during the FF (60.0 +/- 5.2 mmol/kg wet wt) and IL (58.6 +/- 6.2 mmol/kg wet wt) compared with CON (81.8 +/- 7.5 mmol/kg wet wt). There was no difference between FF and IL in the amount of glycogen utilized. Serum triglyceride levels were greater (P < 0.05) at preheparin in FF (1.58 +/- 0.37 mmol/l) and IL (0.98 +/- 0.13 mmol/l) compared with CON (0.47 +/- 0.14 mmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)


Asunto(s)
Grasas de la Dieta/farmacología , Ejercicio Físico/fisiología , Emulsiones Grasas Intravenosas/farmacología , Glucógeno/metabolismo , Músculos/metabolismo , Adulto , Ciclismo , Glucemia/metabolismo , Ácidos Grasos/farmacología , Ácidos Grasos Insaturados/farmacología , Glicerol/sangre , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Masculino , Músculos/efectos de los fármacos , Consumo de Oxígeno/efectos de los fármacos , Triglicéridos/sangre
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