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Biomedical subjects

A L Gómez

Publications and source records attributed to A L Gómez.

18 recordsLinked to original sources
PubMed2003

Influence of muscle strength and total work on exercise-induced plasma growth hormone isoforms in women.

The purpose of this investigation was to determine the influence of physical strength and the ability to do more total work on human growth hormone (GH) variants to a heavy resistance exercise protocol in untrained women. From a distribution of 100 healthy, untrained women, the strongest 10 women (S) and the weakest 10 women (W) were compared for GH responses pre- and post an acute heavy resistance exercise test (AHRET, 6 sets of 10 RM squats, 2 minutes rest between sets). Blood samples were obtained pre-exercise and immediately post-exercise and subsequently analysed in total as well as fractionated by Sephacryl S-100R column chromatography into three molecular weight size classes: fraction A: > 60 kD, fraction B: 30-60 kD, fraction C: < 30 kD. For each total sample as well as each fraction, immunoreactive GH was measured via the Nichols IRMA, while bioactive GH was measured via the hypox rat tibial line bioassay and Diagnostic Systems Laboratory's immunofunctional GH ELISA. No exercise-induced changes or differences between groups were observed in the tibial line bioassay. However, the S group displayed a significantly higher pre-exercise resting value in the total fraction than the W group. Conversely, the W group exhibited a significantly higher pre-exercise value in the smaller molecular weight fraction C. With regards to the immunofunctional and immunoreactive assays, the total fraction, fraction A, and fraction B demonstrated significant (P < or = 0.05) exercise-induced increases in both the S and W group despite no group differences. For the Nichols and immunofunctional assays significant exercise-induced changes were observed in the smaller molecular weight C fraction in the W group but not the S group. However, the S group displayed a significantly higher pre-exercise value in fraction C relative to the W group. These data demonstrate for the first time that differences exist in the GH molecular weight variants between strong and weak untrained women, with the lower molecular weight variants seemingly less responsive to greater amounts of exercise in stronger women, thus suggesting differential regulation of GH molecular weight variants during resistance exercise due to pre-existing physical parameters.

Animals↗
PubMed2002

Effects of an 8-week weight-loss program on cardiovascular disease risk factors and regional body composition.

OBJECTIVE: To determine the influence of weight loss on multiple cardiovascular disease (CVD) risk factors. DESIGN: Overweight women (n = 12; mean 44.2% fat) and men (n = 10; mean 30.7% fat) participated in an 8 week weight-loss program that included dietary, exercise, multi-vitamin/mineral supplementation, and behavior modification components. Measurement of total and regional body composition assessed using dual energy X-ray absorptiometry (DEXA), circumferences and blood sampling for total cholesterol, LDL cholesterol, HDL cholesterol, triacylglycerols, homocysteine, insulin and leptin were performed before and after the weight loss intervention. RESULTS: Subjects increased their physical activity and decreased their energy intake, resulting in a mean decrease in body mass of - 4.3 +/- 3.4 kg in women and -4.7 +/- 3.1 kg in men. Fat accounted for 88 and 58% of the decrease in body mass in men and women, respectively. Proportionally, men lost significantly more fat mass from the trunk region compared to women. Serum total and LDL cholesterol were significantly decreased in men (-11 and -14%, respectively) but not women (-3 and -3%, respectively) and there were no changes in HDL cholesterol and triacylglycerols. Serum leptin was significantly decreased (-36%) and highly correlated to fat mass (r= 0.839). There were no changes in serum insulin and plasma homocysteine. CONCLUSIONS: These data indicate that short-term weight loss resulting from reducing percentage energy from fat, increasing physical activity and vitamin/mineral supplements including folic acid has a favorable effect on regional body composition and total and LDL cholesterol with minimal effects on HDL cholesterol, triacylglycerols, homocysteine and insulin and the effects are greater in men compared to women. Supplementation with folic acid or emphasis on folic acid-rich foods may be an important component of a weight loss program to prevent increases in homocysteine.

Absorptiometry, Photon↗
PubMed2001

Effects of a high-fat diet on postabsorptive and postprandial testosterone responses to a fat-rich meal.

Postprandial testosterone concentrations have been shown to significantly decrease after a fat-rich meal, which may be due to inhibition of testosterone production by chylomicrons. We examined the effects of a high-fat diet known to reduce postprandial chylomicrons on the testosterone response to a fat-rich meal. Total testosterone (TT), free testosterone (FT), cortisol, and insulin responses to a high-fat test meal containing 5.44 MJ (1,300 kcal, 11% carbohydrate, 3% protein, 86% fat) were determined before (week 0) and after (week 8) an 8-week high-fat diet (64% fat) in 11 healthy men. The high-fat diet resulted in significant reductions in postabsorptive and postprandial serum triacylglycerols (55% and 50%, respectively). There were no significant changes in postabsorptive serum TT, FT, and cortisol, but insulin concentrations were significantly (P < or = .05) lower at week 8 (-28%). There was a significant reduction 1 hour after the fat-rich meal for TT (-22%) and FT (-23%), which remained significantly below baseline for 8 hours. Postprandial TT and FT responses were not significantly different after the 8-week high-fat diet. Postprandial serum cortisol concentrations were significantly reduced 1 hour after the meal. There were no significant differences before and after the high-fat diet. Insulin was significantly increased at the 0-, 1-, and 2-hour postprandial time points before and after the high-fat diet. Compared with week 0, insulin concentrations were significantly lower prior to and immediately after the fat-rich meal at week 8. These data indicate a fat-rich meal results in a prolonged reduction in TT and FT concentrations that is not altered by lowering postprandial chylomicrons. Alternative mechanisms (eg, higher uptake at the receptor level of cells) other than chylomicron-induced or insulin-induced inhibition of steroidogenesis are likely responsible for the reduction in TT and FT after a fat-rich meal.

Administration, Oral↗
PubMed2001

Resistance training combined with bench-step aerobics enhances women's health profile.

PURPOSE: The purpose of this study was to investigate the comprehensive physiological alterations that take place during the combination of bench-step aerobics (BSA) and resistance exercise training. METHODS: Thirty-five healthy, active women were randomly assigned to one of four groups that either a) performed 25 min of BSA only (SA25); b) performed a combination of 25 min of BSA and a multiple-set upper and lower body resistance exercise program (SAR); c) performed 40 min of BSA only (SA40); or d) served as a control group (C), only performing activities of daily living. Direct assessments for body composition, aerobic fitness, muscular strength, endurance, power, and cross-sectional area were performed 1 wk before and after 12 wk of training. RESULTS: All training groups significantly improved peak VO(2) (3.7 to 5.3 mL O(2).kg(-1).min(-1)), with the greatest improvement observed in the SAR group (P = 0.05). Significant reductions in preexercise heart rates (8-9 bpm) and body fat percent (5--6%) were observed in all training groups after training. Significant reductions in resting diastolic blood pressure were observed for the SAR and SA40 groups (6.7 and 5.8 mm Hg, respectively). Muscular strength and endurance only improved significantly in the SAR group (21 and 11% respectively). All groups demonstrated increased lower body power (11--14%), but only the SAR group significantly improved upper body power (32%). Thigh muscle cross-sectional areas measured via magnetic resonance imaging (MRI) increased primarily for the SAR group. CONCLUSION: BSA is an exercise modality effective for improving physical fitness and body composition in healthy women. The addition of resistance exercise appears to enhance the total fitness profile by improving muscular performances, muscle morphology, and cardiovascular fitness greater than from performing BSA alone. Therefore, the inclusion of both modalities to an exercise program is most effective for improving total body fitness and a woman's health profile.

Adult↗
PubMed2001

Low-volume circuit versus high-volume periodized resistance training in women.

PURPOSE: The purpose of this investigation was to determine the long-term training adaptations associated with low-volume circuit-type versus periodized high-volume resistance training programs in women. METHODS: 34 healthy, untrained women were randomly placed into one of the following groups: low-volume, single-set circuit (SSC; N = 12); periodized high-volume multiple-set (MS; N = 12); or nonexercising control (CON) group (N = 10). The SSC group performed one set of 8-12 repetitions to muscular failure 3 d x wk(-1). The MS group performed two to four sets of 3-15 repetitions with periodized volume and intensity 4 d x wk(-1). Muscular strength, power, speed, endurance, anthropometry, and resting hormonal concentrations were determined pretraining (T1), after 12 wk (T2), and after 24 wk of training (T3). RESULTS: 1-RM bench press and leg press, and upper and lower body local muscular endurance increased significantly (P < or = 0.05) at T2 for both groups, but only MS showed a significant increase at T3. Muscular power and speed increased significantly at T2 and T3 only for MS. Increases in testosterone were observed for both groups at T2 but only MS showed a significant increase at T3. Cortisol decreased from T1 to T2 and from T2 to T3 in MS. Insulin-like growth factor-1 increased significantly at T3 for SSC and at T2 and T3 for MS. No changes were observed for growth hormone in any of the training groups. CONCLUSION: Significant improvements in muscular performance may be attained with either a low-volume single-set program or a high-volume, periodized multiple-set program during the first 12 wk of training in untrained women. However, dramatically different training adaptations are associated with specific domains of training program design which contrast in speed of movement, exercise choices and use of variation (periodization) in the intensity and volume of exercise.

Adaptation, Physiological↗
PubMed2001

Effect of resistance training on women's strength/power and occupational performances.

PURPOSE: The effects of resistance training programs on strength, power, and military occupational task performances in women were examined. METHODS: Untrained women aged (mean +/- SD) 23 +/- 4 yr were matched and randomly placed in total- (TP, N = 17 and TH, N = 18) or upper-body resistance training (UP, N = 18 and UH, N = 15), field (FLD, N = 14), or aerobic training groups (AER, N = 11). Two periodized resistance training programs (with supplemental aerobic training) emphasized explosive exercise movements using 3- to 8-RM training loads (TP, UP), whereas the other two emphasized slower exercise movements using 8- to 12-RM loads (TH, UH). The FLD group performed plyometric and partner exercises. Subjects were tested for body composition, strength, power, endurance, maximal and repetitive box lift, 2-mile loaded run, and U.S. Army Physical Fitness Tests before (T0) and after 3 (T3) and 6 months of training (T6). For comparison, untrained men (N = 100) (MEN) were tested once. RESULTS: Specific training programs resulted in significant increases in body mass (TP), 1-RM squat (TP, TH, FLD), bench press (all except AER), high pull (TP), squat jump (TP, TH, FLD), bench throw (all except AER), squat endurance (all except AER), 1-RM box lift (all except aerobic), repetitive box lift (all), push-ups (all except AER), sit-ups (all except AER), and 2-mile run (all). CONCLUSIONS: Strength training improved physical performances of women over 6 months and adaptations in strength, power, and endurance were specific to the subtle differences (e.g., exercise choice and speeds of exercise movement) in the resistance training programs (strength/power vs strength/hypertrophy). Upper- and total-body resistance training resulted in similar improvements in occupational task performances, especially in tasks that involved upper-body musculature. Finally, gender differences in physical performance measures were reduced after resistance training in women, which underscores the importance of such training for physically demanding occupations.

Adolescent↗
PubMed2001

Physiological responses to short-term exercise in the heat after creatine loading.

PURPOSE: This investigation was designed to examine the influence of creatine (Cr) supplementation on acute cardiovascular, renal, temperature, and fluid-regulatory hormonal responses to exercise for 35 min in the heat. METHODS: Twenty healthy men were matched and then randomly assigned to consume 0.3 g.kg(-1) Cr monohydrate (N = 10) or placebo (N = 10) for 7 d in a double-blind fashion. Before and after supplementation, both groups cycled for 30 min at 60-70% VO2(peak) immediately followed by three 10-s sprints in an environmental chamber at 37 degrees C and 80% relative humidity. RESULTS: Body mass was significantly increased (0.75 kg) in Cr subjects. Heart rate, blood pressure, and sweat rate responses to exercise were not significantly different between groups. There were no differences in rectal temperature responses in either group. Sodium, potassium, and creatinine excretion rates obtained from 24-h and exercise urine collection periods were not significantly altered in either group. Serum creatinine was elevated in the Cr group but within normal ranges. There were significant exercise-induced increases in cortisol, aldosterone, renin, angiotensin I and II, atrial peptide, and arginine vasopressin. The aldosterone response was slightly greater in the Cr (263%) compared with placebo (224%) group. Peak power was greater in the Cr group during all three 10-s sprints after supplementation and unchanged in the placebo group. There were no reports of adverse symptoms, including muscle cramping during supplementation or exercise. CONCLUSION: Cr supplementation augments repeated sprint cycle performance in the heat without altering thermoregulatory responses.

Adult↗
PubMed2001

Influence of compression therapy on symptoms following soft tissue injury from maximal eccentric exercise.

STUDY DESIGN: A between groups design was used to compare recovery following eccentric muscle damage under 2 experimental conditions. OBJECTIVE: To determine if a compression sleeve donned immediately after maximal eccentric exercise would enhance recovery of physical function and decrease symptoms of soreness. BACKGROUND: Prior investigations using ice, intermittent compression, or exercise have not shown efficacy in relieving symptoms of delayed onset muscle soreness (DOMS). To date, no study has shown the effect of continuous compression on DOMS, yet this would offer a low cost intervention for patients suffering with the symptoms of DOMS. METHODS AND MEASURES: Twenty nonimpaired non-strength-trained women participated in the study. Subjects were matched for age, anthropometric data, and one repetition maximum concentric arm curl strength and then randomly placed into a control group (n = 10) or an experimental compression sleeve group (n = 10). Subjects were instructed to avoid pain-relieving modalities (eg, analgesic medications, ice) throughout the study. The experimental group wore a compressive sleeve garment for 5 days following eccentric exercise. Subjects performed 2 sets of 50 passive arm curls with the dominant arm on an isokinetic dynamometer with a maximal eccentric muscle action superimposed every fourth passive repetition. One repetition maximum elbow flexion, upper arm circumference, relaxed elbow angle, blood serum cortisol, creatine kinase, lactate dehydrogenase, and perception of soreness questionnaires were collected prior to the exercise bout and daily thereafter for 5 days. RESULTS: Creatine kinase was significantly elevated from the baseline value in both groups, although the experimental compression test group showed decreased magnitude of creatine kinase elevation following the eccentric exercise. Compression sleeve use prevented loss of elbow motion, decreased perceived soreness, reduced swelling, and promoted recovery of force production. CONCLUSIONS: Results from this study underline the importance of compression in soft tissue injury management.

Adolescent↗
PubMed2001

Safety measures of L-carnitine L-tartrate supplementation in healthy men.

The purpose of this investigation was to examine the effects of ingestion of L-CARNIPURE (L-carnitine L-tartrate [LCLT]) on alterations in a complete blood cell profile and in circulating metabolic enzymes. Using a balanced, placebo (P), cross-over design (1 week washout), 10 healthy, active men volunteered and acted as their own control taking either a P or LCLT supplement (3 g.day(-1)) for 3 weeks. Postabsorptive morning blood samples were obtained both before and after 21 days of P and LCLT supplementation. Serum samples were analyzed for clinical chemistries including a complete chemistry panel with markers of liver and renal function along with various minerals and electrolytes. In addition, whole blood was analyzed for a complete blood count with differential. It was determined that there were no statistically significant differences between the LCLT and the placebo conditions for any of the variables examined. The results of this study suggest that LCLT, when used as a dietary supplement, has no adverse effects on metabolic and hematological safety variables in normally healthy men.

Adult↗
PubMed2000

The effects of 10 days of spaceflight on the shuttle Endeavor on predominantly fast-twitch muscles in the rat.

The primary purpose of this investigation was to determine the effects of microgravity on muscle fibers of the predominantly fast-twitch muscles in the rat. Cross sectional area and myosin heavy chain (MHC) composition were assessed in order to establish the acute effects of microgravity associated with spaceflight. The extensor digitorum longus (EDL) and gastrocnemius muscles were removed from 12 male Fisher 344 rats which had undergone 10 days of spaceflight aboard the space shuttle Endeavor and from 12 age- and weight-matched control animals. Both groups of animals received similar amounts of food and water and were synchronized for photoperiods, environmental temperature, and humidity. Significant (P < 0.05) reductions in muscle fiber size were observed in the gastrocnemius (fiber types I, IIA, IIDB, and IIB) and EDL (fiber type IIB) muscles after spaceflight. Significant MHC isoform transformations also resulted during this brief period of microgravity exposure with a significant decrease in MHC IId isoform in the EDL muscle. A significant decrease was also observed in the MHC IId isoform in the superficial (white) component of the gastrocnemius muscle after spaceflight, although no alterations in MHC profile were demonstrated in the deep (red) component of this muscle. These findings highlight the rapid plasticity of skeletal muscle during short-term spaceflight. If such pronounced adaptations to spaceflight also occur in humans, then astronauts are likely to suffer severe decrements in skeletal muscle performance with long-term space flight and upon return to earth after both short- and long-term missions. Thus, countermeasures aimed at slowing or even preventing muscle fiber atrophy are warranted.

Animals↗
PubMed2000

Fasting lipoprotein and postprandial triacylglycerol responses to a low-carbohydrate diet supplemented with n-3 fatty acids.

BACKGROUND: The effects of a prolonged low-carbohydrate diet rich in n-3 fatty acids on blood lipid profiles have not been addressed in the scientific literature. OBJECTIVE: This study examined the effects of an eight-week ketogenic diet rich in n-3 fatty acids on fasting serum lipoproteins and postprandial triacylglycerol (TG) responses. DESIGN: Ten men consumed a low-carbohydrate diet rich in monounsaturated fat (MUFA) and supplemented with n-3 fatty acids for eight weeks. Fasting blood samples were collected before and after one week of habitual diet and on two consecutive days after 2, 4, 6 and 8 weeks of the intervention diet. Postprandial TG responses to a fat-rich test meal were measured prior to and after the intervention diet. RESULTS: Compared to the habitual diet, subjects consumed significantly (p < or = 0.05) greater quantities of protein, fat, MUFA and n-3 fatty acids and significantly less total energy, carbohydrate and dietary fiber. Body weight significantly declined over the experimental period (-4.2+/-2.7 kg). Compared to baseline, fasting total cholesterol, LDL cholesterol and HDL cholesterol were not significantly different after the intervention diet (+1.5%, +9.7% and +10.0%, respectively). Fasting TG were significantly reduced after the intervention diet (-55%). There was a significant reduction in peak postprandial TG (-42%) and TG area under the curve (-48%) after the intervention diet. CONCLUSIONS: A hypocaloric low-carbohydrate diet rich in MUFA and supplemented with n-3 fatty acids significantly reduced postabsorptive and postprandial TG in men that were not hypertriglyceridemic as a group before the diet. This may be viewed as a clinically significant positive adaptation in terms of cardiovascular risk status. However, transient increases in total cholesterol and LDL cholesterol were also evident and should be examined further in regard to which particular subfractions are elevated.

Adult↗
PubMed2000

The influence of direct supervision of resistance training on strength performance.

PURPOSE: The purpose of this study was to compare changes in maximal strength, power, and muscular endurance after 12 wk of periodized heavy-resistance training directly supervised by a personal trainer (SUP) versus unsupervised training (UNSUP). METHODS: Twenty moderately trained men aged 24.6 +/- 1.0 yr (mean +/- SE) were randomly assigned to either the SUP group (N = 10) or the UNSUP group (N = 8). Both groups performed identical linear periodized resistance training programs consisting of preparatory (10-12 repetitions maximum (RM)), hypertrophy (8 to 10-RM), strength (5 to 8-RM), and peaking phases (3 to 6-RM) using free-weight and variable-resistance machine exercises. Subjects were tested for maximal squat and bench press strength (1-RM), squat jump power output, bench press muscular endurance, and body composition at week 0 and after 12 wk of training. RESULTS: Mean training loads (kg per set) per week were significantly (P < 0.05) greater in the SUP group than the UNSUP group at weeks 7 through 11 for the squat, and weeks 3 and 7 through 12 for the bench press exercises. The rates of increase (slope) of squat and bench press kg per set were significantly greater in the SUP group. Maximal squat and bench press strength were significantly greater at week 12 in the SUP group. Squat and bench press 1-RM, and mean and peak power output increased significantly after training in both groups. Relative local muscular endurance (80% of 1-RM) was not compromised in either group despite significantly greater loads utilized in bench press muscular endurance testing after training. Body mass, fat mass, and fat-free mass increased significantly after training in the SUP group. CONCLUSION: Directly supervised, heavy-resistance training in moderately trained men resulted in a greater rate of training load increase and magnitude which resulted in greater maximal strength gains compared with unsupervised training.

Adolescent↗
PubMed2000

Influence of compression hosiery on physiological responses to standing fatigue in women.

PURPOSE: The purpose of this investigation was to examine the influence of various designs of commercial hosiery, which use graduated compression, on the physiological and performance responses to standing fatigue. METHODS: Twelve healthy women (age = 23.0+/-2.1 yr, height = 165.7+/-5.0 cm, percent body fat = 22.6+/-4.2%, body mass = 60.0+/-8.9 kg) volunteered to participate in this investigation. All subjects completed four identical standing fatigue protocols with different garment conditions each separated by 7 d. The standing fatigue protocol involved a total of 8 h of standing on hard floors during which subjects participated in various tasks and experimental testing procedures. In addition, all activity and dietary profiles of the subjects were carefully controlled 48 h before each experimental session. Before the standing fatigue protocol, subjects completed a battery of tests to establish morning baseline values. Experimental tests included determination of lower leg venous cross-sectional area, blood pressure, heart rate, perceived discomfort ratings, circumferences measurements, total body water, variation in center of pressure during "quiet" standing, vertical jump performance, and specific regional patterns of foot pressures. RESULTS: This investigation demonstrated that commercial hosiery with various forms of graduated compression and construction were effective in mediating a reduction in edema in the ankles and legs while reducing the amount of venous pooling and discomfort in the lower body. Different constructions of garments may mediate these overall effects via different physiological mechanisms related to fluid shifts and muscle tissue damage. CONCLUSION: Wearing various types of graduated compression hose during the day as it relates to women in standing professions may minimize edema and muscle tissue disruption, thereby increasing comfort in the legs.

Adult↗
PubMed2000

No effect of heavy resistance training and creatine supplementation on blood lipids.

In order to examine the effects of heavy resistance training and the influence of creatine supplementation on nonperformance measures of health status, 19 healthy resistance-trained men were matched and then randomly assigned in a double-blind fashion to either a creatine (n = 10) or placebo (n = 9) group. Periodized heavy resistance training was performed 3-4 times per week for 12 weeks. During the first week of training, creatine subjects consumed 25 g creatine monohydrate per day, while the placebo group ingested an equal number of placebo capsules. Five grams of supplement per day was consumed for the remainder of the study. Body composition, fasting serum creatinine, lipoproteins and triglycerides, and reported changes in body function were determined prior to and after 12 weeks of training and supplementation. After training, significant increases in body mass and fat-free mass were greater in creatine (5.2 and 4.3 kg, respectively) than placebo (3.0 and 2.1 kg, respectively) subjects. There was no change in percent body fat. Dietary energy and macronutrient distribution was not significantly different during Weeks 1 and 12. Serum creatinine was significantly elevated in creatine subjects after 1 (11.6%) and 12 weeks (13.8%); however, values were within normal limits for healthy men. There were no effects of training or supplementation on serum total cholesterol, HDL-cholesterol, LDL-cholesterol, or triglycerides. In healthy men, a 12-week heavy resistance training program, with or without creatine supplementation, did not significantly influence serum lipid profiles, subjective reports of body functioning, or serum creatinine concentrations.

Adult↗
PubMed2000

Effects of exercise and alkalosis on serum insulin-like growth factor I and IGF-binding protein-3.

This investigation examines the effects of orally induced alkalosis on serum IGF-I and IGFBP3 concentrations in response to an acute 90-s bout of high intensity cycle exercise. Ten healthy, active men, ages 24.60 +/- 4.90 years, participated in a randomized, double-blind, counterbalanced trial order with a cross-over design. Subjects ingested an experimental bicarbonate solution or a placebo solution. Blood was sampled at baseline; pre-exercise; and 0, 5, 10, and 30 min postexercise. The pH between groups for pre-exercise and postexercise time points differed significantly (p < or = .05) in the experimental condition (from 7.42 +/- 0.01 to 7.35 +/- 0.02) versus the placebo condition (from 7.36 +/- 0.01 to 7.25 +/- 0.03). Increases in IGF-I over resting conditions occurred with placebo conditions at 5 and 10 min postexercise and in the experimental condition at 5 min postexercise. Concentrations of IGFBP3 were elevated above baseline at IP in both experimental and placebo conditions.

Adolescent↗
PubMed1999

Performance and muscle fiber adaptations to creatine supplementation and heavy resistance training.

PURPOSE: The purpose of this study was to examine the effect of creatine supplementation in conjunction with resistance training on physiological adaptations including muscle fiber hypertrophy and muscle creatine accumulation. METHODS: Nineteen healthy resistance-trained men were matched and then randomly assigned in a double-blind fashion to either a creatine (N = 10) or placebo (N = 9) group. Periodized heavy resistance training was performed for 12 wk. Creatine or placebo capsules were consumed (25 g x d(-1)) for 1 wk followed by a maintenance dose (5 g x d(-1)) for the remainder of the training. RESULTS: After 12 wk, significant (P < or = 0.05) increases in body mass and fat-free mass were greater in creatine (6.3% and 6.3%, respectively) than placebo (3.6% and 3.1%, respectively) subjects. After 12 wk, increases in bench press and squat were greater in creatine (24% and 32%, respectively) than placebo (16% and 24%, respectively) subjects. Compared with placebo subjects, creatine subjects demonstrated significantly greater increases in Type I (35% vs 11%), IIA (36% vs 15%), and IIAB (35% vs 6%) muscle fiber cross-sectional areas. Muscle total creatine concentrations were unchanged in placebo subjects. Muscle creatine was significantly elevated after 1 wk in creatine subjects (22%), and values remained significantly greater than placebo subjects after 12 wk. Average volume lifted in the bench press during training was significantly greater in creatine subjects during weeks 5-8. No negative side effects to the supplementation were reported. CONCLUSION: Creatine supplementation enhanced fat-free mass, physical performance, and muscle morphology in response to heavy resistance training, presumably mediated via higher quality training sessions.

Adaptation, Physiological↗
PubMedDate not supplied

The effect of heavy resistance exercise on the circadian rhythm of salivary testosterone in men.

Circadian rhythms of serum testosterone concentrations in men have been shown, in general, to be highest in the morning and lowest in the evening. Thus, the purpose of this investigation was to determine the effects of acute resistance exercise upon the waking circadian rhythm of salivary testosterone over 2 days (with or without resistance exercise). The subjects included ten resistance-trained men (with at least 1 year of lifting experience) with the following characteristics [mean (SD)]: age 21.6 (1.1) years; height 177.8 (9.5) cm; body mass 80.5 (11.5) kg; percent body fat 7.9 (1.7)%. A matched, randomized, crossover study design was used such that each subject was tested under both the resistance exercise and control (no exercise) conditions. The resistance exercise protocol consisted of ten exercises performed for three sets of ten repetitions maximum with 2 min of rest between sets. Saliva sample 1 was collected at 0615 hours and resistance exercise began immediately afterwards at approximately 0620 hours, and sample 2 was collected at 0700 hours, which corresponded approximately to a mid-exercise (or control) time point. Saliva samples were then obtained every hour on the hour from 0800 hours until 2200 hours. No significant differences were observed between the exercise and resting conditions for salivary testosterone, with the exception of a significant decrease at 0700 hours during the resistance exercise protocol. The results of this investigation indicate that resistance exercise does not affect the circadian pattern of salivary testosterone secretion over a 16-h waking period in resistance-trained men.

Adult↗