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Biomedical subjects

S J Fleck

Publications and source records attributed to S J Fleck.

50 records · Page 3Linked to original sources
PubMed1989

Cardiac MRI of elite junior Olympic weight lifters.

Cardiac magnetic resonance imaging was performed on 14 junior elite Olympic weight lifters and 14 controls (means +/- Se, age = 18.4 +/- 0.5 and 17.8 +/- 0.4 years, weight = 76.5 +/- 3.6 and 78.8 +/- 3.3 kg, % fat = 6.5% +/- 0.8% and 11.5% +/- 1.7%, respectively). Controls were individually matched to the lifters to within 2 years of age and 2.5 kg of body weight. Systolic (S) and diastolic (D) left posterior wall thickness (LPW), left ventricular short axis (LSA), left ventricular transverse long axis (LLA), spetal wall thickness (SW), right ventricular wall thickness (RWT), and right ventricular short axis (RSA) were determined. Variables were examined in absolute (mm), relative to body surface area (BSA, mm/m2), total body weight (BW, mm/kg), and lean body mass (LBM, mm/kg) terms. In absolute terms S LPW (21.1 +/- 1.7 vs 13.3 +/- 0.5 mm), S SW (15.3 +/- 1.3 vs 11.7 +/- 0.6 mm), and D LLA (75.2 +/- 1.6 vs 69.1 +/- 2.4 mm) were significantly greater and S LSA (23.4 +/- 2.4 vs 36.7 +/- 2.3 mm) and S LLA (46.5 +/- 3.7 vs 58.2 +/- 3.8 mm) were significantly less in the lifters vs the controls. S LPW/BW, S LPW/BSA, S LPW/LBM, S SW/BW, S SW/BSA, S SW/LBM, D LSA/BSA, and D LLA/BSA were significantly greater and S LSA/BW, B LSA/BSA, S LSA/LBM, S LLA/BSA, S LLA/LBM, and D SW/LBM were significantly less in the lifters than the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Training responses of plasma beta-endorphin, adrenocorticotropin, and cortisol.

The purpose of this study was to examine the effects of three different run training programs on plasma responses of beta-endorphin (beta-EP), adrenocorticotropin (ACTH), and cortisol to maximal treadmill exercise. Subjects were randomly assigned to one of three training groups: sprint intervals (SI) (N = 8), endurance (E) (N = 10), or combination (C) (N = 7). Training was monitored for 10 wk, and maximal treadmill exercise tests were administered pre-training and after 2, 4, 6, 8, and 10 wk of training. Blood samples were obtained (pre-training and after 10 wk) before, immediately after, and 5 and 15 min following the maximal exercise tests. All groups significantly (P less than 0.05) increased maximal oxygen consumption values at 8 and 10 wk of the training period. Significant exercise-induced increase in plasma beta-EP, ACTH, cortisol, and blood lactate were observed for both pre- and post-training tests in all training groups. The SI group demonstrated significant post-training increases in beta-EP, ACTH, cortisol, and 5 min post-exercise blood lactate concentrations in response to maximal exercise. No training-induced hormonal changes were observed for the E group. While exercise-induced increases were observed, the C group exhibited significant post-training reductions in plasma responses of beta-EP, ACTH, and blood lactate concentrations in response to maximal exercise. Still, resting and post-exercise increases in plasma cortisol concentrations were significantly higher in magnitude in the post-training test. Lactate was significantly correlated with beta-EP (r = 0.72), ACTH (r = 0.70), and cortisol (r = 0.64).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1988

Cardiovascular adaptations to resistance training.

The cross-sectional and longitudinal data available indicate that the following conclusions are warranted concerning the effects of resistance training on the cardiovascular system. Resistance training causes increased absolute left ventricular wall thickness and left ventricular mass. These increases are not as evident when expressed relative to body surface area or lean body mass. There is little or no change in left ventricular internal dimensions, in absolute terms or relative to body surface area, resting heart rate, resting blood pressure, and diastolic function of the left ventricle due to resistance training. No change or slight positive effects are noted in systolic function of the left ventricle with training. During resistance training exercises, a large pressor response occurs and is attenuated in resistance trained athletes as compared to control subjects. Resistance training does result in adaptations of the cardiovascular system, with further research needed to elucidate its nature.

Adaptation, Physiological↗
PubMed1988

Physiological adaptations to resistance exercise. Implications for athletic conditioning.

Resistance training results in a wide spectrum of adaptations in various physiological systems. Increases in muscle size and strength, changes in body composition, neuroendocrine function and cardiovascular responses have been observed following resistance training. Additionally, resistance training may be an effective means by which the incidence of sports injuries can be reduced. The physiological alterations induced by resistance training appear to be specific to the number of sets and repetitions and exercises performed. Thus, special attention is required when developing the exercise prescription for resistance training.

Adaptation, Physiological↗
PubMed1987

Resistance-training experience and the pressor response during resistance exercise.

The purpose of this study was to examine the effects previous resistance-training experience has on the cardiovascular responses to resistance-training exercises. To investigate this, the intra-arterial blood pressure response of four body builders (BB), six novice weight-trained individuals (NT), and six sedentary controls (SC) were monitored during performance of one-arm overhead presses and one-leg knee extensions. One repetition at the maximal weight possible (1 RM) and sets to voluntary fatigue at 90, 80, 70, and 50% of 1 RM were performed. Across groups, the BB demonstrated a significantly (P less than 0.05) lower peak and a lesser magnitude of response (changes from rest to peak) for systolic and diastolic blood pressures than the the NT and SC groups during both exercises. The BB also demonstrated significantly lower values across groups for peak heart rate and magnitude of heart rate response during arm presses. During knee extensions across groups, peak heart rate but not magnitude of the heart rate response was significantly lower in the BB. The results indicate that previous weight-training experience reduces the pressor response to dynamic resistance exercises.

Adult↗
PubMed1985

Physical and physiological characteristics of elite women volleyball players.

The purpose of this study was to compare various physical and performance characteristics of two elite groups of athletes, the 1980 U.S. Women's National Volleyball Team and the collegiate players who composed the 1979 U.S. Women's University Games Volleyball Team. The characteristics compared were age, height, weight, body composition determined via hydrostatic weighing, vertical jumping distance, vertical jumping height, maximal oxygen consumption, heart rate max and respiratory exchange ratio. Significant differences (p less than 0.05) in age (23 +/- 2.6 yr. and 21.5 +/- 0.7 yr.), percent of body fat (11.7 +/- 3.7% and 18.3 +/- 3.4%), and vertical jumping distance (52.4 +/- 4.5 cm and 45.5 +/- 6.4 cm), between the two teams were demonstrated, with the National Team being significantly older, having a lower percentage of body fat and possessing a larger vertical jumping distance. These results indicate trainers of elite (national and international caliber) women volleyball players should consider including techniques to reduce percentage of body fat and increase vertical jumping distance.

Adult↗
PubMed1984

Metabolite changes in aged muscle during stimulation.

Metabolite concentrations of adenosine-5'-phosphate, phosphocreatine, and lactate were compared in adult and aged rat soleus and superficial, medial and deep, lateral gastrocnemius muscles after 3 min of moderate or intense stimulation in situ. The concentration of phosphocreatine in all muscles progressively decreased as contractile frequency increased. In most muscles, lactate increased coincident with greater contractile frequency. These changes were greater in aged muscles. Decreases in the concentration of adenosine-5'-phosphate with stimulation, where evident, were also greater in aged muscles. Metabolite levels in nonstimulated muscles were effected minimally by age. The cytochrome-c concentration was reduced with age in each muscle section. The results indicate that aged skeletal muscle has a lesser ability than adult skeletal muscle to maintain energy balance during contraction.

Adenosine Triphosphate↗
PubMed1983

Types of strength training.

Strength gains may be obtained by performing any type of resistance training if voluntary maximal contractions are performed. It is necessary that the advantages and disadvantages of a particular type of strength training are carefully considered before incorporating it into a program. Variables that should be considered include cost of equipment, motor performance increases, amount of strength gains, and range of motion of the strength gains. Further research comparing the different types of strength training is needed.

Humans↗
PubMedDate not supplied

Influence of resistance training volume and periodization on physiological and performance adaptations in collegiate women tennis players.

Few data exist on the long-term adaptations to heavy resistance training in women. The purpose of this investigation was to examine the effect of volume of resistance exercise on the development of physical performance abilities in competitive, collegiate women tennis players. Twenty-four tennis players were matched for tennis ability and randomly placed into one of three groups: a no resistance exercise control group, a periodized multiple-set resistance training group, or a single-set circuit resistance training group. No significant changes in body mass were observed in any of the groups throughout the entire training period. However, significant increases in fat-free mass and decreases in percent body fat were observed in the periodized training group after 4, 6, and 9 months of training. A significant increase in power output was observed after 9 months of training in the periodized training group only. One-repetition maximum strength for the bench press, free-weight shoulder press, and leg press increased significantly after 4, 6, and 9 months of training in the periodized training group, whereas the single-set circuit group increased only after 4 months of training. Significant increases in serve velocity were observed after 4 and 9 months of training in the periodized training group, whereas no significant changes were observed in the single-set circuit group. These data demonstrate that sport-specific resistance training using a periodized multiple-set training method is superior to low-volume single-set resistance exercise protocols in the development of physical abilities in competitive, collegiate women tennis players.

Adolescent↗
PubMedDate not supplied

Body composition of elite American athletes.

Five hundred twenty-eight male athletes participating in 26 Olympic events and 298 female athletes participating in 15 Olympic events underwent determination of body fat percentage (% fat) and lean body mass (LBM) via hydrostatic weighing and/or anthropometric methods. All groups of athletes were below the average values for % fat of college age men and women of 15% and 25%, respectively. In general, athletes involved in a sport where their body weight is supported, such as canoe and kayak (males, 13.0 +/- 2.5%; females, 22.2 +/- 4.6%) and swimming (males, 12.4 +/- 3.7%; females 19.5 +/- 2.8%), tended to have higher % fat values. Athletes involved in sports where a weight class has to be made to compete, such as boxing (males, 6.9 +/- 1.6%) and wrestling (male, Junior World Freestyle 7.9 +/- 2.7%), events such as the 100, 200, and 400 meters in athletes (male 100 and 200 meters, 6.5 +/- 1.2%; female 100, 200 and 400 meters, 13.7 +/- 3.6%) that are very anaerobic in nature and extremely aerobic events such as the marathon (males, 6.4 +/- 1.3%) demonstrated lower % fat values. Athletes involved in sports where body size is a definite advantage, such as basketball (males, 84.1 +/- 6.2 kg; females, 55.3 +/- 4.9 kg) and volleyball (males, 75.0 +/- 6.6 kg; females, 58.4 +/- 4.5 kg) tended to have a larger LBM.

Adipose Tissue↗
PubMedDate not supplied

Human torque velocity adaptations to sprint, endurance, or combined modes of training.

We had groups of athletes perform sprint and endurance run training independently or concurrently for 8 weeks to examine the voluntary in vivo mechanical responses to each type of training. Pre- and posttraining angle-specific peak torque during knee extension and flexion were determined at 0, 0.84, 1.65, 2.51, 3.35, 4.19, and 5.03 radian.sec-1 and normalized for lean body mass. Knee extension torque in the sprint-trained group increased across all test velocities, the endurance-trained group increased at 2.51, 3.34, 4.19, and 5.03 radian.sec-1, and the group performing the combined training showed no change at any velocity. Knee flexion torque of the sprint and combined groups decreased at 0.84, 1.65, and 2.51 radian.sec-1. Knee flexion torque in the sprint-trained group also decreased at 0 radian.sec-1 and in the combined group at 3.34 radian.sec-1. Knee flexion torque in the endurance-trained group showed no change at any velocity of contraction. Mean knee flexion:extension ratios across the test velocities significantly decreased in the sprint-trained group. Knee extension endurance during 30 seconds of maximal contractions significantly increased in all groups. Only the sprint-trained group showed a significant increase in endurance of the knee flexors. These data suggest that changes in the voluntary in vivo mechanical characteristics of knee extensor and flexor skeletal muscles are specific to the type of run training performed.

Adaptation, Physiological↗
PubMedDate not supplied

Value of resistance training for the reduction of sports injuries.

Many competitive and recreational athletes perform resistance training as a part of their conditioning programmes. Resistance training in addition to increasing muscular strength and hypertrophy may also aid in the prevention of injuries. Research indicates that resistance training promotes growth and/or increases in the strength of ligaments, tendons, tendon to bone and ligament to bone junction strength, joint cartilage and the connective tissue sheaths within muscle. Studies involving humans and animal models also demonstrate resistance training can cause increased bone mineral content and therefore may aid in prevention of skeletal injuries. Investigations to date suggest resistance training can aid in injury prevention. The incidence of various types of overuse injuries, such as swimmers shoulder and tennis elbow, may be reduced by the performance of sport and/or motion specific resistance training activities. Screening of athletes for agonist and antagonist muscle strength imbalances can be utilised to identify possessing a predisposition for injury. Resistance training may then be performed to correct the imbalance and therefore reduce the incidence of injury.

Adaptation, Physiological↗