Insulin action on heart and skeletal muscle glucose uptake in weight lifters and endurance athletes.
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There are no studies comparing myocardial metabolism between endurance- and resistance-trained athletes. We used 2-deoxy-2-[18F]fluoro-D-glucose and positron emission tomography combined with the euglycemic hyperinsulinemic clamp technique to compare the ability of insulin to stimulate myocardial, skeletal muscle, and whole body glucose uptake between weight lifters (n = 8), endurance athletes (n = 8), and sedentary men (n = 9). Maximal aerobic power (ml. kg- 1. min- 1) was higher in the endurance athletes (71 +/- 2, P < 0.001) than the weight lifters (42 +/- 2) and the sedentary men (42 +/- 2). Skeletal muscle glucose uptake (micromol. kg muscle- 1. min- 1) was enhanced in the endurance athletes (125 +/- 16, P < 0.01) but was similar in weight lifters (59 +/- 12) and sedentary (63 +/- 7) men. The rate of glucose uptake per unit mass of myocardium (micromol. kg- 1. min- 1) was similarly decreased in endurance athletes (544 +/- 50) and weight lifters (651 +/- 45) compared with sedentary men (1,041 +/- 78, P < 0.001 vs. endurance athletes and weight lifters). Both groups of athletes had increased left ventricular mass. Consequently, total left ventricular glucose uptake was comparable in all groups. These data demonstrate that aerobic but not resistance training is associated with enhanced insulin sensitivity in skeletal muscle. Despite this, cardiac changes are remarkably similar in weight lifters and endurance athletes and are characterized by an increase in left ventricular mass and diminished insulin-stimulated glucose uptake per heart mass. (+info)
Velocity associated characteristics of force production in college weight lifters.
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OBJECTIVE: To determine velocity specific isokinetic forces and cross sectional areas of reciprocal muscle groups in Olympic weight lifters. METHODS: The cross sectional area of the flexor or extensor muscles of the elbow or knee joint was determined by a B-mode ultrasonic apparatus in 34 college weight lifters and 31 untrained male subjects matched for age. Maximum voluntary force produced in the flexion and extension of the elbow and knee joints was measured on an isokinetic dynamometer at 60, 180, and 300 degrees/s. RESULTS: The average cross sectional area was 31-65% higher, and the force was 19-62% higher in weight lifters than in the untrained subjects. The ratio of force to cross sectional area was the same in both groups. The weight lifters showed a lower velocity associated decline in force than untrained subjects in the elbow and knee flexors but not in the extensors. CONCLUSIONS: These results indicate that for muscle contractions with velocities between 60 degrees/s and 300 degrees/s the difference in isokinetic force between weight lifters and untrained subjects can be primarily attributed to the difference in the muscle cross sectional area. However, the lower velocity associated decline in force implies that weight lifters may have a higher force per cross sectional area than untrained subjects at velocities above 300 degrees/s. (+info)
Ultrastructural muscle damage in young vs. older men after high-volume, heavy-resistance strength training.
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This study assessed ultrastructural muscle damage in young (20-30 yr old) vs. older (65-75 yr old) men after heavy-resistance strength training (HRST). Seven young and eight older subjects completed 9 wk of unilateral leg extension HRST. Five sets of 5-20 repetitions were performed 3 days/wk with variable resistance designed to subject the muscle to near-maximal loads during every repetition. Biopsies were taken from the vastus lateralis of both legs, and muscle damage was quantified via electron microscopy. Training resulted in a 27% strength increase in both groups (P < 0.05). In biopsies before training in the trained leg and in all biopsies from untrained leg, 0-3% of muscle fibers exhibited muscle damage in both groups (P = not significant). After HRST, 7 and 6% of fibers in the trained leg exhibited damage in the young and older men, respectively (P < 0.05, no significant group differences). Myofibrillar damage was primarily focal, confined to one to two sarcomeres. Young and older men appear to exhibit similar levels of muscle damage at baseline and after chronic HRST. (+info)
Human skeletal sarcoplasmic reticulum Ca2+ uptake and muscle function with aging and strength training.
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This study investigated the adaptations of skeletal muscle sarcoplasmic reticulum (SR) Ca2+ uptake, relaxation, and fiber types in young (YW) and elderly women (EW) to high-resistance training. Seventeen YW (18-32 yr) and 11 EW (64-79 yr) were assessed for 1) electrically evoked relaxation time and rate of the quadriceps femoris; and 2) maximal rates of SR Ca2+ uptake and Ca2+-ATPase activity and relative fiber-type areas, analyzed from muscle biopsies of the vastus lateralis. EW had significantly slower relaxation rates and times, decreased SR Ca2+ uptake and Ca2+-ATPase activity, and a larger relative type I fiber area than did YW. A subgroup of 9 young (YWT) and 10 elderly women (EWT) performed 12 wk of high-resistance training (8 repetition maximum) of the quadriceps and underwent identical testing procedures pre- and posttraining. EWT significantly increased their SR Ca2+ uptake and Ca2+-ATPase activity in response to training but showed no alterations in speed of relaxation or relative fiber-type areas. In YWT none of the variables was altered after resistance training. These findings suggest that 1) a reduced SR Ca2+ uptake in skeletal muscle of elderly women was partially reversed with resistance training and 2) SR Ca2+ uptake in the vastus lateralis was not the rate-limiting mechanism for the slowing of relaxation measured from electrically evoked quadriceps muscle of elderly women. (+info)
Effects of resistance training on selected indexes of immune function in elderly women.
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Women aged 67-84 yr were randomly assigned to either resistance exercise (RE, n = 15) or control group (C, n = 14). RE group completed 10 wk of resistance training, whereas C group maintained normal activity. Blood samples were obtained from the RE group (at the same time points as for resting C) at rest, immediately after resistance exercise, and 2 h after exercise before (week 0) and after (week 10) training. Mononuclear cell (CD3+, CD3+CD4+, CD3+CD8+, CD19+, and CD3-CD16+CD56+) number, lymphocyte proliferative (LP) response to mitogen, natural cell-mediated cytotoxicity (NCMC), and serum cortisol levels were determined. Strength increased significantly in RE subjects (%change 8-repetition maximum = 148%). No significant group, exercise time, or training effects were found for CD3+, CD3+CD4+, or CD3+CD8+ cells, but there was a significant exercise time effect for CD3-CD16+CD56+ cells. LP response was not different between groups, across exercise time, or after training. NCMC was increased immediately after exercise for RE subjects at week 0 and for RE and C groups at week 10. The week 0 and week 10 NCMC values were above baseline for both RE and C groups 2 h after exercise. In conclusion, acute resistance exercise did not result in postexercise suppression of NCMC or LP, and 10 wk of resistance training did not influence resting immune measures in women aged 67-84 yr. (+info)
Simultaneous pyloric and colonic obstruction associated with hiatus hernia in a weightlifter: a case report.
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Hiatus hernia is usually attributed to conditions that cause a chronic increase in intra-abdominal pressure such as multiple pregnancies and obesity. A 30-year-old man, a weightlifter, had a massive hiatus hernia causing both high and low gastrointestinal obstruction but no involvement of the gastroesophageal junction or fundus. The onset of the obstruction is attributed to an extreme increase in intra-abdominal pressure caused by the action of lifting weights. (+info)
Effect of 14 weeks of resistance training on lipid profile and body fat percentage in premenopausal women.
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OBJECTIVES: To study the effects of a supervised, intensive (85% of one repetition maximum (1-RM)) 14 week resistance training programme on lipid profile and body fat percentage in healthy, sedentary, premenopausal women. SUBJECTS: Twenty four women (mean (SD) age 27 (7) years) took part in the study. Subjects were randomly assigned to either a non-exercising control group or a resistance exercise training group. The resistance exercise training group took part in supervised 45-50 minute resistance training sessions (85% of 1-RM), three days a week on non-consecutive days for 14 weeks. The control group did not take part in any structured physical activity. RESULTS: Two way analysis of variance with repeated measures showed significant (p < 0.05) increases in strength (1-RM) in the exercising group. There were significant (p < 0.05) decreases in total cholesterol (mean (SE) 4.68 (0.31) v 4.26 (0.23) mmol/1 (180 (12) v 164 (9) mg/dl)), low density lipoprotein (LDL) cholesterol (2.99 (0.29) v 2.57 (0.21) mmol/l (115 (11) v 99 (8) mg/dl), the total to high density lipoprotein (HDL) cholesterol ratio (4.2 (0.42) v 3.6 (0.42)), and body fat percentage (27.9 (2.09) v 26.5 (2.15)), as well as a strong trend towards a significant decrease in the LDL to HDL cholesterol ratio (p = 0.057) in the resistance exercise training group compared with their baseline values. No differences were seen in triglycerides and HDL cholesterol. No changes were found in any of the measured variables in the control group. CONCLUSIONS: These findings suggest that resistance training has a favourable effect on lipid profile and body fat percentage in healthy, sedentary, premenopausal women. (+info)
Effects of anabolic-androgenic steroid use or gonadal testosterone suppression on serum leptin concentration in men.
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OBJECTIVE: Serum leptin concentration shows a sexual dimorphism that is not accounted for by gender differences in adiposity. A strong inverse association exists between serum leptin and testosterone concentrations in men, pointing to a likely influence of gonadal sex steroids on serum leptin concentration. The aim of this study was to investigate whether manipulation of sex steroid hormones in men would alter serum leptin concentration independently of changes in fat mass. DESIGN AND METHODS: The effects of sex steroid suppression on serum leptin concentration were investigated in nine healthy men in whom testosterone had been reversibly suppressed for 5 weeks after treatment with intramuscular triptorelin. The effects of sex steroid supplementation were investigated in nine male bodybuilders who self-administered anabolic--androgenic steroids (AAS) for a mean period of 6.5 weeks. A control group received no hormonal treatment. RESULTS: Testosterone concentration was significantly reduced by triptorelin administration (7.32+/- 1.92ng/ml at baseline compared with 1.15+/-0.57ng/ml at 5 weeks, P=0.002). High-dose AAS use was confirmed by urine analysis. Body fat percentage was unaffected by the AAS or triptorelin intervention (P>0.19). Leptin concentration was significantly reduced after one cycle of AAS use (2.40+/-0. 98ng/ml off cycle compared with 1.63+/-0.37ng/ml on cycle, P=0.012), and was significantly increased by triptorelin administration (2. 96+/-1.50ng/ml at baseline compared with 6.63+/-4.67ng/ml at five weeks, P=0.004). No significant change occurred in the control group. CONCLUSION: Androgenic sex hormone supplementation decreases serum leptin concentration, whereas suppression increases serum leptin concentration, independently of changes in body fat mass in healthy men. The sexual dimorphism evident in serum leptin concentration is likely to be due to a suppressive effect of testosterone on serum leptin concentration in males. (+info)