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  • 1
    Electronic Resource
    Electronic Resource
    The effects of short-term resistance training on endocrine function in men and women (1998)
    Springer
    European journal of applied physiology 78 (1998), S. 69-76 
    Details
    ISSN: 1439-6327
    Keywords: Key words Cortisol ; Testosterone ; Growth hormone ; Sex-hormone binding globulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This investigation examined hormonal adaptations to acute resistance exercise and determined whether training adaptations are observed within an 8-week period in untrained men and women. The protocol consisted of a 1-week pre-conditioning orientation phase followed by 8 weeks of heavy resistance training. Three lower-limb exercises for the quadriceps femoris muscle group (squat, leg press, knee extension) were performed twice a week (Monday and Friday) with every other Wednesday used for maximal dynamic 1 RM strength testing. Blood samples were obtained pre-exercise (Pre-Ex), immediately post-exercise (IP), and 5 min post-exercise (5-P) during the first week of training (T-1), after 6 weeks (T-2) and 8 weeks (T-3) of training to determine blood concentrations of whole-blood lactate (LAC), serum total testosterone (TT), sex-hormone binding globulin (SHBG), cortisol (CORT) and growth hormone (GH). Serum TT concentrations were significantly (P ≤ 0.05) higher for men at all time points measured. Men did not demonstrate an increase due to exercise until T-2. An increase in pre-exercise concentrations of TT were observed both for men and women at T-2 and T-3. No differences were observed for CORT between men and women; increases in CORT above pre-exercise values were observed for men at all training phases and at T-2 and T-3 for women. A reduction in CORT concentrations at rest was observed both in men and women at T-3. Women demonstrated higher pre-exercise GH values than men at all training phases; no changes with training were observed for GH concentrations. Exercise-induced increases in GH above pre-exercise values were observed at all phases of training. Women demonstrated higher serum concentrations of SHBG at all time points. No exercise-induced increases were observed in men over the training period but women increased SHBG with exercise at T-3. SHBG concentrations in women were also significantly higher at T-2 and T-3 when compared to T-1 values. Increases in LAC concentrations due to exercise were observed both for men and women for all training phases but no significant differences were observed with training. These data illustrate that untrained individuals may exhibit early-phase endocrine adaptations during a resistance training program. These hormonal adaptations may influence and help to mediate other adaptations in the nervous system and muscle fibers, which have been shown to be very responsive in the early phase of strength adaptations with resistance training.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050389
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of plasma cortisol elevation on total and differential leukocyte counts in response to heavy-resistance exercise (1996)
    Springer
    European journal of applied physiology 73 (1996), S. 93-97 
    Details
    ISSN: 1439-6327
    Keywords: Immune function ; Strength exercise ; White blood cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to examine the impact of heavy-resistance exercise-induced elevations of plasma cortisol on circulating leukocyte counts. Nine healthy, recreationally weight-trained men volunteered for this investigation. Two exercise protocols were employed. Protocol 1 (P-1) consisted of eight sets of ten-repetition maximum leg-press exercise with 1-min rest periods between sets. Protocol 2 (P-2) was identical except for 3-min rest periods. A non-exercise protocol was used as a control treatment (C). Venous blood samples, heart rates and ratings of perceived exertion were obtained pre-, mid- and 5 min post-exercise. In order to examine the maximal influence of cortisol on leukocyte counts, we placed the subject's highest magnitude of cortisol change in response to one of the heavy-resistance exercise protocols in what we designated as the response protocol (R) and the other value was placed into what was designated as the non-response protocol (NR) for analysis. Significant increases in cortisol occurred from pre- to post-exercise for P-1 [mean (SD) 241.4 (25.0) to 302.0 (60.0) nmol · 1−1] and in the R conditions pre- to mid- and pre- to post-exercise [218.0(0.0) to 302.4(37.1) to 326.8 (51.9) nmol · 1−1]. No significant changes in cortisol occurred for P-2, NR or the control conditions. Significant increases in total leukocyte counts occurred from pre- to mid- and pre- to post-exercise both for R [5.6 (0.4) to 7.4 (0.3) to 7.3 (0.3) cells · 109 · 1−1] and NR [5.7 (0.3) to 6.9 (0.4) to 7.1 (0.4) cells · 109 · 1−1]. No significant changes in differential leukocyte counts occurred. In addition, no significant correlations between cortisol and total or differential leukocyte counts were observed. These data indicate that acute increases in total leukocytes along with no changes in differential leukocyte counts can occur in response to heavy-resistance exercise that does not significantly elevate plasma cortisol concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262815
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Acute hormonal responses to heavy resistance exercise in younger and older men (1998)
    Springer
    European journal of applied physiology 77 (1998), S. 206-211 
    Details
    ISSN: 1439-6327
    Keywords: Key words Aging ; Neuroendocrine ; Resistance exercise ; Growth factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this investigation was to examine the acute responses of several hormones [total and free testosterone (TT and FT, respectively), adrenocorticotropic hormone (ACTH), cortisol (C), growth hormone (GH), and insulin (INS)] to a single bout of heavy resistance exercise (HRE). Eight younger [30-year (30y) group] and nine older [62-year (62y) group] men matched for general physical characteristics and activity levels performed four sets of ten repetitions maximum (RM) squats with 90 s rest between sets. Blood samples were obtained from each subject via an indwelling cannula with a saline lock pre-exercise, immediately post-exercise (IP), and 5, 15 and 30 min post-exercise. Levels of TT, FT, ACTH, C and lactate significantly increased after HRE for both groups. Pre-HRE pairwise differences between groups were noted only for FT, while post-HRE pairwise differences were found for TT, FT, GH, glucose and lactate. Area under the curve analysis showed that the 30y group had a significantly higher magnitude of increase over the entire recovery period (IP, 5, 15, and 30 min post-exercise) for TT, FT, ACTH and GH. Few changes occurred in the INS response with the only change being that the 62y group demonstrated a decrease IP. Lactate remained elevated at 30 min post-HRE. This investigation demonstrates that age-related differences occur in the endocrine response to HRE, and the most striking changes appear evident in the FT response to HRE in physically active young and older men.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050323
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of load and stretch shortening cycle on the kinematics, kinetics and muscle activation that occurs during explosive upper-body movements (1997)
    Springer
    European journal of applied physiology 75 (1997), S. 333-342 
    Details
    ISSN: 1439-6327
    Keywords: Key words  Force velocity relationship  ;  Muscle power  ;  Electromyography  ;  Bench press
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Although explosive power in lower-body movements has been extensively studied, there is a paucity of research examining such movements in the upper body. This study aimed to investigate the influence of load and the stretch shortening cycle (SSC) on the kinematics, kinetics, and muscle activation that occurs during maximal effort throws. A total of 17 male subjects performed SSC and concentric only (CO) bench throws using loads of 15%, 30%, 45%, 60%, 75%, 90% and 100% of their previously determined one repetition maximum bench press. The displacement, velocity, acceleration, force and power output as well as the electromyogram (EMG) from pectoralis major, anterior deltoid, and triceps brachii were recorded for each throw. The results were compared using multivariate analysis of variance with repeated measures. A criterion alpha level of P ≤ 0.05 was used. Similar force velocity power relationships were determined for this multijoint upper-body movement as has been found for isolated muscles, single joint movements, and vertical jumping. The highest power output was produced at the 30% [563 (104) W] and 45% [560 (86) W] loads during the SSC throws. Force output increased as a function of load; however, even the lighter loads resulted in considerable force due to the high accelerations produced. Average velocity, average and peak force, and average and peak power output were significantly higher for the SSC throws compared to the CO throws. However, peak velocity and height thrown were not potentiated by performing the pre-stretch because the duration and range of movement allowed the ability of the muscle to generate force at high shortening velocities to dominate the resulting throw. As such, explosive movements involving longer concentric actions than experienced during brief SSC movements may be limited by the ability of the muscle to produce force during fast contraction velocities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050169
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Reliability of an electrophoretic and image processing analysis of human skeletal muscle taken from m. vastus lateralis (1997)
    Springer
    European journal of applied physiology 75 (1997), S. 532-536 
    Details
    ISSN: 1439-6327
    Keywords: Key words Electrophoresis  ;  Myosin heavy chain  ;   Densitometry  ;  Image processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relative content of myosin heavy chain (MHC) isoforms IIb, IIa and I in human skeletal muscle taken from the m. vastus lateralis of 30 healthy male subjects was analysed using mini-gel electrophoresis. Repeated electrophoretic gels utilizing the same methods were produced for all subjects and the determination of MHC protein bands was performed using a digital scanner and National Institutes of Health (NIH) Image software and laser densitometry. A comparison between the NIH Image processing technique and laser densitometry revealed differences of 6.47%, 6.35% and 6.84% between these measurement techniques for MHC-IIb, -IIa and -I isoforms, respectively. The percentage technical error of measurement (TEM%) between electrophoretic gels was shown to be 19.1%, 17.8% and 14.2%, with regard to percentage of occurrence of MHC-IIb, -IIa and -I isoforms respectively. The variation in electrophoretic gel analyses was shown to be 5.7%, 7.3% and 5.5%, with regard to the percentage of MHC-IIb, -IIa and -I isoforms respectively. Intra-class correlations comparing NIH Image and laser densitometry produced r values in the range 0.38–0.63. Comparisons between and within gel analyses produced r values in the range 0.59–0.94 and 0.93–0.98, respectively. Analyses of variance revealed no significant differences (P 〈 0.05) between analysis techniques, between␣gels or within gels for the measurement of MHC-IIb, -IIa and -I isoforms. The inter-gel error between fibre subgroups was moderate for the two type-II MHC populations and less for type-I MHC; the intra-individual error in the measuring technique used for classifying the MHC-IIb, -IIa and -I protein bands was small. The results obtained in this investigation showed consistent trends which may reflect a false classification of the type-II MHC populations for the inter-gel and intra-individual analyses. The NIH Image software and digitizing process was shown to be a valid and reliable method for distinguishing between MHC protein bands of human skeletal tissue as separated by mini-gel electrophoretic techniques.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050200
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    Paper (German National Licenses)
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