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  • 1
    Electronic Resource
    Electronic Resource
    Comparison of soleus muscles from rats exposed to microgravity for 10 versus 14 days (1998)
    Springer
    Histochemistry and cell biology 110 (1998), S. 73-80 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The effects of two different duration spaceflights on the extent of atrophy, fiber type composition, and myosin heavy chain (MHC) content of rat soleus muscles were compared. Adult male Fisher rats (n=12) were aboard flight STS-57 and exposed to 10 days of microgravity and adult ovariectomized female Spraque-Dawley rats (n=12) were aboard flight STS-62 for 14 days. Soleus muscles were bilaterally removed from the flight and control animals and frozen for subsequent analyses. Muscle wet weights, fiber types (I, IC, IIC, and IIA), cross-sectional area, and MHC content were determined. Although a significant difference was found between the soleus wet weights of the two ground-based control groups, they were similar with regard to MHC content (ca 90% MHCI and ca 10% MHCIIa) and fiber type composition. Unloading of the muscles caused slow-to-fast transformations which included a decrease in the percentage of type I fibers and MHCI, an increase in fibers classified as type IC, and the expression of two fast myosin heavy chains not found in the control rat soleus muscles (MHCIId and MHCIIb). Although the amount of atrophy (ca 26%) and the extent of slow-to-fast transformation (decrease in the percentage of MHCI from 90% to 82.5%) in the soleus muscles were similar between the two spaceflights, the percentages of the fast MHCs differed. After 14 days of spaceflight, the percentage of MHCIIa was significantly lower and the percentages of MHCIId and MHCIIb were significantly higher than the corresponding MHC content of the soleus muscles from the 10-day animals. Indeed, MHCIId became the predominant fast MHC after 14 days in space. These data suggest fast-to-faster transformations continued during the longer spaceflight.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180050267
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  • 2
    Electronic Resource
    Electronic Resource
    Fiber type composition of four hindlimb muscles of adult Fisher 344 rats (1999)
    Springer
    Histochemistry and cell biology 111 (1999), S. 117-123 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The limb and trunk muscles of adult rats express four myosin heavy chain (MHC) isoforms, one slow (MHCI) and three fast (MHCIIa, MHCIId, and MHCIIb). The distribution of these isoforms correlates with fiber types delineated using myofibrillar actomyosin adenosine triphosphatase (mATPase) histochemistry. For example, type I fibers express MHCI and fiber types IIA, IID, and IIB express MHCIIa, MHCIId, and MHCIIb, respectively. Fibers containing only one MHC isoform have been termed ”pure” fibers. Recent evidence suggests that a population of ”hybrid” fibers exist in rat skeletal muscle which contain two MHC isoforms. The purpose of the present investigation was to document the entire range of histochemically defined ”pure” and ”hybrid” fiber types in untreated muscles of the young adult Fisher 344 rat hindlimb. The selected hindlimb muscles (soleus, tibialis anterior, extensor digitorum longus, and gastrocnemius muscles) were removed from 12 male rats and analyzed for muscle fiber type distribution, cross-sectional area, and MHC content. Care was taken to delineate eight fiber types (I, IC, IIC, IIA, IIAD, IID, IIDB, and IIB) using refined histochemical techniques. Hybrid fibers were found to make up a considerable portion of the muscles examined (a range of 8.8–17.8% of the total). The deep red portion of the gastrocnemius muscle contained the largest number of hybrid fibers, most of which were the fast types IIAD (8.5±2.8%) and IIDB (5.2±2.3%). In conclusion, hybrid fibers make up a considerable portion of normal rat limb musculature and are an important population that should not be ignored.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180050341
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of 10 days of spaceflight on the shuttle Endeavour on predominantly fast-twitch muscles in the rat (2000)
    Springer
    Histochemistry and cell biology 114 (2000), S. 349-355 
    Details
    ISSN: 1432-119X
    Keywords: Atrophy Cross sectional area Qualitative histochemistry Microgravity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. 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 Endeavour 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004180000193
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Oxygen consumption following exercise of moderate intensity and duration (1992)
    Springer
    European journal of applied physiology 65 (1992), S. 421-426 
    Details
    ISSN: 1439-6327
    Keywords: Exercise intensity ; Exercise duration ; plasma lactate ; Rectal temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To study the effects of exercise intensity and duration on excess postexercise oxygen consumption (EPOC), 8 men [age= 27.6 (SD 3.8) years, VO2max = 46.1 (SD 8.5) ml min−1 kg−1] performed four randomly assigned cycle-ergometer tests (20 min at 60% VO2max, 40 min at 60% VO2max, 20 min at 70% VO2max, and 40 min at 70% VO2max). O2 uptake, heart rate and rectal temperature were measured before, during, and for 1 h following the exercise tests. Blood for plasma lactate measurements was obtained via cannulae before, and at selected times, during and following exercise. VO2 rapidly declined to preexercise levels following each of the four testing sessions, and there were no differences in EPOC between the sessions. Blood lactate and rectal temperature increased (P〈0.05) with exercise, but had returned to preexercise levels by 40 min of recovery. The results indicate that VO2 returned to resting levels within 40 min after the end of exercise, regardless of the intensity (60% and 70% VO2max or duration (20 min and 40 min) of the exercise, in men with a moderate aerobic fitness level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243508
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of hypnosis on plasma proenkephalin peptide F and perceptual and cardiovascular responses during submaximal exercise (1992)
    Springer
    European journal of applied physiology 65 (1992), S. 573-578 
    Details
    ISSN: 1439-6327
    Keywords: Enkephalins ; Endogenous opioid peptides ; Endurance exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Little information is available concerning the influence of subconscious mechanisms on neuroendocrine function, more specifically, proenkephalin peptide F release. Ten men [5 middle distance runners (21.6 (SD 0.54 years) and 5 untrained men (24.0 (SD 4.3 years)] consented to be volunteers in this investigation. Submaximal exercise intensities of 25% and 50& of peak oxygen consumption ({ie573-1}) (8 min stages) were used for both the control and hypnosis treatments. A traditional hypnotic induction was used, with the suggestion of two higher intensities of exercise stress (50% and 75% peak {ie573-2}) previously experienced in familiarization and testing by each subject. Each minute oxygen consumption was measured using open circuit spirometry, heart rate via an ECG, and ratings of perceived exertion (RPE) using the Borg scale. Plasma peptide F immunoreactivity (ir) [preproenkephalin-(107–140)] in blood sampled from an indwelling cannula was measured by radioimmunoassay at 7–8 min of each stage of the exercise test. Expected significant increases were observed for all cardiorespiratory and perceptual variables over the increasing exercise intensities and there were no significant differences between trained and untrained groups for peptide F it response patterns. Hypnosis did not significantly affect peptide F it concentrations (P 〉 0.05) and did not significantly alter exercise heart rate, RPE or minute ventilation (P 〉 0.05). However, hypnosis did significantly increase oxygen consumption during exercise (P = 0.0095) but not of the magnitude needed for the metabolic demands of the higher exercise intensities. Thus, traditional hypnosis was unable to make functionally significant changes in the cardiorespiratory variables. Training did not alter responses to exercise under hypnosis. The results of this study indicate that when using traditional hypnosis and a suggestion of harder exercise in highly selected groups, it may not be possible functionally to stress adrenal medullary secretion of proenkephalin fragments, RPE or cardiorespiratory variables.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00602368
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of a temperate environment test to predict heat tolerance (1987)
    Springer
    European journal of applied physiology 56 (1987), S. 384-389 
    Details
    ISSN: 1439-6327
    Keywords: Body temperature ; Heat acclimation ; Heart rate ; Exertion ; Heat exhaustion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A temperate environment heat tolerance test (HTT) was formerly reported (Shvartz et al. 1977b) to distinguish heat acclimatized humans from former heat stroke patients. The purpose of this investigation was to evaluate the ability of HTT to measure acute individual changes in the HR and Tre responses of normal subjects, induced by classical heat acclimation procedures, thereby assessing the utility and sensitivity of HTT as a heat tolerance screening procedure. On day 1, 14 healthy males performed HTT (23.2±0.5 ° C db, 14.9±0.5 ° C wb) by bench stepping (30 cm high, 27 steps · min-1) for 15 min at 67±3% $$\dot V_{O_{2\max } }$$ . On days 2–9, all subjects underwent heat acclimation (41.2±0.3 ° C db, 28.4±0.3° C wb) via treadmill exercise. Heat acclimation trials (identical on days 2 and 9) resulted in significant decreases in HR (170±3 vs 144±5 beats · min−1), Tre (39.21±0.09 vs 38.56±0.17 ° C), and ratings of perceived exertion; plasma volume expanded 5.2±1.7%. On day 10, subjects repeated HTT; day 1 vs day 10 HR were statistically similar (143±6 vs 137±6 beats · min−1, p〉0.05) but Tre decreased significantly (37.7±0.1 vs 37.5±0.1 ° C, p〈0.05). Group mean HTT composite score (day 1 vs day 10) was unchanged (63±5 vs 72±6, p〉0.05), and individual composite scores indicated that HTT did not accurately measure HR and Tre trends at 41.2 ° C in 6 out of 14 subjects. Among the physical characteristics of subjects, only $$\dot V_{O_{2\max } }$$ correlated significantly (r 2=0.74, p〈0.001) with HTT, indicating a large aerobic component. We concluded that HTT is not a substitute for classical heat tolerance tests conducted at high ambient temperatures. HTT is apparently most useful in patient or at-risk populations in which preliminary or gross distinctions between heat tolerant and heat intolerant individuals are required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417764
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