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91.
Kraemer WJ Koziris LP Ratamess NA Hakkinen K TRIPLETT-McBRIDE NT Fry AC Gordon SE Volek JS French DN Rubin MR Gomez AL Sharman MJ Michael Lynch J Izquierdo M Newton RU Fleck SJ 《Journal of strength and conditioning research / National Strength & Conditioning Association》2002,16(3):373-382
The object of this study was to examine changes in muscular strength, power, and resting hormonal concentrations during 6 weeks of detraining (DTR) in recreationally strength-trained men. Each subject was randomly assigned to either a DTR (n = 9) or resistance training (RT; n = 7) group after being matched for strength, body size, and training experience. Muscular strength and power testing, anthropometry, and blood sampling were performed before the experimental period (T1), after 3 weeks (T2), and after the 6-week experimental period (T3). One-repetition maximum (1RM) shoulder and bench press increased in RT at T3 (p = 0.05), whereas no significant changes were observed in DTR. Peak power output and mean power output significantly decreased (9 and 10%) in DTR at T2. Peak torque of the elbow flexors at 90 degrees did not change in the RT group but did significantly decrease by 11.9% at T3 compared with T1 in the DTR group. Vertical jump height increased in RT at T2 but did not change in DTR. Neither group displayed any changes in 1RM squat, body mass, percent body fat, or resting concentrations of growth hormone, follicle-stimulating hormone, luteinizing hormone, sex hormone-binding globulin, testosterone, cortisol, or adrenocorticotropin. These data demonstrate that 6 weeks of resistance DTR in recreationally trained men affects power more than it does strength without any accompanying changes in resting hormonal concentrations. For the recreational weight trainer, losses in strength over 6 weeks are less of a concern compared with anaerobic power and upper arm isometric force production. Anaerobic power exercise with a high metabolic component coming from glycolysis might be of importance for reducing the impact of DTR on Wingate power performances. A minimal maintenance training program is recommended for the recreational lifter to offset any reductions in performance. 相似文献
92.
Kraemer WJ French DN Paxton NJ Häkkinen K Volek JS Sebastianelli WJ Putukian M Newton RU Rubin MR Gómez AL Vescovi JD Ratamess NA Fleck SJ Lynch JM Knuttgen HG 《Journal of strength and conditioning research / National Strength & Conditioning Association》2004,18(1):121-128
As a consequence of the physiological demands experienced during a competitive soccer season, the antagonistic relationship between anabolic and catabolic processes can affect performance. Twenty-five male collegiate soccer players were studied throughout a season (11 weeks) to investigate the effects of long-term training and competition. Subjects were grouped as starters (S; n = 11) and nonstarters (NS; n = 14). Measures of physical performance, body composition, and hormonal concentrations (testosterone [T] and cortisol [C]) were assessed preseason (T1) and 5 times throughout the season (T2-T6). Starters and NS participated in 83.06% and 16.95% of total game time, respectively. Nonstarters had a significant increase (+1.6%) in body fat at T6 compared to T1. Isokinetic strength of the knee extensors (1.05 rad.sec(-1)) significantly decreased in both S (-12%) and NS (-10%; p < or = 0.05) at T6. Significant decrements in sprint speed (+4.3%) and vertical jump (-13.8%) were found at T5 in S only. Though within normal ranges (10.4-41.6 nmol.L(-1)), concentrations of T at T1 were low for both groups, but increased significantly by T6. Concentrations of C were elevated in both groups, with concentrations at the high end of the normal range (normal range 138-635 nmol.L(-1)) at T1 and T4 in NS and T4 in S, with both groups remaining elevated at T6. Data indicate that players entering the season with low circulating concentrations of T and elevated levels of C can experience reductions in performance during a season, with performance decrements exacerbated in starters over nonstarters. Soccer players should therefore have a planned program of conditioning that does not result in an acute overtraining phenomenon prior to preseason (e.g., young players trying to get in shape quickly in the 6 to 8 weeks in the summer prior to reporting for preseason camp). The detrimental effects of inappropriate training do not appear to be unloaded during the season and catabolic activities can predominate. 相似文献
93.
Ylitalo K Ala-Rämi A Vuorinen K Peuhkurinen K Lepojärvi M Kaukoranta P Kiviluoma K Hassinen I 《Biochimica et biophysica acta》2001,1504(2-3):329-339
The physiological role of F(1)F(0)-ATPase inhibition in ischemia may be to retard ATP depletion although views of the significance of IF(1) are at variance. We corroborate here a method for measuring the ex vivo activity of F(1)F(0)-ATPase in perfused rat heart and show that observation of ischemic F(1)F(0)-ATPase inhibition in rat heart is critically dependent on the sample preparation and assay conditions, and that the methods can be applied to assay the ischemic and reperfused human heart during coronary by-pass surgery. A 5-min period of ischemia inhibited F(1)F(0)-ATPase by 20% in both rat and human myocardium. After a 15-min reperfusion a subsequent 5-min period of ischemia doubled the inhibition in the rat heart but this potentiation was lost after 120 min of reperfusion. Experiments with isolated rat heart mitochondria showed that ATP hydrolysis is required for effective inhibition by uncoupling. The concentration of oligomycin for 50% inhibition (I(50)) for oxygen consumption was five times higher than its I(50) for F(1)F(0)-ATPase. Because of the different control strengths of F(1)F(0)-ATPase in oxidative phosphorylation and ATP hydrolysis an inhibition of the F(1)F(0)-ATPase activity in ischemia with the resultant ATP-sparing has an advantage even in an ischemia/reperfusion situation. 相似文献
94.
Kyaw Moe Angelina Sijaona Anjana Shrestha Paivi Kettunen Masahiko Taniguchi Keijo Luukko 《Differentiation; research in biological diversity》2012
Timing and patterning of dental pulp innervation are strictly spatio-temporally regulated but it is still not known how they are controlled at molecular level. We analyzed postnatal innervation of the dental pulp in the mandibular first molar of mice deficient for Semaphorin 3A (Sema3A) axon repellant molecule. Immunohistochemical localization of nerve fibers on serial sections covering the whole tooth germs using anti-peripherin antibody revealed that nerve fibers were prematurely present within the preodontoblast layer next to the inner enamel epithelium already at PN0 in Sema3A−/− mice. In contrast, in the wild-type (Sema3A+/+) mice nerve fibers were seen in the pulp only after enamel formation at PN3. The nerves in Sema3A−/− pulp were notably defasciculated and thinner compared to that of Sema3A+/+ mice. A premature formation of an abnormal, enlarged nerve plexus with a high number of arborizations was apparent in the pulp–dentin border target area in Sema3A−/− already at PN2 whereas in the wild-type mice the first sign of plexus formation was seen at PN7. The expression of mRNAs for Ngf, Gdnf and Ncam neuroregulatory molecules in mandibular molar as well as receptors for neurotrophic factors and class 3 semaphorins including Sema3A (TrkA, p75, TrkB, TrkC, Ret, Npn1, Npn2, PlxA4) in trigeminal ganglia were not altered in the Sema3A−/− mice. Collectively, this data show that Sema3A serves an essential role in molar tooth pulp innervation controlling the timing of nerve fiber penetration into the pulp, their patterning and the formation of nerve plexus at pulp–dentin border area, and provide further support for the hypothesis that tooth innervation is regulated by the coordinated activity of locally expressed neuroregulatory molecules exerting positive and negative influences on growing dental nerve fibers. 相似文献
95.
Effect of time-of-day-specific strength training on serum hormone concentrations and isometric strength in men 总被引:2,自引:0,他引:2
A time-of-day influence on the neuromuscular response to strength training has been previously reported. However, no scientific study has examined the influence of the time of day when strength training is performed on hormonal adaptations. Therefore, the primary purpose of this study was to examine the effects of time-of-day-specific strength training on resting serum concentrations and diurnal patterns of testosterone (T) and cortisol (CORT) as well as maximum isometric strength of knee extensors. Thirty eight diurnally active healthy, previously untrained men (age 20-45 yrs) underwent a ten-week preparatory strength training period when sessions were conducted between 17:00-19:00 h. Thereafter, these subjects were randomized into either a morning (n=20, training times 07:00-09:00 h) or afternoon (n=18, 7:00-19:00 h) training group for another ten-week period of time-of-day-specific training (TST). Isometric unilateral knee extension peak torque (MVC) was measured at 07:00, 12:00, 17:00, and 20:30 h over two consecutive days (Day 1 & Day 2) before and after TST. Blood samples were obtained before each clock-time measurement to assess resting serum T and CORT concentrations. A matched control group (n=11) did not train but participated in the tests. Serum T and CORT concentrations significantly declined from 07:00 to 20:30 h on all test days (Time effect, p<.001). Serum CORT at 07:00 h was significantly higher on Day 1 than Day 2 in the control and afternoon group, both in Pre and Post conditions (Day x Time interaction, p<.01). In the morning group, a similar day-to-day difference was present in the Pre but not Post conditions (Time x Group interaction, p<.05). MVC significantly increased after TST in both the morning and afternoon groups (Pre to Post effect, p<.001). In both groups, a typical diurnal variation in MVC (Time effect, p<.001) was found, especially on Day 2 in the Pre condition, and this feature persisted from Pre to Post in the afternoon group. In the morning group, however, diurnal variation was reduced after TST on both Day 1 and Day 2 (Pre to PostxDay x TimexGroup interaction, p<.05). In conclusion, 10 weeks of morning time-of-day-specific strength training resulted in reduced morning resting CORT concentrations, presumably as a result of decreased masking effects of anticipatory psychological stress prior to the morning testing. The typical diurnal pattern of maximum isometric strength was blunted by the TST period in the morning but not the afternoon group. However, the TST period had no significant effect on the resting total T concentration and its diurnal pattern and on the absolute increase in maximum strength. 相似文献
96.
Hatfield DL Kraemer WJ Spiering BA Häkkinen K Volek JS Shimano T Spreuwenberg LP Silvestre R Vingren JL Fragala MS Gómez AL Fleck SJ Newton RU Maresh CM 《Journal of strength and conditioning research / National Strength & Conditioning Association》2006,20(4):760-766
The purpose of this study was to determine the impact of a very slow (VS) velocity and a self-selected volitional (VOL) velocity at varying intensities on repetition number, peak force, peak power, and total volume in the squat and shoulder press exercises. On separate testing days, 9 resistance trained men (age: 23.9 +/- 2.5 years; height: 174.8 +/- 6.5 cm; body mass: 80.1 +/- 12.4 kg) performed a squat (SQ) and shoulder press (SP) exercise at 60 or 80% of 1 repetition maximum (1RM) at either VOL or VS (10-second eccentric and 10-second concentric actions) velocity for as many repetitions as possible. Force, power, and volume (repetitions x kg) were also determined. Subjects performed significantly fewer repetitions (p < or = 0.05) in the VS exercises (60% VS SQ 5 +/- 1 vs. VOL SQ 24 +/- 2; 80% VS SQ 2 +/- 0 vs. VOL SQ 12 +/- 1; 60% VS SP 4 +/- 1 vs. VOL SP 14 +/- 2; 80% VS SP 1 +/- 0 vs. VOL SP 6 +/- 1). Peak force and power were significantly higher at the VOL speed (peak force [in newtons]: 60% VS SQ 564.4 +/- 77.3 vs. VOL SQ 1229.0 +/- 134.9 N; 80% VS SQ 457.3 +/- 27.9 vs. VOL SQ 1059.3 +/- 104.7 N; 60% VS SP 321.6 +/- 37.8 vs. VOL SP 940.7 +/- 144.8 N; 80% VS SP 296.5 +/- 24.7 vs. VOL SP 702.5 +/- 57.7 N; and peak power [in watts]: 60% VS SQ 271.2 +/- 40.1 vs. VOL SQ 783.2 +/- 129.1 W; 80% VS SQ 229.3 +/- 49.5 vs. VOL SQ 520.2 +/- 85.8 W; 60% VS SP 91.3 +/- 21.9 vs. VOL SP 706.6 +/- 151.4 W; 80% VS SP 78.1 +/- 19.8 vs. VOL SP 277.6 +/- 46.4 W). VOL speed elicited higher total volume than the VS velocity. The results of this study indicate that a VS velocity may not elicit appropriate levels of force, power, or volume to optimize strength and athletic performance. 相似文献
97.
Holviala JH Sallinen JM Kraemer WJ Alen MJ Häkkinen KK 《Journal of strength and conditioning research / National Strength & Conditioning Association》2006,20(2):336-344
Progressive strength training can lead to substantial increases in maximal strength and mass of trained muscles, even in older women and men, but little information is available about the effects of strength training on functional capabilities and balance. Thus, the effects of 21 weeks of heavy resistance training--including lower loads performed with high movement velocities--twice a week on isometric maximal force (ISOmax) and force-time curve (force produced in 500 milliseconds, F0-500) and dynamic 1 repetition maximum (1RM) strength of the leg extensors, 10-m walking time (10WALK) and dynamic balance test (DYN.D) were investigated in 26 middle-aged (MI; 52.8 +/- 2.4 years) and 22 older women (O; 63.8 +/- 3.8 years). 1RM, ISOmax, and F0-500 increased significantly in MI by 28 +/- 10%, 20 +/- 19%, 31 +/- 34%, and in O by 27 +/- 8%, 20 +/- 16%, 18 +/- 45%, respectively. 10WALK (MI and O, p < 0.001) shortened and DYN.D improved (MI and O, p < 0.001). The present strength-training protocol led to large increases in maximal and explosive strength characteristics of leg extensors and in walking speed, as well to an improvement in the present dynamic balance test performance in both age groups. Although training-induced increase in explosive strength is an important factor for aging women, there are other factors that contribute to improvements in dynamic balance capacity. This study indicates that total body heavy resistance training, including explosive dynamic training, may be applied in rehabilitation or preventive exercise protocols in aging women to improve dynamic balance capabilities. 相似文献
98.
Hatfield DL Kraemer WJ Volek JS Rubin MR Grebien B Gómez AL French DN Scheett TP Ratamess NA Sharman MJ McGuigan MR Newton RU Häkkinen K 《Journal of strength and conditioning research / National Strength & Conditioning Association》2006,20(1):167-171
The beneficial role of carbohydrate (CHO) supplementation in endurance exercise is well documented. However, only few data are available on the effects of CHO loading on resistance exercise performance. Because of the repetitive use of high-threshold motor units, it was hypothesized that the power output (power-endurance) of multiple sets of jump squats would be enhanced following a high-CHO (6.5 g CHO kg body mass(-1)) diet compared to a moderate-CHO (4.4 g CHO kg body mass(-1)) diet. Eight healthy men (mean +/- SD: age 26.3 +/- 2.6 years; weight 73.0 +/- 6.3 kg; body fat 13.4 +/- 5.0%; height 178.2 +/- 6.1 cm) participated in 2 randomly assigned counterbalanced supplementation periods of 4 days after having their free-living habitual diet monitored. The resistance exercise test consisted of 4 sets of 12 repetitions of maximal-effort jump squats using a Plyometric Power System unit and a load of 30% of 1 repetition maximum (1RM). A 2-minute rest period was used between sets. Immediately before and after the exercise test, a blood sample was obtained to determine the serum glucose and blood lactate concentrations. No significant difference in power performance existed between the 2 diets. As expected, there was a significant (p = 0.05) decrease in power performance between the repetitions in every set. Blood lactate concentrations were significantly higher postexercise with both the high-CHO and the moderate- or lower-CHO diet, but there were no differences between conditions. The results indicated that the power output during multiple sets of maximal jump squats was not enhanced following a higher-CHO diet compared to a moderate- or lower-CHO diet. These data show that elevated carbohydrate intake is not needed to optimize a repetitive power-endurance performance when it is done as the first exercise in a workout. 相似文献
99.
Shimano T Kraemer WJ Spiering BA Volek JS Hatfield DL Silvestre R Vingren JL Fragala MS Maresh CM Fleck SJ Newton RU Spreuwenberg LP Häkkinen K 《Journal of strength and conditioning research / National Strength & Conditioning Association》2006,20(4):819-823
Resistance exercise intensity is commonly prescribed as a percent of 1 repetition maximum (1RM). However, the relationship between percent 1RM and the number of repetitions allowed remains poorly studied, especially using free weight exercises. The purpose of this study was to determine the maximal number of repetitions that trained (T) and untrained (UT) men can perform during free weight exercises at various percentages of 1RM. Eight T and 8 UT men were tested for 1RM strength. Then, subjects performed 1 set to failure at 60, 80, and 90% of 1RM in the back squat, bench press, and arm curl in a randomized, balanced design. There was a significant (p < 0.05) intensity x exercise interaction. More repetitions were performed during the back squat than the bench press or arm curl at 60% 1RM for T and UT. At 80 and 90% 1RM, there were significant differences between the back squat and other exercises; however, differences were much less pronounced. No differences in number of repetitions performed at a given exercise intensity were noted between T and UT (except during bench press at 90% 1RM). In conclusion, the number of repetitions performed at a given percent of 1RM is influenced by the amount of muscle mass used during the exercise, as more repetitions can be performed during the back squat than either the bench press or arm curl. Training status of the individual has a minimal impact on the number of repetitions performed at relative exercise intensity. 相似文献
100.
A simple method to separate and determine radioactive proline and hydroxyproline by paper chromatography is described. The localization of the imino acids separation is achieved by direct nondestructing staining with 1-fluoro-2,4-dinitrobenzene dye. The imino acids are quantitated directly by liquid scintillation counting in the presence of paper strips. The method was applied to bone cultures with good reproducibility, sensitivity and linearity over a wide range of radioactivity. The procedure was also tested in fibroblast cultures. The results for hydroxyproline were in good correlation with the widely used method of Juva and Prockop (Juva, K. and Prockop, D.J. (1966) Anal. Biochem. 15, 77–83), in which hydroxyproline is oxidized to pyrrole, and then extracted and purified by column chromatography before counting radioactivity. 相似文献