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1.
Specificity of velocity in strength training 总被引:2,自引:0,他引:2
Summary Twenty-one male volunteers (ages 23–25 years) were tested pre- and post training for maximal knee extension power at five
specific speeds (1.05, 2.09, 3.14, 4.19, and 5.24 rad·s−1) with an isokinetic dynamometer. Subjects were assigned randomly to one of three experimental groups; group S, training at
1.05 rad·s−1 (n=8), group I, training at 3.14 rad·s−1 (n=8) or group F, training at 5.24 rad·s−1 (n=5). Subjects trained the knee extensors by performing 10 maximal voluntary efforts in group S, 30 in group I and 50 in group
F six times a week for 8 weeks. Though group S showed significant increases in power at all test speeds, the percent increment
decreased with test speed from 24.8% at 1.05 rad·s−1 to 8.6% at 5.24 rad·s−1. Group I showed almost similar increment in power (18.5–22.4 at all test speeds except at 2.09 rad·s−1 (15.4%). On the other hand, group F enhanced power only at faster test speeds (23.9% at 4.19 rad·s−1 and 22.8% at 5.24 rad·s−1). 相似文献
2.
M. V. Narici G. S. Roi L. Landoni A. E. Minetti P. Cerretelli 《European journal of applied physiology》1989,59(4):310-319
Summary Four male subjects aged 23–34 years were studied during 60 days of unilateral strength training and 40 days of detraining.
Training was carried out four times a week and consisted of six series of ten maximal isokinetic knee extensions at an angular
velocity of 2.09 rad·s−1. At the start and at every 20th day of training and detraining, isometric maximal voluntary contraction (MVC), integrated
electromyographic activity (iEMG) and quadriceps muscle cross-sectional area (CSA) assessed at seven fractions of femur length
(Lf), by nuclear magnetic resonance imaging, were measured on both trained (T) and untrained (UT) legs. Isokinetic torques at
30° before full knee extension were measured before and at the end of training at: 0, 1.05, 2.09, 3.14, 4.19, 5.24 rad·s−1. After 60 days T leg CSA had increased by 8.5%±1.4% (mean±SEM,n=4,p<0.001), iEMG by 42.4%±16.5% (p<0.01) and MVC by 20.8%±5.4% (p<0.01). Changes during detraining had a similar time course to those of training. No changes in UT leg CSA were observed while
iEMG and MVC increased by 24.8%±10% (N.S.) and 8.7%±4.3% (N.S.), respectively. The increase in quadriceps muscle CSA was maximal
at 2/10 Lf (12.0%±1.5%,p<0.01) and minimal, proximally to the knee, at 8/10 Lf (3.5%±1.2%, N.S.). Preferential hypertrophy of the vastus medialis and intermedius muscles compared to those of the rectus
femoris and lateralis muscles was observed. Isoangular torque of T leg increased by 20.9%±5.4% (p<0.05), 23.8%±7.8% (p<0.05) and 22.5%±6.7% (p<0.05) at 0, 1.05 and 2.09 rad·s−1 respectively; no significant change was observed at higher velocities and in the UT leg. Hypertrophy produced by strength
training accounts for 40% of the increase in force while the remaining 60% seems to be attributable to an increased neural
drive and possibly to changes in muscle architecture. 相似文献
3.
R. Bulbulian J. H. Heaney C. N. Leake A. A. Sucec N. T. Sjoholm 《European journal of applied physiology》1996,73(3-4):273-277
Isokinetic leg strength and fatigue were measured in 24 male U.S. Marine Corps volunteers in a simulated sleep loss and unusually
heavy work scenario. Knee extension and flexion peak torque (PT) were measured at three isokinetic speeds (1.57, 2.62 and
3.66 rad·s−1) followed by 45 consecutive maximal reciprocal contractions at 3.14 rad·s−1 to measure fatigue index (FI). All subjects were retested 2 days later following 30-h sleep deprivation (SD). The exercise
group (n = 12) spent 25 1-h sessions performing computer tasks, filling out questionnaires and walked 1.61 km with a 50% gross body
mass pack load, during each of the 25 sessions. The control group (n = 12) did likewise but did not exercise. Repeated measures ANOVA indicated that flexion PT at 1.57 rad·s−1 decreases (P < 0.013) after SD. Exercise did not affect Fl but did decrease PT. It was concluded that carrying a 50% load produces decrements
in PT for both extension and flexion but more so for flexion. SD affected PT but had no effect on FI. 相似文献
4.
The human voluntary force:velocity relationship frequently fails to demonstrate the expected high eccentric forces. Possible
explanations include unique activation strategies which might be affected by neural learning mechanisms. We investigated the
effect of practicing eccentric contractions on (1) the force: velocity relationship of the human knee extensor muscles and
(2) the extent of agonist and antagonist muscle activity. Eight healthy adults [seven women, group mean age 31 (SEM 5) years ± ]
practised twice a week for 4 weeks using their non-dominant legs. Each session comprised three isokinetic concentric and eccentric
maximal voluntary contractions (MVC) at randomised angular velocities of 100, 200 and 300° · s−1. Before and after, the force:velocity relationship was determined bilaterally (angular velocities 0–300° · s−1). There were no significant differences in the forces generated or relative electromyogram (EMG) activity after practice,
although there was a trend for dynamic forces to increase. Beforehand, the bilateral eccentric MVC forces were lower than
isometric (P < 0.0025); afterwards they were broadly similar. The agonist EMG was similar during isometric and eccentric contractions, but
lower during concentric (P < 0.03). Antagonist EMG activity showed considerable individual variation, was similar during all contraction types and tended
to be greater during dynamic contractions. These data indicate that neither central learning mechanisms nor total muscle activation
strategies underlie the human failure to produce the expected high eccentric voluntary forces in humans.
Accepted: 19 September 2000 相似文献
5.
The main purpose of this study was to investigate the changes in anthropometric measures and muscle strength that occur during
puberty in children from the age of 11 to 16 years. Special attention was paid to possible gender- and muscle action-type-specific
alterations in torque/velocity and EMG/velocity characteristics. Sixteen children participated in the study (9 boys and 7
girls). Eccentric and concentric muscle strength was measured on an isokinetic dynamometer at angular velocities of 45, 90
and 180° · s−1. Simultaneously, a surface electromyogram (EMG) was recorded from the quadriceps muscle. At the age of 11, the boys and girls
exhibited equal anthropometric measures and strength performance. In both genders, body measures and muscle strength increased
significantly during the 5-year period, with larger increases being recorded for the boys. In addition, the boys increased
selectively their eccentric torque per body mass, indicating an action-type-specific change in muscle quality. The general
shape of the torque/velocity relationship exhibited an adult-like pattern both before and after puberty, and did not differ
between genders. Both pre- and postpuberty, myoelectric activity was generally lower during eccentric than concentric actions,
the highest values occurring for both genders in the concentric 180° · s−1 test. Ratios of eccentric to concentric torque per EMG, which reflect electromechanical efficiency, showed no significant
changes with age. A significant velocity- and gender-specific change in electromechanical efficiency was observed at the highest
speed at postpuberty, where the ratio for the girls was higher than for the boys.
Accepted: 13 June 1999 相似文献
6.
Combined effect of heat stress, dehydration and exercise on neuromuscular function in humans 总被引:3,自引:0,他引:3
This study examined the combined effect of exercise induced hyperthermia and dehydration on neuromuscular function in human
subjects. Six trained male runners ran for 40 min on a treadmill at 65% of their maximal aerobic velocity while wearing a
tracksuit covered with an impermeable jacket and pants to impair the evaporation of sweat. These stressful experimental running
conditions led the runners to a physiological status close to exhaustion. On average, the 40 min run ended at a heart rate
of 196 (SD 8) beats · min−1, a tympanic temperature of 40 (SD 0.3) °C and with a loss of body mass of 2 (SD 0.5)%. Pre- and post-running strength tests
included measurements of maximal knee extension and flexion torques in both isometric and isokinetic (at 60 and 240° · s−1) conditions. A 20 s endurance test at 240° · s−1 was also performed. Surface electromyographic (EMG) activity was recorded from six knee extensor and flexor muscles during
the entire protocol. The treadmill run led to clear decrements in maximal extension torque and EMG activity both in isometric
and at the slowest isokinetic velocity (60° · s−1). However, no differences in these parameters were observed at 240° · s−1. Furthermore, the EMG patterns of the major knee extensor and flexor muscles remained remarkably stable during the treadmill
run. These results demonstrate that the exercise-induced hyperthermia and dehydration in the present experiments had only
minor effects on the neuromuscular performance. However, it is also suggested that high internal body temperature per se could
limit the production of high force levels.
Accepted: 26 September 2000 相似文献
7.
Anderson Souza Oliveira Rogério Bulhões Corvino Mauro Gonçalves Fabrizio Caputo Benedito Sergio Denadai 《European journal of applied physiology》2010,110(6):1127-1133
Single training session (STS) may increase the power output (i.e., maximal torque) in different contraction types; however,
little is known about the neuromuscular adaptations to reach this enhancement. In this way, the present study examined the
differences between knee extensors EMG, kinematics, and dynamometry at 60 and 180° s−1 before (PRE) and after (POST) a STS. Seventeen healthy males completed three different tasks: (1) 5-maximal isokinetic knee
extensions, without previous habituation (PRE) at 60 and 180° s−1; (2) in the same day and after a proper rest, two bouts of 5-maximal isokinetic contractions (STS) at 60 and 180° s−1; and (3) in a new visit, POST consisted in new 5-maximal isokinetic contractions at 60 and 180° s−1. The main parameters examined were: knee extensors peak torque (PT), total work (TW), EMG (prior to the movement onset, agonist
and antagonist activation), rate of force (RFD), and velocity development (RVD). There was significant increase in PT [12%
(60° s−1) and 8.7% (180° s−1)] and TW [13.5% (60° s−1) and 10.7% (180° s−1)] from PRE to POST sessions. Increases in RFD were found for both velocities (p < 0.05); however, RVD and vastus lateralis EMG prior to the movement onset were significantly higher for POST only at 60° s−1. The RFD percentage of change (%change) was significantly correlated to %change for PT at 60° s−1 (r
2 = 0.53) and 180° s−1 (r
2 = 0.45). In conclusion, STS improves neural strategies to contract muscles stronger and faster at the slowest velocity, while
higher velocities present different adaptations and might need more practice to further adaptations. 相似文献
8.
The stretch-shortening cycle (SSC) is a natural muscle function where a concentric action is preceded by an eccentric action, and this leads to a higher concentric torque value in healthy persons. This study aimed to investigate the concentric torque output with and without preceding eccentric or isometric actions in patients with upper motor neuron lesions due to cerebro-vascular disease. Strength measurements of the plantar flexions were made in a dynamometer at different angular?velocities (120°?·?s?1 and 240°?·?s?1) and recordings of electromyogram (EMG) were made simultaneously. The assessment was based on comparisons of the concentric torque values with and without preceding actions. The study showed a significantly higher percentage increase in concentric torque values after preceding actions in the affected leg compared with the nonaffected leg except at 120°?·?s?1 with preceding isometric action. Relative EMG changes showed no differences between the legs except at 120°?·?s?1 with preceding isometric action. We would suggest that the higher performance of the affected leg was caused by better utilization of elastic energy due to muscle stiffness which, despite reduced muscle strength, may have returned the patient's functional ability towards normal. 相似文献
9.
J. L. Ivy R. T. Withers G. Brose B. D. Maxwell D. L. Costill 《European journal of applied physiology》1981,47(3):247-255
Summary Fifteen subjects were assigned to three groups on the basis of the proportion of fast-twitch fibers (%FT) in their vastus
lateralis muscles. Torque production per unit of fat free thigh volume was then determined during knee extension on an isokinetic
dynamometer at 60, 120, 180, 240, and 300‡·s−1. Maximal isometric force was also obtained at 65‡ from horizontal. Subjects with predominantly fast twitch muscle fibers
demonstrated significantly greater peak power, rate of power production and work than subjects with predominantly slow twitch
fibers at all but the lowest velocity of 60‡·s−1. Mean peak power for all subjects occurred at approximately 30% of maximal knee extension velocity (210‡·s−1) and 34% of maximal voluntary isometric contraction. When work, peak power and rate of power production were correlated with
%FT fibers, then the highest correlations of 0.69, 0.57, and 0.73 respectively, all occurred at 180‡·−1. These observations suggest that: 1) the torque-velocity, power-velocity relationship of the quadriceps is similar to the
force-velocity, power-velocity relationship found for excised muscle, 2) when using the knee extension exercise for the prediction
of muscle fiber composition of the quadriceps the most appropriate speed for testing appears to be 180‡·s−1.
Supported by a grant from Lumex Inc. 相似文献
10.
M. Handel T. Horstmann H.-H. Dickhuth R. W. Gülch 《European journal of applied physiology》1997,76(5):400-408
The effects of an 8-week unilateral contract-relax (CR) stretching training program (passive stretch after isometric contraction) on muscular performance were investigated in a group of 16 athletes. The flexibility, maximum torque and angular position as well as contraction work in movements of the knee joint were determined before training and after 4 and 8 weeks of training. The torque measurements were performed under isokinetic conditions, eccentrically at angular velocities of 60°?·?s?1 and 120°?·?s?1, isometrically at five different joint positions, and concentrically at angular velocities of 60, 120, 180 and 240°?·?s?1 using an isokinetic dynamometer. A surface electromyogram (EMG) of the thigh muscles (quadriceps and hamstrings) was recorded simultaneously. As compared to untrained control limbs, significant improvements in active and passive flexibility (up to 6.3° in range of motion), maximum torque (up to 21.6%) and work (up to 12.9%) were observed, and these were especially pronounced under eccentric load conditions. A comparison between integrated EMG recordings during eccentric and concentric loads, as well as the interpretation of the training-induced changes in the EMG, suggest that muscular activity under eccentric loads may be impaired by mental processes. 相似文献
11.
Using recurrent artificial neural network model to estimate voluntary elbow torque in dynamic situations 总被引:1,自引:0,他引:1
Muscle modelling is an important component of body segmental motion analysis. Although many studies had focused on static
conditions the relationship between electromyographic (EMG) signals and joint torque under voluntary dynamic situations has
not been well investigated. The aim of this study was to investigate the performance of a recurrent artificial neural network
(RANN) under voluntary dynamic situations for torque estimation of the elbow complex. EMG signals together with kinematic
data, which included angle and angular velocity, were used as the inputs to estimate the expected torque during movement.
Moreover, the roles of angle and angular velocity in the accuracy of prediction were investigated, and two models were compared.
One model used EMG and joint kinematic inputs and the other model used only EMG inputs without kinematic data. Six healthy
subjects were recruited, and two average angular velocities (60o s−1 and 90o s−1) with three different loads (0 kg, 1 kg, 2 kg) in the hand position were selected to train and test the RANN between 90o elbow flexion and full elbow extension (0o). After training, the root mean squared error (RMSE) between expected torque and predicted torque of the model, with EMG
and joint kinematic inputs in the training data set and the test data set were 0.17±0.03 Nm and 0.35±0.06 Nm, respectively.
The RMSE values between expected torque and predicted torque of the model, with only EMG inputs in the training data set and
the test set, were 0.57±0.07 Nm and 0.73±0.11 Nm, respectively. The results showed that EMG signals together with kinematic
data gave significantly better performance in the joint torque prediction; joint angle and angular velocity provided important
information in the estimation of joint torque in voluntary dynamic movement. 相似文献
12.
Marzorati M Perini R Milesi S Veicsteinas A 《European journal of applied physiology》2000,81(4):275-280
There have been many studies on the effects of isokinetic exercise on muscle performance in training and rehabilitative programmes.
On the other hand, the cardiovascular and metabolic responses elicited by this type of exercise have been poorly investigated.
This study was specifically designed to describe the relationships, if any, between metabolic and cardiorespiratory responses
and power output during maximal intermittent knee isokinetic exercise when a steady state is reached. A group of 18 healthy
subjects (10 men and 8 women, age range 25–30 years) were requested to perform at maximal concentric isokinetic knee extensions/flexions
60° · s−1 and 180° · s−1 for 5 min, with a 5-s pause interposed between consecutive repetitions. The power output (W˙) was calculated; before and during the tasks heart rate (f
c) and arterial blood pressure (APa) were continuously monitored. Pulmonary ventilation (V˙
E) and oxygen uptake (V˙O2) were measured at the 4th and at the 5th min of exercise and blood lactate concentration at rest and at the 3rd min of recovery.
From the 4th to the 5th min only a slight decrease in W˙ was observed, both at 60° · s−1 and 180° · s−1. The V˙O2, V˙
E, f
c and APa showed similar values in the last 2 min of exercise, suggesting that a steady state had been reached. The V˙O2 increased linearly as a function of W˙, showing a significantly steeper slope at 60° · s−1 than at 180° · s−1. The f
c, in spite of a large interindividual variation, was linearly related to metabolic demand, and was not affected by angular
velocity. Systolic and diastolic APa were not related either to V˙O2 or to angular velocity. In conclusion it would appear that the metabolic response to maximal intermittent knee isokinetic
exercise resembles that of dynamic exercise. Conversely, the cardiocirculatory responses would seem to reflect a relevant
role of the isometric postural component, the importance of which should be carefully evaluated in each subject.
Accepted: 21 September 1999 相似文献
13.
Le Chevalier JM Vandewalle H Thépaut-Mathieu C Pujo M Le Natur B Stein JF 《European journal of applied physiology》2000,81(6):513-516
A possible dependence of critical power (CP) and the Y-intercept of the work/exhaustion time relationship (Y
intercept) on maximal muscular strength of the same muscle group has been studied in nine endurance-trained subjects, seven gymnasts,
and seven weight-lifters. CP was calculated as being equal to the slope of the linear relationship between exhaustion time
and the work performed at exhaustion on a knee extension ergometer. Y
intercept was equal to the intercept between this relationship and the work axis. The muscular strength of the knee was evaluated by
measuring the torques exerted on a Biodex knee isokinetic dynamometer at four angular velocities: 0° · s−1 (T0), 90° · s−1 (T90), 180° · s−1 (T180) and 240° · s−1 (T240). The results of the present study do not support the hypothesis that CP depends upon maximal strength. Indeed, CP was not
correlated with T0, T90, T180 or T240 (|r| < 0.01). Y
intercept was significantly and positively correlated only with T90.
Accepted: 1 November 1999 相似文献
14.
Tesch Per A. Wright James E. Vogel James A. Daniels William L. Sharp Dan S. Sjödin Bertil 《European journal of applied physiology》1985,54(3):237-243
Summary This study describes the influence of muscle fiber type composition, enzyme activities and capillary supply on muscle strength,
local muscle endurance or aerobic power and capacity. Muscle biopsies were obtained from m. vastus lateralis in thirteen physically
active men. Histochemical staining procedures were applied to assess the percentage of fast twitch (FT) fibers, muscle fiber
area, and capillary density. Also, the activity of citrate synthase (CS), creatine kinase (CK), hexokinase (HK), lactate dehydrogenase
(LDH), and phosphofructokinase (PFK) were analysed using fluorometrical assays. Peak torque at ‘low’ and ‘high’ angular velocities
was measured during leg extension. Similarly, muscle fatigue (e. g. peak torque decline) and recovery from a short-term exercise
task were measured during maximal, voluntary consecutive leg extensions. Aerobic power (
) and aerobic capacity (e.g. onset of blood lactate concentration; OBLA), as defined by a blood lactate concentration of 4
mol · l−1 were measured during cycling. Peak torque at a high angular velocity was positively correlated with % FT area (p<0.001). Fatigue and recovery were correlated with LDH · CS−1 (p<0.001). WOBLA was best correlated with PFK and PFK · CS−1 (p<0.001). Hence, muscle strength was partly determined by fiber type composition whereas local muscle endurance, recovery and
aerobic capacity reflect mainly capillary supply and the activity of key enzymes involved in aerobic and anaerobic metabolism. 相似文献
15.
We hypothesized that the history of contraction would affect the in vivo quadriceps torque-velocity relationship. We examined
the quadriceps torque-velocity relationship of the human knee extensors at the descending and ascending limb of the torque-position
relationship by initiating the knee extension at a knee angle position of 1.39 rad (80°) or 0.87 rad (50°) over a 0.52 rad
(30°) range of motion under conditions of constant or linearly increasing velocity. Maximal voluntary isometric knee extension
torque (M0) was measured at 1.87 rad, 0.87 rad, and 0.35 rad, and concentric torque was measured. The subjects carried out ten maximal
knee extensions at ten distinct velocities, each velocity ranging between 0.52 rad·s–1 to 5.24 rad·s–1 in steps of 0.52 rad·s–1. Peak concentric torque was measured and mean torque calculated from the respective torque-time curves. Peak or mean torque,
computed from the individual torque-time curves, and velocity data were fitted to the Hill equation under the four experimental
conditions and the curve parameters computed. The M0 was similar at 0.87 rad and 1.39 rad, but it was significantly lower at 0.35 rad. In the low-velocity domain of the torque-velocity
curve where a plateau normally occurs, peak torque was always lower than M0. Peak and mean torque were significantly greater under linearly increasing velocity conditions and the 1.39 rad starting
knee position. Mean torque but not peak torque data could be well fitted to the Hill equation and the two computations resulted
in significantly different Hill curve parameters including the concavity ratio, peak power, and maximal angular velocity.
We concluded that the history of contraction significantly modifies the in vivo torque-velocity relationship of the human
quadriceps muscle. Muscle mechanics and not neural factors may have accounted for the inconsistencies in the human torque-velocity
relationships reported previously.
Electronic Publication 相似文献
16.
The purpose of this study was to examine the effects of moment of antagonistic muscle on the resultant joint moment during
isokinetic eccentric and concentric efforts of the knee extensors. Ten males performed maximum eccentric and concentric knee
extension and flexion efforts on a Biodex dynamometer at 0.52 rad · s−1 (30° · s−1). Electromyographic (EMG) activity of vastus medialis and biceps femoris (hamstrings) was also recorded. The antagonistic
moment of the hamstrings was determined by recording the integrated EMG (iEMG)/moment relationship at different levels of
muscle effort. The iEMG/moment curves were fitted using second-degree polynomials. The polynomials were then used to predict
the antagonistic moment exerted by the hamstrings from the antagonist iEMG. The antagonistic moment had a maximum of 42.92
Nm and 28.97 Nm under concentric and eccentric conditions respectively; paired t-tests indicated that this was a significant difference (P < 0.05). These results indicate that the resultant joint moment of knee extensors is the result of both agonist and antagonist
muscle activation. The greater antagonist muscle activity under concentric activation conditions may be partly responsible
for the lower resultant joint concentric moment of knee extensors compared with the corresponding eccentric activation. The
antagonist moment significantly affects comparisons between the isokinetic moments and agonist EMG and in vitro force measurements
under different testing (muscle action and angular velocity) conditions.
Accepted: 25 February 1997 相似文献
17.
Morrissey MC Hooper DM Drechsler WI Hill HJ Bucknill T 《European journal of applied physiology》2000,81(6):493-496
Resistance-training velocity specificity is known to occur in isotonic training of uninjured subjects and in isokinetic training
of injured patients. Whether velocity specificity occurs with isotonic training in injured patients has not been tested, despite
the common use of this exercise mode in patients. Thirty-two patients recovering from anterior cruciate ligament reconstruction
(ACLR) surgery were tested at approximately 2 and 6 weeks after surgery. The isokinetic injured/uninjured strength ratios
of the knee extensors were compared for the test velocities of 60° · s−1 and 210° · s−1, as assessed before and after a 4-week training period. Isotonic training of the knee extensors at 60° · s−1 was applied in formal sessions three times per week. The isokinetic injured/uninjured strength ratios were compared for the
two test velocities, and there was no indication that training velocity specificity occurred in these patients. Possible reasons
for this finding, which contrasts with previous work, are discussed.
Accepted: 12 November 1999 相似文献
18.
Gajdosik RL 《European journal of applied physiology》2002,87(3):220-227
The purpose of this study was to use a model of aging to examine the relationships between passive properties of the calf
muscles and plantarflexion concentric isokinetic torque characteristics. Eighty-one active women 20–84 years of age were tested
using a Kin-Com isokinetic dynamometer interfaced with electromyography (EMG). The passive properties were tested by stretching
the muscles from relaxed plantarflexion to a maximal dorsiflexion (DF) angle at a rate of 5°·s–1 (0.087 rad·s–1) with minimal raw EMG activity (<0.05 mV). The maximal concentric torque was tested from maximal passive DF into plantarflexion
at four randomly ordered velocities of 30, 60, 120, and 180°·s–1. Pearson correlation coefficients (Bonferroni adjusted) indicated a hierarchical order of high to moderate positive correlations
between four passive properties and the peak and mean concentric torque for all test velocities. Correlation coefficients
for the four passive properties ranged from 0.50 to 0.78 (P<0.001), and the coefficients of determination (r
2) from higher to lower were: (1) maximal DF passive resistive torque (r
2: 0.50–0.62), (2) length extensibility (r
2: 0.40–0.49), (3) maximal muscle length (r
2: 0.28–0.41), and (4) passive elastic stiffness in the last half of the full-stretch range of motion (r
2: 0.25–0.31). The maximal DF passive resistive torque and the length extensibility accounted for 50–62% and 40–49% of the
variability in the concentric torque, respectively. The results indicate that the concentrically stronger calf muscles of
active women were positively correlated with passively stronger, longer, and stiffer calf muscles, which are characteristics
of the calf muscles of younger women. Further studies are needed to examine whether therapeutic interventions, such as stretching
and strengthening, can promote adaptations in the calf muscles of older women to attain these more youthful characteristics.
Electronic Publication 相似文献
19.
Gauthier A Davenne D Martin A Van Hoecke J 《European journal of applied physiology》2001,84(3):249-252
The aim of this study was, firstly, to confirm or refute the existence of circadian rhythms during several velocities of
concentric action of the elbow flexor muscles and, secondly, to compare the characteristics of these circadian rhythms with
those obtained during isometric actions. Eight volunteer subjects participated in this study. The circadian rhythms were obtained
from six test sessions (TS) carried out at different times of day over 6 days with only one TS a day. During each TS, oral
temperature and the torque of the muscle action were measured. The subjects made, on an isokinetic ergometer, two maximal
isokinetic concentric elbow flexions at five angular velocities (60, 120, 180, 240 and 300° · s−1) and at an angle of 60°. Torque-angular velocity relationships, which characterised the functioning of the muscle during
concentric and isometric actions, were established for the different times of day. The values of the torque recorded at each
of the angular velocities presented a clear circadian rhythm. After normalisation of the torque values, no significant differences
were observed among the computed characteristics of the circadian rhythms obtained at different angular velocities. Since
the circadian rhythms during isometric and concentric torque were the same, the characteristics of the circadian rhythms of
the musculo-skeletal system can be studied using either type of muscle action. The results indicated that torque and temperature
varied concomitantly during the day. Thus, the recording of body temperature allows one to estimate the times of occurrence
of maximal and minimal values in the circadian rhythm of muscle torque.
Accepted: 10 October 2000 相似文献
20.
M. Pousson I. G. Amiridis G. Cometti J. Van Hoecke 《European journal of applied physiology》1999,80(4):367-372
The purpose of this study was to show that velocity-specific training may be implicated in modifications in the level of coactivation of agonist and antagonist muscles. Healthy males (n?=?20) were randomly placed in to two groups: one group trained using concentric contractions (n?=?12), the other was an untrained control group (n?=?8). The training group underwent unilateral resistance training at a level of 35 (5)% of a one-repetition maximal contraction of the elbow flexors, executed at maximal angular velocity. Training sessions consisted of six sets of eight consecutive elbow flexions, three times per weak for a total of seven weeks. The velocity of the ballistic movements executed during training were measured using an optoelectronic measuring device (Elite), both at the beginning and at the end of the training period. Subjects were tested pre- and post-training during isokinetic maximal elbow flexions with constant angular torque (CAT) at 90°?(0°?=?full extension), and at different velocities (60, 120, 180, 240 and 300°?·?s?1) for concentric actions, and ?60 and ?30°?·?s?1 for eccentric and isometric contractions at 90°. In order to verify the levels of activation of the agonist biceps brachii (BB) muscles and antagonist triceps brachii (TB) muscles during maximal voluntary activation, their myoelectrical activities were recorded and quantified as root mean square (RMS) amplitudes, between angles of 75 and 105°. The results show that mean angular velocities between elbow angles of 75 and 105° were similar before [302 (32)°?·?s?1] and after [312 (27)°?·?s?1] the training period. CAT significantly increased measures at angular velocities of 240 and 300°?·?s?1 by 18.7% and 23.5%, respectively. The RMS activity of BB agonist muscles was not significantly modified by training. Post-training normalized RMS amplitudes of TB antagonist muscles were inferior to those observed at pre-training, but values were only significantly different at 300°?·?s?1. In conclusion, in this study we attempted to show that an increase of CAT to 240 and 300°?·?s?1, though velocity-specific training, may be due, in part, to a lowering of the level of coactivation. 相似文献