Bisson et al. In addition, increases in the CoP excursion area, velocity, and variability were found in both the anteroposterior and mediolateral planes. Although the muscles affecting the ankles play a crucial role in the control of the quiet upright posture, the knee extensor muscles are proportionately much more greatly used and are therefore also more exposed to fatigue during the performance of activities of daily living and may exhibit responses different from those observed when fatiguing activities are imposed exclusively on the more distal muscles of the lower body.
Therefore, the aim of the present study was to analyze the effect of muscle fatigue induced by resistance training on the knee extensor muscles as well as the stabilometric responses of young individuals in the single-leg stance. A total of 11 young males The volunteers had no history of lower limb injuries, surgery, or fractures and were not using any medications that could compromise the findings of the study. In addition, individuals with heart or respiratory problems, vestibular or visual dysfunction, or physical impairment, as well as users of medications that interfere with the state of wakefulness and balance and could therefore interfere with the performance of tests , were excluded.
The exclusion criteria were applied following interviews conducted with the volunteers; therefore, their potential unawareness of any of the abovementioned conditions was ruled out. The volunteers were instructed to not perform moderate or intense physical activity 24 hours before the period of data collection and avoid the ingestion of alcoholic beverages and medications liable to affect balance. The sample included only males because the genders have been shown to differ with regard to the ability to reach and tolerate fatigue 22 , The volunteers attended an initial experimental session, in which anthropometric parameters were measured body mass and height.
The maximum load was established by maximum attempts based on a value estimated by the experimenters. The load was gradually increased by 5 Kg per attempt, until the moment when the volunteers were no longer able to perform the full knee extension motion. A 3-minute rest interval was established between attempts. During the entire performance of the test, the volunteers remained in the sitting position, with their knees on the distal end of the machine and their back leaning against the chair. Lateral hand grips were used to stabilize the trunk and avoid accessory motions.
Before the 1RM test, the volunteers performed a specific sequence of warming up exercises on the leg extension machine, which included 3 series of repetitions without overload separated by second intervals for recovery.
The second experimental session was scheduled 1 week later. At this time, the volunteers returned to the laboratory and were subjected to a stabilometric test, which was performed before and after the application of a protocol for lower limb exercise designed to induce fatigue. The fatiguing protocol was ended when the volunteers became no longer able to maintain the indicated frequency over 2 consecutive or 3 alternate beats or perform the maximum range of the indicated motion.
The stabilometric test was performed with the volunteers standing on the dominant limb for 60 seconds on a force plate FootWork , AM3, France , which was placed next to the flexion-extension machine to limit the resting time to the bare minimum approximately 5 seconds between the fatiguing exercise and the stabilometric test. Their upper limbs were allowed to hang along the body, and the trunk was kept upright.
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The volunteers were instructed to stare fixedly at a dot with a 0. The force plate comprised a rigid base covered by 2. The force plate was connected to a microcomputer, and the data were analyzed using the FootWork software Arkipelago, version 2. A set of stabilometric parameters was established based on the filtered data, and the following variables were measured using the software: CoP oscillation amplitude on the mediolateral and anteroposterior planes; displacement area; and anteroposterior and mediolateral root-mean-square velocity.
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The Shapiro-Wilk test confirmed the normality of the data, and the repeated-measure t-test was used to establish the effect of the fatiguing protocol on the stabilometric parameters. These tests were performed using the statistical package Statistica 7. The load lifted by the volunteers in the 1RM test was The CoP oscillation on the mediolateral plane before and after fatigue induction was 2. The present study sought to investigate the influence of fatigue of the knee extensor muscles on postural control in healthy individuals, with the hypothesis that fatigue would have acute effects on postural control.
These particular muscles were selected because they play an important role in the performance of motions required for both the activities of daily living and the practice of sports Our results showed that, indeed, fatigue exerted an influence on the somatosensory system and altered certain stabilometric parameters. As the remainder of the components of the control system visual and vestibular were not subjected to direct manipulation and were left unaltered, the changes identified in the present study were mostly attributed to the somatosensory system.
Muscle fatigue is defined as the transient inability to generate force or reduction of the production of force needed to perform a given task The mechanisms underlying the alterations in balance and joint position in localized muscle fatigue have not yet been elucidated but most likely include afferent and efferent components involved in the processes required to maintain functional stability and effective motor control The influence of fatigue on balance was found to occur independently from the CoP displacement plane i. One explanation to account for the decreased ability to maintain body stability may be afforded by the reduction of the muscle capacity to generate fast and precise responses fit to generate the continuous adjustments of the CoP needed to maintain a stable posture.
As a consequence, fatigue may have interfered with the muscle capacity to generate the torque required to control the oscillatory motions of the center of body mass 30 , Although the maintenance of posture demands a low joint torque, the slower speed of torque generation during the state of fatigue seems to play an important role. The changes exhibited by the stabilometric parameters after fatigue induction indicated dependence of the sustained postural control on efferent mechanisms during the state of static balance, and similar findings have been reported by other authors, despite the use of different experimental methods.
For example, Carter et al. Additionally, Johnston et al. Both sets of findings 11 , 32 highlight the effects of fatigue on postural control and also seem to indicate that such changes depend on afferent and efferent mechanisms, a contribution that deserves more thorough attention. Moreover, a previous study involving the induction of fatigue by means of isometric and isokinetic exercises 21 found a similar reduction in postural control for the CoP variables, which suggests that the reduction of the postural control induced by fatigue is independent from the type of muscle contraction involved.
The influence of fatigue on postural control was investigated by Yaggie and Armstrong 7 , who observed greater CoP displacement amplitude in static balance, which lasted until approximately 10 minutes after the end of the fatiguing protocol. Together with the loss of their ability to control the CoP, the volunteers utilized a strategy involving the reduction of the displacement velocity. Thus, one may adduce that such strategies were used to improve body control by increasing the rigidity of the system, which oscillated more slowly and over a larger area, as an attempt to reduce the CoP displacement and the unbalance on the anteroposterior and mediolateral planes.
The difficulty associated with controlling the motions that increase system rigidity increases together with fatigue, and this may be associated with the greater oscillations exhibited by the CoP A previous study investigated muscle fatigue affecting the ankle, knee, and hip joints as well as the abdominal muscles on the control of dynamic balance 35 , and the results showed that fatigue of the knee and hip joint muscles was associated with less balance reduction compared to other groups of muscles. In addition, Miller and Bird 35 observed that fatigue of the lower limb proximal muscles exerted a stronger impact on balance as compared to fatigue of the distal muscles.
Additionally, the results of the present study revealed a strong effect of fatigue on the ability to maintain static balance.
Thus, fatigue of the knee extensor muscles is sufficient to promote significant changes in postural control. In addition to its effect on the contractile tissues, the literature indicates that fatigue may also influence the afferent system and reduce the sensitivity of a set of peripheral mechanoreceptors located in muscles, ligament, tendon, and capsular structures What disturbs Paul in fact is the liminal nature of this non-human object with a human appearance.
Since the needs for artificial legs increased, the manufacturing process clearly intensified.
The manufacturing process quickly evolved into mass-production that followed Taylorist principles. The desubjectivized and de-subjectivizing object could be exchanged for another one, equivalent but different. He therefore owned several duplicates of the same pattern. This principle of substitution or duplication somehow recalls that operated on the paradigmatic axis.
The subjective instability that may derive from the possibility of interchanging artificial limbs and which recalls the flexibility of language itself was inclined to alert people who feared they would become a collage or an assembly of mechanical devices. And the Taylorist rhetoric truly generated ill-grounded confusion. For indeed, though the making of artificial limbs was standardized, each limb was of course adapted to each specific stump Guyatt The grotesque effect of the passage relies on Opphopf being a prisoner on the boat, annoyed because he is unable to join Cendrars for a glass of wine, since his mistress took his wooden leg and his crutches with her in order to prevent him from leaving the spot.
Another such light treatment is when Cendrars, in , is offered an honorific medal.
This replacing principle is a dead metaphor which, when it is brought back to life, clearly reveals the huge and incongruous discrepancy between tenor and vehicle. The three mutilated soldiers comically remind us that the artificial substitution can be laughed at. There is therefore no principle of substitution, but a coextensive relation between the present dead limb and the wheelchair. But paralyzed men were helpless, dependent on others for the most intimate care. Cohen They are the traumatic vestiges of the war and make physical death visible.
If Lawrence, in his treatment of the wheelchair in chapter XIII which will be analyzed further down, condemns the new connection between human body and machine, in the same period other people were truly fascinated by the new partly mechanic body. In it they saw a futuristic version of the human frame.
The modern technical intervention on the human body makes it more efficient. Such passivity is however ironically subverted at the beginning of the crucial passage in chapter XIII when Clifford and Connie go out in the meadow. Through a subtle blend of external and internal focalization, Lawrence depicts Clifford controlling his chair as a captain would command the wheel of his ship:.
Oh last of all ships, through the hyacinthine shallows! Oh pinnacle on the last wild waters, sailing in the last voyage of our civilization! Whither, oh weird wheeled ship, your slow course steering —!! Quiet and complacent, Clifford sat at the wheel of adventure: in his old black hat and tweed jacket, motionless and cautious. Oh captain, my Captain, our splendid trip is done! Not yet though! Downhill, in the wake, came Constance in her grey dress, watching the chair jolt downward. LCL This short dream scene, actually more Romantic than Futuristic, is the prelude to a moment of crisis.
In a slight futuristic fashion, he asserts his power over nature by repeatedly crushing the flowers with his machine. Such savage destruction underlines that Clifford is totally unadapted to nature. There is a confusion between the sick man and the sick machine.
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Clifford is therefore synecdochically associated with his machine, as he is merely a paralyzed part of the paralyzed whole. Clifford, seated a prisoner, was white with vexation […]. But she would not budge. Clifford then is doubly held hostage — of his inert body and prisoner of the inert machine. This episode is precisely a revealing moment of crisis. But the empowering metaphor fails. It is obvious that his paralyzed legs are the visible remains of the war, and the machine constantly draws attention to their inertness.
In our life journey we have the opportunity to plant seeds wherever we go, through our kind words and good deeds. You may have said something to someone 10 years ago, and then you hear that your words bore fruit.
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Once in a while we are blessed to see the impact we have had — not to get to our heads but to show us the power that we have to forever illuminate our corner of the world. When we act kindly and positively impact another person even if we are not aware of their impact , we have eternally changed the world. And our fruit, bear more fruit in a never ending continuum. It comes around full circle: The deeper the roots, the greater the fruits. Go deeper into this subject: Are you growing and bearing fruit? Did you enjoy this? It's free! Click here to find out more.
Have you forgotten how to live a meaningful life? You might be held back by limiting beliefs. Here are concrete, tried-and-true spiritual instructions for transcending a slump. One of the healthiest things you can do to find balance and harmony is to build a spiritual oasis in your life. The following suggestions can help you to grow solid spiritual roots — on a daily basis, at home — that you can always return to.
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