MEDIDAS SANITARIAS A APLICAR EN LA GRANJA O

The investigations in this thesis succeeded m further enhancing the understanding of muscle stiffness and soreness following exercise. Muscle stiffness was quantified and seen to show a "real" increase following exercise to suggest that muscle stiffness following exercise is not merely a perception. It is important to note that, in the present study, muscle stiffness was not measured following concentric or isometric exercise. The changes in muscle stiffness that have been observed following eccentric muscular contractions may also be observed following concentric or isometric exercise. Further research is therefore required in this area, and the results of this thesis must be viewed in this context.

post-exercise. Muscle stiffness exhibited the same adaptive qualities observed in previous research concerning muscle soreness. When a bout of exercise that originally created muscle stiffness was repeated six days later there was no increase in muscle stiffness. This was true for both die resonant frequency (squared) of the arm (RF^) and the range through which the aim would move in response to a set peak torque (AM). Evidence suggests that the adaptation is activity-specific.

The effect of muscle soreness on proprioception was investigated. The ability to copy a series of movements and positions of the dominant arm with the non-dominant arm in its noimal state was unchanged when the test was repeated with the non-dominant arm suffering from muscle soreness. The effect that eccentric exercise has on other aspects of peifoimance, for example, flexibility, stiength, psychology, technique have been investigated more thoroughly over the yeai's.

The physiology behind the increase in muscle stiffness in the forearm flexors is thought to be as follows. Immediately following the eccentric exercise, the arm is in a weakened state. The eccentiic exercise is thought to cause damage to the muscle cell membrane wliich leads to loss of sarcolemmal integrity allowing the contents to leak from within muscle cells. This leads to a build up of fluid which reaches a peak 48-72 hours post-exercise. This has the effect of altering the viscosity around the joint, and in effect makes it more difficult to perform flexion and extension of the foreaim. This build up of fluid partly explains the increase in muscle stiffness.

The damage to the cell membrane is also thought to inhibit the process by which calcium is removed from the calcium-binding sites on troponin and pumped back into the sarcoplasmic reticulum, leading to an increase in intracellular calcium. Eccentric exercise is also thought to dismpt tiie integrity of the sar coplasmic reticulum leading to an increase in the level of extracellular calcium. This build up of calcium is thought to cause involuntary conhaction of the muscle. When the integrity of the cell membrane is restored, the process for the removal of calcium will function effectively once more. This, in effect, switches off the contraction. Exercise in the form of passive flexion and extension of the elbow leads to fluid being squeezed out of the area surrounding the joint, and has the effect of decreasing the stiffness. Following cessation of movement the fluid returns to the area siuxounding the affected joint and stiffness continues to run its normal time course. The eccentric exercise also creates damage to the connective tissue and the site of greatest damage is thought to be in and ar ound

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the musculo-tendinous junction. This relatively inelastic tissue is stretched during the eccentric contractions and as a result micro-tears appear in the tissue. In response to the damage there is thought to be a shortening of the connective tissue, observable by examining the resting angle of elbow flexion post-exercise. This is like a safety mechanism, to protect the arm from extending through its full range, where discomfort is greatest. This shortening of the

connective tissue also partly explains the increase in muscle stiffness. The stiffness peaks 48 hours post exercise and in most cases has returned to its normal value six days following the exercise.

Following a bout of exercise that has created muscle stiffness it is thought tliat some stiengthening of both the muscle and connective tissue takes place. This repair and

over-compensation process can begin 1-3 days following the initial insult and endeavours to remove the damaged tissue and strengthen the remaining tissue. It is during this period that there is a gradual removal of the edema that has built up around the muscle. As a result, when eccentiic exercise is repeated there is little or no damage to the cell membrane, therefore little or no leakage of intracellular proteins (in particulai* calcium), little or no build up of fluid and hence no increase in muscle stiffness. Similarly, the connective tissue is strengthened

sufficiently to be able to cope with the same extent of exercise that has caused the damage in the first place. There is no obseiwable change m the resting angle of elbow flexion to suggest that shortening of the connective tissue has taken place. It is unknown how long the complete adaptation process takes. Byrnes et al. (1985) have shown that the adaptation lasts for six weeks for muscle soreness however it is unknown how long the adaptation wül last for muscle stiffness. Subsequent research may answer this question.

Several questions underlying the explanation of events that leads to muscle stiffness still remain unanswered and could be the subject of further research. The effect that muscle stiffness has on performance could be an area of frrrther research if the variables affecting performance could be controlled sufficiently, to allow skill to be scrutinised and quantified. This would

necessarily mean that a skill would have to be chosen involving the muscles that could be measured for muscle stiffness using the equipment of the present study. Alternatively, equipment could be built to measure muscle stiffness in other muscle groups.

The area of research is captivating because the symptoms have affected most people at one time. No treatment has managed to cure the symptoms of muscle stiffness and muscle

soreness. Exercise seems to be the best measure to prevent these symptoms from manifesting themselves and should involve a gradual increase in the frequency, intensity and volume of

tr aining across the full range of movement likely to be experienced by the sportsman or sportswoman. From the results of the thir d study (Chapter 6) it would seem that muscle stiffness and muscle soreness do not affect the ability to recall movement from memory. It is in the best interests of Sportsmen and Sportswomen to try to avoid muscle stiffness and soreness. Apart from the discomfort experienced, muscle stiffness and soreness can cause unnecessary interruptions to training and may lead to injury. Muscle stiffness and soreness will also reduce performance.

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