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Title: The epidemiology of injuries in elite soccer and the impact of injury-induced detraining on physiological performance
Author: Parry, Leslie
Awarding Body: Liverpool John Moores University
Current Institution: Liverpool John Moores University
Date of Award: 2010
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Abstract:
Injuries in professional soccer are common with the financial cost running into many millions of pounds. The incidence of re-injury on return to competitive action accounts for a high proportion of all injuries with inadequate rehabilitation being identified as one of the major factors when considering re-injury. Methods of improving the rehabilitation outcomes could therefore reduce the overall incidence of injury and may improve team performance through greater player availability. The accuracy of the available literature addressing the epidemiology of soccer injuries is questionable. It was therefore necessary to establish the incidence of soccer injury and reinjury using comprehensive data collection methods. A data collection method based on the principals of first hand injury observation, comprehensive and immediate recording of injuries and accurately timed exposure for both training and competitive matches was therefore designed. Study 1 used these methods to scrutinise the results of previously published literature. Results showed that the definition of the term 'injury' can have a significant effect on the results from epidemiological studies of soccer injuries. It was also observed that estimating exposure can result in an under-calculation of the injury frequency rate when reporting the rate as new injuries per 1000 training or playing exposure hours. The new methods for collecting epidemiological data clearly showed that methodology is important in generating study results and was adopted for the current thesis. The data collected to evaluate approaches to data collection indicated that injury is the major cause of absence in professional soccer although this assumption had never been investigated. Study 2 evaluated this supposition by investigating what percentage of total absences soccer injuries were responsible for. The data showed that injury was the major reason for absence with 50% of the incidents of match absence and 65% of training absence being as a result of soccer related injury. Other reasons for absence were also noted. For example, sickness and suspension were areas where it was suggested that availability could be positively affected by reducing the incidence of absence as a result of these two factors. To highlight the aetiology and severity of soccer injuries at one professional soccer club, a five-season comprehensive epidemiological study was undertaken. Study 3 showed that the average percentage of the playing squad per season sustaining an injury that resulted in more than one days absence from training or playing was 86%. Over the five seasons, an average of 41% of players sustained >1 injury in any one season the severity of which resulted in more than one days absence. Eighty five percent of all injuries throughout the study period were sustained to the lower limb. When analysing both severity and anatomical location of injury, it was found that, during the 5 competitive-season period, 82 injuries were sustained to the lower limbs which resulted in an absence of >14 days. It was suggested that these injuries may necessitate alterations to habitual training patterns which may, in turn, result in detraining. This detraining may result in players returning to competition ill-prepared for the physical and physiological demands of soccer play at the elite level and increase their susceptibility to re-injury. In order that the effects of injury-induced absence could be investigated, changes in players' performance, using a battery of soccer-specific field tests, was investigated in Study 4. All players absent for >2 d through injury were tested on their return to normal squad training. These results were compared with a data set collected when the players were fit and playing competitive soccer. No significant differences were observed in any performance variables for those players absent for <14 d. The results for players absent for >14d showed no significant differences in tests to evaluate flying 20 m sprint speed, counter-movement jump height and hamstring flexibility. Significant decreases in performance were however, found in estimated V̇ O₂max, and repeated sprint ability (RSA) performance. It was suggested that the decrements in aerobic power and repeated sprint ability may be related with high aerobic power being recognised as a requirement for recovery between bouts of high-intensity exercise. It was also suggested that one of the reasons for the performance decrements may be the changes in habitual soccer training patterns during rehabilitation. To investigate this hypothesis, study 5 compared the rehabilitation training load and the training load when participating in normal squad training and playing competitive matches. A 17-month investigation to quantify and compare the two modes of training was undertaken. Players who were absent for >14 d due to soccer injury had their rehabilitation training quantified using a number of established methods. On their return to normal squad training, the same methods were used to quantify training for a period similar to the duration of their rehabilitation programme. The period of rehabilitation when players were unable to run, due to the restrictive nature of their particular pathology, lacked the intensity of exercise normally associated with squad training and playing matches. A comparison of other phases of rehabilitation and normal training found no significant differences in average heart rate or ratings of perceived exertion measures. It was therefore demonstrated that the major difference between the two training periods was during early rehabilitation. In response to the findings of Study 5, Study 6 investigated the effect of increasing the intensity of exercise during early rehabilitation in reducing the effects of detraining following injury. This final study in the thesis investigated the effects of work-matched, constant pace, continuous exercise and intermittent-paced exercise in maintaining aerobic power and RSA performance. Players injured for >14 d (n=16) were randomly allocated to one of the two intervention groups and performed either continuous or intermittent exercise on rowers, cross trainers and cycle ergometers during the period of rehabilitation that they were unable to perform running exercise. Reductions in estimated V̇ O₂max and RSA were observed in both intervention groups with the reductions in performance of the constant-pace group greater than those observed in the intermittent pace group. None of these differences however, reached significance leading to the conclusion that both intervention programmes were effective in preventing performance decrements in V̇ O₂max and one was not superior to the other. The only negative changes observed were in RSA performance decrement for both groups from pre-injury to post-injury tests. Although these changes were found to be significant, the level of change was not sufficiently great to surpass the figure calculated as the smallest meaningful change. This was due to the lack of reliability of this particular test.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.518402  DOI: Not available
Keywords: RC1200 Sports Medicine
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