Although soccer is one of the more researched intermittent team sports, there is a surprisingly modest amount of information available on the effects of fatigue on skill performance. The main reasons for this are due to the problems of overcoming the barriers of controlling the many variables in the field and a lack of reliable and valid skill tests. The Loughborough Intermittent Shuttle running Test (LIST) is a recently developed exercise protocol which closely simulates the demands of multiple-sprint sports such as soccer in a controlled environment. Furthermore, the Loughborough Soccer Passing Test (LSPT) and Loughborough Soccer Shooting Test (LSST) were developed (and modified further as part of this thesis, Chapters 5 and 6) and found to be reliable and valid indicators of soccer skill. Therefore, one of the main aims of this thesis was to investigate the influence of 90 min of the LIST on soccer skill performance. Early researchers (e. g. Karlsson, 1969 and Saltin, 1973) reported the -benefits of maintaining a high muscle glycogen content on soccer performance and more recent investigators looked at the effect of providing carbohydrate (CHO) during exercise on work rate and soccer skill. However, many of these experiments were completed in the field setting and used poor tests of skill. Therefore, the primary aim of these series of experiments was to determine the influence of ingesting a carbohydrate-electrolyte (CHO-E) solution during the LIST on soccer skill performance. There was an 8% deterioration in LSPT performance following 90 min of intermittent high-intensity running, even with fluid ingestion (p<0.05). Furthermore, the ingestion of a CHO-E solution during exercise showed tendencies for better maintenance of skill performance towards the end of exercise. Moreover, CHO-E supplementation better maintained sprint performance and a higher relative exercise intensity during exercise (p<0.05). This is crucial in soccer perfon-nance, as players who are unable to sprint to get to the ball will be unable to perform the necessary skill. From the results of Chapters 5 and 6 it was found that the modified passing (LSPT) and goal-shooting (LSST) tests were valid and reliable tests of soccer skill. Moreover, they were found to be more repeatable when higher calibre players performed the tests. As in previous studies there was a speed-accuracy trade-off' in LSST performance i. e. subjects increased the time taken to complete each shot sequence and reduced the shot speed to maintain shooting accuracy post-LIST. There was a trend for CHO-E ingestion to maintain a better shot speed and time taken for each sequence. The ingestion of CHOE also reduced the perception of effort (p<0.05) and led to more positive feelings of affective valence during the last 30 min of the LIST. Therefore, based on these findings, it was concluded that the ingestion of CHO-E solutions over water alone should be encouraged to soccer players because of the tendency to better maintain soccer skill and the associated physiological, biochemical and psychological benefits during such exercise.

The impact of fatigue on the intermittent high intensity exercise undertaken during participation in team sports has not been extensively studied. Team sports are characterised not only by intennittent exercise, but also by the contribution of a wide range of skills. This thesis describes a series of studies conducted in a controlled environment to assess the influence of fluid ingestion and fatigue on selected soccer skills. The aim of the first study was to examine the effect of 90-min of high intensity shuttle running with and without water ingestion on a socc er-dribb ling test. The subjects were allocated to two randomly assigned trials either ingesting or abstaining from fluid intake during a 90 min intennittent exercise protocol (Loughborough Intermittent Shuttle Test: LIST). In the absence of water ingestion soccer skill deteriorated (p < 0.05) by 5% but was maintained when fluid was ingested. The principal aim of the second study was to understand further the mechanisms contributing to the deterioration observed during the LIST. Subjects completed the LIST ingesting a 6.4% carbohydrate electrolyte solution (CHO), placebo (CON) or no fluid (NON). Free fatty acids, cortisol and aldosterone responses were lower (P < 0.01) at the end of exercise during both CHO and CON in comparison to NON. There was no difference in respiratory exchange ratio between trials. Fluid ingestion did not appear to cause a shift in substrate metabolism even though there were differences in plasma FFA concentrations. The consumption of carbohydrate during exercise has been shown to increase physical performance, capacity and cognitive function. The aim of the third study was to assess the influence of a 6.4 % carbohydrate-electrolyte (CHO) placebo (CON) or no fluid (NON) on passing and dribbling soccer skills following the LIST. During the NON trial performance of the dribbling test followed a similar pattern to that in the first study and performance of the passing test decreased (p < 0.05). This reduction in performance was prevented during the CHO and CON trials. The purpose of the final study was to identify whether a rehydration strategy following the LIST would result in a recovery of skill performance. Subjects were allocated to two randomly assigned trials either ingesting a volume of fluid equivalent to 150% (L) or 9% (S) of body mass loss during the LIST, over a2h recovery period. During the recovery period serum sodium and osmolality returned to resting concentrations in the L trial but remained elevated in the S trial (P < 0.05). Despite body mass returning to resting values following the rehydration period, performance of the skills tests remained impaired. Deterioration in skill test performance may have been related to a reduction in neuromuscular control either by a reduction in muscle glycogen or by an increase in muscle damage during the no fluid trials. The mechanism responsible for the deterioration in skill performance remains to be elucidated.

Sammanfattning Syfte och frågeställningar: Syftet med undersökningen var att ta ett första steg mot att skapa ett testbatteri, som objektivt kan mäta fotbollspelares tekniska prestationsförmåga med boll, samt konstruera en rad övningar som innefattar viktiga fotbolls-specifika tekniker och testa dessa övningars reliabilitet genom ”test-retest”. Syftet med studien var också att göra en jämförelse i prestation mellan varje spelares dominanta och icke-dominanta fot, från tillslagsövningar där båda fötterna används.   Metod: Tolv herrjuniorer (16-19 år) och sju damjuniorer (15-17 år) på elitnivå genomförde ett testbatteri bestående av totalt 21 övningar för mätning av de fotbollsspecifika teknikerna nick, mottagning, driva med boll samt tillslag. Åtta av männen (16-19 år) återgenomförde testbatteriet för utvärdering av testbatteriets reliabilitet. Korrelationen mellan vardera övningens testresultat från den första testomgången (test) och den andra testomgången (retest) bestämdes genom användandet av Pearsons korrelationskoefficienter (r). Skillnader i kvantifierad prestation mellan dominant och icke-dominant fot beräknades med hjälp av ett beroende t-test. Resultat: Fem av övningarna genererade signifikanta korrelationer mellan resultaten från de båda testomgångarna. Dessa övningar var: precisionsskott på stillaliggande boll med dominant fot (r=0,949), skotthastighet med dominant fot (r=0,734), mottagning med bröstkorgen av boll levererad i luften (r=0,743), samt övningarna rak sprint utan boll och rak sprint med boll där kvoten mellan de två sistnämnda övningarna visade på signifikant korrelation (r=0,805). I båda grupperna förelåg en signifikant skillnad i prestation mellan dominant och icke-dominant fot i övningarna; skotthastighet, långpass på marken samt upprepade tillslag. Herrjuniorerna uppvisade dessutom en signifikant skillnad i prestation i övningen skottprecision på studsande boll. Slutsats: Det ringa deltagareantalet gör att resultaten i studien bör tolkas med försiktighet. Studien visa dock att en objektiv utvärdering av flera fotbollsspecifika tekniker är möjlig och några av övningarna visade hög korrelation mellan test och retest. Då resultaten i vissa avseenden pekar på signifikanta skillnader i prestation mellan dominant och icke-dominant fot anser författarna att båda fötterna bör testas i utvärderingar av en spelares tekniska förmåga. / Abstract Aim: The aim of the study was to create and evaluate a test battery, which in an objective way could measure a group of soccer players’ technical performance, and further, to create a series of exercises, which incorporate important soccer-specific techniques, and test the exercises for reliability through “test-retest”. The aim of the study was also to make a comparison between dominant leg and non-dominant leg in exercises where both feet were being used. Method: Twelve male elite junior players (age 16-19) and seven women junior players (age 15-17) underwent a test battery consisting of a total of 21 exercises to measure the soccer-specific techniques of heading, controlling, running with the ball, and touch of the ball. Eight of the men (age 16-19) underwent the test battery again in order to evaluate the reliability of the test battery (”retest”). The correlation between each exercise’s test result from the first test session (”test”) and the second test session (“retest”) was determined by the use of Pearson’s correlation coefficients (r). The differences in quantified performance between dominant leg and second best foot non-dominant leg were calculated by the use of a paired t-test. Results: Five of the exercises showed significant correlation between the results from the two test sessions. These exercises were: dead ball precisionshot using best foot (r=0,949), shotspeed using best foot (r=0,734), controlling airborne ball with chest (r=0,743) and the exercises straight forward sprint without the ball and straight forward sprint with the ball from which the ratio between the two last mentioned exercises showed significant correlation (r=0,805). In both groups there were a significant difference in performance between best and second-best foot in the exercises of; shooting speed, ground long passing, and repeated touches. In addition, the male juniors showed a significant difference in performance in the exercise of shooting precision on bouncing ball. Conclusions: The low number of participants leads to the notion that the results of the study should be interpreted with precaution. The study however shows that an objective evaluation of several soccer-specific techniques is possible and that a couple of the exercises showed high correlation between ”test” and ”retest”. Since the results in some aspects point towards significant differences in performance between second-best foot and best foot, the authors’ opinion is that both feet should be tested in an evaluation of a soccer player’s technical ability.