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
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.
Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.