Six male football players competed in a 90 mini game (4-a-side) on two occasions following
an exercise and diet (either high- ~ 65 % or low- ~ 30 % carbohydrate intake) regimen
designed to manipulate muscle glycogen concentrations. Movement and technical parameters
of performance and selected physiological responses were measured. Pre-game muscle
glycogen concentrations following the high carbohydrate diet (mean±SD) (395.6±78.3
mmol·kg-1 dw) were significantly higher than following the low carbohydrate diet (287.1±85.4
mmol·kg-1 dw). The results of the movement analysis showed that the players performed significantly
more (~33 %) high intensity exercise in the game played following the high carbohydrate
diet. No significant differences were found, between the two dietary conditions, in
any of the measured technical variables. Plasma FFA and glycerol concentrations in
the game played following the low carbohydrate diet were significantly higher after
45 min (905±103 and 293±23 μmol·l-1) and post exercise (1388±122 and 366±36 μmol·l-1) compared to the game played following the high carbohydrate diet (532±137 and 202±55
μmol l-1 and 888±192 and 266±27μmol l-1, respectively). Post-exercise blood glucose levels were significantly lower in the
game played following the low carbohydrate diet (5.8±0.3 vs 7.2±0.3 mmol·l-1). No significant differences were found in the mean blood lactate values (3.5±0.6
and 3.9±0.5mmol·l-1) or mean heart rates (162 vs. 163.5 beats·min-1) between the high and low carbohydrate conditions, respectively. The main finding
from this study was that the carbohydrate content of the diet influenced the amount
of high intensity exercise performed during a small-sided football game. This suggests
that to optimise performances, in not only football but possibly also other multiple
sprint sports of similar duration, a high carbohydrate diet should be administered
in preparation for intense training and competition.
Key words
Blood lactate - carbohydrates - high intensity exercise - muscle glycogen - performance
