The Effects of 120 Minutes of Simulated Match Play on Indices of Acid-Base Balance in Professional Academy Soccer Players

This study investigated changes in indices of acid-base balance during 120 minutes of simulated soccer match-play that included a 30 min extra-time (ET) period. Eight English Premier League academy soccer players participated in a simulated soccer match that required varying intensities of intermittent exercise including 15 m sprints and soccer dribbling throughout. Blood samples were obtained prior to (i.e., baseline, pre-exercise) and throughout exercise (i.e., 15, 30, 45, 60, 75, 90, 105, 120 min), and at half-time. Sprint speeds over 15 m reduced in ET compared to the first (-0.39 ± 0.37 m∙s-1, -7 ± 6%, p = 0.021) but not the second half (-0.18 ± 0.25 m∙s-1, -3 ± 4%, p = 0.086). At 105 min, blood lactate concentrations reduced compared to the opening 30 min (-0.9 to -1.2 mmol·l-1, p < 0.05). Blood pH (-0.03 to -0.04 units), base excess (-0.95 to -1.48 mmol·l-1) and bicarbonate concentrations (-0.9 ± 0.8 mmol·l-1) were depressed at 120 min compared to 105 min, baseline and half-time (all p < 0.05). There were no significant correlations between changes in acid-base balance and sprint speed (all p > 0.05). Although the perturbations in acid-base balance during ET were statistically significant, the decreases in blood pH, lactate, base excess, and bicarbonate concentrations may not represent metabolic acidosis or impairments in buffering capacity that are likely to explain reduced physical performance. Further research is warranted to investigate mechanisms of fatigue during ET and to develop interventions that attenuate decrements in performance.