['Splenic contraction induced by repeated apneas has been shown to increase oxygen availability. Our aim was to determine whether repeated maximal voluntary apnea enhances the performance of cyclists in a subsequent 4-km time trial.', 'Seven male cyclists [age: 27.1 ± 2.1 years; height: 182 ± 8 cm; body mass: 74.8 ± 9.2 kg; peak oxygen uptake: 56.9 ± 6.6 mL min(-1) kg(-1) (mean ± SD)] performed a 4-km time trial on an ergometer with and without four prior maximal bouts of apnea interspersed with 2 min of recovery.', 'The average power output during the time trial was similar with (293 ± 48 W) and without (305 ± 42 W) prior apnea (P = 0.11, d = 0.27). The spleen was reduced in size after the fourth bout of apnea (-12.4 ± 9.0 %), as well as one (-36.6 ± 10.3 %) and 10 min (-19.5 ± 17.9 %) after the time trial, while with normal breathing the spleen was smaller one (-35.0 ± 11.3 %) and 10 min (-23.4 ± 19.7 %) after the time trial. Heart rate; oxygen uptake and carbon dioxide production; tissue oxygen saturation; and the lactate concentration, pH, oxygen saturation, level of hemoglobin and hematocrit of the blood were similar under both conditions.'] Does repeated apnea-induced contraction of the spleen in cyclists enhance performance in a subsequent time-trial?