Middle distance races are characterised by a start at high intensity without progression. Some studies focused on the warming-up (WU) effects on physiological parameters during race from 95% to 120% of the work rate at VO2max. The aim was to determine the efficiency of different WU protocols on time to exhaustion at maximal aerobic speed (M.A.S.). We recruited 11 middle distance runners (mean age 30±4 years, height 177± 7 cm, VO2max 59.7±6.4 mlO2.min-1.kg-1, M.A.S. 17.7±1.16 km/h). Subjects performed a triangular aerobic test to determine M.A.S. and three randomised rectangular tests at M.A.S. after three different WU protocols at 7 days of interval. The three WU protocols consist in no warming-up; 20 min WU at 55% of VO2max (low WU); 15 min WU AT 55% and 5 min at ((speed at LT 1 + speed at O.B.L.A.) / 2) (intense WU). After the WU, subjects observed 5 min rest before the rectangular test. Blood lactate concentration was measured four times (before WU, after WU, before and after rectangular test); whereas heart rate, VO2and ventilation were monitored continually. The mean heart rate during the rectangular test was higher (p<0.05) from the 1st–7th min after low and intense WU than without WU. The VO2max kinetic was the same in the three tests. Average blood lactate concentration was similar at the end of the race in the three protocols (6.9±0.8 mmol.l-1 without WU, 6.8±0.8 mmol.l-1low WU and 6.6±0.7 mmol.l-1 intense WU). Time to exhaustion at M.A.S. was higher (p<0.05) after intense WU. Results suggest that the intense WU has a positive effect on time to exhaustion at M.A.S. and therefore on aerobic performance. This is probably the result of a faster cardiovascular adaptation.