Biochemical evaluation of running workouts used in training for the 400-m sprint.

A 400-m runner relies primarily on the lactate system for energy production. Although several running distances and schemes are used in training for this event, it is not clear which one(s) causes maximal activation of the lactate system so as to optimize adaptations of the lactic capacity. This study examined the effect of 4 running workouts differing in distance (300 vs. 400 m) and mode of execution (continuous/single vs. intermittent) on stimulation of the lactate system and biochemical markers of metabolism and muscle damage. Twelve young men performed 4 runs at maximal effort: 300, 3 x 100, 400, and 2 x 200 m. Blood was drawn before and after exercise for the measurement of lactate, glucose, creatinine, and creatine kinase (CK). Average speed was higher (p < 0.001) in the 300- vs. 400-m tests (7.52 +/- 0.50 vs. 7.08 +/- 0.59 m s(-1)) and in the intermittent vs. continuous tests (7.45 +/- 0.50 vs. 7.15 +/- 0.58 m s(-1)). Lactate was higher in the intermittent vs. continuous tests (16.3 +/- 2.2 vs. 15.0 +/- 2.0 mmol L(-1), p < 0.05). Serum glucose, creatinine, and CK increased after exercise (p <or= 0.001), and glucose was higher in the 400- vs. 300-m trials (5.76 +/- 0.46 vs. 5.33 +/- 0.30 mmol L(-1), p = 0.032). In conclusion, although all 4 running regimens greatly stimulated the lactate system, it appears that the intermittent workouts are superior compared with continuous ones of the same total distance in increasing the ability for energy production via the lactate system. Thus, intermittent workouts can be successfully used by 400-m athletes to develop specific (speed) endurance and should be considered to precede the continuous runs of racing distance within a macrocycle.