Lactacidemia en el umbral anaeróbico. Estudio en varones prepúberes de escuelas deportivas de fútbol.

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It is generally accepted that childrens response to exercise is different from that of adults: children have distinctly lower maximal anaerobic power than do adolescents and adults, the muscle metabolic profile is better equipped for oxidative than glycolytic energy generation and the blood lactate concentrations are lower in children than in adults. The purpose of this study was to know the responses of blood lactate in prepubescent boys. Thirty-two soccer players (mean age 10.6 years) were tested during two days with two weeks in between testing sessions. Before the exercise test a complete physical examination was performed. They had no overt manifestations of any disease. Anthropometric measurements, x-ray of the left hand and wrist and gonadal maturation (orchidometry) were determined. On the first test, each subject performed an incremental triangular exercise (until exhaustion) using a bicycle ergometer. Gas exchange was measured breath by breath. The anaerobic threshold (AT) obtained is called ventilatory threshold 2 of Skiner and McLellan. On the second experimental day, the protocol for the test consisted of loaded cycling 50 watts under the AT during 5 min and after loaded watts of AT. Blood samples were collected after 5 min and every 3 min during the rest of the test, without the boys stopped. On cessation of exercise, blood samples were collected after 2 and 5 min. Free-flowing capillary blood samples for lactate determination were collected from a prewarmed fingertip. For statiscal analysis the packages SPSS 10.0 and BMPD were used. The somatotype turned out to be 3.7-5-2.7. The mean VO2peak was 48,79 ml/Kg/min, and the VO2 at AT was 37,18 ml/Kg/min corresponding to 76% of VO2peak. When the maximal steady state blood lactate (MLSS) concentration was assumed with increase, during all submaximal exercise, lower than 1 mmoll-1 the values were 4,31 ± 1,08 mmoll-1. If the MLSS was assumed with an increase lower than 0,5 mmoll-1, the values were 3,78 ± 1,06 mmoll-1. Our results were similar to those of Mocellin, Gildein and Billat, but higher than those of Williams. But direct comparisons between authors should only be made where identical procedures have been used.
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