Plasma glutamine and glutamate in road cyclists during two seasons of training and races

Abstract

It is well known that athletes practicing exhaustive exercise may present, at the end of a competitive season, signs of “overtraining”/”overreaching”, that comprise loss of performance and many physiological, metabolic and psychological changes. In an attempt to identify possible signs of “overreaching” we studied a group of ten professional cyclists, mass 72.1 ± 3.5 kg, VO2 máx 73.96 ± 3.7 mL.kg-1.min-1, age 23 ± 4.01 yr, for 2 consecutive competitive seasons. The maximal consumption of oxygen and blood lactate concentration, during an maximal incremental test, as a mean to evaluate changes in athletes performance, and plasma cortisol, glutamine and glutamate concentrations, as metabolic markers for “overreaching” were assessed. Blood samples were collected from the antecubital vein 9 times during the two years period, after bouts of high intensity training and competition. The maximal consumption of oxygen (74.9 ± 1.69 mL.kg-1.min-1 and 77.62 ± 3.37 mL.kg-1.min-1, beginning and the end of first season) and plasma lactate concentration did not change during the experiment, but at the end of both seasons the athletes reported early fatigue symptoms, evaluated by using Borg scale, and could not reach the same load at the end of the tests (early exhaustion). Plasma glutamine (559.8 µmo.l-1 to 531.7 µmo.l-1 in the first season and 438.7 µmo.l-1 to 393.06 µmo.l-1 in the second season) and glutamate (214 µmo.l-1 to 167.2 µmo.l-1 in the first season and 244.2 µmo.l-1 to 205.64 µmo.l-1 in the second season) concentration were reduced at the end of both seasons, and plasma cortisol (363.15 µmo.l-1 to 569.66 µmo.l-1 in the second season), increased. Therefore, we conclude that the changes in plasma glutamine, glutamate and cortisol during a competitive season could be used as an early indicative of “overreaching”.