Choice Reaction Time During Graded Exercise in Relation to Blood Lactate and Plasma Catecholamine Thresholds

Abstract

Twenty-two male soccer players (mean age 21.3 yrs) performed an incremental, multistage bicycle ergometer exercise test with work load increasing by 50 W, until volitional exhaustion. The exercise stages lasted 3 min and were separated by 1 min resting periods. Before exercise and during each load an audio-visual five-choice reaction task was administered to assess subjects' psychomotor performance. During resting intervals venous blood samples were taken for lactate (LA), adrenaline (A) and noradrenaline (NA) determinations. It was found that reaction time (RT) decreased gradually during exercise reaching its minimum (approx. 87% of pre-exercise value) at load 236 W (approx. 75% VO2max, HR 164 beats/min). Then, it increased rapidly, exceeding the resting level by 18%. The work load and heart rate (HR) associated with the minimal RT were higher (p < 0.001) than work load and HR associated with the LA threshold (by 46 W and 17 beats/min, respectively). Plasma A and NA showed an exponential increase during exercise with thresholds at 204 and 208 W, respectively (HR 149 and 154 beats/min). Work load at which plasma NA threshold occurred was significantly higher than the LA threshold but it did not differ from the work load associated with the minimal RT. Conversely, plasma A threshold was lower than the load of the minimal RT but did not differ significantly from LA threshold. It is concluded that young athletes continue to improve their psychomotor performance during exercise even at heavy work loads exceeding anaerobic, and plasma adrenaline thresholds. A relationship between reaction time and plasma catecholamines fits the U-shape curve.