The sympatho-adrenal responses to physical exercise following long-term training are unclear. Previous work has demonstrated similar noradrenaline but greater adrenaline responses to high intensity exercise in endurance-trained compared to untrained subjects (Kjaer & Galbo 1988). Other research has reported no differences in sympatho-adrenal responses following maximal exercise between endurance-trained and untrained subjects but found a greater adrenaline response in sprint-trained compared to both endurance-trained and untrained subjects (Zouhal et al. 2001). Therefore, the aim of this study was to investigate the sympatho-adrenal responses of untrained, sprint- and endurance-trained subjects performing repeated brief maximal cycle sprints.

With local ethics committee approval and informed consent sprint-trained (ST n = 7), endurance-trained (ET n = 8) and untrained (UT n = 10) subjects participated in this study. Physical and physiological characteristics of ST, ET and UT were (mean ± S.D.); age 24 ± 7, 30 ± 10, 21 ± 1 years, body mass 73 ± 7, 68 ± 6, 76 ± 10 kg and Î{special}J{special}_max 58 ± 3, 52 ± 5, 67 ± 5 ml kg min^-1. Subjects performed ten 6 s maximal cycle sprints against a frictional load of 0.075 kg kg^-1 body mass with 30 s rest between sprints. Power output was corrected for flywheel acceleration. Blood samples (10 ml) taken from an antecubital vein at rest, immediately following each sprint and 2 and 5 min post-exercise were first used to determine blood lactate, then analysed for plasma catecholamines (adrenaline; AD, noradrenaline; NA and dopamine; DA) by HPLC with electrochemical detection (Davies et al. 1981). Data were analysed using one-way and repeated measures ANOVA with Tukey post-hoc where appropriate. Significance was established at P < 0.05.

ET demonstrated greater resting NA concentration compared to UT (2.0 ± 0.4 vs. 1.3 ± 0.5 nmol l^-1, P < 0.05). Peak NA concentrations occurred immediately following Sprint 10 in all groups (ST 28.3 ± 7.0, ET 16.5 ± 6.2 and UT 17.9 ± 7.0 nmol l^-1) with ST demonstrating greater NA from Sprint 5 onwards compared to ET (P < 0.05) and Sprint 8 onwards compared to UT (P < 0.05). There was an 8 fold increase in AD concentration from rest following sprint 10 in ST but a 3-4 fold increase in ET and UT (ST 5.0 ± 1.7, ET 2.7 ± 1.1 and UT 2.4 ± 1.0 nmol l^-1, P < 0.05). ST demonstrated greater AD following all sprints compared to ET and UT (P < 0.05) with no differences between ET and UT. A greater plasma DA concentration following sprint 9 was found in ST compared to UT (1.7 ± 0.9 vs. 0.8 ± 0.2 nmol l^-1, P < 0.05). Total work done over the ten sprints was greater in ST compared to ET and UT (ST 48195 ± 4897, ET 40597 ± 5890, UT 41706 ± 4131 J, P < 0.05). Blood lactate concentrations were greater 5 min post-exercise in ST (10.6 ± 1.7 mmol l^-1) and UT (10.6 ± 1.4 mmol l^-1) compared to ET (8.4 ± 0.9 mmol l^-1, P < 0.05).

The results of this investigation suggest that sprint but not endurance training may alter the magnitude of the plasma catecholamine response to repetitive brief maximal cycle exercise in man. Additionally, endurance training may alter the resting plasma NA concentration.