Physiological and biochemical responses to exercise and training in adolescent runners

This thesis aims to identify physiological and biochemical variables, comparing sex, training status, age and maturity in sub-elite, endurance trained adolescents. Maximal lactate steady state was investigated and the effects of endurance training programmes measured. The first study assessed the reliability of absolute running speed, V02, and HR that correspond to the fixed blood lactate reference values of 2.0 and 2.5 mmo1. L"1 and the lactate threshold (LT) and found these measures to be reliable after endurance-trained adolescent runners completed two identical incremental treadmill tests within a 7-10 d period The second study was designed to determine the relationship between physiological variables and endurance running performance in this age group. Track-based, running performance times were available for 18 boys and 14 girls for the 800 m, and 16 boys and 13 girls for the 1500 m. The participants were tested using a step-wise incremental treadmill test and a Wingate anaerobic power test (WAnT) on separate occasions. The results from this study found that for the 1500m, running speeds corresponding to the fixed [BLa ] were a useful measure for assessing performance in endurance trained boys and girls. Unlike previous studies, peak V02 was not a significant physiological predictor of 1500m performance in either boys or girls. For the 1500 m performance in girls the anaerobic measure was no longer significant once variations in size or age had been taken into consideration. Whereas V VO2 peak and running economy may prove to be of some value when considering the 800m for boys, the running speed corresponding to a [BLa ] of 2.5 mmol-L-1 was the only meaningful physiological predictor variable for girls once differences in age and body size had been accounted for. The third study had three main objectives: (1) to identify the exercise intensity that corresponds to the (MLaSS) in adolescent, endurance trained runners, (2) to examine possible between sex differences, and (3) to compare the MLaSS with commonly cited fixed blood lactate reference variables. The participants were first tested using a step-wise incremental treadmill test to establish the blood lactate profile and peak VO 2. The running speed and % peak VO 2 at the MLaSS were not significantly different to those corresponding to the fixed [BL& ] of 2.0 and 2.5 mmol-L-1 (P>0.05). The % HR max at 2.5 mmol-L-1 was also not different to that at the MLaSS, whereas at 2.0 mmol-L-1 it was slightly lower (P<0.05). The running speed, % peak VO 2, and % HR max at the fixed [BLa] of 4.0 mmol-L-1 were significantly higher than those at the MLaSS (P