Abstract
As athletes push the limits of physical capacity they undertake training programmes that continue to increase the stress on their bodies. This can lead to an imbalance between the anabolic and catabolic processes, and a loss of fitness and performance potential. An extended periods of rest and recovery is then required before the athlete can resume full training. The research studies presented in this thesis were conducted to improve the understanding of measures commonly used to detect athletes at risk of overreaching.
The initial study, based around a 16 day training camp, measured the response, at rest, of body mass, heart rate and, haematocrit (Hct), creatine kinase (CK), and blood urea nitrogen (BUN), to a cyclic training programme. Small but significant changes in mass within a mean range of 0.77 kg were reported for the male and female subjects (p<0.001). Morning heart rate showed a significant increase to the first training cycle, and sinusoidal variations in response to changes in the training load. There were similar changes in haematocrit for males and females across the training camp although the changes were not significant. Haemoglobin was greater for the males than females (p<0.001) and increased and decreased across the camp (p=0.003). Mean creatine kinase (CK,) concentration were similar for males and females (p=0.084). The males demonstrated greater peak values of CK in response to the first training cycle and this would account for the by-sex difference in the response across the training camp (p=0.009). Blood urea nitrogen (BUN) was greater for males than females (p=0.004) with the BUN concentration increasing for both sexes across the training camp (p<0.001).
In the second study a number of heart rate measures and blood borne markers (haematocrit, CK, creatinine, BUN, lactate and glucose), hormones (total testosterone, cortisol, growth hormone and testosterone:cortisol ratio), were measured both at rest and after a short duration sub-maximal exercise challenge. These measures were made across a three day period of training and three days of recovery designed to mimic the duration of the training implemented in the initial study and as often used by coaches. Supine pre-exercise (p0.001), final sub-maximal heart rate (p<0.001), and heart rate range (p=0.006) demonstrated significant responses to the period of training and recovery. Body mass (p=0.006), Hct (p<0.001), CK (p<0.001), creatinine (p=0.006), BUN (p<0.001), lactate (p<0.001) and total testosterone (p<0.001), responded to the period of training and recovery. Haematocrit (p<0.001), creatinine (p=0.012), lactate (p<0.001), glucose (p<0.001), testosterone (p<0.001) and growth hormone (p=0.004), responded to the sub-maximal exercise challenge.
In the third study data collected were correlated with changes in maximal rowing performance across the three days of training and three days of recovery to determine their usefulness in tracking changes in performance capacity.
Changes in 2000 m ergometer rowing performance indicate that the training load was sufficient to produce a reduction in maximal performance across the three days of training from 382.0 ± 9.4 to 370.6 ± 10.2 watts (p=0.012) and that the performance returned to pre-training levels after the three days of recovery 385 ± 8.8 watts). Changes in the mean power output for 2000 m ergometer performance and measures made in the sub-maximal exercise challenge immediately prior to the 2000 m ergometer performance test demonstrated that immediate post-exercise lactate (r2=0.819, p<0.001), immediate post-exercise testosterone (r2=0.671, p=0.003), immediate and 10 min post exercise blood urea nitrogen (r2=0.724, p<0.001 and r2=0.68, p<0.001 respectively), were correlated with changes in mean power output and are strong candidate markers for tracking changes in maximal performance potential.
The fourth study examined changes in resting Hct and, total and free testosterone of international level male sprint swimmers across two years of training and competition. The results showed no differences between the training and racing periods of the annual training cycles for resting Hct and, total and free testosterone (p= 0.581, 0.771 and 0.983 resp.). The results demonstrated a strong correlation between changes in total testosterone and 50 m butterfly performance (r=-0.758). These results are consistent with measures made in the third study on changes in resting testosterone and 2000 m rowing performance.
The fifth study in this thesis examined the response of metabolic and other measures, at rest and during sub-maximal cycling exercise, in two trained swimmers who had been diagnosed with a recent viral infection. The study also monitored the changes induced by block of low intensity exercise training. Initially there were a number of differences of these subjects with a reference population. These included a lower resting and exercise heart rate (p<0.001), higher rating of perceived exertion in sub-maximal exercise (p<0.001), lower blood glucose (p=0.016) and higher respiratory exchange ratio (p<0.001). Blood lactate increased at a greater rate in exercise for the ill swimmers when compared to a reference population (group x intensity, p<0.001). Oxygen consumption and energy cost of the exercise was not different from the reference population.
In response to the low-intensity training the ill swimmers had an increase in exercise heart rate (p<0.035), a reduction in rating of perceived exertion (p=0.014) and a lower respiratory exchange ratio (p=0.014). Blood glucose was more stable with a minimal change across the intensities at which it was measured (p=0.012).
The results of this series of studies indicate that some measures made to monitor athletes in heavy training may be improved by the inclusion of measures made across a sub-maximal exercise challenge. The results also show that measures made of lactate, total testosterone and BUN immediately and, in the case of BUN, at 10 min after a sub-maximal exercise challenge appear sensitive in tracking changes in maximal performance potential and assist determining when in a taper an athlete may produce a peak maximal performance. Finally, the studies demonstrate the impact that a viral infection may have on the normal functioning of athletes and the effect on measures used to monitor athlete in training.