Preparing for the Olympic Games: Training adaptation in endurance sports

For most elite athletes winning an Olympic gold medal is the ultimate
dream. To make this dream come true, in the first place one needs sufficient
talent. However next to this talent, several years of training with large
amounts of strenuous work is necessary. It is therefore not remarkable that
the time required for adequate recovery may easily be compromised.
Doing so, an athlete is often challenging the optimal balance between
exercise and recovery.
The general purpose of this study was to get more understanding in the
physiological adaptation processes of highly trained elite endurance
athletes during periods of strenuous training.
This thesis is divided into three parts. The first part (chapter 2, 3 and 4)
describes the results of a three-year longitudinal study in professional
Olympic distance (OD) triathletes in preparation for Sydney 2000 Olympic
games. Chapter 2 gives a description of some measured performance
related physiological- and anthropometric variables in OD triathletes
during the different phases of a year. Despite a clear difference in the
amount of training between the several phases during the year, no
significant differences were found between the measured performance
related variables during submaximal and maximal exercise intensities.
In spite of large amounts of training elite OD triathletes have still a lower
maximal oxygen uptake (VO2max) compared to elite distance runners and
elite cyclists. Chapter 3 describes the changes in the hematological blood
profile, as a result of endurance- and altitude training. As red blood cells
play an important role in the transport of oxygen to the working muscles,
it is important to get insight into the dynamics of the red blood profile
and its possible changes in athletes, for instance with very intensive
training and altitude training. Over a three-year period, in a group of elite
male and female OD triathletes' blood samples were collected during
several moments throughout the year. It was found that intensive
endurance training had not much influence on the red blood cell profile in
male and female OD triathletes. However, it was found that most of the
athletes examined (female even more than male athletes), had
hematological values (particularly hemoglobin and ferritin) close to or in
some cases below the lower limit of the normal range. Altitude training
did alter the red blood profile significantly only when altitude training was
performed above 2000 meters above sea level. In chapter 4, the effects of
endurance training on the endocrine system throughout a year in OD
triathletes are described. Changes in hormonal plasma values are often
mentioned as good indicators for the balance between training and
recovery. Despite the significant differences in the amount of training
between the different phases of a competitive season, no significant
changes were found in the measured hormones throughout the year in
elite male and female triathletes.
In the second part (chapter 5 and 6) some exercise protocols that are
generally used to evaluate training and performance are addressed. In
chapter 5 (cycling) and chapter 6 (running), the effect of stage duration
on physiological variables in an incremental exercise test was studied.
For measuring reliable lactate values during an incremental cycling
exercise tests a stage duration of at least 5 minutes has to be taken into
account. In a running protocol, the stage duration for obtaining blood
lactate values that match exercise intensity, should be at least 6 minutes.
When measuring maximal values such as peak VO2, peak heart rates or
maximal workload incremental protocols with increments every minute
are sufficient.
In the third part (chapter 7 to 9) training intervention studies are described.
The purpose of these studies was to get more insight into the physiological
changes of the human body during periods of imbalance between training
load and recovery. Chapter 7 describes the effects of a 50% reduction in
training load over a period of 21 days on some performance-related
variables. Many trainers and athletes are afraid to reduce the training as
they think this will cause a loss in performance. However, the results
described in this chapter show that this fear is not supported by evidence.
Furthermore, it was found that an intermittent training program had no
benefit above a long slow distance training program. In chapter 8, the
results of a training intervention study (overreaching) are described.
The main purpose of this study was to investigate whether the generally
accepted overtraining markers are useful, and can be used as early markers
for overreaching. The main outcome of this study was that simple psychological
questionnaires appear to be a more indicative and sensitive markers
for detecting overreaching/overtraining in an early stage compared to the
measured biochemical- endocrinological- and physiological variables.
Furthermore, it was found that overreaching is associated with early
changes in cognitive performance, which can be detected by simple
cognitive performance tests. In chapter 9, possible differences in blood
chemical, neuro-endocrine and psychological parameters in response to an
intensified training period in runners and cyclists were investigated. The
results of this study indicate that runners experienced a period of
strenuous training as heavier compared to the cyclists. This difference of
subjective feeling was not reflected in the measured blood chemical and
neuro-endocrine variables.
In conclusion, the most important findings in this thesis are:
'' OD triathletes show hardly any variation in generally in sport measured
biochemical-, hormonal-, or performance related variables.
'' Regular control of the red blood profile is useful in well-trained endurance
athletes as many of these athletes have blood values close to or below the
lower limit of the normal range
'' The results of this study indicate that there exists an 'altitude threshold'
above which hematological alterations occur.
'' The endocrine system is (with the exception of cortisol) not a good tool
to prevent overtraining.
'' Cognitive performance tests appear to be useful to detect overreaching in
its earliest stage.
'' Endurance athletes are able to maintain their performance level for some
weeks in spite of reducing the training volume.
'' The subjective perception of very intense training is different between
cyclist and runners
'' To ensure a reliable lactate level in incremental exercise tests, a stage
duration of at least 5 minutes is required.