| dc.description.abstract | A variety of studies have been conducted which
have attempted to relate biomechanical and
physiological variables to cross-country skiing
performance. These investigations have taken place in
different settings including in the laboratory, outside
on roller skis, or on-snow on skis during time trials
and competitions. The design of these studies
undoubtedly provided the researchers with considerable
control over a variety of confounding variables.
However, these attempts at controlling variables may
have inadvertently created artificial situations with
little or no relevance to actual racing situations.
Forsberg (1992) pointed out that no one variable can
fully account for the observed differences in skiing
performance. A more integrated approach to studying the
sport was suggested by Hoffman & Clifford (1992)
combining physiological and biomechanical measurements
in order to achieve a better understanding of which
variables affect performance. The primary purpose of
this study was to develop a physiological and
biomechanical profile of the athletes competing in the
free technique legs of the 1994 World Cup Men’s Cross-Country Ski Relay event in Thunder Bay, Ontario,
Canada. The secondary purpose was to describe the
statistical contributions of specific kinematic and
temporal variables to the race velocity of World Cup
level cross-country skiers. The tertiary purpose of
this study was to compare the top international skiers
to the Canadian skiers on the basis of specific
physiological and kinematic variables.
The study involved the collection of physiological
data from six male members of the Canadian National
Cross-Country Ski Team four months prior to the relay
event and the collection of physiological,
biomechanical, and timing study data during the event.
Further biomechanical and timing study data were
collected from the remaining 18 international
competitors in the skating legs of the relay.
The lab testing involved V02peak testing and
monitoring of heart rates. The race site testing
included the monitoring of heart rates during the race,
of whole blood lactates immediately before and after
the race, of kinematic and temporal analysis of the
offset skating technique on a steep uphill, of skating
techniques used on different terrain, and of times
taken to ski different parts of the race course. The physiological, technique census, and timing study data
were analyzed using descriptive statistics. The
kinematic and temporal data were analyzed using a
combination of descriptive, multiple correlation, and
multiple regression statistics.
The kinematic and temporal analysis revealed
several significant relationships with race velocity.
Cycle length was positively correlated with race
velocity at the p<.01 level of significance. Cycle
velocity and percentage of the full cycle skating on
the downhill ski were positively correlated with race
velocity at the p<.05 level of significance. Further
significant correlations were found among the remaining
selected variables. Cycle length was negatively
correlated (p<.05 level) with the percentage of the
full cycle skating on the downhill ski. Cycle time was
negatively correlated (p<.05 level) with the percentage
of the full cycle time skating on the uphill ski.
Percentage of the full cycle time skating on the uphill
ski was negatively correlated (p<.05 level) with
percentage of the full cycle time skating on the
downhill ski. A multiple regression equation revealed
that cycle length was the best predictor of race
velocity.
The Canadian skiers were found to differ in terms
of their physiological and biomechanical profiles as
they related to race performance.
The physiological analysis of the Canadian
subjects revealed several interesting relationships
between heart rates and whole blood lactate values and
race velocity. The subjects anaerobic thresholds were a
good indicator of their relay race performance. The
faster subjects raced close to 90 percent of their
maximum heart rate. Pre-race and post-race whole blood
lactate values were similar to values reported by other
studies for top skiers. The peak post-race lactate
values did not show any trend in relation to race
velocity. However, the fastest subjects had the highest
whole blood lactate clearance rates.
A comparison of the Canadian subjects on the basis
of several kinematic and temporal variables did not
show any trends in relation to their race performance.
However, a closer look at their skating technique
preferences on different terrain showed some variation.
The fastest subject preferred to use the 2-skate
technique on 1-5 degree slopes, but the other subjects
used a combination of the 1-skate, 2-skate, or offset
skate techniques.
There were some distinct differences between the
top skiers and the Canadian skiers in terms of their
physiology, skating technique, and mean race velocities
for different parts of the race course. The relatively
low peak VO2 values for the Canadian skiers compared to
previous values reported for top skiers may have set an
upper limit to their anaerobic thresholds. The top
skiers had higher mean race velocities throughout the
course, higher cycle velocities, longer cycle lengths,
a more balanced skate off either ski, and a smaller
uphill pole angle at the moment of pole plant as
compared to the Canadian skiers. The full cycle times
and the percentage of the full cycle poling were
similar between the two groups. The top skiers
preferred to use the 2-skate technique on the 1-5
degree slopes while the Canadians used a variety of
techniques. Both groups of skiers used the offset skate
on slopes greater than five degrees.
The intent of this study was to develop a
physiological and biomechancial profile of World Cup
level cross-country skiers. Clearly the lack of
physiological data on the competitors other than the
Canadian subjects limited the inferences that were made
regarding the two groups. Despite these limitations this study has revealed some interesting physiological
and biomechanical differences between the top skiers
and the Canadian skiers. Further studies need to be
conducted on the physiological and biomechanical
demands of cross-country ski skating on elite level
athletes. | |
