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|Title: ||Subjective and objective assessment of tennis racket performance play|
|Authors: ||Statham, Andrew|
|Issue Date: ||2007|
|Publisher: ||© Andrew Statham|
|Abstract: ||Assessment of wielded implement performance is important to a variety of human
endeavours and often critical to success in a sports context, particularly so in the game
of tennis. Tennis racket design and manufacture is a multimillion business involving
10 major international companies. Tennis participation is currently estimated at
around 60 million individuals worldwide. Thus the importance of optimum racket
performance to maximise competitive advantage and minimise the risks of injury is
This thesis presents work to enable advances in tennis racket performance with
respect to player feel perception, measurement of physical phenomena and the
correlation of these aspects within real play contexts.
To investigate feel perception a methodology was adapted from the existing literature.
Interview testing was conducted to elicit a comprehensive range of tennis specific
vocabulary. The end goal was to create a perception relationship map or ‘feel map’.
The inductive analysis was used to link all the related clustered themes identified
from the vocabulary to sub and base themes describing the relationship. Further
analysis introduced higher level general dimensions that unified common base
themes. The resulting feel maps were created from both English and German sample
groups, with a view to subsequent comparison.
To complete the map and broaden its application a wide scale questionnaire was
distributed to a tennis playing population. The responses provided data indicating
percentile use of selected vocabulary within the tennis community and the relative
importance players associate with assorted perception groups. Visual representations
of the data were introduced to the map for quick and easy use and an associated
lexicon compiled to provide a reference for more detailed information.
The feel maps and lexicon provide users with a versatile tool in the form of a
‘perception relationship model’. The map itself can act as an overall research guide for future work in the field. The addition of percentile use and relative importance
data mean the map can be used to create more informed and subtle player test
questionnaires or as a design aid, with interdependency links indicating which
additional factors should be considered or exploited for their influence on the
characteristic areas in question. Interestingly the general dimensions of highest
relative importance were sound and grip respectively. This may be due to the basic
level of interaction between player and racket which ultimately has to be perceived
either through the grip or from the sound. A perception test questionnaire was also
created with the use of the feel map and later used to study the correlation between
objective and subjective measures.
To best attain objective measures from the racket an innovative instrumentation
system was created. Two alternative systems were designed and tested, the first based
on wired instrumentation and data capture the second based on wireless technologies
as these became available. Both systems were required to take measures of grip
pressure and acceleration with 6 degrees of freedom.
The first system utilised uniaxial accelerometers mounted on an aluminium bracket,
and a triaxial accelerometer inserted inside the butt of the racket arranged to allow
measurement and calculation of acceleration from the required 6 degrees of freedom.
The system could be adapted to include either TekScan multi-cell full grip coverage
force measurement, or 2 single point higher sample rate single cell grip force sensors.
All data was fed via 15 m of cable to data acquisition systems. This restricted the
participants’ freedom of movement and encumbered the racket and thus the systems
application, making it unsuitable for extensive perception or fatigue testing.
The second system utilised a compact data logger with an integrated on board tri-axial
accelerometer small enough to be mounted within the racket handle. A revised mount
overcame the need for the aluminium throat bracket, moving the uniaxial
accelerometers into a bulbous addition to the butt of the racket. The system was
capable of capturing 8 channels simultaneously which allowed for the 6
accelerometers and two single cell grip force sensors to be located under the grip. The
system was more difficult to adapt and maintain than the wired system, but improved freedom and reduced added weight to the racket made the system far more suitable for
the planned perception and fatigue testing.
Fatigue testing conducted with the wireless device investigated the effect of full body
fatigue on players’ performance by monitoring the resultant effects in the racket. The
protocol was based on the multistage fitness test, designed to progressively increase in
difficulty until volitional fatigue. Heart rate data indicated that the protocol was
successful in fatiguing the participants to a point at or near their VO2max.
Unfortunately, with the wireless system in its early stages of development, the device
failed mid way through testing. The limited data set that was collected indicated that
technique was affected by fatigue. Further research is required to confirm this finding
and to make comparisons between racket types during the fatiguing process.
The wireless device was adapted to make it more durable and reliable before the
planned perception testing was conducted. A protocol was developed to investigate
the affect of changing racket moment of inertia on player perception and physical
measures. The test questionnaire developed from the feel map was used to evaluate
player perception ratings of various elements of racket feel, and the wireless
instrumentation system was used as part of methodology designed to compile a set of
comparable physical data. A detailed analysis of the results revealed that there was
some evidence of correlation between the perceptions of power, balance, flexibility
and control and the moment of inertia of the racket. In a design optimisation context,
however, more definitive correlations would be more useful. These would be
expected to be found with future testing utilising a wider range of racket properties.
The research proves to a large extent the original hypothesis that through the use of
non invasive instrumentation and improved player perception elicitation techniques it
is possible to substantially and usefully improve the objective and subjective
assessment of tennis racket performance in play to enable investigation of better
design characteristics and fatigue related injury phenomena.|
|Description: ||A doctoral thesis submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Mechanical, Electrical and Manufacturing Engineering)|
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