A COMPARISON OF KINEMATICS AND PERFORMANCE MEASURES OF TWO ROWING
1Department of Musculoskeletal Surgery, Imperial
College London, Charing Cross Campus, UK
2Bioengineering, Imperial College London, UK
22 June 2005
Journal of Sports Science and Medicine (2006) 5, 52
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injuries have been attributed to poor technique, suggesting a need
to understand the mechanics of rowing and the influence on technique
of different training regimes and ergometers. The aims of this study
were to investigate the repeatability of the kinematics of the lumbopelvic
region during rowing and to compare these kinematics between rowing
on two different ergometers. An electromagnetic motion measuring device
in conjunction with a load cell was used to determine the ergometer
rowing kinematics of 12 rowers. Subjects were tested on three occasions
at two different stroke rates, with an interval of one week between
testing. Two datasets were obtained for the Concept II, to establish
the repeatability of the kinematics, and one for the WaterRower. Bland
and Altman's mean difference technique was used to test for consistency
of technique, and the difference between ergometers was assessed using
Students' paired T-tests. The kinematic measures of the lumbo pelvic
region during rowing demonstrated high repeatability. The two ergometers
showed a similarity in force profiles but some significant differences
in rowing kinematics. There was greater rotation of the thigh segment
in the sagittal plane throughout the stroke on the WaterRower (p <
0.01). There were also trends indicating that rotation of the pelvis
in the sagittal plane was different between the two ergometers, for
example on the Concept the mean angle of the pelvis at the catch was
5.4° and on the WaterRower it was 2.4° (p < 0.05). Measurement
of lumbopelvic kinematics during rowing on a Concept II ergometer
is repeatable. However, rowing kinematics varies between ergometers.
Because a full analysis comparing rowing kinematics on water with
rowing ergometers has not been made in this study, no conclusions
regarding which ergometer simulates rowing on water can be made. The
implications of the effect of these differences in technique requires
WORDS: Lumbo-pelvic rhythm, spinal biomechanics.
is a skillful sport with distinct phases to each stroke, which have
to be combined in an effective manner to ensure maximum power output
and acceleration of the boat through the water. These phases can
be summarised as the catch, drive, finish and recovery (Redgrave,
An understanding of the mechanics of the rower in achieving these
stages of the stroke is slowly evolving (Bull and McGregor, 2000;
Holt et al., 2003),
however, it is not yet clear how this is related to both performance
and injury. Rowing injury rates are low, indeed much lower than
in contact sports (Budgett and Fuller, 1989).
However, injuries still occur and lead to elite rowers missing an
average of 24 training days per year (Bernstein et al., 2002),
and can relate to the success or failure of a crew.
A common and widely studied problem in rowing is that of low back
pain and related lumbar spine injuries (Bull and McGregor, 2000;
Caldwell et al, 2003;
O'Kane et al., 2003; O'Sullivan et al., 2003; Reid and McNair, 2000; McGregor et al., 2004; Roy et al., 1990; Teitz et al., 2002;).
The spine and trunk extensor muscles play a vital role in the rowing
stroke by providing a stable base for transfer of the power generated
by the arms and the legs to the blade (Holt et al., 2003;
Roy et al., 1990).
Consequently, during the stroke cycle great forces are placed on
the flexed lumbar spine.
It has been postulated that the repetitive action of the stroke
with loading and unloading of the spine predisposes the rower to
low back injury. This however, requires further research (Bernstein
et al., 2002;
Caldwell et al., 2003;
McGregor et al., 2002;
Reid and McNair, 2000).
Other studies incriminate land training and in particular the use
of the rowing ergometer (Bernstein et al., 2002;
Teitz et al., 2002). Rowing ergometers are designed to simulate the movements
performed during rowing on water. They are used in training and
routine testing of oarsmen and women, and have been noted to do
this with a high level of success (Lamb, 1989). However, there are no data to compare the rowing kinematics
of the body on water with that on ergometers. Most notable is the
discrepancy between sweep rowing that includes an out-of-plane rotation,
and ergometer rowing that is essentially a planar activity. Whilst
the ergometer has been indicated to have high reliability in performance
measures (MacFarlane et al., 1997; Schabort et al., 1999), less is known regarding the technique the rowers used
to achieve these performance measures.
Traditionally, rowing machines have provided simple data on time
taken to row a set distance. More recently many machines have been
adapted to allow further parameters to be measured such as stroke
length and force data. Such information has been used as a feedback
to rowers to refine and correct faults and weaknesses in their stroke
(Bernstein et al., 2002;
Bull and McGregor, 2000; Lamb, 1989). One study went on to measure spinal kinematics of the
rowing during the rowing stroke (Bull and McGregor, 2000) and through a series of subsequent studies identified
key factors which influence the rowing stroke (Holt et al., 2003; McGregor et al., 2004, O'Sullivan et al., 2003). Through this type of work, information pertaining to
injury mechanisms and injury prevention can be gathered. However,
at present the repeatability of these kinematics measurements of
ergometer rowing are not known.
Additionally it is not known how the design of the ergometer impacts
body kinematics. Two basic designs of ergometer exist, the fixed
head or stationary (for example, Concept II ergometer - Concept
II, Morrisville, Vt, U.S.A.) and floating or moving head (for example,
RowPerfect ergometer - Care Rowperfect BV, Hardenberg, The Netherlands).
Bernstein et al. (2002)
postulated that the moving head design leads to a more realistic
rowing stroke and noted differences in parameters of the stroke
profile when compared to the fixed head design. However, the relevance
of these differences is unclear. In an attempt to more closely replicate
the rowing action a new fixed flywheel ergometer, the WaterRower
(WaterRower UK Ltd, London, United Kingdom), was designed, the flywheel
of which moves a mass of water rather than air. This system, unlike
the others is claimed by the manufacturers to be able to maintain
a constant resistance through the stroke in order to more realistically
represent the on-water scenario. However, the mechanics and kinematics
of this ergometer have not been examined.
Therefore, the aims of this study were firstly to determine the
repeatability of kinematic measurements of rowing performance that
relate to the lower back and pelvis and secondly to examine how
these parameters of performance vary between two different fixed
head rowing ergometers.
Twelve novice male rowers were recruited from the Imperial College
School of Medicine Boat Club and written informed consent obtained.
All rowers had rowed a minimum of one year and a maximum of five
years. The subjects had an average age of 21.7 ± 1.8 years (SD),
an average height of 1.79 ± 0.05 m and an average mass of 74.4 ±
7.0kg. All were sweep rowers with 7 also being scullers. Subjects
with a current episode of low back pain or any other serious illness
or injury were excluded from participation in this study. All subjects
regularly trained on a Concept II ergometer; their experience of
the WaterRower system was limited to a familiarisation session in
the laboratory that consisted of rowing on the WaterRower for a
short period until the rowers were confident of rowing according
to normal training protocols.
Assessment of rowing kinematics
The kinematics of the lumbo-pelvic region was assessed during the
rowing stroke using the Flock of Birds (Ascension Technology, Vermont,
USA) electromagnetic measuring device as previously described (Bull
and McGregor, 2000). This was further integrated with a load cell (Oarsum,
NSW, Australia) positioned on the handle of the ergometer that permitted
measurement of tensile force at the handle during the stroke and
a further motion sensor to determine stroke length (Holt et al.,
2003). Data were captured at 35 Hz. From these measurements
a detailed investigation of lumbo-pelvic rhythm and force production
during the stroke was obtained.
Subjects were asked to perform a brief warm-up on the rowing ergometer
to accustom themselves to the equipment. After this, they performed
a 300 metre training session at a rate of between 18-20 strokes
per minute. This also consisted of maintaining a heart rate of between
130-150 beats per minute. Once the rate was maintained, data were
recorded from approximately 50 m into the piece until 10 m from
the end of the piece. All strokes recorded during the 240 m were
used in the subsequent analysis. This exercise was then repeated
at a rate of 28-30 strokes per minute. The procedure was repeated
on two further occasions each with an interval of one week between
recordings. At each session either a Concept II ergometer or a WaterRower
ergometer was used in a random order such that by the end of the
experiment two recordings were made on the Concept II and one on
the WaterRower. The two sets of measurements on the Concept II were
used to assess the repeatibility of the measurement technique. The
first one of these was used to compare with the WaterRower measurements.
The study did not compare the individual repeatibility of each ergometer.
The synchronised output from the Flock of Birds and load cell was
run through an in-house custom programme (Holt et al., 2003). This programme focused on sagittal plane motion and
characterised the stroke into percentage points with 0% representing
the catch position of the stroke that was determined from the onset
of tensile force production, and 100% being the return to this catch
position. Kinematic and tensile force data were averaged over each
rowing session and presented in terms of force, anterior-posterior
roation of the thigh in the sagittal plane, anterior-posterior rotation
of the pelvis in the sagittal plane, and anterior-posterior rotation
of the lumbar region in the sagittal plane (Figure
The following data points were determined from the averaged data;
peak force, power, work done through the stroke, and stroke length
(determined by the travel of the handle). The point at which different
phases of the stroke occurred were examined including where peak
force was achieved and when the drive phase ended. The following
kinematics variables were examined: thigh, pelvic and lumbar rotation
at the catch and finish position and the angle and stage in the
rowing stroke where maximal and minimum rotation of these segments
occurred. Finally the ratio of lumbar to pelvic rotation was determined
at the catch and finish positions.
The mean and standard deviation of each of the variables generated
for each data set was calculated using Microsoft ExcelTM.
The two sets of data generated on the Concept II rowing ergometer
were compared at both rowing rates to look at the consistency of
the rowers' technique using Bland and Altman's (1986)
mean difference technique. A good level of repeatibility was set
at a calculated difference of less than 1.85 N for force and 1.85°
for rotations. The first Concept II readings were then compared
with the WaterRower data using Students' paired T-tests, with the
statistical threshold being set at p = 0.05, again this was done
at both rowing rates recorded.
Considering the force curve data (Table
1), the mean difference values were all near zero (within ±1.85)
indicating good repeatability for these variables. The mean difference
values for the stroke power and peak force were, however, higher,
suggesting lower levels of repeatability. For the kinematic data,
the majority of variables had low mean difference values at both
stroke rates, indicating that the data were repeatable. However,
the repeatibility of the lumbo-pelvic ratio at the catch had very
high standard deviations. On closer inspection of the data, it was
noted that at the low rate there were two subjects with very much
higher ratios than the other subjects, with one rower's ratio being
-243° and the other 41°, while the majority remain between ±20°.
If these outliers are removed, the mean difference would become
1.33 ± 25.57 with the range -24.24 to 26.89. A similar finding was
observed at the high stroke rating for this variable.
Table 2 summarises the findings
in terms of force curve profiles. There were no significant differences
in between the two ergometers for all variables.
Differences were, however, noted when the kinematic variables were
compared (Table 3). When body
segment angles at the finish were considered, no significant differences
were observed between the ergometers in terms of pelvic or lumbar
from at the low stroke rate where lumbar rotation posteriorly (corresponding
to back extension) was noted to be greater on the WaterRower (p
< 0.05). Significant differences were observed in thigh rotation
(rate 18-20 p=0.005 and rate 28-30 p=0.04) at the finish of the
stroke (Figure 2). The reduced
thigh rotation suggests the rowers were not fully straightening
their legs on the WaterRower.
The lumbar rotation recorded at the point of peak force did not
alter significantly between the Concept II and the WaterRower ergometers.
The thigh rotation was different (rate 18-20 p = 0.001 and rate
28-30 p = 0.01) with the thigh demonstrating more rotation when
rowing on the WaterRower ergometer.
Lumbar rotation at the catch position for the low stroke rate did
not change significantly between the ergometers; there was a significant
difference (p = 0.03) in the pelvic rotation (Figure
3). At the catch the pelvis had less anterior rotation on the
WaterRower than on the Concept II. Interestingly, the data indicate
that the lumbar spine rotation was greater on the WaterRower than
the Concept, although there is not a significant difference (p =
0.39). The higher stroke rate demonstrates a similar trend but it
does not reach significance (p = 0.06). This would indicate that
the rower is utilising flexion of the back rather than hip flexion
to achieve the catch position on the WaterRower. The other significant
difference noted was an increase in thigh rotation at the catch
on the WaterRower (Figure 4),
this occurred at both stroke rates (rate 18-20 p = 0.004 and rate
28-30 p = 0.024).
study examined the repeatability of rowers' technique in terms of
spinal kinematics and force curve output on a Concept II rowing
ergometer. Overall technique was found to be highly repeatable for
kinematic variables, however, some loading differences were observed,
such as in peak force and stroke power. These parameters are, however,
more susceptible to variation as a consequence of the rowers' training
schedule and subsequent fatigue, a factor previously noted by Holt
et al. (2003).
appear to correlate with the findings of Schabort et al. (1999) who found a high level of repeatibility of physiological
performance by rowers when they were repeatedly tested on the Concept
II ergometer. Greater consistency in these measures would be anticipated
in more senior rowers.
The second aspect of this study was to compare rowing technique,
again in terms of kinematics movement of the spine and force curve
output, of two fixed head designs rowing ergometer, the Concept
II and the WaterRower. Previous studies have compared technique
between a fixed head and a floating head ergometer, and noted that
the oarsmen take a longer stroke on the fixed head ergometer, and
generated a longer stroke length as they fatigued (Bernstein et
The comparison of the two fixed head ergometers demonstrated many
similarities in the force curve data and stroke length. The kinematic
data, however, were not so comparable, with the most striking differences
observed in thigh rotation. Throughout the stroke the thighs were
held in posterior rotation on the WaterRower, so that at the finish
the athlete's legs did not fully extend, and at the catch the thighs
were in greater posterior rotation than on the Concept II ergometer.
One of the basic principles all rowers are taught is that at the
finish of the stroke the legs should be straight (Redgrave, 1995). The data demonstrates that this was only achieved on
the Concept II ergometer. The reasons and full implications for
this are unclear.
While the subjects were given a chance to familiarise themselves
with the WaterRower ergometer and were personally confident that
they achieved a good rowing technique, there is a possibility that
they did not use it for long enough to develop a consistent technique.
Schabort et al. (1999) found that familiarisation with the test environment,
including the ergometer used, led to enhanced and more consistent
performances. They postulated that this could be in part due to
decreased anxiety levels. However, the problems observed on the
WaterRower related to poor, rather than inconsistent technique.
An alternative explanation for the differences observed relate to
the design of the WaterRower. One possibility was that the angle
of the footplate and its relation to the seat was different between
the two ergometers, and it was this that led to the differences
observed. Modification of these design details was not the aim of
this current project.
A further interesting trend with respect to body posture was seen
at the catch. At the catch, a clinical understanding would be that
the rotation of the lumbar segment should be of a similar magnitude
to that of pelvic rotation to keep the spine in a strong position.
A large difference between these rotations would suggest an increased
loading of the soft tissues due to the greater motion of one segment
relative to the other. On the WaterRower the lumbar spine was not
in line with the pelvis, it was held in greater anterior rotation,
while the pelvis tended to be in posterior rotation. The thighs
were more anteriorly rotated on the WaterRower (clinically termed
'compression'), which could be related to this poorer posture. This
suggests lumbo-pelvic rhythm and control may be altered on the WaterRower,
the effects of which require further investigation with respect
to loading of spinal structures. Previous studies have suggested
that alterations in lumbo-pelvic rhythm are a factor associated
with low back trouble in rowers (McGregor et al., 2002; O'Sullivan et al., 2003).
Large forces are postulated to act on the spine during rowing (Reid
et al., 2000), and an alteration in lumbo-pelvic rhythm may
lead to an uneven distribution of this load which may in turn lead
to damage, this however, requires further research.
conclusion, rowing kinematics on the Concept II ergometer can be quantified
in an accurate and repeatable manner. These measures demonstrate that
differences in technique exist between ergometer designs, and the
findings suggest that the WaterRower can lead to what is thought to
be an aberrant technique. The implications of this require further
of lumbopelvic kinematics during rowing on a Concept II ergometer
kinematics varies between the WaterRower and Concept II
Employment: Medical student
Employment: Senior lecturer
Degree: MSc PhD.
Research interests: Spinal mechanics, biodynamics, and
Research interests: Musculoskeletal mechanics with an
interests in joints of the extremities, tools for orthopaedic
surgery, and the kinematic analysis of the musculoskeletal system.