LONGITUDINAL CHANGES IN THE SPINAL KINEMATICS OF OARSWOMEN
DURING STEP TESTING
Biodynamics Group, Imperial College London, UK
21 June 2006
Journal of Sports Science and Medicine (2007) 6, 29 - 35
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studies have investigated the biomechanics of rowing during step testing
with a focus on lumbo-pelvic kinematics and force output and noted
that these parameters change with work intensity. The aim of this
study was to investigate how the biomechanics of the rowing stroke
changes over time as a result of coaching and training and to see
if these change were related to a change in physiological performance.
An electromagnetic motion measuring device in conjunction with a load
cell was used to determine the ergometer rowing kinematics of 7 elite
international oarswomen during routine step tests over a two year
period. Force output was observed to improve over the two year time
period, with peak force significantly rising by 40-80 N. This was
associated with significant increases in stroke length of between
15 and 19 cm. Both of these are indicative of improvement in performance.
Kinematic variables were also observed to change, with greater pelvic
rotation and associated lumbar spine motion at the later time point.
The findings of this study demonstrate that rowing technique changes
with time, and suggest that kinematics measures of rowing technique
may be important tools to monitor athletes.
WORDS: Stroke length, performance, lumbo-pelvic motion force
rowing is primarily an endurance activity, with almost 80% of the
rower's metabolic contribution to a rowing race coming from the aerobic
energy pathway (Pripstein et al., 1999).
Maximal oxygen uptake and maximal aerobic power are significantly
correlated to 2000m performance (Soper and Hume, 2004),
with many studies suggesting that changes in physiological profiles
are associated with increased winning potential (Messonnier et al.,
Fiskerstrand and Sieler, 2004).
Consequently physiological factors, particularly cardiorespiratory
and metabolic changes, are frequently used to assess aerobic performance
and changes in performance with time and aging (Hagerman et al., 1996).
There are a number of physiological tests that assess a rower's endurance
capacity and work output (Ingham et al 2002,
Secher et al., 1983).
An incremental "step test" measure the relationship between
the work output of the rower and the physiological response to that
work. This may be achieved through measuring the rower's oxygen uptake
or heart rate response and lactate accumulation (Beneke, 1995,
Forsyth and Reilly 2004).
When the physiological parameters are plotted against the rower's
work output, a curve is formed that allows individualised training
intensities to be set, as well as monitoring the effectiveness of
the rower's training (Beneke, 1995).
Recently this form of incremental testing on rowing ergometers at
different work intensities has been utilised to quantify biomechanical
parameters of technique in terms of musculoskeletal kinematics and
force production (McGregor et al., 2005).
Although such tests are not of maximal race performance, they do permit
a range of performance levels to be assessed in a controlled manner.
Studies focusing on the biomechanics of boat performance have suggested
that performance cannot be predicted from propulsive power, synchrony
of propulsive force and drag and indicated that other biomechanical
parameters were involved (Baudouin and Hawkins, 2002;
Although the kinematics of rowing technique are thought to contribute
to rowing performance (Soper and Hume, 2004),
it is still not clear what aspects of technique are important in terms
of predicting 'on water' performance, although stroke length has been
highlighted by coaches to be of importance. Similarly, it is not known
how technique changes in response to training load and coaching and
whether such changes are of importance with respect to performance,
although intuitively it is believed that such measures enhance technique.
Therefore, the aim of the present study was to examine whether biomechanical
measures of the kinematics of rowing technique assessed during a routine
step test change over time in a group of international female rowers
as a result of training and additional trunk strengthening work.
This study received local ethical approval, and all participants
provided written informed consent. In the initial phase of this
study, 12 elite oarswomen from the Great Britain National Team were
recruited. By the 2nd phase of the study performed 2 years later
but at the same point in the training year only 7 of the 12 remained
in the National Team; this study focuses on these 7. During this
2 year interval all were full time athletes following the same basic
training programme provided by their head coach which included an
additional twice weekly trunk strengthening programme. Due to the
competitive level and size of the training squad it was not possible
to have a control group. On completion of the study, their mean
age was 25.6 years ± 4.3 [sd], mean height 1.83 m ± 0.06, and mean
weight 75.1 kg ± 4.6.
of rowing kinematics
An electromagnetic system, the Flock of BirdsTM (Ascension Technology,
Vermont, USA) was used to assess the kinematics of the lumbopelvic
region. This system quantifies the motion of sensors (which can
be aligned to body segments) in an electromagnetic field in terms
of rotation about and translations along an electromagnetic transmitter
axis, and has been shown to have acceptable accuracy (Bull et al.,
The receivers of the system were attached to the skin at the thoracolumbar
junction (T12) (thereby measuring anterior-posterior lumbar segment
rotation that is lumbar flexion and extension), the lumbosacral
junction (S1) (measuring anterior-posterior sacral rotation or
pelvic tilt), and 10 cm proximal to the lateral epicondyle of the
right femur (measuring anterior-posterior femoral rotation or thigh
flexion-extension) as described and validated by Bull and McGregor,
and Bull et al., 2004.
The electromagnetic transmitter was aligned with the plane of movement
of the ergometer, so that sensor movement on the landmarks was recorded
as a rotation in the sagittal plane (flexion/extension), and out-of-plane
rotations. This system 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 (Holt
et al., 2003).
An additional sensor was placed on the handle to determine the position
of the handle in space and to permit the calculation of stroke
length, work performed, and power.
Each athlete performed an incremental exercise test comprising
5 steps on a Concept II model C rowing ergometer (Concept Inc, Vermont,
USA). This step test is defined as follows: each rower's initial
power output was determined from her current personal best 2000
m ergometer time. Five sub- maximal steps each of four minutes in
duration and separated by a one minute rest are defined so that
the power output of each of the five submaximal steps increased
by 25W and scaled for the power to be approximately 80% of their
2000 m level at the fifth step. Athletes are asked to maintain
the following stroke rates for the five submaximal steps; 18, 20,
22, 24, 26 strokes per minute.
The receivers of the electromagnetic motion system were positioned
on the subjects and a brief warm-up was performed on the ergometer
for 10 minutes using a low rating of between 18-20 strokes per
minutes. The receivers were checked to ensure that the sensor remained
appropriately attached to the subject, and the incremental 'step'
test was performed. Tests were performed on the same group of athletes
twice with a two year interval between testing (time A and time
B) with testing performed at the same point in the training season,
using the same protocol and same equipment.
The synchronised output from the Flock of Birds and load cell was
run through an in-house custom software program. This program 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% representing the return to this catch
position. This data normalisation allows kinematic data to be compared
within and between individuals. This technique is common in kinematic
analysis of repetitive activities (Shapiro et al., 1981).
The following derived data were recorded for each stroke: peak force,
work done through the stroke (ie area under curve), and power (work
done divided by time of the stroke). Stroke length which was defined
as the maximum horizontal travel of the handle was also noted (Holt
et al., 2003).
The data were averaged over each of the steps, with the initial
and final strokes eliminated from the analysis, and presented in
terms of force, anterior-posterior femoral rotation (thigh flexion-extension),
anterior-posterior sacral rotation (anterior/posterior pelvic tilt),
and anterior-posterior lumbar rotation (back flexion and extension).
The point at which different phases of the stroke occurred were
examined, including where peak force was achieved and when the drive
phase ended. For the kinematic analysis the catch was defined as
the onset of tensile force production and the finish as the point
at which there was no force application at the handle. Using these
definitions, the angle of the femur, lumbar spine and pelvis were
determined in both catch and finish position. Further, the angle
and position in the stroke of maximum flexion and extension of all
three markers was determined. Finally, the ratio of lumbar spine
rotation to sacral rotation was determined at the catch and finish
Statistical analysis of the data was performed using Analyse-It
(Analyse-It Software Ltd., Leeds, U.K) add-in for Excel (Microsoft
Corp., Seattle, Wa, U.S.A). Differences between the 5 rowing incremental
steps for each of the variables during each of the step tests at
each time point were examined using repeated measures ANOVA. Paired
Student T-tests and Bonferroni adjustments were utilized to explore
these differences. The statistical threshold was set at p< 0.0.
were collected successfully on all seven subjects at each time point.
For both time A and B, peak force was observed to increase significantly
over the 5 steps (p < 0.001), showing incremental rises with
each step. The average stroke rating for each incremental step
however were slightly lower at time B. In addition, a significant
rise in peak force occurred at time B ranging from an increase of
40 to 80 N for the five steps (p < 0.01, Table
1), with steps 2and 5 demonstrating significant improvements
in force output between time points A and B (p < 0.05). An example
of the changes can be seen for one athlete in Figure
1. The position during the stroke when peak force occurred did
not alter between time A and time B, although within incremental
tests it was observed to occur later in the stroke with increased
stroke ratings with each incremental step. The changes between steps
and time points were observed when power and work done were considered
(Table 1), with significant
rises in power and work done with incremental step (p < 0.001)
and time point (p < 0.0001), these rises were observed for all
incremental steps (p < 0.05).
A non-consistent stroke length was observed at time A. This appeared
more stable by time B (Figure 2)
and showed a significant increase in overall stroke length (p <
0.0001) which ranged from 14.9 -18.9 cm in terms of group average
across incremental steps, these differences were significant for
each incremental step (p<0.05). The point at which the end of
the drive phase occurred was earlier in the stroke at time B suggesting
a more efficient stroke profile and a faster more co-ordinated drive
phase, allowing more time for the recovery phase. This is supported
by the fact that the stroke length and force has increased, leading
to a rise in power for the same physiological work load. Further,
Table 1 suggests that if anything stroke rates
for the later step tests were slightly lower again enhancing the
suggestion of a more efficient stroke.
rotation (thigh flexion/extension)
Minor changes were seen in the magnitude of femoral rotation at
the catch position (thigh flexion) during the step test at both
times A and B (Table 2). However,
there was a clear reduction in the magnitude of thigh flexion at
time B (p < 0.001), at all incremental steps apart from the 3rd.
This may be associated with the kinematic changes noted below. A
similar reduction was observed in maximal thigh flexion occurring
during the stroke (Table 2). The point during the stroke at which occurred showed
no clear trend.
Femoral rotation (thigh extension) at the finish position fluctuated
more at time A. For both times A and B thigh extension was lower
at the later incremental steps (Table 2). Overall, more thigh extension was observed at the
finish at time B (p < 0.05) but only
in the 4th and 5th incremental steps. Similarly, greater maximal
thigh extension over the whole stroke was observed at time B but
this did not reach significance, and no differences were observed
with respect to the point at which this occurred in the rowing stroke.
rotation (pelvic rotation)
Sacral rotation (anterior rotation of the pelvis) at the catch remained
consistent throughout each incremental step, however, by time B,
the athletes were able to achieve significantly greater anterior
rotation (p < 0.001) during steps 1-4. This was also reflected
in the magnitude of maximal anterior rotation that they could achieve
(p < 0.001), and there was a non-significant trend (p = 0.09)
for the athletes to achieve this earlier in the stroke (Table
At the finish position, the data from time A revealed variability
in the degree of posterior rotation achieved at each of the different
incremental steps (Table 3).
In contrast, time B revealed greater consistency and a greater
magnitude of posterior rotation at the finish position, (p <
0.01, Table 3), this only reached
significant at step 1. This increased magnitude was also observed
with respect to maximum posterior rotation over the whole stroke,
and this maximal rotation occurred significantly earlier in the
stroke (p < 0.001) at time B.
rotation (lumbar spine flexion/extension)
The above changes in pelvic rotation were complemented by changes
in lumbar rotation (lumbar spine flexion/extension). At the catch,
values of lumbar flexion remained approximately the same at each
incremental step (Table 4).
However, they were observed to increase as greater forward lumbar
rotation or lumbar flexion was achieved (p < 0.001) at time B
during incremental steps 1-4. This can be attributed to the improved
pelvic position noted above. The magnitude of this increase in flexion
was less when maximum forward lumbar rotation (flexion) during the
stroke was considered, although the increase was still statistically
significant (p < 0.001). This maximal forward lumbar rotation
occurred later in the stroke as incremental step increased (p <
0.001), but tended to occur earlier in the stroke at time B compared
to time A (p < 0.0001).
Lumbo-pelvic ratio was determined at the catch and finish and represents
the ratio of the lumbar rotation to the sacral rotation, where a
value of 1 demonstrates equal contribution of each body segment
to the forward motion of the trunk as a whole. At time A, the lumbo-pelvic
ratio was observed to increase with incremental step indicating
a predominance of lumbar motion, however, by time B not only had
this ratio improved (become close to 1), it demonstrated greater
consistency with minimal changes
in the value with incremental step. This did not reach statistical
difference (p = 0.14 at the catch and p = 0.29 at finish when time
points A and B were compared). Lumbo-pelvic ratio values at the
finish were more consistent than at the catch at both time points
across incremental steps, this being particularly the case for time
B, (Figure 3).
The initiation of movement of the handle towards the body (hands
forward) and the point at which the handle ceased moving towards
the ergometer flywheel and started moving away from the flywheel
(hands away) were examined. Hands away initiation occurred earlier
at time B. Both demonstrated that this movement occurred later with
each incremental step (p < 0. 001). For example, at time A and
step 2 it occurred at 32% of the stroke (35.4% at time B). This
increased to 29.7% at step 4 (33.3% at time B). However, the initiation
of "hands forward" demonstrated less consistency between
time points and steps. For example, for step 2 it occurred at 96.9%
and 96.6% of the stroke for time A and time B, respectively. At
step 4 it occurred at 97.1% 96.3% at time A and time B, respectively.
and Seiler, 2004
noted that international rowers undergo intense training. Traditionally
the athlete's response to this training have been recorded using
physiological parameters including lactate threshold with increased
tolerance indicative of training adaptation. Enhanced rowing performance
is associated with improved lactate exchange and removal abilities.
However, whether such physiological changes are associated with
changes in the biomechanics of the rowing stroke is not known. This
study focused on whether biomechanical parameters of technique measured
during performance testing change with time. Further studies will
be required to ascertain what these changes are related to; they
may relate to direct coaching issues, strengthening strategies or
to; they may relate to direct coaching issues, strengthening strategies
or changes in physiological performance.
Stroke length has previously been related to high level rowing performance
(Holt et al., 2003,
thus the observed increase in stroke length amongst this group of
athletes would suggest a rise in performance which was observed
by their coach and their medal winning ability which rose from making
race finals to winning races (2 silver medals and 1 bronze at the
Athens Olympics). Associated with this is greater consistency in
stroke length and suggestions of more efficient stroke profiles
as indicated by the earlier completion of the drive phase. Also,
peak force and power were seen to rise over the 2 year period by
80 N. Bourdin et al., 2004
suggested that peak power output is the best predictor of overall
rowing ergometer performance with direct correlations to VO2max
and rowing gross efficiency. A more efficient stroke is further
supported by the fact that the stroke length and force has increased,
leading to a rise in power for the same physiological work load.
Indeed the associated performance lactate testing findings suggested
that for each given workload the work performed at 2mM and 4mM increased
by 13.8W and 17.0W respectively suggesting that for the same physiological
cost greater work was performed i.e. the rowers were more efficient,
rather than unconsciously pulling a harder stroke rate.
Soper and Hume, 2004
suggested that body segment velocities influence performance, particularly
boat velocity. Whilst segment velocities have not been analysed,
aspects of body kinematics have been shown to change, in particular
lumbo-pelvic kinematics. These changes focus around the use of the
pelvis during the rowing stroke with a progression over time to
greater anterior rotation of the pelvis at the catch. This facilitates
an improvement in lumbar spine range and resultant stroke length,
suggesting that the improvements in stroke length may be attributable
to better lumbo-pelvic kinematics. When considered in terms of lumbo-pelvic
ratio this suggests a straighter trunk position which previous authors
have indicated may be beneficial (McGregor et al., 2005;
Reid and McNair, 2000;
Poor lumbo-pelvic rotation was identified as a limitation of technique
in novice rowers (McGregor et al., 2004)
and poor pelvic rotation may lead to an increased loading at the
junction of the lumbar spine and pelvis, with loading of the spine
in rowers being an area of concern (Bahr et al., 2004;
Morris et al., 2000;
Reid and McNair, 2000).
Alterations in lumbo-pelvic motion have also been noted in rowers
with and without low back injury (McGregor et al., 2003;
O'Sullivan et al., 2003),
and altered hamstring-quadriceps ratios have been noted in rowers
with low back pain a factor which may also influence pelvic motion
(Koutedakis et al., 1997)
Greater consistency was observed in spinal kinematics at the finish
position, a factor which will again contribute to the improved stroke
length observed. In novice rowers, a tendency to slouch at the finish
position was noted, depicted by an excessive posterior rotation
of the pelvis (McGregor et al., 2004).
This was not the case at either time A or B as can be seen from
the lumbo-pelvic ratio data, which suggested improved control of
the finish position at time B. This would suggest that the changes
in stroke efficiency may be in part related to these changes in
Few differences were observed with timings of handle movement and
thus hand position between time A and time B. Bompa in 1980 suggested
that elbow position impacted on force transmission through the handle,
noting that extending the elbows during the drive whilst keeping
them in at the trunk at the finish generated greater force. Such
changes were not investigated in these athlete.
|In conclusion, this study demonstrates that rowing technique
changes with time. The reasons for such changes could be attributed
to a variety of sources including coaching, changes in strength, improved
neuromuscular coordination and training programmes, as well as changes
in overall physiology of the athletes concerned. Of particular interest
was the suggested increased biomechanical efficiency for the same
physiological workload suggesting future work should focus on integrating
the biomechanical and physiological variables more closely.
of rowing technique change with time and reflect improvements
kinematics appear to be associated with improved rowing efficiency
in stroke length linked in part to improvements in lumbo-pelvic
Employment: Senior Lecturer, Biodynamics Laboratory, Ergonomics
Group Biosurgery & Surgical Technology Division of Surgery,
Oncology, Reproductive Biology & Anaesthetics (SORA) Faculty
of Medicine, Imperial College London, Charing Cross Hospital.
Degree: PhD, MSc, MCSP.
Research interests: Spinal mechanics, biodynamics, and
rowing in particular.
Employment: Reader in Musculoskeletal Mechanics
Department of Bioengineering
Imperial College London.
Research interests: Joints of the extremities, tools
for orthopaedic surgery, and the kinematic analysis of the musculoskeletal
Employment: Medical engineer, research student Biodynamics
Laboratory Ergonomics Group Biosurgery & Surgical Technology
Division of Surgery, Faculty of Medicine Imperial College London.