Abstract
Rowing technique is a crucial component of the sport as it is highly correlated with performance. Moreover, proper technique is recognised to be associated with injury prevention, specifically low back pain (LBP), the most prevalent rowing-related injury among rowers at all levels. In the absence of a clear definition or guidelines for the optimum rowing technique, coaches and rowers are only offered evidence-based suggestions from biomechanical analyses. Stroke rate plays a key role in competitive rowing by increasing boat velocity. However, the effect of stroke rate on rowing kinematics and intersegmental coordination is still poorly understood. Additionally, despite suggestions that leg strength is associated with LBP in rowing, the relationship between lower limb strength and rowing kinematics is yet to be investigated. The primary aim of this study was to examine the effect of stroke rate on rowing technique by comparing three-dimensional (3D) kinematics and intersegmental coordination patterns of the trunk and lower limbs in university-level male rowers. Second, this study aimed to examine the relationship between isokinetic knee strength and kinematic knee angles demonstrated in the rowing stroke cycle.
Fifteen experienced university-level male rowers (age: 21.7 ± 2.1 years, height:184.5 ± 6.6 cm, body weight: 75.5 ± 6.7 kg, years rowing: 6.4 ± 2.1 years) participated in this descriptive cross-sectional study. The experimental protocol required two visits for each participant. In the first visit, rowers were required to complete a protocol on the rowing ergometer consisting of 60s of rowing at stroke rate 20, 30s at stroke rate 26, and 30s at a maximum stroke rate with one minute rest intervals. Trunk and lower limb kinematic data were recorded in the sagittal plane using a 3D motion capture system at 100 Hz. In the second visit, the concentric (CON) and eccentric (ECC) knee extensors and flexors muscle strength were measured using an isokinetic dynamometer at 60 °/s and 180 °/s. All continuous data were time normalised and analysed using statistical parametric mapping (SPM). Specifically, one-way repeated-measures analysis of variance (ANOVA) was used to determine differences in the kinematic variables across the three-stroke rates. Post hoc two-tailed paired t-test analyses were only performed in kinematic variables that presented significant differences across the stroke rates. Intersegmental coordination patterns of the trunk and lower limb (thoracic-lumbar, hip-knee, and knee-ankle) segment pairs in the sagittal plane were quantified using angle-angle plots and the vector coding method. An spm1d regression analysis was performed to determine the relationship between isokinetic knee strength and the knee angles demonstrated during the rowing stroke. Increasing stroke rate revealed significant differences (p<0.05) in lumbar spine and lower limb angles during the drive and recovery phases of the stroke cycle. The percentage of the stroke cycle spent in the drive phase increased, which was shown by the significantly reduced angles and delay in the occurrence of maximal extension of the lumbar spine and lower limbs. In contrast, the percentage of time spent in the recovery phase reduced with significantly larger joint angles observed. Joint range of motion (ROM) was found to be affected the greatest during maximum stroke rate, displaying reduced angles throughout the rowing cycle, especially at the catch and finish. No significant differences with increasing stroke rate were reported for the thoracic spine.
The thoracic-lumbar segment pair exhibited primarily inferior phase coordination during stroke rate 20 (36% of stroke cycle) and 26 (42% of stroke cycle), and then in-phase during maximum stroke rate (48% of stroke cycle). The hip-knee and knee-ankle segment pairs displayed in-phase for more than 50% of the stroke cycle at all stroke rates. The time spent in each coordination pattern was not significantly affected by stroke rate (p=1.000). Finally, no significant relationship was found between CON and ECC knee torque and the continuous knee joint angles at any of the stroke rates (20, 26, and maximum).