Biomechanical asymmetries and joint loading in elite rowers

Abstract

Rowing is a technical sport which requires a high skill level in order to optimise performance and reduce the risk of injury. Previous studies investigating the biomechanics of rowing technique and performance have focussed on two-dimensional lumbar-pelvic kinematics as well as more detailed three-dimensional descriptions of the lower extremity. However, limited research has examined lower limb asymmetries during rowing, with the majority of studies focussing on the action of a single leg. This study aims to quantify lower limb asymmetries during ergometer rowing, and the effect that asymmetries might have on the dynamics of the lumbar-pelvic joint, a commonly injured area in rowers, and subsequent performance. Kinematic asymmetries of the lower limbs were quantified using an electro-magnetic motion capture system. Symmetry of foot force production was also examined through custom force measuring footplates, with the design and output of these being developed and refined as part of this project. Inter-segmental loading of the lower limb and lumbar-pelvic joints were estimated with a five-segment inverse dynamics model, which utilised foot force and kinematic data as inputs. A final aim was to examine the effect of changing foot stretcher height on rowing performance and technique from a biomechanical perspective. The results indicate that rowing is in fact an asymmetrical activity, with significant bilateral differences identified at the footplates. From a movement perspective knee and hip joints were bilaterally asymmetrical, with hip range of motion asymmetries significantly associated with lumbar-pelvic flexion in the sagittal plane. Inter-segmental joint moments were not influenced by the presence of foot force asymmetries. However, they were influenced by increased rowing intensity. Large lumbar-pelvic extension moments were present during the rowing stroke, and these increased with respect to stroke rate. This is unlikely to be a measure of greater performance, as corresponding increases in performance measures such as foot and handle force were not observed. In fact, it may be an indicator of technique decline at higher work rates, as larger peak lumbar-pelvic moments occurred alongside increases in lumbar-pelvic flexion and loading of the seat – both of which are considered deleterious to performance. Therefore, rowers may be at greater risk of developing lower back pain when training at high intensities. A performance intervention, which involved raising the height of the foot-stretchers, was found to have little positive effect on the horizontal forces measured at the feet. In addition, there was a negative influence on stroke length and lumbar-pelvic posture. From a coaching perspective these results provide information regarding athlete set-up and their immediate implications on rowing performance. These studies have shown that elite rowers demonstrate biomechanical asymmetries of the lower limbs, and these could negatively influence the dynamics of the lumbar-pelvic joint and predispose them to low back pain. High intensity rowing and increases in foot stretcher height were also seen to increase lumbar-pelvic flexion through the rowing stroke. Key kinematic characteristics of the lower limbs which positively influence force production were also identified, thus providing rowing coaches with important biomechanical insight into performance optimisation and reduction of injury risk.