OBJECTIVES: The main aim of this study was to analyse selected biomechanical aspects of the asymmetrical loading of the human postural system when riding the C1 speed canoe and their influence on the development of muscular imbalances. METHODS: 3D kinematic analysis of a simulated forward stroke of the canoeist in a pool with a counter-current (N = 9) and analysis of MRI data with selected individuals (N = 5), videoanalysis of actual paddling top athletes (N = 12), the kinesiological analysis of movement. RESULTS: Can be stated that when riding a C1 speed canoe the postural system is exposed to two types of asymmetric loading. In the first place, there is lateral asymmetry, which stems from the very nature of the one-sided paddling on this type of vessel. The canoeist has to compensate for the consequent instability by shifting the body's centre of gravity higher above the kneeling lower limb. This effect is achieved by the so-called pelvic lateralisation from the paddling side and by this side's skewing to the kneeling lower limb. Another asymmetry is connected to the forward-backward body movement and its time-dependent deviation from the neutral posture. A significant disproportion between generally fixation movements of the lower part of the body and phasic movements of the upper part of the body has been confirmed. These asymmetrical positions result in a significant unilateral overloading of the quadratus lumborum on the side of the supporting lower limb (side without the paddle), as well as an overloading of the spine straighteners in the lumbar area, in particular on the part of a supporting lower limb, and bilateral yet asymmetric overloading of m. iliopsoas, which in addition takes place in different isometries. The analysis of MRI data indicates that, during longitudinal training, lateral disproportion in the volume and intensity of postural system loading is the cause of different cross sections of the iliopsoas muscle and quadratus lumborum muscle on the side of the kneeling and supporting lower limbs. With both muscles, larger cross sections with a statistical significance level α = 0.05 and thus also strength on the side of the supporting lower limb can be expected. CONCLUSION: When canoeing on the C1, a significant unilateral overloading occurs with m. quadratus lumborum on the part of the supporting lower limb (side without paddle). Furthermore, spine straighteners in the lumbar area are overloaded, in particular in the part of the supporting lower limb. Last but not least however, the bilateral asymmetric overloading of m. iliopsoas occurs.

Faculty of Health Sciences University of Primorska Polje 42 6310 Izola Isola Slovenia

Faculty of Mechanical Engineering Technical University of Liberec Studentská 2 46001 Liberec Czech Republic

Faculty of Physical Education and Sport Charles University Prague José Martího 31 16252 Prague 6 Czech Republic