Haverinen, Mikko (2017). Leg Force, Stroke Force and Timing of Paddling in Experienced and Young Paddlers on a Kayak Ergometer. Biology of Physical Activity, Faculty of Sport and Health Sciences, University of Jyväskylä. Master's thesis, 63p. Kayak paddling is a diverse sport demanding endurance characteristics, force production and technical skills. In kayak paddling the force is produced by forward stroke and it is an important factor in succesful paddling performance as it contributes to kayak's acceleration and, thus, to the success in competition. In kayak paddling the force production is started by leg work and the force is transmitted by trunk to upper body to perform the stroke. The purpose of this study was to find out the biomechanical differences in 40-second maximal kayak ergometer performance between experienced and young paddlers. Also connections between different variables in kayak paddling performance were studied. Nine subjects took part of this study. They were divided into two groups: experienced paddlers (E, N=5), who were paddling at national team level or at challenge group level (age 22,8 ± 2,5 years) and young paddlers (Y, N=4), who were academy level paddlers (age 16 ± 1,8 years). The subjects performed a maximal 40-second test in the kayak ergometer. The forces were measured with force transducers. Stroke rate, maximal forces and impulses of the stroke and the leg work, a total impulse of the strokes, a time interval between the start of leg and stroke force production (Int_Fstart) and a time interval between the maximal value of leg and stroke force (Int_Fpeak) were analysed. Sroke rate (E: 83,6 ± 2,5 strokes/40s and Y: 70,3 ± 5,4 strokes/40s, p = 0,002), peak stroke force (E: 272, 8 ± 27,5 N and Y: 198,1 ± 35,5 N, p = 0,009) and total stroke impulse in 40second performance (E: 3949 ± 105 Ns and Y: 2918 ± 222 Ns, p = 0,001) were significantly greater with the group of experienced paddlers. Leg impulse (Y: 197,4 ± 35,5 Ns and E: 154,7 ± 13,7 Ns, p = 0,028) and Int_Fstart (Y: 0,093 ± 0,015 s and E: 0,047 ± 0,026 s, p = 0,017) were significantly greater with the group of young paddlers. Significant negative correlations were found between Int_Fstart and stroke rate (r = -0,906, p = 0,001) and between Int_Fstart and total stroke impulse (r = -0,693, p = 0,039). There were no significant correlations between the leg force and the stroke force variables. Main conclusions of this study were: 1) Experienced paddlers had better peak stroke force production. 2) The peak force or the impulse of leg work is not crucial factor to achieve high stroke force. 3) Int_Fstart of the young paddlers was longer which may affect negatively to the stroke rate. Also the early timing of the leg work with young paddlers did not help them to achieve greater stroke force or impulse than experienced paddlers. 4) Stroke rate and the total stroke impulse were greater with the experienced paddlers which indicates better total power of the performance.