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Title: Evaluation of post-activation potentiation effect on performance indicators of sprint following crouch start Objectives: The main objective of this thesis is to evaluate the influence of post- activation potentiation phenomenon on sprinter step performance indicators following crouch start by using Optojump system. Secondary objectives are firstly - to complile systematic up-to-date review based on recently published evidence, and secondly - to compare acquired results with current trends described in this review. Methods: Fifteen (n = 15) moderate to well trained male athletes completed the experimental procol of controlled sprints (20 m), activation of post-activation potentiation / post-activation performance enhancement elicited by series of squats (3 series, 5 repetition, load of 75 % of 1RM, resting interval 2 mins). Following the activation, all participants completed 1x20 m of sprinting performance from crouch start at 5 min, 10 min, 20 min and 40 min. All measurments were made by using the Optojump system. Acquired measurments were further analyzed and statistically evaluated. Results: Evaluation of acquired data did not result in significant positive effect of activation protocol on measured variables. Furthemore, series of squats were associated with decreased peak velocity and...

Foot strike type affects running mechanics and may influence overuse injury occurrence. Measuring the interaction between cumulative load and foot strike type may provide additional information that could eventually help with understanding injury mechanisms. The purpose of this study was to determine how foot strike type affects cumulative loading in runners, and to determine if individual metrics change throughout a 5-kilometer sub-maximal run. 30 participants ran on an instrumented treadmill for 5 km at 3.15 m/s with their preferred foot strike type (14 rearfoot strike, 16 non-rearfoot strike). Stride rate, foot strike angle, loading rate, per stride and per km (cumulative) vertical ground reaction force impulse, impact peak, absolute peak, knee negative work, and ankle negative work were calculated and compared across time and between groups. Per stride between-group main effects were seen for stance time (p=0.003), foot strike angle (p<0.001), and loading rate (p=0.040), all of which were greater for rearfoot strike runners. Per stride and cumulative ankle and knee negative work also showed significant differences, with ankle negative work being greater for non-rearfoot strike runners (p=<0.001 per stride, p=<0.001 cumulative) and knee negative work being greater for rearfoot strike runners (p=0.014 per stride, p=0.008 cumulative). Both loading rate and cumulative vertical ground reaction force impulse decreased significantly over time (p=0.035, p=<0.001 respectively). In summary, we found a few differences in per stride and cumulative metrics between foot strike groups, namely ankle and knee loading as previously observed. However, as a whole, individual variability in vertical ground reaction force loading patterns was more apparent than any group distinctions. We also found patterns in previous research suggesting that study design components, specifically self-selected speed and habituation, affect variables such as stride rate and peak vertical ground reaction force. The common perception that non-rearfoot strike runners have a higher stride rate was not supported in this study. Lastly, we determined that cumulative calculations can be different if taken at the beginning vs the end of a run. Quantifying injury risk is complicated and cumulative damage models should take into account individual load capacity and training session characteristics (e.g., warm-up time, length, intensity, and rest time).