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Purpose: This study aimed to determine the accuracy of a 4 split time modelling method to generate velocity-time and velocity-distance variables in elite male 100-m sprinters and subsequently to assess the roles of key sprint parameters with respect to 100-m sprint performance. Additionally, this study aimed to assess the differences between faster and slower sprinters in key sprint variables that have not been assessed in previous work. Methods: Velocity-time and velocity-distance curves were generated using a mono-exponential function from 4 split times for 82 male sprinters during major athletics competitions. Key race variables—maximum velocity, the acceleration time constant (t), and percentage of velocity lost (vLoss)—were derived for each athlete. Athletes were divided into tertiles, based on 100-m time, with the first and third tertiles considered to be the faster and slower groups, respectively, to facilitate further analysis. Results:Modelled split times and velocities displayed excellent accuracy and close agreement with raw measures (range of mean bias was –0.2% to 0.2%, and range of intraclass correlation coefficients (ICCs) was 0.935 to 0.999) except for 10-m time (mean bias was 1.6% ± 1.3%, and the ICC was 0.600). The 100-m sprint performance time and all 20-m split times had a significant near-perfect negative correlation with maximum velocity (r ≥ –0.90) except for the 0 to 20-m split time, where a significantly large negative correlation was found (r = –0.57). The faster group had a significantly higher maximum velocity and τ (p < 0.001), and no significant difference was found for vLoss (p = 0.085). Conclusion:Coaches and researchers are encouraged to utilize the 4 split time method proposed in the current study to assess several key race variables that describe a sprinter's performance capacities, which can be subsequently used to further inform training.

peer-reviewed Each distinct phase of a 100 m sprint is dependent on key race variables e.g. acceleration ability, maximum velocity and speed endurance. Consequently, sprinters frequently supplement their sprint training with resistance training to develop qualities such as maximum strength and reactive strength. The literature assessing the association between these strength qualities and sprint performance has found contrasting results. Additionally, the literature on the prescription of resistance exercises to sprinters is sparse and consequently, evidence based prescription of resistance training is limited. Thus, the aims of this programme of research were to explore the relationship between race variables and 100 m time, explore the role of maximum strength and reactive strength in sprinting and to investigate the prescription and suitability of resistance training exercises for sprinters. Chapter 3 investigated world class male 100 m sprint performance data and found that the acceleration-time constant was an excellent indicator of relative acceleration ability and therefore merits monitoring. Furthermore, maximum velocity was highly related to each 20 m section of the sprint (r = -0.57 to -0.98) and overall 100 m time (r = -0.97) highlighting the crucial importance of maximum velocity to a 100 m sprinter. Chapter 4 investigated the relationship between maximum strength, reactive strength and maximum velocity, 10 m split times and sprint mechanical properties assessed during a 40 m sprint. Peak force and relative force, measured in an isometric mid-thigh pull, and reactive strength index, measured in drop jumps and hopping, had no statistically significant relationship with any of sprint performance measures. However, a high correlation (r = 0.61) was found between peak force and peak horizontal power in men only. The lack of a significant relationship between drop jump reactive strength and any of the sprint performance measures indicated that the use of the reactive strength index as a measure of an athlete’s reactive strength warranted further investigation. Consequently, Chapter 5 assessed how differing performance strategies affect measures of reactive strength in drop jumps. Limiting group variance in contact time was recommended to improve the validity of reactive strength measurements. In Chapter 6 a survey of sprint coaches’ prescription of resistance training exercises was conducted with the hurdle jump found to be the most widely prescribed exercise (93% of coaches). Based on the findings of Chapter 6, a biomechanical comparison between the kinematics of maximum velocity sprinting and hurdle jumping was conducted in Chapter 7. Based on Chapter 7’s findings, the hurdle jump is recommended as a suitable exercise for sprinters due to the greater demand placed on the athlete to reverse the velocity of their centre of mass, similar peak knee extension angular velocities and greater ankle dorsiflexion angular velocities. Common themes emerging from the thesis are also discussed including the implications for using ratio-based measures, using ground contact time as a monitoring tool and recommendations for individualised assessment and training.

peer-reviewed This study examined the relationships between reactive strength measures and sprint performance. Ten female sprinters performed bilateral vertical hops and drop jumps (DJs) from 0.3 m and 40 m sprints. Ground contact time, flight time, height jumped and the reactive strength index (RSI) were calculated during hops and drop jumps. Sprint times over 10, 20, 30 and 40 m were also assessed. High positive correlations, calculated using Pearson’s r correlations, were found between Hop RSI and DJ RSI (r = 0.672) with no other significant correlations found. Although RSI values in hopping and drop jumping are related they should not be used interchangeably as they represent somewhat distinct reactive strength qualities. The results suggest that RSI values, calculated during hopping and drop jumping, were not related to sprint performance.

peer-reviewed Introduction Although the use of resistance training in athletics is commonplace, a paucity of research exists examining the longitudinal effects of resistance training and its effect on performance in sprinters (Bolger et al. 2014). A significant gap in the literature exists about which resistance training exercises are most effective for sprint athletes. The aim of this study was therefore to identify the most commonly prescribed resistance training exercises by sprint coaches to their sprint athletes. Method An online survey was electronically mailed to a database of all coaches registered with Athletics Ireland with a total of 170 individuals responding. Respondents were excluded from the analyses if they were not involved in coaching sprint athletes or if they failed to complete the survey. A total of 50 coaches met the inclusion criteria and were included in the final analyses. The survey separated resistance training exercises into three categories i.e. heavy resistance training exercises, dynamic resistance training exercises and plyometric or jump type exercises. Subjects were asked to name and describe prescribed exercise that was not listed. Subjects were also asked to name the two exercises from each category that they prescribed most often. Results Overall, the repeated (i.e. rebound) hurdle jump was the most popular exercise with 94% (n=47) of coaches reporting that they prescribed it. The jump squat was the most popular dynamic resistance training exercise with 58% (n=29) of coaches reporting that they prescribed it whereas the back squat was the most popular heavy resistance training exercise with 56% (n=28) of coaches reporting that they prescribed it. Discussion The plyometric and jump type exercises were overall, the most prescribed exercises. This is not surprising since plyometric exercises develop the stretch shortening cycle which is very important in sprinting (Sáez de Villarreal et al. 2012). Traditional heavy resistance training exercises were prescribed least, possibly due to concerns of poor specificity and transfer to performance (Young, 2006). Conclusion Coaches prescribe a wide variety of resistance training exercises to their sprint athletes. Plyometric exercises are the most commonly prescribed type of exercise, potentially due to their biomechanical specificity to sprinting. In an effort to maximise the potential transfer between resistance training exercises and sprint performance, coaches should prescribe exercises based on their ability to develop physical qualities that are beneficial to sprinting such as the stretch shortening cycle.

peer-reviewed The purpose of this study was to compare the use of both a force platform and Optojump photocell system (Microgate, Bolzano, Italy) to examine double leg and single leg drop jumps. Thirteen physically active individuals performed 5 double leg drop jumps and 5 single leg drop jumps from a height of 0.3 m. Ground contact time (CT), flight height (FH) and reactive strength index (RSI) were calculated concurrently for both jump types. Despite intraclass correlation coefficients for all variables being very close to 1, a significant systematic difference was consistently observed between both devices with the Optojump system overestimating CT and underestimating both FH and RSI for both jump types. Both devices demonstrated excellent test- retest reliability with all ICCs for CT, FH and RSI above 0.940. PUBLISHED peer-reviewed

peer-reviewed The purpose of this study was to compare force calculated using accelerometer data from the SHIMMER device, with force platform data on countermovement and drop jumps. Twelve physically active adults performed 5 counter movement jumps and 5 drop jumps from a height of 0.30 m. An accelerometer was attached near the participant’s centre of mass and simultaneous force and acceleration data were obtained for the jumps. Minimum eccentric force and peak concentric force were calculated concurrently for countermovement jumps and peak landing forces were calculated concurrently for drop jumps. The results showed moderate to poor levels of agreement in forces and a consistent systematic bias between the results from the force platform and accelerometer. PUBLISHED peer-reviewed