The aim of this study was to assess the concurrent validity of the Optojump™ system (Microgate, Bolzano, Italy) versus a force platform in the estimation of temporal and reactive strength measures. In two separate investigations, twenty physically active males performed double-leg and single-leg drop jumps from a box height of 0.3 m and a 10 s vertical bilateral hopping test. Contact time, flight time and total time (the sum of contact and flight time) were concurrently assessed during single and double-leg drop jumps and during hopping. Jump height, the reactive strength index and the reactive strength ratio were also calculated from contact time and flight time. Despite intraclass correlation coefficients (ICCs) for all variables being close to 1 (ICC > 0.975), a significant overestimation was found in contact time (0.005 ± 0.002 s) and underestimations in flight time (0.005 ± 0.003 s), the reactive strength index (0.04 ± 0.02 m·s-1) and the reactive strength ratio (0.07 ± 0.04). Overestimations in contact time and underestimations in flight time were attributed to the physical design of the Optojump™ system as the transmitter and receiver units were positioned 0.003 m above the floor level. The Optojump™ demonstrated excellent overall temporal validity with no differences found between systems for total time. Coaches are advised to be consistent with the instrumentation used to assess athletes, however, in the case of comparison between reactive strength values collected with the Optojump™ and values collected with a force platform, regression equations are provided.

Purpose:To assess the relationships between reactive strength measures and associated kinematic and kinetic performance variables achieved during drop jumps. A secondary aim was to highlight issues with the use of reactive strength measures as performance indicators.Methods:Twenty-eight national- and international-level sprinters, 14 men and 14 women, participated in this cross-sectional analysis. Athletes performed drop jumps from a 0.3-m box onto a force platform with dependent variables contact time (CT), landing time, push-off time, flight time, jump height (JH), reactive strength index (RSI, calculated as JH/CT), reactive strength ratio (RSR, calculated as flight time/CT), and vertical leg-spring stiffness recorded.Results:A Pearson correlation test found very high to near-perfect relationships between RSI and RSR (r = .91–.97), with mixed relationships between RSI, RSR, and the key performance variables (men:r = −.86 to −.71 between RSI/RSR and CT,r = .80–.92 between RSI/RSR and JH; women:r = −.85 to −.56 between RSR and CT,r = .71 between RSI and JH).Conclusions:The method of assessing reactive strength (RSI vs RSR) may be influenced by the performance strategies adopted, that is, whether athletes achieve their best reactive strength scores via low CTs, high JHs, or a combination. Coaches are advised to limit the variability in performance strategies by implementing upper and/or lower CT thresholds to accurately compare performances between individuals.

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. 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 (τ), and percentage of velocity lost (v_Loss)—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. 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 v_Loss (p = 0.085). 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.

THIS ARTICLE EXAMINES THE APPLICATION OF A VARIETY OF MODALITIES TO ELICIT A POSTACTIVATION POTENTIATION (PAP) RESPONSE IN SPRINTING. WE PRESENT THE EXISTING LITERATURE ON THE ACUTE EFFECTS OF BACK SQUATS, POWER CLEANS, PLYOMETRICS, AND SLED PULLING ON SPRINT DISTANCES RANGING FROM 5 TO 50 M. WE ALSO DISCUSS AND PROVIDE AN EXAMPLE OF HOW COACHES CAN ASSESS THE INDIVIDUAL EFFECTS OF PAP PROTOCOLS ON THEIR ATHLETES TO IDENTIFY WHETHER A PROTOCOL ELICITS AN ACUTE IMPROVEMENT OR IMPAIRMENT IN PERFORMANCE. FINALLY, WE PROVIDE PRACTICAL RECOMMENDATIONS ON HOW COACHES CAN INCORPORATE THESE METHODS INTO A SPRINT TRAINING SESSION.

Healy, R, Smyth, C, Kenny, IC, and Harrison, AJ. Influence of reactive and maximum strength indicators on sprint performance. J Strength Cond Res 33(11): 3039–3048, 2019—The primary aim of this study was to assess the relationship between reactive and maximal strength measures with 40 m sprint performance and mechanical properties. Fourteen male and 14 female sprinters participated in this study. On the first day, subjects performed 40 m sprints with 10-m split times recorded in addition to maximal theoretical velocity, maximal theoretical force and peak horizontal power, which were calculated from force–velocity relationships. On the second day, subjects performed isometric midthigh pulls (IMTPs) with peak force (PF) and relative PF calculated, drop jumps (DJs) and vertical hopping where the reactive strength index (RSI) was calculated as jump height (JH) divided by contact time (CT). Pearson correlations were used to assess the relationships between measures and independent samples t-tests were used to assess the differences between men and women. No significant correlations were found between DJ and hopping RSI and sprint measures. A significant strong positive correlation was found between IMTP PF and peak horizontal power in men only (r = 0.61). The male sprinters performed significantly better in all recorded measures apart from hopping (CT, JH and RSI) and DJ CT where no significant differences were found. The lack of association between reactive and maximal strength measures with sprint performance is potentially because of the test's prolonged CTs relative to sprinting and the inability to assess the technical application of force. Several methods of assessing reactive strength are needed that can better represent the demands of the distinct phases of sprinting e.g., acceleration, maximum velocity.