Seasonal Shifts in Jumping Patterns: A Study of Countermovement Jump Strategies in High School Football Athletes

Modern sporting trends have begun to adopt sport science and load monitoring to identify in-season trends with the goal of improving performance and reducing injury. Although these resources have become increasingly common in professional and collegiate sports, many high school athletic programs have yet to adopt such technologies. While previous research has demonstrated season-long changes in jump performance, no research has investigated the impact of in-season demands on the changes in jump strategy in male high school football athletes. PURPOSE: The purpose of this study was to examine changes in jump strategy in high school football players over a single football season. METHODS: Sixty-nine male high school football athletes, including 25 offensive skill, 23 linemen, 12 linebackers, 7 defensive backs, and 2 special teams players were tested for maximal jump performance at the beginning and end of a high school football season. Testing was conducted using three attempts of a maximal hands-on-hips countermovement jump on portable force plates, with the average of the three jumps used for analysis. A minimum of 10-weeks between sessions accounted for the time between pre- and post-testing. A dependent-samples t-test was performed to calculate differences between the two time points. RESULTS: Significant reductions were observed across all phases of the jump movement revealed significant differences from pre- to post- testing. The largest reduction was seen during the unweighting phase (0.40 to 0.36s), followed by braking phase (0.22 to 0.19s), and finally propulsive phase (0.30 to 0.28s). Resulting in a total time to takeoff decrease of 0.92 seconds to 0.83 seconds, resulting in an increase in mean jump height (14.15 to 14.89 inches). Jump strategy differences were also significantly different between time points for modified reactive strength index (0.40 to 0.47 and stiffness metrics (-4996.86 to -5622.46N/m). No differences were seen for countermovement depth (t(68) = 0.44, p=0.663) between the two time points. CONCLUSION: At the end of a competitive season, high school football athletes increased their speed at all phases of the jumping motion. Despite the increased speed during the movement, there were no changes in the countermovement depth prior to takeoff. Our research indicates that football athletes become faster and more efficient with their CMJ strategy to achieve increased performance as measured by Jump Height. Future studies may benefit from collecting follow-up data collection to examine the detraining effect that can occur post-competition, and to incorporate differences between double and single leg jumping strategy. Doing so has the potential to identify injury risk and asymmetries throughout the season

Countermovement Jump Performance Trends in High School Football Players Throughout a Competitive Season

Football is the largest participation sport amongst male high school athletes in the country with over one million participants. Previous research has demonstrated that countermovement jump (CMJ) performance is negatively affected by in-season fatigue in contact sports such as rugby and hockey. However, little data are available to describe how CMJ performance and force metrics change in high school athletes throughout a competitive football season. PURPOSE: The purpose of this study was to examine the changes in strength and power metrics in high school football players over a single football season. METHODS: Sixty-nine male high school football athletes comprised of 25 offensive skill players, 23 linemen, 12 linebackers 7 defensive backs, and 2 special teams players were tested for maximal lower body force output at the beginning and end of a high school football season. Testing was conducted using three attempts of a maximal hands-on-hips countermovement jump on portable force plates, with the average of the three jumps used for analysis. Pre-testing occurred prior to the first game of the season, and post-test was conducted after the final game of the season with a minimum of 10-weeks between sessions accounted for the time between pre- and post-testing. A dependent-samples t-test was performed to calculate differences between the two time points. RESULTS: Significant improvements in jump height (14.15 to 14.89 inches), relative force at minimum displacement (220.36 to 235.77% body weight), peak relative braking force (220.72 to 236.39% body weight), peak relative propulsive force (238.07 to 248.02% body weight), peak braking velocity (-1.17 to -1.30m/s), and takeoff velocity (2.64 to 2.71m/s). No significant differences were seen in relative peak landing force (t(68) = 0.53, p=0.600). CONCLUSION: At the end of a competitive season, high school football athletes produced more force and increased their movement velocity, resulting in improvements in jump height compared to the beginning of the season. However, there were no significant differences in landing metrics indicating no changes in force absorption capacity. These increases in jump performance do not reflect results previously reported in contact sports such as rugby and hockey where jump performance typically decreased over the course of a season. Future studies may benefit from collecting additional performance data to assess the impact seasonal fatigue has on other body systems separate to lower body power production, and the effect to which practice and strength and conditioning programming impact force metrics. Without appropriate monitoring strategies, coaches are leaving the assessment of load management to chance, which can potentially lead to decreased performance and an increased chance of injury