Jump Screening For Non-functional Overreaching In Special Operations Unit Training

A unit training (UTP) cycle for US Special Operations Forces (SOF) consists of a strenuous period of training and includes two 3–4-week training exercises (TEX1, TEX2). This training is hypothesized to elicit non-functional overreaching (nFOR), or training that results in a net decrease in physical performance. Countermovement jump screening (CMJ-S) is believed to be an effective method of identifying nFOR, but its effectiveness in tactical athletes is unknown. PURPOSE: To determine the effectiveness of CMJ-S to identify nFOR in SOF personnel during UTP. METHODS: 38 SOF personnel were recruited from the same unit entering a 5-month UTP. Subjects performed CMJ-S on force plates sampling at 1000 Hz using commercial software at baseline (week 0), post-TEX1 (week 3), pre-TEX2 (week 14), post-TEX2 (week 17) and post-UTP (weeks 21-23). 11 subjects completed baseline and at least one follow-up screen. Bodyweight (BW), jump height (JH), peak force (PF), mean power (MP), peak power (PP), and the ratio of flight time to contraction time (FT:CT) were analyzed. Multivariate analysis of variance (MANOVA) was performed to determine an interaction between variables and time. A one-way repeated measures analysis of variance (ANOVA) was performed to determine differences across timepoints. Significance was determined a priori as <0.05. RESULTS: MANOVA yielded no significant interaction between timepoints for all variables (F = 0.06, p = 0.86). ANOVA yielded no significant main effect across timepoints. Individual variability was high, with some subjects experiencing a negative trend in performance while others remained consistent throughout. CONCLUSION: Given the high attrition rate, unit-level feasibility for CMJ-S may be low, however there is some evidence that jump variables are sensitive to overreaching in tactical athletes. Casual inferential analysis indicates that some subjects experienced negative trends across multiple variables. Five out of 11 subjects experienced a downward trend in four or more variables following intense training exercises that did not return to baseline. CMJ-S may be able to identify nFOR on an individual basis. Supported by the Office of Naval Research N0004-21-1-2682