(37) DYNAMIC STRENGTH INDEX WITHIN POSITIONAL GROUPS IN NCAA FEMALE LACROSSE ATHLETES

Dynamic strength index (DSI) is the ratio between dynamic peak force production, assessed via countermovement jump peak propulsive force (CMJ), and isometric peak force production, assessed via isometric mid-thigh pull peak isometric force (IMTP). This measurement is commonly used to assess an athlete's capacity to effectively use maximum strength during dynamic tasks. To our knowledge, only two studies have assessed DSI ratio in collegiate female lacrosse players, and neither compared positional differences.

Purpose: To assess the differences in CMJ, IMTP, and the resultant DSI ratio between positional groups in college female lacrosse athletes.

Methods: Nineteen National Collegiate Athletics Association Division I women’s lacrosse athletes (21.5±1.5 years, 168.0±6.2 cm, 65.5±7.0 kg) participated in this study in the preseason. Following an off day, participants completed a standardized warm-up, three maximal effort CMJs were completed on dual force platforms (Hawkin Dynamics, Westbrook, ME) with 30-60 seconds rest between each then completed three maximal effort IMTPs were completed on dual force platforms (PASCO Scientific, Roseville, CA) with 60 seconds rest between each. Force platforms were measured at a frequency of 1000Hz and at least 3 minutes of rest was taken between CMJs and IMTPs. The DSI ratio was calculated by dividing the peak force production during the propulsive phase of CMJ by the peak force production of IMTP. One-way ANOVAs were used to determine differences between attackers (ATTK), midfielders (MID), and defenders (DEF) for peak propulsive force during CMJ and IMTP, and the resultant DSI ratio.

Results: No significant differences between positions were found for CMJ (ATTK: 1556.9±126.9 N, MID: 1409.8±119.6 N, DEF: 1392.2±180.5 N; p=0.104), IMTP (ATTK: 1922.2±357.4 N, MID: 1794.1±238.7 N, DEF: 1814.4±196.3 N; p=0.675), or DSI ratio (ATTK: 0.83±0.11 MID: 0.80±0.11, DEF: 0.77±0.11; p=0.681).

Conclusions: To our knowledge, this is the first study to look at positional differences in CMJ, IMTP, and DSI ratio.  While we observed no significant differences between position groups, previous research has found positional differences between on-field workloads in female lacrosse athletes. This leads us to believe off field training stimulus does not mimic on-field training impulse. PRACTICAL APPLICATIONS: Strength and conditioning coaches could use the DSI ratio to individualize training stimulus (strength/power) based on positional groups in order to optimize training and performance outcomes. Ideally, a power-oriented training program is individualized for ATTK while a strength-based program is individualized for DEF, with MID having a combined program to optimize both aspects. Since on-field positional differences have been shown in previous research, off-field strength and conditioning programs should mimic on-field positional differences to optimize positional performance on the field.

Acknowledgements: None