(37) FORCE PLATE METRICS ARE COMPLIMENTARY, NOT REDUNDANT, TO MOVEMENT ASSESSMENTS WHEN ANALYZING LOWER EXTREMITY ASYMMETRIES

Introduction: There is a significant financial cost associated with time lost from lower extremity musculoskeletal injuries (MSKI) in tactical athletes. The presence of lower extremity asymmetries may result in alterations in movement patterns and lead to MSKI. Specifically, single leg stance anterior reach asymmetry (ARA) between limbs has been associated with a two-fold greater likelihood of injury. More recently, with increased portability, dual force plates (FP) are a viable option for evaluating asymmetries. FP metrics during a countermovement jump (CMJ) are commonly used to assess fatigue and subsequently injury risk. At present its unclear whether FP asymmetry metrics are redundant or complimentary to ARA.

Purpose: The purpose of this study was to analyze whether ARA show agreement with FP asymmetry metrics during a CMJ.  

Methods: 77 ROTC cadets (58 males, 19 females, age=21.5±2.8) participated. Cadets’ right and left leg length were recorded, then cadets performed three trials per leg of a unilateral anterior reach with the greatest reach distance on each stance leg used to compute the ARA. Cadets performed two maximal CMJs on dual FP. Mean eccentric, braking and landing phase asymmetries were averaged across the two attempts then converted to percent difference. Dependent t-tests assessed differences in leg asymmetries between anterior reach and FP metrics. Bonferroni corrections for multiple comparisons were used. Pearson correlations assessed relationships between FP metrics.

Results: ARA percent difference were significantly greater than percent difference in landing force (p=0.006), braking RFD (p=0.036) and eccentric force asymmetries (p< 0.001). There was no significant correlation between ARA and landing force (R=0.11, p=0.34), braking RFD (R=0.02, p=0.95), and eccentric force asymmetries (R=0.03, p=0.79; Figure 1). There was a significant correlation between braking RFD and landing force asymmetries (R=0.32, p=0.005) and eccentric and landing force asymmetries (R=0.26, p=0.025). There was no significant correlation between braking RFD and landing force asymmetries (R=0.01, p=0.915).

Conclusion: The findings from the study indicate that FP metrics are complimentary and not redundant to ARA. This could be expected when considering differences in biomotor abilities required of a single leg anterior reach compared to a bilateral CMJ. Explosive bilateral movements (i.e. CMJ) require large bilateral muscle groups to perform coordinated force production while the anterior reach is sensitive to limitations in flexibility and neuromuscular control to stabilize the stance leg.  

 
PRACTICAL APPLICATIONS: FP based CMJ assessments should be viewed as complimentary to a unilateral anterior reach movement assessments when creating a tactical athlete’s movement profile. Considering that both are time expedient and reliable measures of movements associated MSKI risk factors it would be advised to perform both assessments when possible.

Acknowledgements: None.