(57) THE RELATIONSHIP BETWEEN ISOMETRIC STRENGTH TESTS AND DYNAMIC PERFORMANCE: A COMPARISON OF TWO BAR TYPES

Research shows that different biomechanics during isometric strength tests can enhance or diminish the relationship between isometric strength and dynamic performance. Previous studies report muscle activation differences during isotonic back squat strength tests when comparing conventional barbells (CB) and safety squat bars (SSB). While different bar types used during isometric strength tests can alter biomechanics, no research to date has directly compared available bar types used for isometric testing.

Purpose: The purpose of this study was to examine the relationships between relative peak force (rPF) derived from unilateral maximal isometric tests using a SSB and CB with dynamic sport-specific performance in elite athletes.

Methods: Forty-one high-performance university athletes attended a single testing session (age: 21.1 ± 2 yr, height: 184.7 ± 8.5 cm, mass: 95.5 ± 14.5 kg). Following a standardized dynamic warm-up, participants completed a 40-yard dash and a counter movement jump (CMJ), prior to isometric testing. In an order-randomized fashion, participants completed eight maximal unilateral isometric squat (ISqT) tests: four tests using the SSB and four using the CB divided evenly between dominant and non-dominant limbs. rPF (normalized to body weight) was assessed using a custom-built apparatus and two force plates. Sprint performance was evaluated using a 40-yard sprint with split times measured at 10 and 40 yards, and jump height and modified reactive strength index (mRSI) were extracted from the CMJ using the force plates. A 2(bar) x 2(leg dominance) repeated measures analysis of variance (RM ANOVA) was used to assess differences in rPF. Eight regression analyses were used to assess the relationships between dynamic performance variables (dependent variables: sprint splits, jumper height, mRSI) and rPF (dominant and non-dominant limb ISqT SSB and CB trials).

Results: RM ANOVA revealed a main effect for bar type (F_1,40=46.5, p< 0.001, η²_p=0.537) with the SSB producing a higher rPF (mean difference of 27.4% BW). Regression analyses showed all equations predicting sprint split times were significant (all p< 0.01; Table 1) while those predicting jump height and mRSI were not. In each significant regression equation, the rPF from the SSB trial was a significant predictor of dynamic performance (all p< 0.05) while the CB trial was not.

Conclusions: The SSB produced higher rPF than the CB during unilateral isometric tasks and accounted for variance in predicting sprint times. Greater force output and a stronger relationship with dynamic performance during the SSB ISqT may be due to biomechanical positions which allow for greater torque development. PRACTICAL APPLICATION: These findings suggest that strength and conditioning coaches as well as rehabilitation professionals can consider the SSB in isometric testing for high-performance athletes, as it produces higher peak force values and better predicts dynamic performance than CB.

Acknowledgements:

A special thanks to Mitacs Accelerate Grant for funding our research project, our industry partner for collaborating, and to the research team that made it possible.