(8) THE RELATIONSHIP BETWEEN NOVEL UNILATERAL ISOMETRIC STRENGTH TESTS AND DYNAMIC PERFORMANCE

Dynamic performance is an essential part of many sports. Studies have shown that dynamic performance is strongly correlated with isometric strength tests, leading to broad interest in assessing maximum isometric strength in athletic populations using peak force and force-time metrics. Most research to date has focused on bilateral isometric pulling tests as the intervention or applied metric. Unilateral isometric pushing tests could improve specificity and correspondence to dynamic performance where single limb involvement is necessary such as during sprinting tasks.

Purpose: The purpose of this study was to extract relative peak force (rPF), rate of force development (RFD), and impulse (IP) from two pushing tests: the unilateral isometric squat (_uniISqT) and the unilateral isometric calf raise (_uniCalf); and examine the relationship between rPF and force-time variables (RFD, IP) and dynamic performance metrics (40-yard sprint and the counter movement jump (CMJ) in athletes.

Methods: Forty-one high-performance university athletes (age: 21.1 ± 2 yr, height: 184.7 ± 8.5 cm, mass: 95.5 ± 14.5 kg) attended a single testing session. After a standardized dynamic warm-up, participants completed a 40-yard dash followed by CMJ and four maximal isometric strength test conditions using a safety squat bar (dominant and non-dominant _uniISqT and _uniCalf). Each effort was five seconds with two minutes of passive recovery. Force-time data were collected using two force-plates and rPF, RFD in 50ms intervals up to 300ms, and IP (over 100, 200, and 300ms) were calculated using custom MATLAB scripts. Sprint performance was evaluated using split times at 10, 20, and 40 yards. Jump performance was evaluated using jump height and modified reactive strength index (mRSI) extracted from the CMJ on the force-plates. Bivariate correlations were run to compare rPF with RFD, IP, sprint split times, jump height, and mRSI for each unilateral test. If two or more isometric tests were significantly correlated, a Hittner’s correlation comparison analysis was conducted to statistically compare the magnitude of correlation.

Results: Correlation results are shown in Table 1. Hittner’s follow-up tests show that nondominant isometric _uniISqT rPF had a greater relationship with RFD 100-150ms than nondominant isometric _uniCalf rPF. Also, the relationship between rPF and mRSI was stronger for the dominant than for the nondominant isometric _uniISqT test.

Conclusions: The results suggest that the non-dominant isometric squat test correlated with the most performance metrics, highlighting the importance of considering unilateral testing and specificity in strength assessments. PRACTICAL APPLICATION: The outcomes from this study will improve strength and conditioning coaches’ ability to develop and test effective training programs for athletic populations that aim to improve performance metrics.

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.