Position-specific isometric strength tests and their relationship with dynamic performance in collegiate athletes

Dynamic performance is an essential part of many sports and its correlation with isometric strength tests has garnered substantial attention considering the practical utility of isometric testing. Practitioners have assessed maximal isometric strength in athletic populations predominantly using bilateral isometric pulling tests to reveal force-generating capabilities of athletes. However, there is a growing interest in exploring the relationship between dynamic performance and unilateral isometric pushing tests to enhance the specificity and correspondence, particularly in unilateral activities such as sprinting or jumping tasks. Moreover, the relationship between isometric strength and dynamic performance is influenced by biomechanical factors that emerge when conducting tests with different positions and equipment. Notably, while the biomechanics of isometric strength tests can be modified by the type of bar used, there remains a gap in the literature regarding a direct comparison of available bar types and pushing tests. This study aims to bridge this gap by investigating the relationship between dynamic performance and isometric strength, considering two unilateral pushing tests and the influence of two different bar types. Purpose: This study presents a twofold purpose: 1) to investigate and compare the relationships between relative peak force (rPF) obtained through unilateral maximal isometric strength tests using two different bar types including a safety squat bar (SSB) and a conventional barbell (CB); and dynamic sport-specific performance metrics in elite athletes and 2) to extract and compare rPF, rate of force development (RFD), and impulse (IP) from two unilateral pushing strength tests designed to mirror the acceleration and top speed phases of sprinting, the unilateral isometric squat ( uni ISqT) and the unilateral isometric calf raise ( uni ICalf), and examine their relationship with dynamic performance metrics. Methods: Forty-one male high-performance university athletes (age: 21.1 ± 2 yr, height: 184.7 ± 8.5 cm, mass: 95.5 ± 14.5 kg) volunteered to attend a single testing session. A standardized dynamic warm-up was followed by a sprint test and a counter-movement jump (CMJ) and finally isometric testing. In a randomized order, participants performed eight maximal uni ISqT tests – four with a SSB and four with a CB, evenly distributed between dominant and non-dominant limbs. A custom apparatus and two force plates were used to assess rPF normalized to body weight. To evaluate sprint performance, a 40-yard sprint was conducted, and split times were recorded at 10 and 40 yards. Jump performance was assessed by measuring jump height and recording the modified reactive strength index (mRSI) during the CMJ performed on the force plates. A 2(bar) x 2(position) x 2(limb) repeated measures analysis of variance (RM ANOVA) was used to assess differences in rPF between bar types. Separate regression analyses were used to assess the relationships between dynamic performance variables (dependent variables: sprint splits, jump height, mRSI) and rPF variables (independent variables: dominant and non-dominant limb ISqT SSB and CB trials). To explore the relationship between the sprint-specific isometric strength testing positions, correlation and regression analyses were run for each unilateral test, using rPF from isometric tests to predict RFD, IP, sprint split times, jump height, and mRSI. 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: RM ANOVA revealed a main effect for bar type (F1,40=97.481, p<0.001, η2p=0.709) with the SSB producing a higher rPF than CB (mean difference of 30.8% BW). Moreover, a main effect for position type (F1,40=81.171, p<0.001, η2p=0.670) was revealed with the uni ISqT producing a higher rPF than uni ICalf (mean difference of 54.1% BW). Regression analyses showed all equations using uni ISqT to predict sprint split times were significant (p<0.01; Table 3) 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 (p<0.05) while the CB trial was not. Regression analyses reveal that the uni ISqT position accounted for more variance than the uni ICalf position in the 10 and 40 yard sprint performances. Hittner’s follow-up tests showed no significant magnitude of correlation difference across any of the performance metrics. Conclusion: This study revealed that the choice of testing position and bar type significantly impacts rPF production. Furthermore, this study revealed a strong relationship between unilateral isometric tests and dynamic performance, with uni ISqT emerging as a better predictor than uni ICalf on sprinting split times, jump height, and mRSI. This study introduces an efficient, replicable, and low-injury-risk strength assessment method for athletes. The application of this work extends beyond performance measurement, offering potential insight in return-to-play scenarios, and for the development of safer and more effective athlete rehabilitation strategies.

Name thesis:degree_name

Master of Science (M.Sc.)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Kinesiology

Grantor

University of Saskatchewan

Year dc:date.issued

2024

Author dc:creator

• Scott, Parker AP

Advisor dc:contributor.advisor

• Farthing, Jon P

Committee members dc:contributor.committeemember

• Lanovaz, Joel
• Friesen, Kenzie
• Jordan, Matt

• Isometric Strength, Dynamic Performance, Performance Testing, Strength testing, Reliability, Relationship with performance

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/15508

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/15508