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Comparison of Different Functional Tests for Leg Power and Normative Bilateral Asymmetry Index in Healthy Collegiate Athletes

Link to Original Research

Spencer W Sullivan, Niles A Fleet, Vanessa A Brooks, Jennifer Bido, Benedict U Nwachukwu, Peter H Brubaker


This research aimed to measure lower leg asymmetry in healthy collegiate athletes utilizing functional tests like the single leg hop for distance (SLHD), single leg vertical jump (SLVJ), and peak power assessments with the Keiser Air420 seated leg press. By analyzing 88 student-athletes across various varsity teams, the study sought to understand the correlation between these tests and establish normative bilateral asymmetry indices (BAI) for determining readiness to return to play (RTP) after injury.


The study found significant bilateral asymmetries across all tests, with mean absolute BAIs of 5.42%, 6.64%, and 5.36% for the SLHD, SLVJ, and Keiser tests, respectively. The SLVJ and Keiser tests showed a higher correlation, indicating that these measures may be more reliable indicators of leg power and symmetry. Athletes exhibited less than 15% BAI at the 90th percentile, suggesting that a combination of tests is preferable for assessing lower limb symmetry and RTP readiness, rather than relying on a single 10% reference asymmetry.


The research highlights the importance of utilizing a comprehensive battery of tests to evaluate lower limb symmetry and power in collegiate athletes accurately. The findings suggest that combined weight and pneumatic training could significantly benefit athletes by enhancing power endurance and peak power. This approach, which leverages both traditional weight training and innovative pneumatic resistance, offers a more effective method for improving athletic performance and ensuring a safer return to competitive play post-injury.


  • Bilateral Asymmetry Index (BAI): A metric to compare differences in strength, power, or function between an athlete's legs, aiming to quantify symmetry.
  • Single Leg Hop for Distance (SLHD) and Single Leg Vertical Jump (SLVJ): Functional tests used to assess leg strength, power, and symmetry by measuring the distance of a hop or height of a jump performed on one leg.
  • Keiser Air420 Seated Leg Press: A pneumatic resistance training machine that measures peak leg power, offering insights into an athlete's strength and rehabilitation progress.
  • Return to Play (RTP): The process or decision-making involved in determining when an injured athlete is ready to resume competitive sports safely.

Open Access Journal of Sports Medicine 2021:12 119–128

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