This week we discuss considerations when utilizing the limb symmetry index (LSI) as a metric for return to sport testing following ACL reconstruction. Limb symmetry index is a popular metric which compares the performance of the involved limb to the uninvolved limb during a test. Commonly, a 90% threshold is used to determine if there is acceptable levels of asymmetry. However, there are a few points to consider when utilizing this metric. First, after an ACL rupture the contralateral side also loses strength and functional capacity. Therefore, comparing to the post-surgical performance of the uninvolved side can give an artificially inflated LSI, so it is important to ground the test outcomes in normative data or benchmark data. Second, variability in movement is a "hallmark of normal function" and understand humnas, and sport, are not always symmetrical. Although, an argument can be made that the test is to see if you have the capacity to be symmetrical, which does not mean you have to be symmetrical all the time, especially at submaximal efforts. Is your maximal effort symmetric on each side? If not, then you may be more likely to be hurt. Third, biomechanical asymmetries can persist past 9 months post ACLR, so don't just look at the numbers: look at the movement strategy. Finally, assess the functional capacity across a load continuum via testing considering the end goal as the sport.

The abstract can be found here: https://journals.lww.com/nsca-scj/abstract/2024/08000/testing_limb_symmetry_and_asymmetry_after_anterior.3.aspx

As always, if you enjoy what you hear, be sure to follow us on your favorite podcast platform and on Instagram @readingrehabpod. If you have any article recommendations be sure to send them our way!