Impact Of Lower Extremity Injury History On Countermovement Jump Kinetics And Tissue Thickness

A history of injury has consistently been identified as a risk of future injury. Understanding biomechanical differences between cohorts with a history of lower extremity injury and those without may be valuable in avoiding subsequent injuries. To best translate to athletic populations, a kinetic assessment of countermovement jumps provides insight into performance indicators and injury risk factors in one task. Further insight can be provided through sonographic images and understanding tissue thickness as a sign of maladaptation. PURPOSE: To identify differences in jump kinetics during takeoff and landing events between cohorts with and without a history of injury, along with determining differences in plantar fascial and achilles tendon thickness. METHODS: Participants with a history of injury to the lower leg were recruited (n = 19, 169 ± 7 cm, 65 ± 12 kg, 22 ± 1 yrs, 240 ± 80 min/week). Healthy controls (n = 19, 169 ± 6 cm, 66 ± 8 kg, 23 ± 2 yrs, 230 ± 80 min/week) were then matched for physical activity and age. All participants completed three countermovement jumps at maximal effort, during which vertical ground reaction force was collected via a force platform (1000 Hz). The tissue thickness of the plantar fascia and achilles tendon was imaged using a portable diagnostic ultrasound machine. Independent t-tests and Hedge’s g effect size were used to determine the significance of cohort comparisons and their clinical value. RESULTS: Participants jumped the same height with (26 ± 6 cm) and without (24 ± 4 cm) a history of injury. Differences were identified in the rate of force development during the propulsive phase (p = 0.04, g = 0.67), where those with a history of injury produced force at a lower rate (No History of Injury: 21.7 ± 4.8 BW/s, History of Injury: 18.2 ± 5.4 BW/s); representing a 16% reduction. No differences were noted between cohorts for either tissue thickness (p ≥ 0.21). CONCLUSION: The present data does not demonstrate a different movement strategy for jumping in those with a history of lower extremity injury; however, a lower rate of force development during a countermovement jump may indicate a need for more time to generate the same relative force. Further, thicker tissue was not found in persons with a history of injury.