| Chronic ankle sprain (CAS) is a common sequela of an initial ankle sprain. The cause of CAS is unknown. Ligamentous laxity, muscle weakness, and impaired joint position sense have been postulated as risk factors associated with CAS; however, evidence to support any one of these factors in isolation is inconclusive. Joint stiffness, defined as change in force divided by change in length, may represent a composite variable that reflects lax ligaments, impaired strength, and impaired joint position sense. Because of its composite nature, this stiffness variable may be more effective in identifying a potential association with CAS than previously studied factors. The mass-spring model provided the theoretical basis of the lower-limb stiffness formula used in this study.;The purpose of this study was to investigate differences in lower-limb stiffness in between experienced vertical jumpers with and without unilateral CAS (UCAS). Participants were Division I varsity volleyball and basketball players with (n=15) or without (n=15) a history of UCAS, who met the inclusion criteria. Participants performed vertical jump landings while lower-limb stiffness data were collected by means of a computerized motion analysis system and two forceplates. This researcher hypothesized that there would be (1) no differences in lower-limb stiffness between sides of non-UCAS participants (2) a significant difference between sides of the UCAS participants, and (3) greater inter-limb stiffness scores in UCAS participants than in non-UCAS participants. Data were analyzed using three t-tests. A Bonferroni adjustment was done, giving an alpha level of 0.017 (0.05/3).;No significant difference was found in lower-limb stiffness between sides of the non-UCAS group (p = .76). As hypothesized, the UCAS group demonstrated a statistically significant difference between the involved and uninvolved sides (p = .01), with less stiffness evident in the involved leg. Differences in inter-limb stiffness between the UCAS and non-UCAS groups did not reach statistical significance. Findings suggest that lower-limb stiffness may be related to UCAS. Further research is necessary, however, to confirm this relationship, as well as to assess the role of ankle joint stiffness alone in UCAS. |
