Study Design: Cross-sectional descriptive study. Objectives: To examine the factors of gender and age, stratified by 10-year increments, on hamstring muscle length (HML) as measured by passive straight leg raise (PSLR) and popliteal angle (PA). Background: Differences in HML between men and women have not been examined for a large group of healthy adults over a wide range of ages. The usefulness of these data is to provide some typical values of HML for future reference. Methods and Measures: Two hundred fourteen adults (108 women, 106 men; age range, 20-79 years) with no known history of hip or knee joint disease and no history of recent hamstring strain participated in the study. PSLR (trunk-thigh angle) and PA (thigh-leg angle) were estimated with a goniometer. A 2-way analysis of variance (ANOVA) was used to analyze the effects of 2 independent variables (gender and age) on 2 dependent variables (PSLR and PA). Statistical significance was established at a<.05. Results: HML differed significantly (P<.001) between genders for both methods of measurement, with females demonstrating greater flexibility than their male counterparts. The difference between genders was 8° for PSLR and 11° for PA. HML was not influenced by age. Conclusions: This study provides physical therapists with typical values of HML in healthy men and women.

J Orthop Sports Phys Ther. 2005;35(4):246-252. doi:10.2519/jospt.2005.1428

Key Words: flexibility, hip extensors, lower extremity, straight-leg raise

There are many 2-dimensional and 3-dimensional kinematic measuring systems available on the commercial market for studying and analyzing human movement. Although each system gathers data by use of different technologies, the systems use similar mathematical methods to generate 2- or 3-dimensional coordinates of surface markers reconstructed from a spatial calibration of multiple planar views. The reconstructed marker coordinates are the basis for deriving kinematic parameters of displacement, velocity, and acceleration used to describe human movement. Because numerous motion analysis systems exist, considerable literature exists addressing the accuracy and application of such systems, primarily in relation to measurement of static or dynamic linear and angular segmental variables applied to studies of human movement. It is possible to assess intrinsic knee joint dysfunction such as ligamentous instability or degenerative pathology by measuring the instantaneous center of rotation (ICR) derived from segmental kinematic data. During planar motion between any two segments and at each instant through the joint's excursion, there exists a unique point, the ICR, at which the instantaneous velocity is zero and about which pure rotation of one segment relative to the other occurs. The ICR is stationary through the joint's range of motion with a true hinge joint. Most human joints, however, are not true hinge joints; the ICR moves during a joint's excursion, creating a pathway of the instantaneous center of rotation, or PICR. Location of the PICR relative to joint surfaces can be used to infer joint function. Information concerning joint surface velocity, joint surface compression and distraction, and the rolling/gliding mechanism can also be inferred from the PICR This technical report presents methodology using videographic motion analysis to calculate 2-dimensional ICR. It represents an initial step in developing a valid and reliable method for determining PICR of the knee joint during dynamic activities. We intend to assess the accuracy of videographic methodology for measuring ICR under the ideal conditions of a true hinge joint model.

J Orthop Sports Phys Ther. 1999;29(8):463-469.

Key Words: kinematic measurement systems, motion analysis, ICR, PICR