Effects of IMU Sensor Location and Number on the Validity of Vertical Acceleration Time-Series Data in Countermovement Jumping

Many devices are available for measuring the height of a CMJ. An inertial measurement unit (IMU) measures linear acceleration, orientation, and angular velocity. As an alternative to using IMU estimates of flight time, CMJ height could be estimated by integrating the IMU time-series signal for vertical acceleration to derive CMJ take-off velocity in order to track whole-body center of mass (WBCoM) movement, yet this approach would require valid IMU acceleration data. Thus, the purpose of this study was to quantify the effects of IMU sensor location and number on the validity of vertical acceleration estimation in CMJ. Thirty young adults from a university setting completed this study. Seven IMUs were placed at the approximate center of mass of the trunk, thighs, shanks, and feet. A total of 15 WBCoM models were created from the 7 IMUs. Using the four segments of the lower body, 1-,2-,3-, and 4-segment IMU models were constructed. Root mean square error (RMSE) was estimated between the acceleration derived from each IMU model against acceleration derived from a force platform. RMSE values from the best performing 1-,2-,3-, and 4-segment IMU models were analyzed for main effects using a 1-way analysis of variance. Notably, all of the best performing models contained IMU acceleration data from the trunk. The best performing 2- and 3-segment IMU models returned significantly lower RMSE values, on average, than the 4- segment model (p = 0.041, p = 0.021, p = 0.061). The average RMSE of the best performing 2- and 3-segment models produced an error of 20% relative to gravitational acceleration, with this error likely to be lower when viewed within the context of specific CMJ events and peak forces. Further investigation into improving IMU technology, procedures, and data processing are needed to reduce RMSE errors to a more acceptable level of validity relative to force platform dynamometry

Late Night Confessions in the Hart and Wechsler Hotel

I began my work in this field about a decade ago, as a teacher, quite simply, trying to find some coherence, some sense in the notoriously complex doctrine. Finding a scheme of coherence, a framework, really is the process of understanding. To merely observe that the field is chaotic, arcane, or incoherent is to decline the work of understanding. That rejection of the subject matter may be a fair and appropriate reaction: witness my colleagues who regard Federal Courts as a mind game or a crossword puzzle. (Indeed, vast numbers bf laypersons have this reaction to the entire subject of law.) But assuming we accept the work of teaching Federal Courts, we must search for frameworks and coherencies as a necessary means of thinking about the subject. At the very least, we need heuristic devices. Over the years I developed a theory, an explanation of the proper basis for allocating cases to the state and federal courts and I have used this theory in class and in a number of articles. In applying this theory, I would receive and review the Supreme Court decisions, hang them out to dry on my framework, and see how they looked. Of course the decisions themselves provided the basis for the framework: this is always a two-way process. One could scarcely come up with a theory of federal courts that had nothing to do with the case law. A theory is refined out of the case law and other articles that have been refined out of the case law; the case law then is used to support the theory; the theory is turned back on the case law; and because of the process of refining the case law, the theory shows why some case law deserves praise and some demands criticism. This entirely circular, inbred process has gone on for so long, in so many diverse voices, and in such lofty and abstract terms that we can regard it as a culture and feel that it is a rather substantial thing-not at all embarrassing or ridiculous. So we operate within this culture and can continue to write articles ad infinitum in this mode

Federalism, Untamed

Do you rankle at those amorphous rhapsodies about Our Federalism indulged in by judges who relegate civil rights litigants to state courts?\u27 Why would anyone see cases in which state officials stand charged of violating the rights of individuals as presenting an occasion for deference to the states? If federal rights take precedence over state policies and practices, is it not perverse to prefer adjudication in the courts that have the strongest bias in favor of state interests? If jurisdiction is a duty and declining jurisdiction consequently a dubious business, shouldn\u27t we reject judge-made doctrine and statutory interpretation that restrict access to federal court? And when the cases excluded involve matters of individual rights, shouldn\u27t our disapproval become active condemnation? If we address the Supreme Court\u27s federalism-based jurisdictional doctrine with questions of this kind, we will probably tend to conclude that the Court has turned the proper hierarchy of values upside down, either through inept reasoning or active hostility to rights. In this essay, I turn away from that perspective and posit a theory that harmonizes the Court\u27s federalism with the notion that federal rights take precedence over state policies and practices. I suggest that the Court\u27s supposedly deferential moves in the name of federalism are little more than a strategy to exploit the state courts, conscripting them into a national agenda. That is, the Court\u27s federalism is in reality quite tame. While individual rights frequently receive something decidedly less than expansive vindication, this federalism nevertheless constrains the state courts in a system structured according to national interests and policies

Why a Narrowly Defined Legal Scholarship Blog Is Not What I Want: An Argument in Pseudo-Blog Form

Written in the form of a blog, this paper highlights the creative and communicative benefits of blogging, in particular legal blogging. This comment argues that aside from being intrinsically rewarding, blogging offers a concise scholarly model addressing a wider-ranger of topics. In this way, the paper claims that blogging has the potential for self-discovery and innovation in a way that legal scholarship might not