Changes in tibiofemoral contact forces during running in response to in-field gait retraining

We evaluated the efficacy of an in-field gait retraining programme using mobile biofeedback to reduce cumulative and peak tibiofemoral loads during running. Thirty runners were randomised to either a retraining group or control group. Retrainers were asked to increase their step rate by 7.5% over preferred in response to real-time feedback provided by a wrist mounted running computer for 8 routine in-field runs. An inverse dynamics driven musculoskeletal model estimated total and medial tibiofemoral joint compartment contact forces. Peak and impulse per step total tibiofemoral contact forces were immediately reduced by 7.6% and 10.6%, respectively (P < 0.001). Similarly, medial tibiofemoral compartment peak and impulse per step tibiofemoral contact forces were reduced by 8.2% and 10.6%, respectively (P < 0.001). Interestingly, no changes were found in knee adduction moment measures. Post gait retraining, reductions in medial tibiofemoral compartment peak and impulse per step tibiofemoral contact force were still present (P < 0.01). At the 1-month post-retraining follow-up, these reductions remained (P < 0.05). With these per stance reductions in tibiofemoral contact forces in mind, cumulative tibiofemoral contact forces did not change due to the estimated increase in number of steps to run 1 km.     

Predicting College Performance of American Indians: A Large‐Sample Examination of the SAT

Extensive research has examined the validity and fairness of standardized tests in academic admissions. However, due to their underrepresentation in higher education, American Indians have gained much less attention in this research. In the present study, we examined for American Indian students (1) group differences on SAT scores, (2) the predictive and incremental validity of SAT over high school grades, (3) the effect of socioeconomic status on SAT validity, (4) differential prediction in the use of SAT scores, and (5) potential omitted variables that could explain differential prediction for American Indian students. Results provided evidence of predictive and incremental validity of SAT scores, and the validity of SAT scores was largely independent of socioeconomic status. Overprediction was found when using SAT scores to predict college performance and it was reduced when including high school grades as an additional predictor. This study provides substantial evidence of the validity and fairness of SAT scores for American Indians.     

The design of a nuclear reactor

The aim of this largely pedagogical article is to employ pre-college physics to arrive at an understanding of a system as complex as a nuclear reactor. We focus on three key issues: the fuel pin, the moderator, and lastly the dimensions of the nuclear reactor.