The Effect of Initial Knee Angle on Concentric-Only Squat Jump Performance

Purpose: There is uncertainty as to which knee angle during a squat jump (SJ) produces maximal jump performance. Importantly, understanding this information will aid in determining appropriate ratios for assessment and monitoring of the explosive characteristics of athletes. Method: This study compared SJ performance across different knee angles—90º, 100º, 110º, 120º, 130º, and a self-selected depth—for jump height and other kinetic characteristics. For comparison between SJ and an unconstrained dynamic movement, participants also performed a countermovement jump from a self-selected depth. Thirteen participants (M_age = 25.4 ± 3.5 years, M_height = 1.8 ± 0.06 m, M_weight = 79.8 ± 9.5 kg) were recruited and tested for their SJ performance. Results: In the SJ, maximal jump height (35.4 ± 4.6 cm) was produced using a self-selected knee angle (98.7 ± 11.2°). Differences between 90°, 100°, and self-selected knee angles for jump height were trivial (ES ± 90% CL = 90°–100° 0.23 ± 0.12, 90°–SS ?0.04 ± 0.12, 100°–SS ?0.27 ± 0.20; 0.5–2.4 cm) and not statistically different. Differences between all other knee angles for jump height ranged from 3.8 ± 2.0 cm (mean ± 90% CL) to 16.6 ± 2.2 cm. A similar outcome to jump height was observed for velocity, force relative to body weight, and impulse for the assessed knee angles. Conclusions: For young physically active adult men, the use of a self-selected depth in the SJ results in optimal performance and has only a trivial difference to a constrained knee angle of either 90° or 100°.     

Developing a measurement tool for assessing physiotherapy students’ self-efficacy: a pilot study

The aim of this research was to determine if self-efficacy can be correlated with prior academic achievement and whether self-efficacy can be an outcome measure of education. A self-efficacy instrument was developed and administered to physiotherapy students following completion of their pre-clinical theory experience. The questionnaire results completed by students regarding their self-efficacy were compared with their pre-clinical theory performance prior to clinical placement. Sixteen third-year physiotherapy students completed and returned the self-efficacy questionnaire. Correlation of the self-efficacy questionnaire results with the students’ pre-clinical grade was undertaken with a statistical correlation of 0.55 found between pre-clinical grade and students’ total self-efficacy score. This indicates that self-efficacy measurement is a possible outcome for educational interventions.     

Telecommunications

MISUNDERSTANDING MEDIA by Brian Winston (New York: Oxford University Press, 1986---$22.50)

SERVICES IN TRANSITION: THE IMPACT OF INFORMATION TECHNOLOGY ON THE SERVICE SECTOR edited by Gerald Faulhaber, et al. (Cambridge, MA: Ballinger, 1986---$29.95)

BUSINESS TELEMATICS: CORPORATE NETWORKS FOR THE INFORMATION AGE by Byron Belitsos and Jay Misra (Homewood, IL: Dow, Jones-Irwin, 1986---$25.00)

COMPUTER & TELECOMMUNICATIONS ACRONYMS edited by Julie Towell and Helen Sheppard (Detroit: Gale Research, 1986---$60.00)

Three recent publications from the Program on Information Resources Policy (200 Aiken, Harvard University, Cambridge, MA 02138---inquire of publisher for prices, paper)

COMPUTER III: A NEW ERA—A GUIDE TO THE FCC'S LANDMARK DEREGULATORY RULING edited by Dick Stirba (Telecom Publishing Group, Capitol Publications, 1101 King St., Alexandria, VA 22314---$140, paper)

MARKET AND STRATEGIC IMPACTS OF BYPASS by the Bethesda Research Institute (Phillips Publishing, 7811 Montrose Rd., Potomac, Md. 20854---price not given, paper)

SATELLITE COMMUNICATION SYSTEMS ENGINEERING by Wilbur Pritchard and Joseph Sciulli (Englwood Cliffs, NJ: Prentice-Hall, 1986---$42.95)

GUIDE TO SATELLITE TELEVISION INSTALLATION by John E. Traister (Englewood Cliffs, NJ: Prentice-Hall, 1986---$24.95)     

The action of hydrogen peroxide on photographic gelatino-silver halide emulsions

1. The sensitometric characteristics of photographic plates exposed to hydrogen peroxide and developed are strikingly similar, both for time of exposures, time of development, and intensity i.e., concentration). Characteristic curves similar to H. and D. curves were obtained, including a period of “reversal.”2. A tentative theory of the action of hydrogen peroxide is suggested. It is supposed that the decomposition of peroxide is chemi-luminiscent, short wave-length radiation being afforded at the surface of the silver halide grain, and particularly at check the hypothesis that these nuclei consist of colloid silver.The authors desire to express their thanks to Mr. R. F. Quirk and Mr. E. Huberth for painstaking assistance in the experi- mental work, and to Miss Anber J. Benedict for making the pH measurements.