The Drinkwater-Ross anthropometric fractionation of body mass: comparison with measured body mass and densitometrically estimated fat and fat-free masses

The Drinkwater-Ross anthropometric fractionation of body mass (mass = sigma skeletal, residual, fat and muscle masses), lean body mass (LBM = sigma skeletal, residual and muscle masses) and fat mass (FM) were compared with the measured body mass, together with the densitometrically estimated fat-free mass (FFM) and fat mass (FM), of 205 male (mean +/- S.D.: 74.66 +/- 10.55 kg; 10.1 +/- 3.7% BF by densitometry) and 177 female (mean +/- S.D.: 59.14 +/- 8.85 kg; 18.5 +/- 5.1% BF by densitometry) South Australian State representatives in a variety of sports. Most absolute differences (d) between the measured body masses and those resultant from the sum of the four fractionated masses (male: d = 2.15 kg or 2.9%; female: d = 1.27 kg or 2.2%) were within what one would expect from random day-to-day variation. However, this was not so for the comparisons between the fractionated LBM (male: d = 2.54 kg or 3.8%; female: d = 2.45 kg or 5.2%) and FM scores (male: d = 1.67 kg or 30.0%; female: d = 2.40 kg or 20.0%) and their densitometric counterparts. These differences are probably related to a combination of the densitometric and fractionation assumptions.     

Reliability of power output measurements during repeated treadmill sprinting in rugby players

The non-motorized treadmill system initially reported by Lakomy in 1984 has been used extensively to assess sprinting performance. However, there has been limited research into the reliability of power output measurement using such systems. The aim of this study was to design a system and protocol capable of measuring treadmill sprinting performance in rugby players and to assess the reliability of this system for measuring power output. Twenty-seven rugby players, all of whom were familiar with treadmill sprinting, performed three maximal 6 s sprints with 2 min recovery between sprints, on two occasions 1 week apart. Both tests were performed on a non-motorized Woodway tramp treadmill, interfaced to a data acquisition system. There were no significant differences (P > 0.05) between power output for repeated trials on the same day (between trials) or for repeated trials on different days (between days). Limits of agreement for maximum average power (the average of 100 readings per second) were 4+/-98 and 30+/-157 W for between trials and between days, respectively. When reported as ratio limits of agreement, these were 1.07 (*/divided 1.12) and 1.03 (*/divided 1.16), respectively. The limits of agreement for maximum instantaneous power (the highest of 100 readings per second) were 51+/-464 and 105+/-588 W for between trials and between days, respectively. When reported as ratio limits of agreement, these were 1.02 (*/divided 1.20) and 1.04 (*/divided 1.21) for between trials and between days, respectively. The coefficients of variation for all measures of power output were less than 9.3%. Hence, the treadmill system and protocol developed in this study provide a reliable measure of power output for rugby players.     

Computer-assisted instruction for dispersed populations: System cost models

Provision of CAI of any sophistication requires-at least with present technology-the existence of a large central computing system. Thus, if rural regions or dispersed populations (e.g. deaf students) are to be able to share in the potential of CAI, an extensive communication system is required. This paper provides cost estimates for a CAI system capable of handling 1300 highly despersed student terminals; in order to do this it develops cost models for alternative te restrial and satellite communication systems. Perhaps the most interesting result to emerge from the analysis is the viability of a satellite based system; for average terminal to computer distances on the order of 500 miles there is a distinct advantage for satellite based systems. Assuming 2,000 hours per year usuage of the student erminals, the system cost for a satellite based system serving a highly dispersed population is $ 0.85 per student contact hour.This work was supported by Grant No. OEG-0-70-4797 from the Bureau of Education for the Handicapped, U.S. Office of Education, to the Institute for Mathematical Studies in the Social Sciences (IMSSS), Stanford University. Portions of the paper were previously presented at the XXII International Congress of the International Astronautical Federation, Brussels, September 1971, and at the International School on Computers in Education, Pugnochiuso, Italy, July 1972.John Ball is the manager of the Computer Based Laboratory of IMSSS; Dean Jamison is a staff member of IMSSS, Assistant Professor of Management Science, Graduate School of Business, and Assistant Professor (by courtesy), School of Education, Stanford University. The authors are indebted to J. E. G. Ferraz and Joanne Leslie Jamison for valuable assistance with this paper.