here is the abstract for everybody to read for one of the studies you posted.
J Strength Cond Res. 2007 May;21(2):628-31.
The application of training to failure in periodized multiple-set resistance exercise programs.
SourcePhysical Education Department, Eastern Illinois University, Charleston, Illinois 61920, USA. [email protected]
Few studies and reports in the body of literature have directly addressed the issue of whether resistance exercise sets should be performed to failure. Research has clearly demonstrated the superiority of performing multiple sets vs. single sets for increases in maximal strength. However, there is little direct evidence to decide conclusively whether or not multiple sets should be performed to failure. Therefore, the purpose of this research note was to discuss what is currently known concerning the application of training to failure and to stimulate further research on this topic. Although not essential for increases in muscular characteristics such as strength and hypertrophy, training to failure might allow advanced lifters to break through training plateaus when incorporated periodically into short-term microcycles. Because muscular hypertrophy is a key contributor to long-term increases in maximal strength, advanced lifters should consider training to failure occasionally. The potential mechanisms by which training to failure might provide an advantage are through greater activation of motor units and secretion of growth-promoting hormones. However, training to failure is not an effective stimulus without lifting at a sufficient intensity (percentage of 1 repetition maximum). Furthermore, training to failure should not be performed repeatedly over long periods, due to the high potential for overtraining and overuse injuries. Therefore, the training status and the goals of the lifter should guide the decision-making process on this issue.
PMID: 17530977 [PubMed – indexed for MEDLINE]
Some of the common factors affecting the external validity of this type of research are such as percent max of weight used and total volume differences as pointed out in other research by Len Kravitz, Ph.D. You have posed a very good topic here Joanne and have aroused my curiosity as it would appear that NSCA’s journals favor repetitions to failure. I am definitely going to have to do more research on the subject at the CALU library.
Some resources on the matter that I have and highly regard as the sources for some of my programming structure are as follows:
Science and Practice of Strength Training 2nd ed – Zatsiorsky
Supertraining 6th ed – Mel Siff
Periodization for Sports 2nd ed – Tudor Bompa & Michael Carrera
Periodization Training: Theory and Methodolgy 4th ed – Tudor Bompa
Serious Strength Training 2nd ed – Tudor Bompa, Mauro Di Pasquale and Lorenzo Cornacchia
Designing Resistance Training Programs 3rd ed – Steven Fleck and William Kraemer
Physiology of Sport and Exercise 4th ed – Dr. Jack H. Wilmore, Dr. David Costill and W. Larry Kenney
All very good books on this subject by credible authors.
Thanks for posting this question!