Here's the study from the top link:
J Strength Cond Res. 2009 Nov 6. [Epub ahead of print]
Comparison Between Linear and Daily Undulating Periodized Resistance Training to Increase Strength.
Prestes J, Frollini AB, Lima CD, Donatto FF, Foschini D, Marqueti RD, Figueira A Jr, Fleck SJ.
1Physiological Sciences Department, Exercise Physiology Laboratory, Federal University of São Carlos, São Carlos, Brazil; 2Health Sciences Department, Physical Education Post-graduation Program, Methodist University of Piracicaba, Piracicaba, Brazil; 3Physical Education and Physiotherapy Faculty, Methodist University of São Paulo, São Paulo, Brazil; and 4Sport Science Department, Colorado College, Colorado Springs, Colorado.
To determine the most effective periodization model for strength and hypertrophy is an important step for strength and conditioning professionals. The aim of this study was to compare the effects of linear (LP) and daily undulating periodized (DUP) resistance training on body composition and maximal strength levels. Forty men aged 21.5 +/- 8.3 and with a minimum 1-year strength training experience were assigned to an LP (LP, n = 20) or DUP group (DUP, n = 20). Subjects were tested for maximal strength in bench press, 45 degrees leg press, and arm curl (1 repetition maximum [RM]) at baseline (T1), after 8 weeks (T2), and after 12 weeks of training (T3). Increases of 18.2 and 25.08% in bench press 1 RM were observed for LP and DUP groups in T3 compared with T1, respectively (p </= 0.05). In leg press 45 degrees , LP group exhibited an increase of 24.71% and DUP of 40.61% at T3 compared with T1. Additionally, DUP showed an increase of 12.23% at T2 compared with T1 and 25.48% at T3 compared with T2. For the arm curl exercise, LP group increased 14.15% and DUP 23.53% at T3 when compared with T1. An increase of 20% was also found at T2 when compared with T1, for DUP. Although the DUP group increased strength the most in all exercises, no statistical differences were found between groups. In conclusion, undulating periodized strength training induced higher increases in maximal strength than the linear model in strength-trained men. For maximizing strength increases, daily intensity and volume variations were more effective than weekly variations.
========
Pretty interesting. My recent experience with the Smolov Squat Base Cycle sort of bears this out. It was more akin to non-linear/DUP than LP in that you squat with a different rep range/load four days a week. Total reps each day stay pretty much the same which is a bit different to a typical DUP program. Still, it worked well.
