Bump! This is an interesting thread!
Here is one contribution on how to maximize metabolic stimulation after the mechanic stimulation. It addresses how to get appropriate TUT also:
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">Time under tension and blood lactate response during four different resistance training methods.
Gentil P, Oliveira E, Bottaro M.
College of Health Sciences, University of Brasilia, Brazil.
paulogentil@hotmail.com
Mechanical stimuli have often been suggested to be the major determinant of resistance training adaptations; however, some studies suggested that metabolic changes also play an important role in the gains of muscle size and strength. Several resistance training methods (RTM) have been employed with the purpose of manipulating mechanical and metabolic stimuli; however, information about their physiological effects are scarce. The objective of this study was to compare the time under tension (TUT) and blood lactate responses among four different RTM reported in the literature. The four RTM were performed in a knee extension machine at 10 repetition maximum (RM) load by 12 recreationally trained young men. The RTM tested were: 10RM, super-slow (SL-subjects performed one 60-second repetition with 30 seconds for eccentric and 30 seconds for concentric phase), functional isometrics (FI-in each repetition, a five-second maximal isometric contraction was executed with the knees fully extended) and adapted vascular occlusion (VO-subjects performed a 20-second maximal isometric contraction with the knees fully extended and immediately proceeded to normal isoinertial lifts). According to the results, all RTM produced significant increases in blood lactate levels. However, blood lactate responses during FI (4.48+/-1.57 mM) and VO (4.23+/-1.66 mM) methods were higher than the SL method (3.41+/-1.14 mM). The TUT for SL (60 s), FI (56.33+/-6.46 s), and VO (53.08+/-4.76 s) methods were higher than TUT for 10RM (42.08+/-3.18 s). Additionally, TUT for the SL method was higher than TUT during the VO method. Therefore, the SL method may not be recommended if one wants to provide a high metabolic stimulus. The FI method appeared to be especially effective in promoting both type of stimuli.
J Physiol Anthropol. 2006 Sep;25(5):339-44.</div>
Here is a recipe for HST practioners, seeking to maximize stimuli and still keeping the volume down (TUT approx. 60+ seconds):
- I figured during 15RMs the FI was more appropriate, since 15RMs is more about metabolic stress.
- During 10RMs I actually have no idea, but you should try to get the most TUT out of the set, by combining FI and regular reps, using a 10RM weight, for the sake of weight progression.
- During 5RMs you do your 5 reps with 5RM, then perform VO and then 15 reps of 50% of 1RM.
- Going beyond 5RMs, focus on upping the weights on the beginning of the set by any means possible (negatives, partials, isometrics, max stim) to achieve maximum mechanic stimuli, and then continue with metabolic stress, again by performing a VO and then finishing off the excercise with 15 reps of 50% of 1RM.
- Thus we are beginning with mostly metabolic stimuli when the weights are light, and moving on towards more mechanic stimuli as the weight increases. Sooner or later the RBE will catch up and stiffen the muscle, preventing mechanic stimuli to be truly effective.
Why 50% of 1RM? The following study should answer why:
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">A single set of low intensity resistance exercise immediately following high intensity resistance exercise stimulates growth hormone secretion in men.
Goto K, Sato K, Takamatsu K.
AIM: The purpose of the present study was to examine the effects of an additional set immediately following high intensity resistance exercise on growth hormone (GH) response. METHODS: Subjects (n=8) performed 4 resistance exercise protocols (bilateral knee extension exercise) on separate days. The protocols were categorized into 2 types of protocol, namely "Strength-up type (S-type)" and "Combination type (Combi-type)". The S-type was resistance exercise which consisted of 5 sets at 90% of 1 repetition maximum (RM) with 3-min rest periods between sets, whereas the Combi-type is a training protocol which adds an additional set (either 50% of 1 RM [C50-type], 70% of 1 RM [C70-type] or 90% of 1 RM [C90-type]) to the S-type. Serum GH concentration and blood lactate concentration were determined pre-exercise and at 0-60 min postexercise. Relative changes in thigh girth and maximal unilateral isometric strength were determined pre-exercise and immediately postexercise. RESULTS: The increasing values of GH concentration (DGH) in the S-type was the lowest of all protocols. On the other hand, DGH in the C50-type showed a significantly (p<0.05) higher increase than in the S-type and C90-type, and a relatively higher increase than in the C70-type. CONCLUSION: These results suggests that a high intensity, low volume training protocol to induce neural adaptation resulted in little GH response, but GH secretion was increased by performing a single set of low intensity resistance exercise at the end of a series of high intensity resistance sets.
J Sports Med Phys Fitness. 2003 Jun;43(2):243-9.</div>
However, in the study 5 sets of approx 5RMs (90% of 1RM) were performed. I don´t know if reducing the number of 5RMs sets will distort the outcome. You be the judge.
Taken all together these studies address both mechanical and metabolical stimulation issues.
Best regards,
nkl