Thursday, May 30, 2013

Slow Down to Build Up? 4x Higher Growth Hormone After Slow (4s) Eccentric Biceps Curls, But What's It Worth?

Fast or slow for eccentric biceps curls? Is that a question of faith or can science provide us with an adequate answer?
"What the ****? Training slowly is for pussies!" Ok, admittedly the subjects in the study today's SuppVersity article is going to deal with were ladies (obviously no pussies), but I do not need a study, to tell you that the "pussy" training can hurt significantly more than the "bro" version that usually ends in ballistic movements that are meant to impress the male and female "pussies" at the gym and will yield astonishing increases in trap-size from "bicep curls". Now, I am digressing from the topic at hand, which is: Does it just hurt or does it also work? What? Ah, yeah... I am talking about training at a slow velocity. Eccentric training to be specific. Exactly the kind of training researchers from the ), State University of Campinas have investigated in their latest experiment (Libardi. 2013).

Fast or slow, what's the way to go?

What did the workout look like? Subjects performed five sets of six maximal eccentric contractions of the elbows flexors with the non-dominant arm on an isokinetic dynamometer (Model 4; Biodex Medical Systems Inc.) at two different angular velocities, 30°/s (SV) and 210°/s (FV)  After each eccentric action, the lever arm of the isokinetic dynamometer returned passively to its original position, at the specific velocity of each group, that is, 30°/s for SV and 210°/s for FV (1:1 work-to-rest ratio). The rest interval between sets was 60 s for both groups.
The intention of the scientists was to elucidate, whether there is an influence of the velocity at which previously untrained young women in their early 20s on the workout-induced systemic growth hormone, corstisol, free and testosterone response.  To shit ends the 17 subjects were randomly assigned to two groups
  • the slow velocity group (SV), which performed their machine biceps curls at a velocity of 30°/s
  • the fast velocity group (FV), which performed the identical exercise at a velovity of 210°/s and thus 7x faster
The range of motion was from 125° to 5° of elbow flexion for both groups. The workouts were performed on an isokinetic dynamometer (Model 4; Biodex Medical Systems Inc., New York, NY, USA) at the given velocity. The decision to use eccentric exercises was taken based on previous results by Farthing & Chilibeck, which indicate that isolation exercises will yield greater adaptations such as higher muscle hypertrophy and muscle strength gains compared to concentric actions (Farthing. 2003).

All participants were "encouraged" by the investigator equally, and "visual feedback was provided via Biodex monitor to maximize torque output for each repetition" (Libardi. 2013). Total work and mean peak torque developed in the eccentric exercise were recorded for further analysis and pre-and post.

The slower you go the more you grow?

The Blood samples (20 ml) which were drawn at baseline (Pre), immediately postexercise (IP), and 5, 15 and 30 min following the training session, would in fact suggest that the subheading "the slower you go, the more you grow" wasn't to way off the truth.
Figure 1: Total work, mean peak torque and growth hormone levels immediately, 5 min, 15 min and 30 min after the workout; data expressed relative to arithmetric mean at the given timepoints (Libardi. 2013)
After all, the only significant difference was the post-workout elevation in growth hormone, which was 3.7x, 4.1x and 3.5x higher immediately, 5 min and 15 min after the eccentric biceps curls.

How did this come about? Well the data in figure 1 would suggest that it's neither the total workload or the peak power, but it does not take a physicist to tell that the way the "total workload" is measured has absolutely nothing to do with the associated physiological energy expenditure. "Way times force" may theoretically yield Newton meters and is as such often used as the unit of energy (un-)fortunately the human body is a little more complex than that and I do honestly not know of any way that can accurately calculate the energy expenditure during a workout based on standard equations like these. The same goes for the nondescript term "exercise intensity", so that both - a higher energy expenditure and higher "intensity" are both candidates that could explain the increase in GH (the former would by the way suggest that they are irrelevant for the growth response and and are mainly meant to tap into the energy stores to fuel the workout / post workout glycogen replenishment).

So what does that mean, practically? Similar differences (or trends) were not observed for either free, or total testosterone or the corstiol response to the workout. This is yet not the only reason why the real world significance of the increase in the allegedly growth promoting eponymous hormone remain highly questionable.
Figure 2: The real world speaks a different language - Biceps muscle CSA in young men before and after 8 weeks of fast or slow eccentric biceps training in a previous study (Shepstone. 2005)
  • Firstly, we still don't really know to which extend the immediate changes in the expression of theoretically growth promoting hormones in the vicinity of a workout can actually induce or at least promote the adaptive response to exercise. It may, for example, well be that there is a certain threshold level beyond which additional increases in GH, teststosterone & co don't make a significant difference.
  • And secondly, and more importantly, it is not impossible that the results would be very different for (a) a different group of subjects, (b) complete reps (=concentric + eccentric reps), (c) other muscle groups like classic "push" muscles as the pecs or the legs, etc. 
Moroever, the results of practically relevant 8-week studies such as Shepstone et al. (2005; see figure 2) do actually speak a very different language and support those researchers who doubt the physiological relevance of improvements in the acute anabolic milieu after a workout.

Suggested reads: 

  • The expression of local GH & IGF splice variants may be of much greater importance than their systemic values (read more)
    Does the testosterone and overall hormonal response to workouts even count, or are we still chasing a hormonal ghost? In the Short News from Saturday, March 2, 2013
  • IGF-1 and its Splice Variants MGF, IGF-IEa & Co - Master Regulators or a Bunch of Cogs in the Wheel of Muscle Hypertrophy?  In the Intermittent Thoughts in Dec. 2011 
  • Differences in Growth Hormone, Insulin and IGF-1 Response in Trained and Untrained Resistance Trainees - Further Evidence That GH Builds Neither Muscle Nor Strength (read more)

  • Farthing JP, Chilibeck PD. The effects of eccentric and concentric training at different velocities on muscle hypertrophy. Eur J Appl Physiol. 2003 Aug;89(6):578-86.
  • Libardi CA, Nogueira FR, Vechin FC, Conceição MS, Bonganha V, Chacon-Mikahil MP. Acute hormonal responses following different velocities of eccentric exercise. Clin Physiol Funct Imaging. 2013 May 15.
  • Shepstone TN, Tang JE, Dallaire S, Schuenke MD, Staron RS, Phillips SM. Short-term high- vs. low-velocity isokinetic lengthening training results in greater hypertrophy of the elbow flexors in young men. J Appl Physiol. 2005 May;98(5):1768-76.