Wednesday, August 6, 2014

Is Eccentric Training More Anabolic Than Hypertrophy or HIT Training? If We Go by mTOR, Akt & Other "Anabolic" Signalling Proteins, the Answer is Yes!

Is eccentric training the long-thought shortcut to the body of your dreams?
I have never been a fan of HIT training - at least not in its classic version of doing three to maximal 5 reps with extreme heavy weights. The recently publishes study by Schoenfeld et al. (I wrote about it here) did yet already suggest that volume-matched high(er) intensity training is at least as efficient in building strength and size as your classic 3x sets of 8-12 reps in the so-called hypertrophy range.

From other studies, we know that eccentric exercises appear to have a pretty profound effect on the strength and hypertrophy response, as well - you have read that only less than a week ago in "Supramaximal Eccentrics (+38%) on Leg Presses & Calf Raises Pay Off in Form of Extra Strength and Significantly Higher Lean Mass Gains of the Trained Muscles" (read more).

The question is thus: Are high intensity and eccentric training viable alternatives to the classic 3x sets of 10x reps training protocols? And how do they compare to all-or nothing high intensity training to absolute failure?
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A group of German researchers from the German Sport University Cologne wanted to know what the signal protein response to the different training regimen would be and recruited a group of twenty-two healthy male sport students (age 24±6 years, height 181±9 cm and weight 79±2 kg) who hat to perform 70° (ROM) leg extensions, which were chosen as a reference exercise, in hypertrophy (HT), high intensity (HIT) and eccentric training (ECC) fashion:
  • HT: Three sets of ten unilateral concentric and eccentric leg extensions with 3-min rest between sets and 75 % of maximum eccentric and concentric force. Movement speed 65°/s with 66 s TUT
  • HIT: One single set of twenty unilateral concentric and eccentric leg extensions with the highest possible force generation in every contraction. Movement speed 40°/s with 70 s TUT.
  • ECC: Three sets of eight unilateral maximum eccentric leg extensions with 3-min rest between sets and 100 % maximum eccentric force in each repetition. Movement speed 25°/s with 67.2 s TUT.
All subjects of the HIT and ECC group were verbally encouraged during the exercise session to perform all contractions in RE modes with maximum voluntary force. A visual feedback of their 100 % force reference curve was shown on a screen for further encouragement during each contraction. For subjects of the SD group, concentric and eccentric power was set to 75 % of their determined 100 % curve.
Keep in mind: This is an acute study that won't tell you what will happen if you train eccentrically and like a madman during all of your training sessions - let alone on a 5x / week high volume schedule. In that case, overtraining may soon shut all anabolism down.
An analysis of the blood samples that were taken before, as well as 15, 30, 60, 240 min and 24 h after the individual trials, the scientists sought to investigate the acute cellular impact of distinct RE modes via essential signalling measures.
Figure 1: pmTOR and pAKT response to HT, HIT and ECC regimen (Gehlert. 2014)
As you can see, the researchers' hypothesis, "that higher force generation and mechanical demands of skeletal muscle induce higher signalling responses than RE modes with lower force generation" (Gehlert. 2014) held, albeit only if you compare the mTOR and p-AKT response of the eccentric training protocol to the HT and HIT programs.
"The phosphorylation levels of pFAK Tyr397, pJNK Thr183/Tyr185, pAKT Thr308/Ser473, pmTOR Ser2448, p4E-BP1 Thr37/46, p70s6k Thr389 / Ser421/Thr424 and pS6 Ser235/236 were significantly higher in ECC than those in STD and HIT at several time points (P < 0.01). pJNK Thr183/Tyr185 and pS6 Ser235/236 levels were significantly higher in type II myofibres in ECC compared with STD and HIT. HIT exerted throughout the weakest signalling response." (Gehlert. 2014)
Based on these observations, the scientists conclude that  "high force development durin acute RE is superior for anabolic skeletal muscle signalling than fatiguing RE with lower force output but similar TUT" (Gehlert. 2014), which is a true statement, but one that ignores the discrepancy between anabolic signalling and effective muscle growth.
Table 1: Results of meta-analyses of muscle mass gains in previous studies on concentric vs. eccentric training; con, concentric; CSA, cross-sectional area; ecc, eccentric - see bottom line for discussion (Roig. 2008)
It is, for example true that the phosphorylation of p70s6k Ser421/424 and p70s6k Thr389 , p4E-BP1 Thr37/46 and pS6 Ser235/236 directly contributes to regulate protein synthesis, but this does not imply that the ECC exercise will in fact maximize protein synthesis, which is something the scientists didn't measure "[o]wing to technical limitations" (Gehlert. 2014) - major bummer!
Figure 2: The increased strain during the eccentric workouts (see force production, bottom) comes at the cost of significantly increased muscle damage as signified by the elevated creatine kinase levels (learn more) 24h post workout (top; Gehlert. 2014).
Bottom line: I would be cautious about granting the results of the study at hand too much weight. If you look at one of the few studies comparing the results of different trials, you will yet find that eccentric training...
  • is more effective at increasing total and eccentric strength than concentric training
  • appears to be more effective at increasing muscle mass than concentric training
Interestingly, Roig et al. explain these findings much like Gehlert et al. by refering to the "higher forces developed during this type of exercise" (Roig. 2008). In that, they highlight that the adaptations after eccentric training are highly specific to the velocity and type of contraction and thus try to explain the discrepancies between various studies.

If you asked me, the increased muscle damage and the corresponding need for longer recovery times may still render the "eccentric advantage" void - I'm not saying it may not be worth a try, but certainly warning you not to train like this 5x per week.
Reference:
  • Gehlert, Sebastian, et al. "High force development augments skeletal muscle signalling in resistance exercise modes equalized for time under tension." Pflügers Archiv-European Journal of Physiology (2014): 1-14.
  • Roig, Marc, et al. "The effects of eccentric versus concentric resistance training on muscle strength and mass in healthy adults: a systematic review with meta-analyses." British journal of sports medicine (2008).