Think of it: It's simple physics. The force you apply is the product of the mass you move and the acceleration you exert on that mass. It's F = m · a - Force equals mass times acceleration. If you go slow to achieve a maximal time under tension, the acceleration will be low and so will be the force. Since my friends from the exercise physiological department tell me that F ~ EMG, meaning there's a in parts proportional increase in muscle activity when the force you applied increases, it should be obvious why the previously phrased hypothesis that "a higher time under tension would yield greater EMG" cannot be correct.
Unfortunately, things are not as simple as they may seem. After all, the activation patterns are reversed on the way down. Whut? Yes, they are. The slower you lower the weight (almost) onto your chest, the higher the negative acceleration you apply, ... and you know what that mean, right? YES! The greater the force.
So under physically ideal (no one says that this must be physiologically ideal, at this point!) conditions, you'd be exploding on your way up and going super-slow on your way down.
Unfortunately, this is not what any of the thirteen males, all of whom were familiar with the bench press exercise, did in the BA study by Gustav Mårtensson (2015 | still great work for a bachelor's thesis, by the way). What they did was to perform the bench press at their individual 6 RM with a tempo of either
- 4 second per total repetitions, 6 second per total repetitions, or
- each repetition intentionally performed as fast as possible (as Lawrence rightly points on on Facebook, that's not going to look much faster than normal speed with a 6-RM weight)
deltoideus anterior, Mårtensson also counted the number of repetitions his subjects performed and recoreded the total time under tension for each test in seconds.
|Figure 1: Normalized (rel. to maximal voluntary contractinos) EMG values (Mårtensson. 2015) - p < 0.05 for pecs, only.|
|In this SV Classic you can learn about potential benefits of of combining va-rious training types: "Building the Jack-of-All-Traits Legs Workout With Squats, Jump Squats and Body Weight Plyo-metrics - This is it" | read more|
Addendum: In a very recent study that has not yet been published Jenkins et al. found no link between increased muscle activation and size gains in a non-volume equated comparison of 80% and 30% 1-RM training (Jenkins. 2015). In view of the completely different training scenario and the considerable impact of differences in volume, metabolic byproduct accumulation, and muscle swelling, said study is yet probably of little relevance to the question at hand.
|Figure 2: Number of reps (indiv., left) + average (right) during the three BP conditions (Mårtensson. 2015)|
- Caserotti, Paolo, et al. "Explosive heavy‐resistance training in old and very old adults: changes in rapid muscle force, strength and power." Scandinavian journal of medicine & science in sports 18.6 (2008): 773-782.
- Jenkins ND1, Housh TJ, Bergstrom HC, Cochrane KC, Hill EC, Smith CM, Johnson GO, Schmidt RJ, Cramer JT. "Muscle activation during three sets to failure at 80 vs. 30 % 1RM resistance exercise." Eur J Appl Physiol. 2015 Jul 10. [Epub ahead of print]
- Mårtensson, Gustav. "The effect of lifting speed on factors related to resistance training: A study on muscle activity, amount of repetitions performed, and time under tension during bench press in young males." (2015).
- McGuigan, Michael R., et al. "Effect of explosive resistance training on titin and myosin heavy chain isoforms in trained subjects." The Journal of Strength & Conditioning Research 17.4 (2003): 645-651.
- Newton, Robert U., and William J. Kraemer. "Developing Explosive Muscular Power: Implications for a Mixed Methods Training Strategy." Strength & Conditioning Journal 16.5 (1994): 20-31.
- Paavolainen, Leena, et al. "Explosive-strength training improves 5-km running time by improving running economy and muscle power." Journal of applied physiology 86.5 (1999): 1527-1533.
- Sakamoto, Akihiro, and Peter J. Sinclair. "Effect of movement velocity on the relationship between training load and the number of repetitions of bench press." The Journal of Strength & Conditioning Research 20.3 (2006): 523-527.
- Sakamoto, Akihiro, and Peter James Sinclair. "Muscle activations under varying lifting speeds and intensities during bench press." European journal of applied physiology 112.3 (2012): 1015-1025.
- Santos, Eduardo JAM, and Manuel AAS Janeira. "Effects of complex training on explosive strength in adolescent male basketball players." The Journal of Strength & Conditioning Research 22.3 (2008): 903-909.