Time Under Tension (TUT) Another Under-Appreciated Determinant of the Protein Synthetic Response to Exercise?

Image 1: Is it really time to buy some revolutionary new exercise equipment to time your time under tension? Or should you keep pumping away like there was no tomorrow?

If you have been following the SuppVersity news for some time now, you know that I am a "fan" of the research Stuart Phillips and his colleagues at the Department of Kinesiology at McMaster University in Hamilton, Ontario, are doing. Before I get to some details on their latest coup, I must yet express some concerns about Phillips' focus on immediate changes protein synthesis. Yes, amino acid ingestion and particularly leucine increase protein synthesis, yes, bolus ingestion of whey protein increases protein synthesis over sipping and yes, training with low loads (30%) and slow reps, as in the study at hand, increases protein synthesis,... but hey. Do you really give a damn about protein synthesis? No, you don't. Either you want to gain muscle or you want to get stronger and exactly here I am missing a link that would connect the short-term increases in the protein synthetic response to exercise Phillips and his colleagues are investigating in one study after the other and the long(er)-term real-world outcomes in terms of muscle size and strength gains.

Wait! Is protein synthesis really that important?

I will probably touch on this issue in tomorrow's installment of the Intermittent Thoughts, as well, so let me just say this: Muscle protein synthesis is only one out of two (maybe three processes) and probably not even the most important one, when your goals are getting really big or really strong. I mean, if increasing protein synthesis was all it would take to get as buffed as Phil Heath and as strong as Derek Poundstone, everyone would be training like a sissy (like in this study), take his BCAAs and whey protein and see amazing results... but I am once again getting off a tangent here, and as I already said, you will read more on that here at the SuppVersity in the future. So, for the time being, let's get back to the time under tension, i.e. the exact number of seconds your muscles are actually working (meaning contracting) during a given set.

Figure 1: Basic outline of the study first and second testing session (based on Burd. 2011)

For their most recent study Nicholas A. Burd et al. recruited 8 recreationally resistance-trained men (23.5 ± 1 years; 88.3 ± 5 kg; BMI=26.5 ± 1.0 kg/m²) who had performed lower body resistance exercise training with a frequency of at least 2x/week in the course of the last 2 years prior to the study [note: this certainly is a huge plus of the study, because we all know that you can have a newbie do nothing but climb stairs and he will still grow ;-] The individual one rep-max for leg-extensions was accessed once prior to the infusion trial (105kg right, 101kg left leg) and dietary intakes were recorded prior to both the resting and the exercise infusion trials, in the course of which the participants reported to the lab fasted (at 7am) before a catheter for the tracer infusion was inserted into their arm and a first (fasted) muscle biopsy was taken from their legs (3.5h after reporting to the lab).

Participants subsequently performed bouts of unilateral leg extension exercise at 30% of
their previously established concentric 1RM. Legs were randomized and balanced for dominance based on maximal strength to perform exercise at a slow lifting (SLOW) or an external work-matched control (CTL) conditions. The leg assigned to the SLOW condition performed exercise with a lifting/lowering cadence of 6 s concentric phase and a 6 s eccentric phase with no pauses until volitional fatigue (i.e. failure). Failure was defined as the point at which the participant could not lift through the full range or their technique to lift the load included motions at joints other than the knee. The CTL condition was completed with the contralateral leg and was matched to the experimental condition for contraction volume such that the leg performed an identical number of repetitions at an equivalent load, but not to failure, and was performed with a lifting cadence of 1 s concentric phase and a 1 s eccentric phase.

The participants performed a total of 3 sets with 2 minutes of rest between the sets for each condition. Lifting cadence was monitored by an instructor and by the use of a metronome. Moreover, the exact knee-joint angles were recorded by the means of a goniometer. After a subsequent 2nd blood sample was taken, all participants consumed 20g of whey protein isolate. 6h after, a 2nd bilateral biopsy was taken and the participants were fed a standard cafeteria meal. For the rest of the day they were advised to follow a diet that would mirror their previously recorded food intake, with the last meal being consumed before 22h, "to ensure a 10 h fast prior to the beginning of the 24 h post-exercise protein synthesis measurement", which took place the next morning after the consumption of another 20g of a tracer-enriched whey protein supplement.

Figure 2: Fractional protein synthesis (in % per hour) - left; and relative differences in protein synthesis of slow vs. ctrl condition - right (based on Burd. 2011)

The data in figure 2 clearly shows that going to failure (and this is what I consider even more important than time under tension when training with sissy 30%1RM loads) produces profound (compare the relative increases in the smaller graph on the upper right corner) increases in fractional protein synthesis, which are, in the time-window right after the exercise bout, particularly pronounced in the mitochondrial and sarcoplasmic compartment of the muscle. In this regard, Burd et al. point out that

[w]hat we observed here was a potentiated effect, from that seen in the fasted-state, of prior exercise in enhancing the feeding-induced myofibrillar protein synthetic rates. This effect appears to be dependent on maximal fibre activation during exercise, [...] The current study is noteworthy in that an enhanced effect of protein feeding during late exercise recovery was induced by a longer time under muscle tension rather than intensity-independent contraction volume, which we have previously examined (Burd. 2010).

As far as the delay in the normally immediate increase in myofibrillar protein synthesis is concerned, the researchers speculate that both the timing of the biopsies, as well as the training status of the subjects and the specificity of their protocol about which they state that with its long loading times at relatively low intensities it must have shifted the protein (immediate) myofibrillar protein synthetic response "toward increased synthesis of proteins in the mitochondrial and sarcoplasmic pools" (cf. figure 2) - a process the underlying causes and mechanisms of which are yet unclear.

Why would you change a winning team?

Image 2: When it comes to SST and all the other training types from the alphabet soup, I alway wonder why people keep questioning what has worked well for the majority of bodybuilders and athletes, they are looking up to and whose physiques they are admiring!?

Actually this observation takes us full circle to my introductory remarks on the possible short-sightedness of measuring acute fractional protein synthesis. After all, what we are seeing here is rather the response we would expect as a consequence to a rather endurance-oriented exercise regimen. Whether the latter would entail the "size" (and strength) gains everyone currently associates with the magic words "increases in protein synthesis" remains thusly highly questionable.

This is particularly true if we take into account the results of another pretty recent study be Eonho Kim et al. (Kim. 2011), which found that an even slower (10s concentric, 10s eccentric) training protocol at 50% or the 1RM led to greater increases in flexibility but highly variable and overall lower strength gains than a traditional protocol with (4s total TUT at 80%RM) in college-aged women. This basically confirms what previous studies by Keeler et al. (+39% in traditional, only +15% in slow training; Keeler. 2001) have already established: (Super) Slow Training works, but it does not work as well classic resistance training.

And no matter whether you train slow or fast - in the end, intensity will always be determined by a matrix of loads, volume, TUT and training density and I doubt we will see a study that controls for all this variables even in the remote future (and if that happens you know that the SuppVersity is the place where you will read about it, first) - so the best thing you can do, is to rely on what worked for generations of physical culturists and that was definitely not training with 6s concentric and 6s eccentric reps ;-)

"Go Hard or Go Home?" Study Reveals Different Anabolic Signalling in Response to "Heavy" vs. "Medium" Intensity Leg Extensions at Different Times Under Tension

Working out ain't child's play, right? "Go Heavy or Go Home!" this is the mantra of true champions, but is it also the mantra of skeptical scientists?

I guess, it's important to say this first: The results of the study Daniil V. Popov et al. conducted at the Institute of Biomedical problems of Russian Academy of Sciences in Moscow need to be interpreted to have any relevance in terms of the question all of you keep asking yourselves: "What is the best training intensity to make fabulous gains?"

The data the Russian researchers offer is acute, not chronic. It's not based on muscle size measurements, but on the measurement of anabolic signalling proteins and the expression of MyoD, IGF-1, myostatin & co. We know that all of them are involved in the process of skeletal muscle hypertrophy, but even if all of them are elevated, this is not identical to muscle size increases as you would measure them in a long(er)-term study.

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I hope that the previous elaborations were detailed and convincing enough to increase your awareness of the limitation of the data I am about to cite.

Figure 1: Toque and angle during knee extensions in the high intensity (HI), medium intensity (MI) and medium intensity continuous tension trial (MIR) - the subjects did bilateral leg extensions (Popov. 2014)

Data that was recorded with 10 strength-trained athletes who performed high-intensity [HI, 74% of 1 repetition maximum (RM)], middle-intensity (MI, 54%1RM), or middle-intensity (54% 1RM) no-relaxation exercise (MIR; continous tension on the trained muscle).

"High intensity" vs. HIGH intensity: I am pretty sure most of you read my articles closely, for the rest it's important to note that the high intensity group trained at ~74% of the 1-RM - that's about 10 Reps to failure and actually not as heavy as some people may expect, when they hear "high intensity". Just remember one thing: Heavy ≠ intense - I see guys at my gym training with maximal weights and minimal intensity.

Figure 2: Changes in p21, MyoD, myostatin and MGF in response to each of the three training regimen (Popov. 2014)

The previously mentioned parameters were measured before, 45 min, 5h, and 20 h after exercise - you can see the results in Figure 2. The lactate concentration, which is not shown in Figure 2 was approximately 2-fold lower in the MI vs. the MIR & HI. It was the highest in the MIR session, and would thus coincide with the expression of the pro-anabolic protein p21 and the maximal early reduction in myostatin.

Over the course of the 24 study period, however, the high intensity trial yielded distinctively more pronounced anabolic effects.

A more pronounced and sustained elevation in p21, a maximal increase in MyoD, a marker of satellite cell (muscle precursor cell) activity, a significantly more pronounced increase in the intramuscular isform of IGF, i.e. MGF (learn more) and, last but not least, a sustained reduction of the muscle growth break myostatin.

Learn more about the fundamental signals that trigger and sustain muscle hypertrophy at the SuppVersity | more

Bottom line: The 24h+ reduction in myostatin in response to the high intensity trial alone would support the statement "Go Hard or Go Go Home!" In conjunction with the significant increase in MGF, the data Popov et al. present in their latest paper provide compelling evidence in favor of heavy resistance training as a means to trigger a maximal hypertrophy response - and that despite the fact that another often-measured indicator of skeletal muscle hypertrophy, i.e. ERK-1/2 (linked to protein synthesis) did not depend on exercise intensity and was thus identical for the similarly stressing MIR and HI trials.

As mentioned in the introduction, though, the acute changes in any of these measures are indicative of muscle growth, they are not identical to muscle growth. Thus, only a 6-12-week study with a training regimen that mimics the different training intensities could prove that high intensity is required to maximize muscle growth, when the basal stress is identical (i.e. HI would build more muscle than MIR).

References:

• Popov, Daniil V., et al. "The Influence of Resistance Exercise Intensity and Metabolic Stress on Anabolic Signaling and the Expression of Myogenic Genes in Skeletal Muscle." Muscle & nerve (2014).

Fast Paced High-Resistant Explosive Circuit Training Burns More Fat and Builds More Muscle Than Classical Weight Training. Trainees Dropped 1.5% Body Fat and Gained 3 Pounds of Lean Mass in 8 Weeks.

Figure 1: Outline of the HRC protocol
used by in the study.

The beneficial effects of fast-paced (indicating short / no rest periods between exercises) circuit training on fat loss have long been established. With the original intention being the addition of an aerobic component to traditional strength training routines, the loads (weights) that are usually used in these types of exercise regimens are often to low to elicit significant strength or muscle gains. This, however, was different in the study protocol Pedro E. Alcaraz and his collegues from Spain and Australia used in their most recent study (Alcarez. 2011).

Alcarez et al. recruited 33 healthy men, who "had been regularly performing resistance training (RT) in a gymnasium (e.g., ca. 6–12 repetitions per set, 3 sets per exercise, 2–4 d/week" (in other words recreational weight lifters) and assigned them to one of two training regimens:

• High resistance circuit training (HRC): 2x 3-6 circuits à three exercises with 5 minutes rest between circuit I and circuit II. There was a bi-weekly progression from 1 to 2 to 3 rounds on each of the two circuits. This means that in their 3 workouts per week (at least one rest-day in-between) the subjects performed 18-36 sets per workout of 6 repetitions at 85%-90% of their individual 1RM_max [1RM_max = maximal weight a person can perform a single repetition with adequate form with] with roughly 35 seconds 'rest' between exercises (this was the time it took them to move from one exercise to the next). Notwithstanding the high workload, each of these workouts took them only 55min-78min to complete.
• Traditional strength training (TS): For the same exercises that were used in circuit I and II in the HRC group (cf. figure 1), the subjects in the TS group performed 2x warm-up sets at 10 and 8 repetitions of the 6% max (1 minute rest in-between) followed by 3 sets of 6 repetitions at 85%-90% of their individual 1RM_max. Due to the one minute rest between individual sets, as well as the 5-minute pause in between exercises 1-3 and exercises 4-6, the supervised workouts of the TS group were on average 125min long.

One specifically important and oftentimes under-appreciated parameter, both groups had in common, was the lifting tempo:

The eccentric phase of each exercise was performed for approximately 3 seconds, whereas the concentric phase was performed at maximum velocity. This sequence was standardized in the first training week and eccentric phase duration was regularly timed as feedback for the subjects.

In that, what the subjects did was fundamentally different from what I am (unfortunately) forced to look at day in and day out in my gym: people just moving weights instead of training muscles for strength or hypertrophy. With an emphasis on the explosiveness of the concentric part (where push / pulling the weight) of the movement and an accentuation of the deceleration in the course of the 3 second eccentric part (where lowering of the weight) of the exercise, you do just that - you train your muscle for strength and hypertrophy. The data in figure 2 underlines that this strategy works, regardless of whether you stick to the classical strength training protocol with longer rest periods (TS) or if you innovate your training by integrating some explosive strength circles.

Figure 2: Bench press concentric peak power [in W] increase measured for different loads (45%, 60% and 80% of 1RM_max) after 8 weeks on a traditional or a high resistance circuit training program (data adapted from Alcarez. 2011)

Obviously the classical strength training, where the three sets of bench presses were performed one after another and with more than adequate rest of 3 minutes produced greater increases in peak bench press performance with the most significant advantages for the traditional training routine (TS) in the range of 60% of the individual one-repetition maximum (1RM_max). So, if you are all about strength and can afford to invest 120 minutes three times à week into your training and like what you have been doing, you can stick to what worked for generations of lifters. If, however, you still don't have your summer-six-pack ready, have only 60 minutes to train, or - as almost 90% of the gym-goers claim - "just want to look good naked", or even just try something new, you should give the explosive strength circuits a try.

Figure 3: Changes in fat and lean body mass [in kg] after 8 weeks on a traditional vs. a high resistance circuit strength training protocol (data adapted from Alcarez. 2011)

Although the advantages of high resistance circuit training over traditional strength training in terms of on body composition (cf. figure 3) appear to be less significant than those TS has over HRC in the strength department (cf. figure 2), the significance of the data must be relativized in view of the large standard deviations which are as high as ~70%-110% of the improvements of both strength and body composition.

Note: I think I do not have to tell you, the educated readership of the SuppVersity, that it goes without saying that it is very likely (yet still warrants scientific validation) that high resistance circuit training will also produce better results in terms of body (re-)composition (less fat, more muscle) than cardio training (cf. Exercise! Beneficial Effects of Resistance Training on Variables of General Health) or dieting (cf. Calorie Restriction vs. Exercise for Optimal Body Composition?), alone.

Consequently, the conclusions of the authors, that the gains in strength and body composition in the HCR group "are identical to those obtained with traditional, heavy strength training" is spot on: In the end, it is probably all about your personal training-philosophy, -style and -preference what will work better for you as an individual. One thing you should keep in mind though is to explode on the way up and slow down on the way down; or, in other words, Add high resistance circuit training to your repertoire, if you will, but don't forget: Train the muscle, don't just move the weight!

Time Under Tension (TUT) - Random Numbers or Forgotten Determinant of Training Success? What Does Science Say?

"Go slow, grow fast" - does it really work this way?

I have to admit that I didn't have time to write "complete" article, so I will just work out an introduction and a bottom line to a never-finished draft that discusses an - in my humble opinion -  still unresolved question:  "Does the time under tension, which must not be confused with the simple number of reps let alone the set, matter when it comes to strength or muscle gains?"  As I said, based on my knowledge of the contemporary literature this is still an unresolved issue. Mostly, because slow (by necessity) means "light weight" and is hard / impossible to distinguish from the rep-number.

The methodological issues are probably also part of the reason that it would be an exaggeration to say that there are only "few" studies that investigate the influence of the time under tension (TUT) on hypertrophy or strength gains - but alas, I have collected the science-crumps for you. So here you go (for a preliminary list):

• 

  Figure 1: Myofibrillar fractional protein synthesis (%/h; Burd. 2012)

  Low load + slow movement = high TUT ➫ increased protein synthesis -- The 175% increase in muscle protein synthesis in response to leg extensions that were performed with a TUT of 6s in the concentric, and 6s in the eccentric phase of the movement Nicholas A. Burd et al. report in their a 2012 paper in the Journal of Physiology is one of the is one of the few very concrete results from studies that were designed to isolate the effect of the time under tension (Burd. 2012).
  
  In view of the pathetic load (30% of the 1RM) and the matched volume, the practical relevance of these figures is yet highly questionable. For me personally, it is thus more surprising that the difference between ...
  
  • doing 12, 7 and 6 reps @ 30% of the 1 rep max to failure for 198±10 s 119±9 and 90±7s, respectively (SLOW condition w/ TUT of 606), and 
  • performing the same number of reps with the same weight, this time obviously not to failure, within 25±2s, 14±1s, and 11±1s, respectively,
  ...was not even more pronounced than the +/- 49% difference (175% vs. 126%) Burd et al. observed in their eight young male subjects after performin three sets of unilateral leg extensions. 
• Longer TUT, greater anaerobic energy expenditure - Inspite of the fact that it appears logical that longer times under tension would be associated with increases in energy expenditure, you as a SuppVersity reader know very well that not all things that exercise and nutrition science is not necessarily logical.
  
  In view of the overall scarcity of literature it is thus more than worth mentioning that Christopher B. Scott's 2012 study into the effects of time-under-tension and weight lifting cadence on aerobic, anaerobic, and recovery energy expenditures found that both, the anaerobic (=glyoclytic) energy expenditure and post energy oxygen consumption (EPOC) were significantly increased, when you train with a cadence of 4:1 or 1:4 and a corresponding TUT of 25s instead of 1.5:1 (TUT = 15s).

  

  Figure 2: Anaerobic energy expenditure, post exercise oxgen consumption and total energy expenditure (all in kJ) in the low TUT (1.5:1.5; 15s) vs. high TUT trials (Scott. 2012)

  It is thus only logical (you see, sometimes there is logic in exercise science ;-) that the total energy expenditure in the 25s TUT trials was ~30% higher than in the 15s TUT trial with its 1.5s up : 1.5 down cadence (see Figure 2).
  
  In view of the fact that the majority of us are hopefully not hitting the gym to "burn calories" (learn why that's simply dumb), these findings are interesting, but of similarly irrelevant as the previously cited increases in protein synthesis in the Burd study.
• Concentric tension time is key to muscle growth -- I know that broscience dictates otherwise, but the evidence from a human study by Gillies, Putman & Bell suggests just that: It's the concentric portion of the exercise that stimulates skeletal muscle hypertrophy in response to leg presses, parallel squats, knee extensions and knee flexions in 28 healthy young women with previous strength training experience (Gillies. 2006).

  

  Figure 3: Fiber area (µm²) of type I & II fibers before and after the 9-week training intervention (Gillies. 2006)

  As you can see in Figure 3, the baseline fibre size(s) of the subjects were yet so different that the participants that had been randomized to the group with an emphasis on the concentric phase (4:1 cadence) had an unfair growth advantage compared to the ladies in the eccentric emphasis group.
  
  In view of the fact that the eccentric emphasis group did also record greater strength gains, it appears unwarranted to change your training regimen from explosive / fast concentric vs. slow eccentric movements to the "concentric emphasis" pattern with its 4s : 1s cadence that was used in the study at hand. 
• Heavy and fast or "slow" and long - it does not even matter -- In 2006 and thus 6 years before the previously discussed study by Burd et al., Michiya Tanimoto and Naokata Ishii, two scientists from the University of Tokio conducted a similar, yet more realistic study which compared
  

  • 

    Figure 4: Cross-sectional area of the knee extensor before (open bars) and after (solid bars) LST, HN, and LN exercise training for 12 wk (Tanimoto. 2006)

    a low-intensity training regimen [ 50% of onerepetition maximum (1RM)] with slow movement and tonic force generation (3 s for eccentric and concentric actions, 1-s pause, and no relaxing phase; LST), to a
  • a high-intensity training regimen ( 80% 1RM) with normal speed (1 s for concentric and eccentric actions, 1 s for relaxing; HN), and 
  • a low-intensity with normal speed training regimen (same intensity as for LST and same speed as for HN; LN)
  and found what most of you will probably already have expected: As far as muscle growth there was no difference to be seen between the LST and the HN regimen after 12 weeks. The LN = low-intensity, normal speed training on the other hand sucked was a total waste of time and did not increase the size of the quadriceps muscle that had been hammered with three sets thrice a week at all.

Bottom line: As a seasoned SuppVersity reader you should not need me to tell you that the data does not allow for a conclusive decision if (a) time under tension matters at all, and if so, if it may (b) actually be the main determinant of muscle growth.

The green dots are satellite cells, muscle precursors as they are built with high volume leg training | more

I know at first that may sound hilarious, but if you think about the average bro in your gym who complains about "no gains", he will either be making tons of reps at a velocity that generates a momentum that reduces the TUT of an already fast 1-s rep to 0.1s, or he will tell you that only hitting it hard counts and his three reps on the bench press which are over in 6 seconds should actually make him grow.

To elucidate if (a) or (a) and (b) was right, we would yet need at least a dozen of well-designed studies, where - just as it was the case in the Burd study - the time under tension is the primary variable and reps, sets and weights only a means to modulate it. Until this data is available, it does probably not matter that I didn't have to dig up each and every article on that matter that exists... and if it did, I will just write another article ;-)

References: 

• Burd, N. A., Andrews, R. J., West, D. W., Little, J. P., Cochran, A. J., Hector, A. J., ... & Phillips, S. M. (2012). Muscle time under tension during resistance exercise stimulates differential muscle protein sub‐fractional synthetic responses in men. The Journal of physiology, 590(2), 351-362. 
• Gillies, E. M., Putman, C. T., & Bell, G. J. (2006). The effect of varying the time of concentric and eccentric muscle actions during resistance training on skeletal muscle adaptations in women. European journal of applied physiology, 97(4), 443-453.
• Scott, C. B. (2012). The effect of time-under-tension and weight lifting cadence on aerobic, anaerobic, and recovery energy expenditures: 3 submaximal sets. Applied Physiology, Nutrition, and Metabolism, 37(2), 252-256. 
• Tanimoto, M., & Ishii, N. (2006). Effects of low-intensity resistance exercise with slow movement and tonic force generation on muscular function in young men. Journal of Applied Physiology, 100(4), 1150-1157.