Exercise Research Update Nov '14 (1/2): Planking in Slings, Burpees for the Ultimate HIIT Experience, the Different Motors of Strength Gains in Young & Old Chaps + More!

There is a good reason drill-instructors love their burpees ;-)

Today's installment of the short news is a collection of shorter news items that deal with what's really important in life... well, maybe we should say some of the things that are really important in life: Building muscle, strength and a better physique.

That being said, we will take a look at the efficacy of sling-based planking, lean mass vs. neuromuscular efficacy as drivers of strength gains in young men and women and burpee-based high intensity interval training (HIIT) vs. classic ergometer / spinning based HIIT sessions and the changes the bodies of college students will undergo within one semester of conditioning training.

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• Old vs. young - 1:1 for strength. Study shows similar increases in strength after short-term resistance training due to different neuromuscular adaptations in young and older Men... or put simply: The mechanisms by which the strength of the 23 young (29 ± 9 years) and 26 older men (64 ± 8 years) who completed 10 weeks of high-volume, medium load “hypertrophic” resistance training with low frequency (twice per week) with 10 young (34 ± 11 years) and 11 older men (65 ± 3 years) acting as nontraining control subjects, was different, the strength increase, on the other hand, was identical.
  
  More specifically, the training regimen led to significant increases in 1 repetition maximum (1RM) leg press performance in both training groups (young: 13 ± 7%, p < 0.001; older: 14 ± 9%, p < 0.001), who had been advised to consume ~20 g of protein within 1 hour of training and make sure to get a total ~1.5–1.8 g of protein per kg body mass per day, to optimize the muscle hypertrophy response.
  

  

  Figure 1: Lower-limb lean mass (upper left), vastus lateralis cross-sectional area (lower left), and voluntary activation level (lower right) before and after training in young and older men, as well as relationship between changes in 1RM performance and lower-limb lean mass during training in young men (upper right). ** p , 0.01 compared with before training. C = p # 0.05 compared with control group; YT = p # 0.05 compared with young training group (Walker. 2014).

  In that, the performance improvement, however, was accompanied by increased muscle activation, assessed by voluntary activation level (29 ± 51%, p ≤ 0.05) and electromyography amplitude (35 ± 51%, p < 0.01) in older men only. In the young men, on the other hand, the increase in strength was mediated by increases in lean mass (2.4 ± 2.5%, p < 0.01), not increased muscle activation.
  
  As Walker & Häkinnen point out, the study clearly indicated this form of "resistance training may induce similar improvements in strength between young and older men, it appears that different mechanisms underpin these improvements" (Walker. 2014)... unfortunately, for the old guys, their way of becoming stronger is very limited. In the end, continuous strength gains can only be achieved, when they are driven by skeletal muscle hypertrophy. Accordingly, the results would probably have looked much different, if the guys in the "old trainees" group had been resistance training and not endurance training regularly before.
• Plank(ing) in slings is highly effective (edited). While conlusion of the abstract misleading says that Jeanette Byrne et al. (2014) didn't find an increase in the abdominal muscle activation during planks, when they were done in slings, a closer look at the full-text of the study reveals that doing your planks in slings is a very useful way to increase the activation of the rectus femoris, the external obliques and the serratus anterior (see Figure 2).
  

  

  Figure 2: Root mean square (RMS) muscle activation recorded from (A) rectus abdominis and external oblique (B) rectus femoris and serratus anterior during each 3-second plank. Significant difference in activation between the plank type indicated by a, b, c, d, e ( p < 0.05). Norm—plank on floor; FeetIn—feet suspended; ArmsIn—forearms suspended; Full—forearms and feet suspended. MVC = maximal voluntary contraction (Byrne. 2014).

  As mentioned previously in context of the study by Snarr & Esco, "caution should be taken for those individuals with a previous history or weakness in the lumbar region due to the increases in erector spinae activation during instability planks." (Snarr. 2014 | learn more in the corresponding SuppVersity Facebook news)
• Alternate interval training for superior results. Scientists from the University of Georgia conducted an experiment to determine the cardiorespiratory, metabolic, and perceptual responses to a low-volume, high-intensity protocol of calisthenic exercise.
  "The purpose of the study was to document and compare the physiological responses to 2 high-intensity intermittent exercise protocols: repeated bouts of sprint interval cycling (SIC) and repeated bouts of high-intensity intermittent calisthenics (HIC)" (Gist. 2014)
  The authors of the corresponding paper hypothesized that HIC would elicit physiological responses similar to SIC and of sufficient cardiovascular strain to classify its peak responses as vigorous... and guess what?
  
  

  

  Table 1: Physiological VO2 & heart rat (HR) response to cycling (SIC) and calisthenics (HIC) training in the study at hand (Gist. 2014)

  The physiological response to the calisthenics vs. cycling trial was more or less identical (see Table 1). A statistical significant difference in the cardiovascular response of the 11 (8 men and 3 women) normal-weightmoderately trained, college-aged participants was observed only at the onset of the exercise, where the VO2peak increased to a significantly greater extend in the cycling vs. calisthenics group, in which the subjects performed as many burpees as possible for 30 seconds followed by 4 minutes of active recovery (stepping in place at self-selected pace).
  
  Overall, the results of the study at hand do thus suggest that those of you who hate cycling can as well do their burpees to elicit a similar physiological response. And while we would theoretically have to confirm that the long-term outcomes of both training protocols will be identical, as well. I personally believe that the burpee protocol will have significantly more pronounced effects in the body composition and overall conditioning domain. Previous studies have after all suggested that exercises that involve the whole body are generally more effective than exercises like cycling where only one muscle group is working.
• 14 weeks of regular exercise will improve some health markers, but won't have college students lose weight or fat. That's the relatively unsurprising finding of a recent study from the George Washington University.
  
  The authors of the corresponding papers measured whether the college “activity” courses that are designed to give participants exposure to, and practice with, safe exercise techniques will also alter physiological characteristics, such as blood pressure or strength. The study involved 79 students from several sections of exercise and conditioning classes at our university. The classes included a variety of fitness- and strength-oriented exercises. Physiological and performance measurements were collected in weeks 2 (pretest) and 14 (posttest), and compared pre with post using paired t-tests subject to Bonferroni correction (significant p < 0.0055).
  

  

  Table 2: Pre and post values for the measured parameter | *HR = heart rate; SBP = systolic blood pressure; DBP = diastolic blood pressure; BW = body weight; %BF = percent body fat; HG = hand grip strength; PU = push-ups; SU = sit-ups; HRrec = HR recovery (Danoff. 2014)

  As you can see in Table 2, there were significant improvements in resting heart rate (HR) (73 vs. 70 b·min-1, p < 0.002), hand grip strength (250 vs. 272 N, p < 0.001), push-ups (29 vs 37, p < 0.001), sit-ups (32 vs. 35, p < 0.001), and step test HR recovery (122 vs. 110 b·min-1, p < 0.001).
  
  What did not change, though were systolic and diastolic blood pressures, body weight, and percent body fat did not change - a typical result for any low(er) intensity exercise only (no dietary component) intervention.

If you are looking to increase your bench, you may want to try training with elastic bands | learn why.

Come back tomorrow! If you liked today's research update, I highly suggest you come back tomorrow for more news from the realms of exercise science, including the effects of interval, strength and combined training on muscle fiber size and myostatin expression, the surprisingly pronounced increase in lower body muscle mass in response to six weeks of vibration training, the differential effects of caffeine on large and small muscle groups and much more... and while you are waiting for part II of this research update to be published, I recommend doing a couple of sets of burpees | Post video evidence on FB ;-)

References:

• Byrne et al. "Effect of Using a Suspension Training System on Muscle Activation During the Performance of a Front Plank Exercise." Journal of Strength & Conditioning Research 28.11 (2014): 3049–3055.
• Danoff & Raupers. "Effect of a One-Semester Conditioning Class on Physiological Characteristics of College Students." Journal of Strength & Conditioning Research 28.11 (2014):3115–3120.
• Gist, et al.  "Comparison of Responses to Two High-Intensity Intermittent Exercise Protocols." Journal of Strength & Conditioning Research 28.11 (2014): 3033–3040.
• Snarr & Esco. "Electromyographical Comparison Of Plank Variations Performed With And Without Instability Devices." Journal of Strength & Conditioning Research: Post Acceptance: September 26, 2014 
• Walker & Hakinnen. "Similar Increases in Strength After Short-Term Resistance Training Due to Different Neuromuscular Adaptations in Young and Older Men." Journal of Strength & Conditioning Research 28.11 (2014): 3041–3048.

Blood Flow Restriction, Where Are We? "Don't Hold Your Breath", the Valsalva Maneuver Revisited. Ageless Growth, It's Never Too Late to Start. Plus: EMS as Recovery Tool & HIIT to Heal a Scarred Heart After Myocardial Infarctions

I guess it is a cultural thing that there is apparently a lot more of persuading to be done in the US and Europe to familiarize trainees with (a) the idea of limiting the blood supply to their musculature and (b) the notion that heavy weights are not all that counts.

After the huge success of the SuppVersity Exercise Science Week (read all posts), I did actually intend to put a greater emphasis on training related news in the future. Unfortunately, the number of pertinent papers that don't look at the benefits obese post-menopausal women can derive from walking on a treadmill in the fat burning zone is very limited (Please don't misunderstand this as an offense against the obese women. I anything it's meant as an offense against "experts" still advising those women to do just that). If you look closely enough, there are still a couple of newsworthy papers that have been published within the last weeks... and let's be honest, in the end it does not really matter, if they are from last week, as long as the information they provide is "news" in terms of not being part of common knowledge, yet - right?

Kaatsu - a review: Blood flow restriction research still work-in-progress

(Pope. 2013) -- Pope, Wilardson and Schoenfield have recently published an ahead-of-print paper that offers a very comprehensive overview of the current scientific perspective on training with cuffs (aka Kaatsu training). As the authors point out, the most intriguing aspect of blood flow restricted training (BFR) is that it is totally juxtaposed with the "traditional [strength training] paradigm, which suggests that lifting only higher intensity loads increases" muscle strength and size.

Figure 1: Concurrent lactate & GH increases support the metabolic accumulation hypothesis, one of the most popular explanations for the effects of BFR  (Inagaki. 2011).

One of the most commonly head explanations of the unexpected efficacy of blood flow restricted strength training at low intensities relates to the accumulation of what you could jovially call "metabolic waste" in the trained muscle. The results of a 2011 EMS study by Inagaki et al. (see figure 1), for example; suggest that the accumulation of lactate in the cuffed muscle went hand in hand with a +200% increase in growth hormone (GH) compared to the control condition. 

As Pope et al. rightly point out, these results do yet conflict with previous findings by Reeves et al. who observed similar increases in GH in trainees who wore a cuff while they were doing biceps curls at 30% of the 1-RM, despite identical lactate levels in the cuffed an not-cuffed condition (Reeves. 2006). Accordingly, alternative or rather synergistic effects such as an increase in reactive hyperemia (excess of blood) have been brought forward to explain the growth response to BFR.

I am not going to reiterate the whole review here, but still want to point out a couple of other interesting points, the Pope, Willardson and Schoenfield make. There would be, for example the increase in type II (fast, glycolytic) muscle fiber recruitment that was observed in some, yet not all studies, an increase phosphorylation of the protein synthesis gauge S6K1 (likewise a type II fiber dominant effect) and the accumulating evidence that BFR may "enhance recruitment of higher threshold motor units". In the end, the latter means that you will see similar activation patterns as you would expect them in "classic" heavy duty resistance training with comparably light loads and a cuff.

Will BFR soon become a common training technique?

"Chicken legs no more!" In a previous study even walking on a treadmill provided a growth stimulus, when the legs were cuffed before the participants hopped on the torture machine (learn more).

Yet while the implication (=similar results) appear obvious, Pope et al. are correct, when they point out that the "precise relationship between BFR and muscle recruitment still has to be elucidated" before definite conclusions wrt to the fundamental mechanism and their relation to the well-established metabolic and endocrine and paracrine responses, which do in fact share some, yet not all of the characteristics of "classic" resistance training (e.g. no increase in testosterone in response to BFR training; cf. Reeves. 2006; Fujita. 2007; Abe. 2012) can be made.

Once we have gained a better understanding of the processes that take place during and after BFR resistance training, researchers will probably also be able to provide more concrete advice how training with reduced blood flow can be successfully incorporated into the resistance training regimen of trainees on both ends of the performance continuum that ranges from the cancer cachetic patient to the elite level athlete.

Until then and in the absence of someone who's actually knowing what he/she to "cuff me up", I for my part will stick to traditional high intensity weight and interval training and would suggest that you do the same ;-)

"Deadlift, bench and squat, but God forbid: Never hold your breath!" - True or false?

(Hacket. 2012) -- I guess you will have heard about the fallacy of holding your breath while you bench squat and deadlift. It's one of those things every "I got 2h of instructions, now I am a trainer"-expert will tell his clients: "Don't hold your breath... breath!" On the other hand you will hear some of the "big dudes" tell you that you simply cannot lift weights as heavy as they do, if you don't resort to the Valsalva maneuver (VM) which is actually pretty much what most of us are doing, when we are "holding our breath", when lifting. If you carefully observe yourself, when you try to deadlift 80%+ of your 1-RM max you will realize that you do in fact hold your breath, but not like an apnoe diver would do it, on the contrary actually it's like breathing out yet with having your airways closed up.

So why are we doing bullsh*t like that 100% unvoluntarily? Well, the opponents of "holding your breath" will tell you that the pressure that's building up in your abdomen will stabilize your spine and protect you from injury. Against that background it seems only logical that we are naturally programmed to perform such a maneuver whenever we have to lift a heavy object from the ground or free ourselves from a tree that's lying right across our chest by benching it away ;-)

Even  when you are training for strength, heavy weights are not everything. A study I covered back in 2011 here at the SuppVersity showed - allegedly to my own surprise - that reducing rest times from week to week is another way to make progress and gain more mass and strength - particularly in the legs (read more)

Unfortunately, we all know that not all the things we are programmed to do - e.g. eating as much sugar as humanly (in the literal sense) possible, whenever we hit onto a honey-pot - is not necessarily conducive to our health. The existing literature on the matter appears to confirm this notion. It does however also tell us that the majority of healthy resistance trainees do not just get away pretty well when they follow their instincts and perform the Valsalva maneuver, but also achieve the desired increase in spine stability.

How effective this type of all-natural spine protection actually is, has yet never been fully elucidated. The same goes for the performance increases which are, as the scientists point out, "likely", but not adequately quantified in well-controlled studies. That there is a non-negligibly increased risk involved, especially for people with pre-existing cerebrovascular disease, cardiovascular disease and hernias, on the other hand, is non-debatable.

Against that background and in view of the fact that the hemodynamic response (=increase in blood pressure, etc.) decreases over years of training, the authors conclude that the deliberate use of the Valsalva maneuver for brief time-periods (<3s) should remain a prerogative of the more experienced trainees. 

Electrical muscle stimulation (EMS) as a recover tool

SuppVersity veterans know: Recovery begins before you even hit the gym. "Pre-covery" would in fact be an appropriate term for the scientifically proven benefits of taking a hot bath 2 days before a particular strenuous workout or competition. Sounds hilarious? Well, if that's what you think, you better go back and read up on the results of the 2012 study by Touchberry et al., then.

(Kibisa. 2013) -- Ever since the huge disappointments with EMS ab-trainers, the electro-myostimulation is pretty much depreciated by the average trainee. If you still got one of those belts lying around (don't be ashamed ;-) you may want to wrap it around your calves, instead of your abs to use it as a recovery tool similar to the obviously way more sophisticated EMS devices the scientists from the Lithuania Kaunas College used in their latest study.

Kibisa et al. had recruited a group of 19 long-distance runners who had then been randomize to two groups who performed either their regular post-training routine or were attached to the said EMS device in order to apply what you may call a "post-workout recovery stimulus". Interestingly this treatment lead to significant increases in a subsequent maximal voluntary contraction (MVC) and work capacity (WC) tests, as well as profound decreases in in the 72h post muscle soreness.

As you probably would have guessed, the scientists ascribe these benefits to an "improved blood flow in the stimulated muscles and an increased venous blood pump". This however is nothing you could not achieve by an extended cool down, as well so that the study at hand won't qualify as an excuse to go and buy an EMS belt for your abs from the shopping channel ;-)

HIIT after infarction reduces scarring of heart tissue

In the unfortunate case you missed the Making HIIT a HIT! Series I highly suggest .you go back and learn about the fundamental and not so fundamental rules of how to HIIT it right. Part I comprises a brief research overview to give you an idea of what you can expect from HIIT workouts. Part II provides some theoretical considerations and a comprehensive list of 10 rules of thumbs to follow, in order to make HIIT a HIT ;-)

(Godfrey. 2013) -- The longstanding paradigm that rest facilitates recovery in the really sick is crumbling. Against that background it's not totally surprising to see that researchers from the School of Sport and Education at the Brunel University in the UK dared publishing a case-report dealing with a 50-year old post-myocardial infarction patient, who participated in 60 weeks of increasingly intense (obviously according to what a post-myocardial infarction patient can tolerate) high-intensity aerobic interval exercise.

The man who had sustained an idiopathic acute myocardial infarction had been diagnosed with 16% myocardial scar tissue early after the event saw successive improvement in the physiology of his hard, with an MRI-confirmed decrease in myocardial scar tissue. As the scientists point out, he is thus living proof for the "high efficacy and low risk" of high intensity aerobic interval training as a means not just to prevent future cardiac complications, but even to reverse existing damage.

Resistance training works *fullstop* - Regardless of age

(Mero. 2013) -- In the March issue of the European Journal of Applied Physiology Mero et al. report that their 21-week progressive resistance training regimen (two full-body workouts per week classic progression from 15 reps at 40-60% to 5-8 reps at 70-80%) yielded significant strength and size gains in old and young previously untrained subjects.

Figure 2: Changes in muscle cross sectional area and strength at the end of the 21-week study period (Mero. 203)

What's certainly surprising is the fact that there were no differences in terms of strength gains at the end of the study period between the young and old trainees. This is particularly interesting, because the "old chaps" obviously caught up, in the 2nd (=higher intensity) phase of the study. After 10.5 weeks, the young trainees had had a statistically significant advantage as far as the concentric strength was concerned. This advantage did yet melt away in the subsequent weeks.

Remember the article on the usefulness of HMB for the older trainees? With its anti-catabolic effect it would leave more of the scarce satellite cells for growth. Plus: It appears to have anti-obesity effects as well (read more)

In a way the presence of strength in the absence of size gains fits in nicely with the high myostatin expression in the older trainees which increased by >50% in the course of the study (read more about the role of myostatin building muscle) and the even more pronounced increase in myogenin, which suggest that the recruitment of satellite cells is slow / non-function in older trainees and further growth would hamper the function of the muscle cells (which is what myostatin is supposed to prevent learn more).

That two training sessions per week did yield statistically significant increases in muscle size and strength and that despite suboptimal energy and protein intake in the older individuals (<1g/kg body weight protein per day for many of the older subjects vs. 1.5g/kg of protein in the young guys; overall significantly lower energy intake than the young guys) is still impressive and goes to show you that it's never to late for you to start lifting weight.

---

It's never too late! I could hardly imagine a better bottom line to this short potpourri of recent studies and it's unfortunate that for way too many of our fellow men, even an eye-opener like a heart attack is not enough to divert from the well-worn path of a sedentary life... ok, that was more than enough finger wagging for today. After all, the fact that you've found your way to the SuppVersity is evidence tells me that your path probably ain't going to end in the emergency room.

Well, unless you are a post-menopausal woman taking who's determined to take high dose folate supplements for the next 6+ years. In that case, you may well end up in the ER when the tumor in your colon you've been cultivating over the past 72 months bursts. You have now idea, what I am talking about? In that case you probably haven't yet subscribed to the SuppVersity Facebook Channel yet. Certainly a mistake, but as you've learned today, it's never too late and once you've read the respective post, you can still mae up for this lapse ;-)

References:

• Abe T, Loenneke JP, Fahs CA, Rossow LM, Thiebaud RS, Bemben MG. Exercise intensity and muscle hypertrophy in blood flow-restricted limbs and non-restricted muscles: a brief review. Clin Physiol Funct Imaging. 2012 Jul;32(4):247-52.
• Fujita S, Abe T, Drummond MJ, Cadenas JG, Dreyer HC, Sato Y, Volpi E, Rasmussen BB. Blood flow restriction during low-intensity resistance exercise increases S6K1 phosphorylation and muscle protein synthesis. J Appl Physiol. 2007 Sep;103(3):903-10. Epub 2007 Jun 14.
• Godfrey R, Theologou T, Dellegrottaglie S, Binukrishnan S, Wright J, Whyte G, Ellison G. The effect of high-intensity aerobic interval training on postinfarction left ventricular remodelling. BMJ Case Rep. 2013 Feb 13;2013.
• Hackett DA, Chow CM. The Valsalva maneuver: Its effect on IAP and safety issues during resistance exercise. J Strength Cond Res. 2012 Dec 4.
• Inagaki Y, Madarame H, Neya M, Ishii N. Increase in serum growth hormone induced by electrical stimulation of muscle combined with blood flow restriction. Eur J Appl Physiol. 2011 Nov;111(11):2715-21.
• Kibiša R, Grūnovas A, Poderys J, Grūnovienė D. Restoration of the work capacity of the skeletal muscle with electrical myostimulation. J Strength Cond Res. 2013 Feb;27(2):449-57. 
• Mero AA, Hulmi JJ, Salmijärvi H, Katajavuori M, Haverinen M, Holviala J, Ridanpää T, Häkkinen K, Kovanen V, Ahtiainen JP, Selänne H. Resistance training induced increase in muscle fiber size in young and older men. Eur J Appl Physiol. 2013 Mar;113(3):641-50.
• Pope ZK, Willardson JM, Schoenfeld BJ. A Brief Review: Exercise And Blood Flow Restriction. J Strength Cond Res. 2013 Jan 28.
• Reeves GV, Kraemer RR, Hollander DB, Clavier J, Thomas C, Francois M, Castracane VD. Comparison of hormone responses following light resistance exercise with partial vascular occlusion and moderately difficult resistance exercise without occlusion. J Appl Physiol. 2006 Dec;101(6):1616-22.

Exercise Quickie: HIIT as 24h+ Muscle Builder for the Elderly | Caffeine Without Ergogenic Effects on Biceps Curls

Caffeine won't do the "last rep" for ya.

Time for a brief review of the latest exercise and supplementation science in the SuppVersity Short News. You can see an overview of all previous articles in an RSS feed here.

This time you can take a look at the surprisingly lasting pro-anabolic effects of HIIT as measured by skeletal muscle protein synthesis in the elderly and the similarly surprising finding that caffeine - even if it's consumed in significant doses before a workout - will not have you curl an extra pound on either barbell or dumbbell curls.

Read more short news at the SuppVersity

Exercise Research Uptake Nov '14 1/2

Exercise Research Uptake Nov '14 2/2

Weight Loss Supplements Exposed

Exercise Supplementation Quickie

Exercise Research Uptake Jan 12, 2015

Read the Latest Ex. Science Update

• 27% increase in protein synthesis even 24h after HIIT exercise in the elderly - Resistance exercise (RE) and aerobic exercise are recommended for older adults for fitness and strength. High-intensity interval exercise (HIIT) is an understudied but potent potential alternative to aerobic exercise. A recent study from the McMaster University aimed to determine how each mode of exercise affected the integrated day-to-day response of muscle protein synthesis.
  
  To do so, they recruited 22 sedentary men (mean age = 22; 67±4 years; body mass index: 27.0±2.6 kg m- 2 [mean ± SEM]) who were randomly assigned to perform resistance training, aerobic exercise, or HIIT. The participants consumed a stable isotope tracer (D2O) for 9 days. Daily saliva samples were taken to measure tracer incorporation in body water. Muscle biopsies were obtained on Days 5-8 of D2O consumption to measure tracer incorporation into muscle at rest, 24 hours, and 48 hours following each exercise bout: RE (3 × 10 repetitions: leg extensor and press, 95% 10RM), HIIT (10 × 1 minute, 95% maximal heart rate [HRmax]), or aerobic exercise (30 minutes, 55%-60% HRmax).
  

  

  Figure 1: Myofirillar (left) and sarcoplasmic (right) protein fractional synthesis rate (FSR) at baseline and postexercise. Data are means ± SEM. Bars bearing different letters are signifiantly different within each exercise group | AE = aerobic exercise; HIIT = high-intensity interval exercise; RE = resistance exercise (Bell. 2015).

  What the scientists found is quite surprising: While resistance training showed, as it was expected, the greatest increase in fractional protein synthesis immediately, post workout, only the HIIT protocol lead do significant increases in sarcoplasmic protein fractional synthetic rate 24-hour postexercise (2.30±0.34% d- 1 vs 1.83±0.21% d- 1).
  
  That does not mean that HIIT is the better muscle builder, though. Specifically in view of the fact that it's the myofibrilar, not the sarcoplasmic protein synthesis rate that bunks with aging (Balagopal. 1997), the higher myofibrilar post-workout protein synthesis after the relatively low volume resistance training session is more important than the long-lasting elevation of the protein influx into the sarcoplasma, a muscle protein fraction that is involved in the anaerobic ATP production, intracellular transport, and several other enzyme functions. 
• Stronger biceps with caffeine? No, ... at least during insometric contractions the administration of 5 mg/kg and 10 mg/kg caffeine does not have ergogenic effects on the elbow flexors.
  That's at least what the latest study from the University of Kansas shows. In their 13 recreationally trained male subjects, the ingestion of the aforementioned amounts of caffeine in form of of a caffeineated drink did not lead to significant increases in any of the relevant performance markers.
  

  

  Figure 2: Caffeine did not have significant ergogenic effects; at least the rate of torque development did increase, though (Trevino. 2015).

  In contrast to previous research which has indicated that under certain conditions, caffeine may increase muscle force production during anaerobic activities (3,6,15,17). The results of our study revealed that caffeine did not significantly affect peak torque during the maximal isometric contractions. As Trevino et al. point out, this finding may result from a variety of factors:

  

  Figure 3: In contrast to the study at hand a study by Beck et al. found significant increases in bench press performance in slightly better trained subjects (Beck. 2006).

  "Past equivocal findings with caffeine ingestion and anaerobic performance may have resulted from the type of muscle action and exercise performed, caffeine dose used, muscle group tested, or training status of the subjects. Our protocol used a single-joint isometric exercise to test the effects of caffeine doses of 5 and 10 mg/kg of body mass on maximal strength of the elbow flexors in resistance trained males (participating in at least 2 training sessions per week). Beck et al. (2006) reported that a 201 mg dose of caffeine significantly increased bench press 1RM in resistance trained males (participating in at least 4 training sessions/week). 

  Because significant results were found with a caffeine dose less than ours (average absolute doses in the current study were 426.7 and 853.4 mg for the 0 and 5 mg/ kg body mass conditions, respectively), it seems that the exercise test and training status may have led to different findings between the studies" (Trevino. 2015).

  Next to the training status and the lack of familiarity with performing maximal muscle contrations (the subjects in Beck et al. (2006) trained 4 times per week, the ones in the study at hand only two times), the exercise may play a role as well. The bench press is after all a multi-joint exercise requiring dynamic involvement of the pectoralis major, deltoid, and triceps. The biceps curl, on the other hand is the classic single-joint exercise, where the CNS activating effect of caffeine may simply offer less benefits than on bench presses, squats and other multi-joint exercises. The same may be true for comparisons of large and small muscle groups and could explain why Astorino et al. (2010), Jacobson, et al. (1992) and Kalmar et al. (1999) found beneficial effect of caffeine on the leg extension performance of their subjects, while Trevino et al. were not able to detect ergogenic effects for the small elbow flexors.

The Latest on Caffeine, Exercise, Fat & Weight Loss - Increased Performance, Energy Expenditure (6%) & Fatty Acid Oxidation (27%) vs. Decreased Sleep Quality & Burnout | Learn how caffeine can benefit your exercise performance and energy expenditure and how much caffeine is too much caffeine in a recent SuppVersity article.

Bottom line: Let me make this clear. Neither of the two studies refutes any of the given truths of strength training and muscle building. The Bell study does in fact confirm that resistance training triggers the most pronounced increases in skeletal muscle protein synthesis - the fact that HIIT may have longer lasting overall effects, specifically in the sarcoplasmic protein fraction, is nice, but its practical relevance is highly questionable.

Similarly, the study by Trevino et al. which shows minimal, but non-significant beneficial effects of caffeine on the elbow flexors does not negate the many previously established beneficial effects of caffeine supplements on exercise performance. What it does, however, is to remind us that it is not possible to transfer the results obtained in one group of trainees on one particular muscle group 1:1 to another group of trainees and/or another muscle group | Comment on Facebook!

References

• Astorino, Todd A., et al. "Effect of two doses of caffeine on muscular function during isokinetic exercise." Medicine and science in sports and exercise 42.12 (2010): 2205-2210.
• Balagopal, P., et al. "Effects of aging on in vivo synthesis of skeletal muscle myosin heavy-chain and sarcoplasmic protein in humans." American Journal of Physiology-Endocrinology And Metabolism 273.4 (1997): E790-E800.
• Beck, Travis W., et al. "The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities." The Journal of Strength & Conditioning Research 20.3 (2006): 506-510.
• Bell et al. "Day-to-Day Changes in Muscle Protein Synthesis in Recovery From Resistance, Aerobic, and High-Intensity Interval Exercise in Older Men." J Gerontol A Biol Sci Med Sci (2015). 
• Jacobson, B. H., et al. "Effect of caffeine on maximal strength and power in élite male athletes." British journal of sports medicine 26.4 (1992): 276-280.
• Kalmar, J. M., and E. Cafarelli. "Effects of caffeine on neuromuscular function." Journal of Applied Physiology 87.2 (1999): 801-808.
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