Differences in Growth Hormone, Insulin and IGF-1 Response in Trained and Untrained Resistance Trainees - Further Evidence That GH Builds Neither Muscle Nor Strength

Image 1: Rookie (top) or veteran (bottom, Jack Lalanne), their hormonal response to push-ups is different, but does not explain the different outcomes of strength training.

If you are a regular, here at the SuppVersity, you will have hear me lament the fact that in many of the mainstream studies on the effects of exercise on body composition, endocrine parameters and so on, the study participants are either sickly, obese or both... admittedly, whenever measures of muscle hypertrophy are involved, the subjects are usually healthy rookies, which is by  no means better, as you all know from your first weeks in the gym that, despite doing everything wrong, your strength and size gains were tremendous. Now, the obvious question is, are the endocrine adaptations / responses distinct, as well? According to the results of a recent study by Rasani Ranjbar et al. they are (Hasani-Ranjbar. 2011) - surprisingly, though, on paper, the endocrine milieu of the veterans appears more conducive to strength and size gains than that of the rookies... but let's take a look at the actual results, before we even start discussing their implications.

The Iranian scientists recruited 15 previously strength trained and 19 untrained male (how else could it be in this lovely country?) students at the Tarbiat Moallem University, divided them in an experimental (trained) and a control group and took blood samples at 10am (pre-test) after the students, who had arrived at the lab at 7am, had been served identical breakfasts (at 7:30-8:00am). Subsequently, the training groups (E1 = previous strength training experience; E2 = rookies) performed a resistance training protocol at 70-80% of their maximum strength in the 10-12rep range (i.e. a classical "hypertrophy training"), consisting of 4 sets of chest presses, stretch wires [I have no clue what kind of Iranian specialty that is], leg extensions and leg curls to failure with rest times of 2 minutes in between sets and 4 minutes between exercises.

Figure 1: Training induced changes in growth hormone (GH) compared to untrained control (Hasani-Ranjbar. 2011).

Blood was drawn at four timepoints: pre-test (T1), immediately after cessation of the exercise session and before lunch was served (T2), five hours post training (T3) and seven hours post training (T3). The samples were analyzed for growth hormone (GH), insulin, insulin-like-growth-factor 1 (IGF1), IGF1 binding protein 1 and 3 (IGFBP1 & IGFBP2). I have plotted the relevant data (i.e. data where you see meaningful changes) in figures 1 & 2.

Figure 2: Training induced changes in insulin and IGF1 compared to untrained control (Hasani-Ranjbar. 2011).

Now, what do we make of these results? Obviously the immediate GH response to resistance training is more profound in the veteran group, it is yet more sustained in the rookies, whose insulin levels interestingly skyrocket in the late post exercise period, yet in the absence of any significant increases in IGF1 levels (the same was true for the binding proteins) over the untrained control group.

Figure 1: Absolute IGF1 levels (in ng/ml) in trained and untrained rookies and veterans (Hasani-Ranjbar. 2011).

I don't know which data the Iranian scientists analyzed, but despite the fact that there is as they state a steady decline in IGF1 this probably isn't a result of the strength training regimen (as the Iranians would have it) but simply related to the lack of food intake in the 5-7h post lunch, which was ingested right after the post blood draw, i.e. exactly 5 hours before the 5h post blood was drawn....

Be that as it may, the more relevant result is that there may be differences in the endocrine response to exercise, but those are exactly contrary to what we would have to see, if the highly marketable GH increase, you are supposed to spike with all sorts of supplements had any effect on your gains in the gym. After all, you bet that if any of the two groups had had measurable strength or size increases at a subsequent training session / body composition measurement, it would have been the rookie group. That being said, this study further supports the position of the Phillips group from McMaster University (cf. Arms Don't Grow Faster with Prior Leg Training), who maintain that the exercise induced GH increase has absolutely no effect on strength or size gains... in other words, spending money on respective supps or focusing on training techniques that have been shown to increase GH (and have not been shown to be productive in terms of size and strength gains) is not advisable.

Romanian Deadlift is Hamstring Exercise #1: Glute-Ham Raises Not Bad Either, Leg Curl Less Efficient Than Thought

Study leaves no doubt: For the biceps femoris, Romanian deadlifts rule.

I am not quite sure if some of the guys at my gym even know what the hamstrings, are... I guess if I told them that they're also started biceps femoris, they were more likely to train it, instead of telling me that they play soccer and thus wouldn't have to train legs (I have honestly never heard something that stupid - I mean, it's like, I don't train jumping, because I am a high jumper ;-).

Now, if we assume for the moment that my arguments are convincing enough to include a single hamstring exercise on their every-day-international-chest-and-biceps-day, what should it be, then?

Chest	Biceps	Back	Core	Legs	Triceps	Shoulders
Navigate the SuppVersity EMG Series - Click on the desired body part to see the optimal exercises.

If you look back at the SuppVersity EMG Series, it would be the lying leg curl with tighs raised from the pad or hamstring exercises on the hip pendulum. If, on the other hand, you take a look at the data Matt J. McAllister & colleagues are about to publish in the next issue of the venerable Journal of Strength and Conditioning Researchers, one of the few places, where editors actually care about the interests of muscle-headz like us, the answer would be different.

Figure 1: EMG activity of biceps femoris and semitendinosus durinc ecccentric (light) and concentric (dark) phase of the romanian deadlift, the prone leg curl, good mornings and glute-ham raises in 12 subjects w/ 9y+ training exp. (McAllister)

What? You want to know where this difference comes from? Well, the reason should be obvious, Boeckh-Behrens & Buskies who conducted the study the EMG Series is based on did not test the weighed Romanian deadlift w/ maximum weight for "security reasons".

The leg curl, on the other hand, was significantly less effective when it was done with the tighs lying on the pad (as it was done in the study at hand) - exercise selection and execution did thus both contribute to the surprisingly different study outcomes, which do yet have one thing in common: The insight that activities of similar kinematics, don't necessarily produce similar muscle activation. As McAllister et al. poin out, this revelation may...

"[...] also indicate that the kinematics are not as similar as they appear to be, especially when you consider possible variance of internal and external rotation. For instance, the ST [semitendinosus] and SM  [semimembranosus] insert at the upper medial surface of the tibia, and the BF inserts at the head of the fibula. The greater amount of activity from ST may be related to the fact that ST contributes to the internal rotation of the knee, whereas BF contributes to the external rotation of the knee. Although the potential impact is unclear, the absence of control for hip rotation (internal or external) may have obviated the identification of specific patterns of muscle recruitment. Foot position was not standardized in this study because the investigators felt that the subjects’ experience would allow foot position to be habitual and consistent. This delimitation must be considered when interpreting our results." (McAllister. 2014)

In contrast to the semitendinosus & semimembranosus, the EMG activity for the biceps femoris (BF) was similar for the concentric prone leg curl and concentric romanian deadlift. As McAllister et al. point out, "[t]hese results are consistent with a previous investigation that reported no significant difference in activity from the concentric actions of the BF between the leg curl and stiff-leg deadlift." The authors of the corresponidn study did also find that the biceps femoris was significantly more active during the eccentric portion of the leg curl in comparison with the stiff-leg deadlift - the exact opposite of the findings McAllister et al. present in the study at hand, which showed significantly greater activity from the BF during the eccentric RDL as compared with the eccentric prone leg curl.

EMG activity (concentric) of erector spinae muscle during romanian deadlifts, leg curls, good mornings and glute-ham raises (McAllister)

Bottom line - Are concentrics the key? In the end, the results of the study at hand speak in favor of classic movements with a greater body involvement vs. isolation exercises such as the prone leg curl. In view of the large inter-individual difference indicated by the long error bars in Figures 1 & 2. The overall take-away message of the study at hand is not to put too much faith into electromygraphically measured mucle activities of someone else ;-)

Start with the Romanian deadlift and the glute-ham raise (see videos), learn how to execute the exercise correctly and keep perfect form; and if that does not "feel right" switch to another exercise.

Exercise Research Update: Sprints for Endurance Athletes, Bench vs. Band-Assisted Push Up, HIIT in Hypoxia, Stiff-Legged Deadlifts vs. Leg Curls + 5 Add. Recent Studies

If you want the latest in strength and conditioning research, today's SuppVersity article is for you!

I am not sure if you are following belong to the readership of the Journal of Strength & Conditioning Research. As a SuppVersity reader you have yet read your share of analyses and interpretations of data from studies that have been published in this journal.

Usually, only two to three articles per publication cycle make the SuppVersity Cut and are discussed at length, here at www.suppversity.com. For January 2015, I have decided to go take a different approach. I will present a broader range of articles and selected results to give you a better idea of what's going on this field of research. If you like this approach, let me know... who knows, maybe this is going to be the first in a new series of articles ;-)

Are you looking for muscle builders? Find inspiration in these articles:

Tri- or Multi-Set Training for Body Recomp.?

1, 2, or 5 sets per Exercise? What's "best"?

Pre-Exhaustion Exhausts Your Growth Potential

Full ROM ➯ Full Gains - Form Counts!

Battle the Rope to Get Ripped & Strong

Study Indicates Cut the Volume Make the Gains!

• Doing deadlifts builds core strength, strength that transfers to other exercises (Thompson. 2015) - I suppose you will have heard that "deadlifts are the #1 all-round strength builder". Now, I guess you will agree that this may be an overgeneralization, if not an exaggeration; and still, the results of the latest study from the Human Performance Laboratory at the Texas Tech University confirm once again: deadlifts ain't for meat heads only.
  
  In their well-powered study in young soccer players, Thompson et al. examined the effects of 10 weeks of barbell deadlift training on rapid torque characteristics of the knee extensors and flexors and analyzed the relationships between training-induced changes in rapid torque and vertical jump performance.
  
  Fifty-four subjects (age, mean ± SD = 23 ± 3 years) were randomly assigned to a control (n = 20) or training group (n = 34). Subjects in the training group performed supervised deadlift training twice per week for 10 weeks. All subjects performed isometric strength testing of the knee extensors and flexors and vertical jumps before and after the intervention. Torque-time curves were used to calculate rate of torque development (RTD) values at peak and at 50 and 200 milliseconds from torque onset.
  

  

  Figure 1: The deadlifts pay off in terms of strength gains and those gains transfer to other explosive, performance-based tasks - in this case vertical jumps (Thompson. 2015).

  As you can see in Figure 1, the barbell deadlift training induced significant pre- to post-increases of 18.8–49.0% for all rapid torque variables (p < 0.01). Vertical jump height increased from 46.0 ± 11.3 to 49.4 ± 11.3 cm (7.4%; p < 0.01), and these changes were positively correlated with improvements in RTD for the knee flexors (r = 0.30–0.37, p < 0.01–0.03).

Deadlifting can help w/ back pain, but it ain't for everyone.

Deadlifting for back pain?! Recently Berglund et al. investigated whether there are certain criteria that identify patients with back pain who will benefit from deadlifting. What they found was that participants with less disability, less pain intensity and higher performance on the Biering-Sorensen test, which tests the endurance of hip and back extensor muscles, at baseline benefit from deadlift training. In that the Biering-Sorensen test, a test for asymptomatic subjects and subjects reporting current or previous nonspecific low back pain, was the strongest predictor. Pain intensity was the next best predictor as it was included in two predictive models.

Accordingly, the authors conclude that "strength and conditioning professionals who use the deadlift as a rehabilitative exercise for individuals with mechanical low back pain, it is important to ensure that clients have sufficient back extensor strength and endurance and a sufficiently low pain intensity level to benefit from training involving the deadlift exercise" (Berglund. 2015).

• The scientists point out that their findings prove that "a 10-week barbell deadlift training program [is] effective at enhancing rapid torque capacities in both the knee extensors and flexors" (Thompson. 2015). Furthermore, the changes in rapid torque were associated with improvements in vertical jump height, which suggest that doing deadlifts is not a waste of time if you are no powerlifter. After all, the adaptations from deadlift training obviously transfer to other explosive, performance-based tasks. Accordingly, Thompson et al. conclude: "Professionals may use these findings when attempting to design effective, time-efficient resistance training programs to improve explosive strength capacities in novices" (Thompson. 2014).
• Having athletes performing in aerobic sports to add. anaerobic training is nothing but beneficials (Stevens. 2015) -  The researchers from the Western University had 16 trained oarsmen perform a 2,000-m time-trial performance to test whether replacing part of their regular aerobic training with spring training would have beneficial or negative effects on their exercise performance.
  
  What Stevens et al. found was that the EBTSIT protocol which involved 10 sprint interval (SIT) sessions over 4 weeks, in addition to 12 continuous exercise sessions, 2 anaerobic threshold exercise sessions, and 4 strength training sessions lead to significant improvements in time trial performance, while the classic approach did not.
  

  

  Figure 2: Changes in time trial performance (left) and peak power (right) after regular (aerobic only) or regular + sprint training in 16 trained oarsmen (Stevens. 2015).

  Furthermore, the power-output in a 60-second “all-out” anaerobic capacity test increased significantly with EBTSIT (PPO: EBTSIT: baseline = 566 ± 82, post = 623 ± 60 W; p = 0.02) but not with EBTAlone (EBTAlone: baseline = 603 ± 81, post = 591 ± 123 W; p = 0.59).
  
  Accordingly, the scientists conclude that "replacing a portion of EBT with SIT can improve both 2,000-m erg performance and anaerobic capacity, while maintaining aerobic fitness in trained oarsmen" (Stevens. 2015). For trainees and trainers it can thus be recommended to incorporate SIT within endurance training programs during periods of low-volume training, to improve performance without sacrificing aerobic capacity.

• 

  Burpees have proven to be a conditioning HIIT, already | learn why!

  Burpees beat traditional weight training - as far as the metabolic response is concerned (Ratamess. 2015) -- The purpose of this recent study from the College of New Jersey was to quantify and compare the acute metabolic responses to resistance exercise protocols comprising free-weight, body-weight, and battling rope (BR) exercises.
  
  Ten resistance-trained men (age = 20.6 ± 1.3 years) performed 13 resistance exercise protocols on separate days in random order consisting of only one exercise per session.
  
  For free-weight exercise protocols, subjects performed 3 sets of up to 10 repetitions with 75% of their 1 repetition maximum.
  
  • For the push-up (PU) and push-up on a BOSU ball protocols, subjects performed 3 sets of 20 repetitions.
  • For the burpee and PU with lateral crawl protocols, subjects performed 3 sets of 10 repetitions.
  • For the plank and BR circuit protocols, subjects performed 3 sets of 30-second bouts.
  A standard 2-minute rest interval (RI) was used in between all sets for each exercise. Data were averaged for the entire protocol including work and RIs.
  
  

  

  Table 1: Ventilation (VE) and heart rate (HR) in response to the different exercises (Ratamess. 2015).

  Mean oxygen consumption was significantly greatest during the BR (24.6 ± 2.6 ml·kg−1·min−1) and burpee (22.9 ± 2.1 ml·kg−1·min−1) protocols. For the free-weight exercises, highest mean values were seen in the squat (19.6 ± 1.8 ml·kg−1·min−1), deadlift (18.9 ± 3.0 ml·kg−1·min−1), and lunge (17.3 ± 2.6 ml·kg−1·min−1). No differences were observed between PUs performed on the floor vs. on a BOSU ball. However, adding a lateral crawl to the PU significantly increased mean oxygen consumption (19.5 ± 2.9 ml·kg−1·min−1). The lowest mean value was seen during the plank exercise (7.9 ± 0.7 ml·kg−1·min−1).
  
  As the authors point out, their "data indicate performance of exercises with BRs and a body-weight burpee exercise elicit relatively higher acute metabolic demands than traditional resistance exercises performed with moderately heavy loading" (Ratamess. 2015).
• Fat does, muscle doesn't impair an endurance athlete's performance (Maciejczyk. 2015) - Recent evidence suggests that not only body fat (BF) but high lean body mass (HLBM) adversely affects aerobic performance and may reduce aerobic endurance performance as well. However, the influence of body composition on anaerobic performance remains controversial.
  
  The latest study by scientists from the University of Physical Education in Krakow was thus aimed to examine the effects of increased body mass (BM) and body composition on cycling anaerobic power. Peak power (PP) and mean power (MP) measurements were conducted in 2 groups of men with similar total BM but different body compositions resulting from (a) high level of BF [HBF group] or (b) high level of lean body mass [HLBM group] and in a control group.
  

  

  Figure 3: Absolute peak power vs. body fat (left) and lean mass (right) - both correlate (Maciejczyk. 2015).

  As you can see, the absolute PP (shown in Figure 3 and MP (not shown) were significantly higher in the HLBM group compared with the control and HBF groups. However, PP and MP relative to BM and using allometric scaling were similar in the HLBM and control groups, yet significantly higher than in the HBF group. There were no significant differences between groups in PP and MP when presented relative to LBM.
  
  Therefore, the scientists are right, when they say that "it seems that it is not BM but rather body composition that affects PP," the only problem is: By taking people who were "fat" and "lean" in the first place, it's impossible to tell which came first: Being fat or having a reduced cycling performance.

Wow, this article is getting longer and longer!Obviously, there are more studies. Studies I am about to review even more briefly to keep you up-to-date without however keeping you up all night reading an article that's longer than 10,000 words ;-)

• 

  Band assisted push ups. This is how it's supposed to look like if you want them to be as potent as regular bench presses (photo from Calatayud. 2015)

  Bench and band-assisted push up activate the pecs to the same degree and result in similar strength gains (Calatayud. 2015) - That's the unsurprising result of a recent study by Calatayud et al. (2015). A result that must be interpreted with caution, though, because it was observed in previously resistant trained, but not necessarily "bodybuilder-" or "powerlifter-like" trainees.
  
  Whether the same holds true for elite bodybuilders and powerlifters would have to be seen. Plus: I am not sure if all of you are willing to scrap their beloved bench presses for the band-assisted push-ups shown in the image to the right ;-)
• Specific performance benefits of HIIT in hypoxia (Brocherie. 2015) - Compared to regular high intensity interval training, the addition of 10 repeated-sprint training sessions performed in hypoxia vs. normoxia to their regular football practice over a 5-week in-season period was more efficient at enhancing repeated-agility (RA) (6 × 20 m, 30-s rest) ability (including direction changes) youth highly trained football players.
  
  The scarcity of oxygen during the HIIT sessions had yet no additional effect on improvements in lower-limb explosive power, maximal sprinting, and run-based high-intensity repeated-sprint ability (RSA) performance.
• No need to warm up your inspiratory muscles (Arend. 2015) - Well, the statement may be a tad too general, but at least for the protocol used in a recent study by Arend et al. it appears as if - despite some changes in respiratory parameters -  it "does not have a significant influence on submaximal endurance performance in highly trained male rowers" (Arend. 2015).
  
  The fact that there were no acute benefits also doesn't negate beneficial effects of chronic inspiratory muscle training. Many of the previous studies on chronic benefits are with some exceptions (Chatham. 1999) mostly similarly disappointing (Inbar. 2000; Williams. 2002), though.
• Stiff-legged deadlifts and leg curls differentially activate the hamstring muscles (Schoenfeld. 2015) - It's a good question whether you can do only one, or have to do multiple exercises to maximally stimulate a given muscle group.
  
  In the case of the hamstrings, a recent study by Schoenfeld, et al. suggests that two exercises, more specifically, the stiff-legged deadlift and the hamstring curl, may be better than one.
  

  

  Figure 4: EMG activity of the lower lateral and lower medial part of the hamstring during lying leg curls (LLC) and stiff-legged deadlifts (SLD) in 10 experienced resistance trainees (Schoenfeld. 2015)

  In their study which used surface electromyography to record mean normalized muscle activity of the upper lateral hamstrings, lower lateral hamstrings, upper medial hamstrings, and lower medial hamstrings, the lying leg curl (LLC) elicited significantly greater normalized mean activation of the lower lateral and lower medial hamstrings compared with the stiff-legged deadlift (SLDL) (p ≤ 0.05).
  
  As Schoenfeld et al. point out, "[t]hese findings support the notion that the hamstrings can be regionally targeted through exercise selection." The authors are yet also right, when they say that "[f]urther investigations are required to determine whether differences in activation lead to greater muscular adaptations in the muscle complex" (Schoenfeld. 2015), because in contrast to what most trainees believe, this is often not the case.
• Caffeine is ergogenic, adding nitrates on top is useless (Glaister. 2015) - In a randomized, counterbalanced, double-blind study, the 14 competitive female cyclists (age: 31 ± 7 years; height: 1.69 ± 0.07 m; body mass: 61.6 ± 6.0 kg) experienced the same performance increases on a 20-km time trials on a racing bicycle regardless of whether the ingested 5mg/kg caffeine alone or in combination with a 70-ml dose of concentrated beetroot juice containing either 0.45 g of dietary nitrate.
• Hitting the weights elicits the same testosterone response in the AM & PM (Shariat. 2015) - Based on the results Shariat et al. present in their recent paper, there is no difference in the testosterone response between AM and PM resistance training.
  

  

  Figure 5: There is no correlation between the post-workout increase in testosterone and lean mass gains (left) or strength gains (right) during a std. 12-week resistance training program, anyway (West. 2012). So, even if the study had yielded different results, they would have been of questionable practical relevance.

  And honestly, even if there was a difference, the latter would probably be irrelevant, because there is as of yet no evidence that the post-workout increase in testosterone correlates with increased long(er) term strength or size gains (West. 2012).
  
  Since this is not much different for IGF-1, the results of another study from the latest issue of the Journal of Strength and Conditioning Research by Vilaça-Alves et al. (2015) is of similarly questionable practical relevance. In said study, the researchers observed significantly higher post-workout increase in IGF-BP3, an IGF binding protein that increases proportional to IGF-1, when the strength workout was done after the endurance training vs. the other way around.
• Six weeks "on the vibrator" are good for rusty, old muscle (Perchthaler. 2015) - In spite of the fact that I am 100% convinced that six weeks of "real" resistance training would have produced significantly more beneficial effects, I cannot ignore that the 6-week vibration training intervention led to significant increases in jump height increased by 18.55% (p < 0.001) and corresponding increases in multijoint strength performance of the lower limbs.
  
  In view of the fact that the exercise was perceived as "very easy" to "somewhat hard", i.e. having a score of only 7-13 of Borg's scale, it would be a good ans easy starter for those grandpas and grandmas who feel that lifting weights or machine training is too hard for them. That the latter would be the better / more effective choice should be obvious, though.

Push-ups and pull-ups burn 50% and 62% more energy than previously thought, study from January 2014 shows | read the full article

You made it! And I made it, too. This article got significantly longer than I had intended it to be. I hope it was worth the effort and you still enjoyed it (comments welcome). My personal, highlight by the way is the "Burpee" study by Ratemess. Why? Well, it makes me feel good that the subjects found those body weight exercises similarly exhausting as I did, when I reincorporated them into my workouts about 6 months ago ;-)

Alright, now enjoy your day and let me know if you want future long(ish) research updates like this one to appear in regular intervals here | Comment on Facebook.

References:

• Arend, M, Mäestu, J, Kivastik, J, Rämson, R, and Jürimäe, J. Effect of inspiratory muscle warm-up on submaximal rowing performance. J Strength Cond Res 29(1): 213–218, 2015 
• Berglund, Lars M.Sc., RPT; Aasa, Björn M.Sc., RPT; Hellqvist, Jonas M.Sc., RPT; Michaelson, Peter Ph.D., RPT; Aasa, Ulrika Ph.D., RPT. "Which patients with low back pain benefit from deadlift training?" Journal of Strength & Conditioning Research: Post Acceptance: December 31, 2014.
• Brocherie, F, Girard, O, Faiss, R, and Millet, GP. High-intensity intermittent training in hypoxia: A double-blinded, placebo-controlled field study in youth football players. J Strength Cond Res 29(1): 226–237, 2015.
• Chatham, K., et al. "Inspiratory muscle training improves shuttle run performance in healthy subjects." Physiotherapy 85.12: 676-683, 1999.
• Calatayud, J, Borreani, S, Colado, JC, Martin, F, Tella, V, and Andersen, LL. Bench press and push-up at comparable levels of muscle activity results in similar strength gains. J Strength Cond Res 29(1): 246–253, 2015 
• Glaister, M, Pattison, JR, Muniz-Pumares, D, Patterson, SD, and Foley, P. Effects of dietary nitrate, caffeine, and their combination on 20-km cycling time trial performance. J Strength Cond Res 29(1): 165–174, 2015.
• Inbar, O, et al. "Specific inspiratory muscle training in well-trained endurance athletes." Medicine and science in sports and exercise 32.7: 1233-1237, 2000.
• Maciejczyk, M, Wiecek, M, Szymura, J, Szygula, Z, and Brown, LE. Influence of increased body mass and body composition on cycling anaerobic power. J Strength Cond Res 29(1): 58–65, 2015.
• Perchthaler, D, Grau, S, and Hein, T. Evaluation of a 6-week whole-body vibration intervention on neuromuscular performance in older adults. J Strength Cond Res 29(1): 86–95, 2015
• Ratamess, NA, Rosenberg, JG, Klei, S, Dougherty, BM, Kang, J, Smith, CR, Ross, RE, and Faigenbaum, AD. Comparison of the acute metabolic responses to traditional resistance, body-weight, and battling rope exercises. J Strength Cond Res 29(1): 47–57, 2015.
• Schoenfeld, BJ, Contreras, B, Tiryaki-Sonmez, G, Wilson, JM, Kolber, MJ, and Peterson, MD. Regional differences in muscle activation during hamstrings exercise. J Strength Cond Res 29(1): 159–164, 2015.
• Stevens, AWJ, Olver, TT, and Lemon, PWR. Incorporating sprint training with endurance training improves anaerobic capacity and 2,000-m erg performance in trained oarsmen. J Strength Cond Res 29(1): 22–28, 2015.
• Shariat, A, Kargarfard, M, Danaee, M, and Bahri Mohd Tamrin, S. Intensive resistance exercise and circadian salivary testosterone concentrations among young male recreational lifters. J Strength Cond Res 29(1): 151–158, 2015.
• Thompson, BJ, Stock, MS, Shields, JE, Luera, MJ, Munayer, IK, Mota, JA, Carrillo, EC, and Olinghouse, KD. Barbell deadlift training increases the rate of torque development and vertical jump performance in novices. J Strength Cond Res 29(1): 1–10, 2015 
• West, Daniel WD, and Stuart M. Phillips. "Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training." European journal of applied physiology 112(7): 2693-2702, 2012.
• Vilaça-Alves, J, Fernandes, HM, Saavedra, FJ, Pinto, RS, and dos Reis, VM. Order effects of combined strength and endurance training on testosterone, cortisol, growth hormone, and IGF-1 binding protein 3 in concurrently trained men. J Strength Cond Res 29(1): 74–79, 2015—
• Williams, James S., et al. "Inspiratory muscle training fails to improve endurance capacity in athletes." Medicine and science in sports and exercise 34.7: 1194-1198, 2002.