Are You Overtraining? Two Scientifically Proven Methods to Test Yourself - Method 2: The ABEL Sport Test. Plus: 54 Item Questionnaire + 8 Additional Clues to Identify Overtraining

Theoretically it's already available for everyone. Costs are yet not the only thing you should keep in mind before you buy into Knight Scientific's overtraining analysis system

I've got plenty of positive, skeptic and euphoric feedback in response to last week's first installment of this two-part series on "proven" methods to test for overtraining syndrome (OTS). Before I tackle method number two in today's second installment, I do thus want to briefly remind you that the HRV method is not going to work, when you are chronically overtrained, already. It's also questionable, whether it will be able to identify parasympathetic overtraining syndrome (POTS). The latter is associated with marked decreases, not increases in the ratio of high / low frequency component (Portier. 2001). In people who train intense and with a high volume this effect can even mask the early increase in sympathetic tone and would thus render the HRV method basically useless.

You can learn more about overtraining at the SuppVersity

Heart Rate Variablity (HRV)

ABEL Sports Test + More

Overtraining & Undereating

Calculate your Energy Intake!

There Are No Magic Macros!

Reinvent Your Training!

More alternative tests / indicators of overtraining:

• increased sensitivity of 5HT receptors ➯ early fatigue (Budgett. 2010)
• free testosterone and testosterone/cortisol ratio higher than 30% (Cunha. 2006)
• increasing serum urea and decreased ammonia at rest w/ identical protein intake, indicative of higher gluconeogenesis from protein (Urhausen. 2002)
• low urinary catecholamines, esp. during night and w/ parasympathetic overtraining (Lehmann. 1992) and low ACTH and/or GH response to maximal exercise (~adrenal fatique; cf. Urhausen. 2002)
• inverse ‘iceberg profile’ in Profile of Mood State (POMS) scale (Morgan. 1987) and messed up sleep (Urhausen. 1998)
• decreased glucose & increased fat oxidation during high intensity exercise (Urhausen. 2002)

None of these markers can serve as a sole marker of overtraining. They can however support conclusions you make based on questionnaires, performance data and HRV analyses.

For method number two, so-called ABEL-Sport Test, these interferences between symathetic (~intensity, short(er) term) and parasympathetic (~volume, long(er) term) overtraining shouldn't be a problem. The test is easy, but it's not free. You will after all have to buy a portable luminometer to measure the optical properties of your blog. In other words, the ...

"[...] test does not measure a single biomarker of OTS [overtraining syndrome] but instead utilises hidden information acquired by circulating leucocytes as they patrol the body spotting pathogens, responding to markers of inflammation (cytokines and chemokines) and other changes in the blood that occur after strenuous exercise." (Knight. 2013)

As J Knight, M Wakeman, J Reeves, who have a vested interest in research into their own products, which have been used by elite and amateur athletes in many different fields and were "successfully used" by Skandia Team GB for two years prior to and in the final run up to the Olympics in Beijing in 2008, when Britain’s squad topped the medal table in the Olympic sailing competition, point out, the test is designed to elicit this "hidden information from the cells" (and I should add "hidden information that requires interpretation"!).

The technology relies on the bioluminescent protein Pholasin. It emits light, when it gets in contact with reactive oxygen specimen (ROS). To test the amount of leucocytes in a 5-20µL sample your blood you do thus just have to react it with Pholasin, activate the ROS response of the leukocytes and measure the light response (Roberts. 1985, 1987; Knight. 1999). By superimposing the results on a set of reference sample curve, Knight et al. are then (that's at least the claim) able to identify various responses during training, "indicating if the athlete is heading towards OTS and identifying infections, superimposed on training curves." (Knight. 2013)

With score way beyond 25 (15 is the first signal of OT), it's usually a good idea to take some time off and re-start your training at a saner intensity / volume - irrespective of ABEL or HRV results.

Stay skeptic! Despite the fact that a very similar technology has already been used in the analyses of the effects of foods and cosmetics, there is as of yet no independent comparison of the accuracy of the interpretation of the leukocyte ROS responsible on which Knight et al. base their assessments of the training status.

The word "interpretation" should have made you sit up: Even if the scientists are able to provide a cost-effective solution for individual hobby athletes, it is not guaranteed that the results are actually going to help you control your training load. Before the beneficial real-world effects Knight et al. observed in sailors, footballers and other athletes are confirmed in a well-controlled study by an independent team of researchers, I would thus suggest you rely on the traditional rules of thumb, your personal training experience, the HRV method and the overtraining questionnaire on the right of this "bottom line".

References:

• Budgett, R., Hiscock, N., Arida, R., & Castell, L. M. (2010). The effects of the 5-HT2C agonist m-chlorophenylpiperazine on elite athletes with unexplained underperformance syndrome (overtraining). British journal of sports medicine, 44(4), 280-283. 
• Cunha, G. D. S., Ribeiro, J. L., & Oliveira, A. R. D. (2006). Overtraining: theories, diagnosis and markers. Revista Brasileira de Medicina do Esporte, 12(5), 297-302.
• Knight, J. (1999). Rapid, simple and sensitive blood biocompatibility tests with the light emitting protein Pholasin®. Proceedings of the TechMed/Medical Device Technology Conference. Advanstar Communications UK Ltd, Chester, 3-17.  
• Knight, J., Wakeman, M., & Reeves, J. (2013). Abel-Sport™ Test For Assessing Over Training Syndrome And Detecting Infection. British journal of sports medicine, 47(17), e4-e4.
• Lehmann, M., Gastmann, U., Petersen, K. G., Bachl, N., Seidel, A., Khalaf, A. N., ... & Keul, J. (1992). Training-overtraining: performance, and hormone levels, after a defined increase in training volume versus intensity in experienced middle-and long-distance runners. British journal of sports medicine, 26(4), 233-242.
• Morgan, W. P., Brown, D. R., Raglin, J. S., O'connor, P. J., & Ellickson, K. A. (1987). Psychological monitoring of overtraining and staleness. British Journal of Sports Medicine, 21(3), 107-114.
• Portier H, Louisy F, Laude D, Berthelot M, Guézennec CY (2001). Intense endurance training on heart rate and blood pressure variability in runners. Medicine and science in sports and exercise, 33(7), 1120-1125.
• Roberts, P. A., Knight, J., & Campbell, A. K. (1985). Pholasin®: a new bioluminescent indicator for cell activation. Biochem. Soc. Trans. 1140, 1139-1140. 
• Roberts, P. A., Knight, J., & Campbell, A. K. (1987). Pholasin®: a bioluminescent indicator for detecting activation of single neutrophils. Anal. Biochem. 160, 139-148.
• Urhausen, A., Gabriel, H. H. W., Weiler, B., & Kindermann, W. (1998). Ergometric and psychological findings during overtraining: a long-term follow-up study in endurance athletes. International journal of sports medicine, 19(2), 114-120.
• Urhausen, A., & Kindermann, W. (2002). Diagnosis of overtraining. Sports medicine, 32(2), 95-102.

Endurance Training ↔ Overtraining & Muscle Loss? Run to Exhaustion & Sympathetic, Medium Intensity Steady State & Parasympathetic, HIIT-Like Training & No Overtraining

HIIT-like 400m sprinting is exhausting, but unlike running to exhaustion and medium intensity steady state cardio it's not going to mess up your nervous system.

Not one but two recent studies confirm what many of us have experienced first hand: Endurance training - specifically during a cut - is a double-edged sword. On the one hand, it's a neat way to augment the energy deficit, when you're dieting and maintain in a eucaloric state, when you're not. On the other hand, however, even moderate endurance training can alter the sympathetic and parasympathetic balance and thus create an imbalance that is characteristic of any form of overtraining.

Speaking of overtraining: As a SuppVersity reader you should actually be aware of the fact that scientists distinguish two different types of overtraining: Sympathetic and parasympathetic overtraining

You can learn more about HIIT, which appears to be less overtraining prone than MISS.

Never Train To Burn Calories!

Tabata = 14.2kcal /min ≠ Fat Loss

30s Intervals + 2:1 Work/Rec.

Making HIIT a Hit Part I/II

Making HIIT a Hit Part II/II

Triple Your Energy Exp.

Due to the fact that the symptoms (see Figure 1) closely resemble those Morbus Basedow (engl. Grave's Diseases) and Addison's Disease, respectively, sympathetic and parasympathetic overtraining are also called Basedowoid and Addisinoid overtraining.

Figure 1: Overview of the symptoms of the two major forms of overtraining.

You can see that the symptoms partly overlap. That's yet not the only problem you have if you want to diagnose the type of overtraining. In many resistance trainees, for example, you find either mixed forms or see a transition from classic sympathetic to parasympathetic overtraining over time (assuming the athlete doesn't do anything to normalize his / her sympathetic nervous system function).

There is no formula to calculate how much exercise you can sustain, but I'd suggest you take a look at my previous articles on heart rate variability and overtraining ("Are You Overtraining? Two Scientifically Proven Methods to Test Yourself - Method 1: Heart Rate Variability Analyses" | read more). They will help you to check, where you're at, if you have a baseline reading that was taken, when you've been completely rested  | learn more.

For the average study participant in a recent experiment that was conducted by scientists from the , The 42nd Hospital of PLA, the Xinqiao Hospital and the Chongqing Normal University in China, the duration and intensity of their cardio workouts (running) determined, whether the prescribed workout routines that consisted of ...

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  There is such a thing as overtraining, folks | read more

  4 times a week running at 100% of their maximal heart rate until they were exhausted (utmost intensity group)
   
• 30 minutes of running four times per week (moderate intensity group)


• 3 - 5x 1200 m runs per day with a  5-min break every 400 m four times per week (high intensity group)

made them overtrain or not, and whether their para- or sympathetic nervous system was overreacting.

Table 1: Characteristics of study groups at pre and post | Data are means XS± . Pre, pretraining; post, at the end of 8-week training; mid, at the end of 4-week training. Utmost, utmost intensity endurance training; moderate, moderate intensity endurance training; high, high intensity endurance training (Tian. 2014)

The subjects, 72 nonsmoking male students whose characteristics are summarized in Table 1, followed the routine they had been randomized to for 8 weeks. As you can see, there were no statistical significant changes in body composition over the course of the 8-week study. Although, it sould seem that the body fat percentage (I assume BFR is body fat) declined a tad bit more in the high intensity group.

Greater fat loss with HIIT, this wouldn't be a surprise - That's no news for you as a SuppVersity reader. I've repeatedly pointed out that the short intense workouts are more suitable for fat loss; and that not in spite of, but rather because they may burn less body fat during exercise.

If you have no idea what I am talking about, I suggest you take another look at my June 2012 article "Are You Still Burning Calories or Already Losing Fat? Study Shows: 5x15 Min HIIT Reduce Body Fat & Improve Fitness Twice as Effectively as 5x40min of Classic Cardio" (learn more) after you've finished this article.

Where the subjects differed, however, was in their response to the specific aerobic exercise programs they've been assigned to (I will directly quote the results from Tian et al (2014) and briefly comment on each of them):

• Heart rate variability (HRV): No significant changes in HRV parameters were found in all groups at pre and mid. But at post, the moderate intensity group showed more significant increases in RMSSD, PNN50, HF, LF and SDNN (P < 0.05 or 0.01) and much greater reduction in LF/HF than the other two groups (P was 0.033, 0.037 respectively). HFn of the moderate intensity group was significantly higher than that of the utmost intensity group (P = 0.012), while the opposite pattern occurred in LFn and LF/HF of the two groups (P was 0.025, 0.015 respectively).
  
  As you would expect the changes in HRV in the moderate and utmost intensity group reflect increases in parasympathetic and sympathetic nervous system activity, respectively.
• Circadian Changes in Cold Pressor Test (CPT): From pre to post marked differences were not found in SBP and DBP of all groups and their increases. At post HR was much less increased in utmost intensity group during CPT than the other two groups (average P < 0.05).
  
  Next to a high basal heart rate an inhibited increase in heart rate is another characteristic of later stages of sympathetic overtraining.
• Plasma catecholamine (NE & EPI): Norepinephrine (NE) concentration was considerably lower in utmost intensity group than the other two groups (P was 0.001, 0.00 respectively). At post marked inter-group differences were still not found in plasma PEI concentration.
  
  A reduced catecholamine release is a classic characteristic of long(-er) term sympathetic overtraining - a phenomenon, some people may call "adrenal fatique" that occurs after an initial phase of catecholamine overproduction in sympathetic overtraining.

Overall, the results of the study at hand confirm previous research that found associations between classic "moderate intensity" endurance training and parasympathetic dominance (Yamamoto. 2001; Pichot. 2002; Myslivecek. 2002).

For the utmost intensity group, on the other hand, the scientists diagnosed an "over-excited SN [sympathetic nervous system]" (Tian. 2014), which is in contrast to the medium intensity and high intensity group, where the head-up tilt test did not indicate an "impairing effect on autonomic regulation" (Tian. 2014).

What about muscle loss? Oh, yes! I almost forgot that scientists from the University of the Witwatersrand (Oost- huyse. 2014) in South Africa have recently been able to show that 3 h of race- simulated cycling on 4 consecutive days may improve the cyclists' ability to tap into their fat stores as an energy reserve. Unfortuna- tely, it will also lead to a 28-46% greater reliance on endogenous protein catabolism during exercise on day 2-4.

Now, every SuppVersity reader knows that protein catabolism doesn't necessarily translate ot "muscle loss", but for the average 10h of cardio + 20% energy deficit "dieter", it could.

Bottom line: A least in the study at hand, the intense, albeit better short bouts of high intensity exercise in the HIIT-like high intensity group of the study at hand turn out to be the least overtraining prone type of aerobic activity.

Even the classic medium-intensity cardio training appears to be more overtraining-prone, due to the comparatively long duration and the subsequent increase in parasympathetic nervous system activity. If you're looking for a "side-effect free" cardio regimen, 3-5x intervals of 3x400m sprints could be a good way to incorporate cardio training into your exercise routine.

One thing we should keep in mind, though, is that someone who is sympathetically overtraining in the gym with all its negative consequences (see Figure 1) would probably be better of with classic "moderate intensity cardio" to bring up the parasympathetic tone and avoid "weight lifting induced" sympathetic dominance | Comment on Facebook!

References:

• Myslivecek, P.R., Brown, C.A. and Wolfe, L.A. (2002) Effects of Physical Conditioning on Cardiac Autonomic Function in Healthy Middle-Aged Women. Canadian Journal of Applied Physiology, 27, 1-18. 
• Oosthuyse, T., & Avidon, I. (2014). Changes in substrate utilisation and protein catabolism during multiday cycling in well-trained cyclists. Journal of Sports Sciences, (ahead-of-print), 1-11.
• Pichot, V., Busso, T., Roche, F., Garet, M., Costes, F., Duverney, D., Lacour, J.R. and Barthélémy, J.C. (2002) Autonomic Adaptations to Intensive and Overload Training Periods: A Laboratory Study. Medicine & Science in Sports & Exercise, 34, 1660-1066. 
• Tian, Kaixin, et al. "Effect of Endurance Training on the Autonomic Nervous System Function of Young Male." International Journal of Clinical Medicine 5.19 (2014): 1189.
• Yamamoto, K., Miyachi, M., Saitoh, T., Yoshioka, A. and Onodera, S. (2001) Effects of Endurance Training on Resting and Post-Exercise Cardiac Autonomic Control. Medicine & Science in Sports & Exercise, 33, 1496-1502. 

Gear for Your Ear! Fast & Slow Songs Can Both Speed You Up on the First 800m of a 5K. Plus: Calm Songs Increase Vagal Tone & CNS Activity, Fast Songs Spike You Up!

One of the runners in the study (original image from Bigliassi. 2014)

Music-related interventions have been widely used in sports and exercise; and despite the fact that you've read about respective studies here at the SuppVersity before I thought the publication of a recent study from the Center of  Physical  Education  and  Sports at the State  University of Londrina was a good reason to address the issue once more.

It goes without saying that there are numerous external factors which determine the optimal workout music, as well as how and when to use it. Against that background, it should be obvious that the following study outcomes are not entitled to be "universal".

HIIT workouts probably require different music than LISS workouts

Never Train To Burn Calories!

Tabata = 14.2kcal /min ≠ Fat Loss

30s Intervals + 2:1 Work/Rec.

Making HIIT a Hit Part I/II

Making HIIT a Hit Part II/II

Triple Your Energy Exp.

Just think about personal preferences, for example. A classic fan is probably not going to work out listening to music by Dr. Dre... well unless he's boxing, maybe! A thought that takes us to another important factor: Who knows if the same music that helps you to lift harder will also make you run longer and vice versa?

Why is this important? Well, in the study at hand, the exercise of choice was running. An exercise type the authors considered particularly fit for their study, because it's "a common physical exercise worldwide, due to its own features (low cost and availability for practice) and high aerobic benefits". Moreover, previous research has demonstrated that music can aid running by acting in parallel to exercise. It was thus logical to try to expand our still incomplete knowledge of the effects of music on exercise performance - albeit this time in a long term study with many degrees of freedom:

"Acoustic gear" - (Re-)Read my previous research summary from 2013 | go ahead

"This study was divided into 3 stages that were performed in the course of 30 weeks. In the first stage, all participants were interviewed separately before the experiment. At this time, they gave their anthropometric measures (weight and height), personal information (age, time of continuous training, number of running competitions and training volume), and answered the Eysenck personality questionnaire (EPQ), which gives possible stratifications according to personality, checking whether music could act differently in accordance with personal features."

The subjects had to select 30 motivational songs (10 – slow speed tracks, 10 medium speed tracks and 10 fast speed tracks) and the only provided information was to select songs capable of increasing their vigor and motivation to accomplish a severe aerobic physical exercise (when the number of tracks did not achieve the required number, they were asked to choose other songs to complete the playlist). The song stratification was performed initially via specific software solutions and thereafter by the examination of an expert musician.

How did the tests look like? The actual exercise tests consisted of 5 physical tests. Each of them involved a 5km run which was to be completed as fast as possible. The time between the tests ranged from 3-7 days. All tests were performed at the same time of the day.

In the second stage, all participants were called in to the laboratory, where they had to fill their questionnaires and to perform a neuroimaging test involving listening to a variety of songs. This technique was conducted to demonstrate how self-selected songs could act in emotional areas of the brain and how the subsequent activation of specific brain correlates with physiological assessments and the effectiveness of motivational music in inducing emotional consequences and downstream metabolic / ergogenic effects. All-in-all, the present study evaluated five experimental conditions:

• PM: Motivational songs, ranging from 110 – 150 bpm, applied before 5 km of running; 
• SM: Slow motivational songs, ranging from 80 – 100 bpm,applied during 5 km of running;
• FM: Fast motivational songs, ranging from 140 – 160bpm, applied during 5 km of running; 
• CS: Calm songs condition – calm songs applied after 5 km of running; 
• CO: Control condition, without intervention. 

The CO trial was considered the baseline, all other trial were compared to. The CO trial was performed in a silent environment to allow the subjects to focus exclusively on their body signals.

Figure 1: Parasympathetic tone during recovery (in min on x-axes) after control trial (no music)
vs. calm music (left) and motivational music (left | Bigliassi. 2014)..

As you can see the 15 amateur runners (24.87 ± 2.47 years;78.87 ± 10.57 kg; 178 ± 07 cm; 24.92 ± 2.79 kg/m²; 4.85 ± 1.85 years of training; 7 ± 3.49 weekly training hours; 5.67 ± 2.85 competitions) had a significantly reduced parasympathetic tone during recovery, when they trained with motivational music (low parasympathetic tone = "spiked up").

Slow or fast? Does it matter or is it just about music in general?

The calm music (Figure 1; left), on the other hand, led to an increase in parasympathetic tone, as you would expect to see it in someone who meditates or "chills" as the kids like to call it ;-) Now that sounds great for weed-heads, but from a performance perspective it was obviously as detrimental - interestingly, though, not much more detrimental than not listening to music at all.

Figure 2: Effects of control (CO), motivational (PM), slow (SM), fast (FM) and calm (CS) music / songs on fatigue, tension, vigor, and 5k times (in s) - the effects are visible, but not significant (Bigliassi. 2014).

The most important and yet unquestionably somewhat disappointing observation Bigliassi et al. made is however the statistical non-significance of the the visible time-differences in Figure 2. 

If we investigate, why the visible advantage was "no advantage" in the strict sense (i.e. it was statistically non-significant), we will obviously get back to what I said initially: Inter-individual differences and preferences loom too large to make any generalizable recommendations with respect to the optimal workout music.

Performance ain't everything: What could be of interest in future studies, are the recovery effects of an increase in vagal turnus (=pa- rasympathetic acti- vity) after 5 km of running with calm music (P < 0.05) - it's not ergogenic, but could be a great tool to calm down after an intense strength training workout; and thus probably even to speed up recovery and re- duce the likelihood of overtraining.

Bottom line: The scientists are right when they highlight that "the present study accomplished a very real training situation (5 km of running – open space and self-selected songs), making the present findings useful for further applications" (Bigliassi. 2014). Accordingly, the prefrontal cortex activity the researchers observed and the positive emotional consequences they detected via autonomous system analyses have a similar real-world relevance.

Whether this is also true for the significant performance increases on the first 800 meters in the slow and fast music trials is questionable. Personally, I suspect that some of you will benefit from the fast, while others from the slow songs. This conclusion would also be supported by the significant inter-individual differences in the study at hand.

So, if there is any general take home message from the study at hand, it would probably be the notion that there is a "high probability of improving running performance when music [is] applied (SM: 89%; FM: 85%; PM: 39%)," at all - which one is the "best", on the other hand, will depend on the individual, as well as the type of exercise | comment on Facebook!

References:

• Bigliassi, Marcelo; León-Domínguez, Umberto; Buzzachera, Cosme F.; Barreto-Silva, Vinícius; Altimari, Leandro R. "HOW DOES MUSIC AID 5 KM OF RUNNING?" Journal of Strength & Conditioning Research: Post Acceptance: July 15, 2014.

There is Such a Thing As Overtraining, Beware! When IGF-1, MyoD & Myogenin Plummet and MAFbx Gnaws Away Your Muscles, It'll Already be Too Late to Acknowledge

Overtraining is real and it's blocking future and reversing past gains.

I am well aware that somewhere out there in the broscientific spheres of the pseudo-experts on the various bulletin boards of a world people call the Internet statements like "there is no overtraining, just undereating" are not uncommon. And in fact, there is a certain connection between the effects / symptoms we usually associate with overtraining on the one, and the consequences of undereating on the other hand. It's a perfect synergy, if you will - a synergy I have been writing about in the past (suggested read: "The SuppVersity Athletes' Triad Series" | read more), but it's not what the most recent study from the Sao Paulo State University in Brazil is about (Alves Souza. 2014).

Overtraining comes in two forms

If this is not your first visit to the SuppVersity the phrases "sympathetic" and "parasympathetic" overtraining will probably sound vaguely familiar. While the latter is the form of overtraining that develops after weeks of 2-4h of daily cardio-training - usually in the presence of undereating, the former is supposed to occur after heavy lifting sessions and is thus more common in sprint type sports.

Check your training status with a heart rate monitor: In spite of the fact that there is no 100% reliable method to test, whether you're overtraining, the heart rate variability - or rather the way it's changing in the course of a training cycle can give you a good idea of whether you're doing too much, already (learn more in "Are You Overtraining? Two Scientifically Proven Methods to Test Yourself" | Part I, Part II).

In the early phases sympathetic overtraining may feel like being "overstimmed", i.e. similar to the strange agitated weakness caffeine naive individuals may experience after their fourth cup of coffee. That's before a deliberating fatigue will take over, episodes of hypoglycemia during (and after) exercise will occur and your life will start to suck as much as your performance (yes, depression is another symptom of overtraining).

Muscle loss instead of gains

While performance oriented athletes usually pull the emergency break, when the notice that their strength, speed, agility, dexterity and all the other qualities that are relevant for world-class performance decline, Mr. Average Joe and his wife Jane tend to ignore the signs until it's already too late and the hormonal changes, Alvez Souza et al. observed in their latest study have already started to gnaw on their precious muscle mass.

Figure 1: Expression of hyptrophy relevant protein and hormones after 12 weeks of (over-)training, as well as subsequent effects on cross-sectional area (CSA) of plantaris muscle; trained vs. sedentary animals (Alves Souza. 2014)

What you can see in Figure 1 are the consequences of 12 weeks of training, in the course of which, the labrats of the Brazilian researchers were subjected to a 1training program with excessive training
load and insufficient recovery time between bouts using a water jump-exercise model of squatting (Figure 1, right):

"Briefly, rats underwent to consecutive training sessions (5 day/week) that consisted of jumps (repetitions) to the water surface (38 cm deep; approximately 150% of rat body length), carrying an overload strapped to a vest on the animal's chest. Initially, all animals completed a 1-week pretraining (once daily) that consisted of a progressive number of sets (2-4) and repetitions (5-12) with a 30-s rest between each set, and carrying an overload of  50%  body  weight  (BW).  Subsequently,  the  rats  began  the  12-week  training  program,  which consisted of progressive overload corresponding to  60% (1 to 3 week), 65% (4 to 6 week), 70% (7th to 8th week), 80% (9th to 10th week), and 85% (11th to 12th week) of BW." (Alves Souza. 2014)

As Alves Souza et al. point out, they have previously demonstrated that this training protocol is effective in promoting type IIA and IID  fiber  atrophy  in  rat  plantaris  muscle  - as long as it is done in a sane and not the typically Western "more helps more" way that was applied in the study at hand.

Overtraining leads to significant changes in muscle specific hormones and proteins: If you discard the fact that most gymbros don't train legs at all (you know, they play football or soccer, right ;-) the above looks pretty much like the "5-days a week, why don't I grow" regimen of the average self-proclaimed hardgainer, whose consternation about his lack of gains is hardly surprising in view of ...

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  When it comes to IGF-1 looking at systemic levels is not enough - rather than the circulating "full" version of MGF, it's the presence of its local splive-variants like MGF that's actually igniting muscle growth. You can learn more about MGF and other factors that contribute to muscle growth in the "Intermittent Thoughts on Building Muscle" Series | go ahead!

  the upregulation of MAFbx, a muscle protein and that is released if you bath muscles in petri dishes full of glucocorticoids has emerged as a central regulator of skeletal muscle catabolism in previous studies (6, 13, 34),
• the reduction in MyoD and myogenin and the consequent inability to compensate for the exercise induced damages (let alone build new muscle) due to the lack of satellite cell (=muscle stem cell | learn more) activity,
• the drop in IGF-1 and it's local splice variants that decline with decreasing systemic levels of IGF-1 and play an (imho) still largely underestimated role in the concert of skeletal muscle hypertrophy (see "IGF-1 and its Splice Variants MGF, IGF-IEa & Co - Master Regulators or a Bunch of Cogs in the Wheel of Muscle Hypertrophy?" | read more)

Although we may still be light-years away from understanding the exact interplay of all these factors, I can tell you one thing for sure: As productive as a short 2-week phase of overreaching may be - don't be fooled to believe that the gains would keep coming if you just kept pushing.

References:

• Alves Souza et al. "Resistance Training With Excessive Training Load and Insufficient Recovery Alters Skeletal Muscle Mass-Related Protein Expression." Journal of Strength and Conditioning Research (2014). Publish Ahead of Print