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 ...

• 

  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. 

Medium Intensity Interval Training (MIIT) Increases Fitness of Overweight Sedentary Women Slower, But Eventually Just As Effectively as HIIT. Neither Cuts Fat / Body Weight

It does not always have to be "all out", but 70% is probably the minimum for intervals - esp. for the non-obese.

If you know all SuppVersity articles by heart, the name Astorino may ring a bell. I mentioned a previous study by Todd A. Astorino in my 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" (read more). In their most recent study, the researchers from the Department of Kinesiology at the California State University took another look at HIIT exercise for the average female US citizen, to be precise. And the observation they made is actually quite astonishing.

MIIT vs. HIIT: Can both be equally effective?

In this group of healthy sedentary (<1h/week of regular physical activity) women (n=30; age 18-40; BMI >35kg/m²) it did effectively not make a difference, whether the participants trained at a high or medium intensities.

As you can see in figure 1, over time, both workouts yielded the exact same increases in VO2Max (marker of cardiovascular fitness)., What is however significantly different is the slope and the general look of the VO2max graph.

Figure 1: Study design and results of the 12-week intervention; training was performed 3 days/week on a cycle
ergometer and consisted of 6–10 bouts of 1 min duration at the given intensities; the asterisk after the week # indicates that the intensity values were adapted to the increase in W-Max over the past weeks (Astorino. 2013)

While the latter is clearly logarithmic for the high intensity interval training arm (HIIT; intensities see figure 1, left), the MIIT (LO in figure 1) VO2Max development is much more linear and does not display the same ceiling effect you see in the HI group. It would thus be reasonable to argue that...

MIIT hits HIIT, but...

... it is VERY likely that this is a "overweight woman phenomenon". After all, the heart rate was essentially the same regardless of whether the ladies worked out at an average intensity of 176W (MIIT) or 202W.

Figure 2: Heart rate and workload develoment over the 12-week study period (Astorino. 2013)

At first that may seem odd, but to push your heart rate through the 200 mark, you actually need a pretty decent fitness level. If you have been sitting around your whole life, you will be up to 190bpm when you simply take the stairs instead of the elevator; and while this is no health benefit it makes the same walk in the park that's just a nasty way of locomotion for the average athletic person an intense workout for the morbidly obese.

And what do we know about "intense workout"? Right, those are the true "cardio workouts" adaptation does not happen in the comfort zone and it does not entail weight loss (!) - I don't know how often I have to repeat that, but weight loss happens in the kitchen. You can only steer and promote what and how much you lose by working out... but that's the topic of another article.

---

"Men are different women, too..." We all know that, but can we still train together or will women have to do cardio first, while men would be better off starting out lifting weights? (learn more)

Bottom line: If you, family or friends are starting out to work out - keep things at a pace that's intense for YOU - not for whomever you are trying to emulate or you are training with. If there is one beauty of doing cardio in the gym instead of outside, it is that you can train right next to a friend at your personal intensity level.

So don't put a spoke into your own wheels by trying not too look bad in front of a friend. Stick to your own tempo and use yourself as a reference to judge your progress - and if the latter looks like the orange graph in figure 2 (right) you know you are on track, no matter what the absolute wattage (or RPMs) say.

References:

• Astorino TA, Schubert MM, Palumbo E, Stirling D, McMillan DW, Cooper C, Godinez J, Martinez D, Gallant R. Magnitude and time course of changes in maximal oxygen uptake in response to distinct regimens of chronic interval training in sedentary women. Eur J Appl Physiol. 2013 Sep;113(9):2361-9.

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

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

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

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

Learn more about effective training techniques at the SuppVersity

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Battle the Rope to Get Ripped & Strong

Up Your Squat by 25% With Sodium Bicarbonate

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

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

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

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

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

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

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

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

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

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

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

References:

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

Continuous Exercise But Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults - Really!?

Sled pulling in the sand?! For someone with her height, but twice or thrice the weight with a primary on fat loss, on the other hand, it's suboptimal.

"HIIT", about a year ago this was the buzzword in the health and fitness industry. Doing anything but "hiiting it hard" was thought to be a waste of time and the acronym "LISS" [Light Intensity Steady State] became synonymous with "lose" as in loser.

As a SuppVersity reader you're immune against hype and constant overgenerealization. You are aware of the "specificity principle", and the usefulness of all type of exercise. And you know that there is a place and time for each form of cardio training: Light, moderate and high intensity (interval) training.

Speaking of cardio,...

... if your main concern really is your myocardium (=the large heart muscle), what type of exercise do you have to perform then? Right! "CARDIO" = Light exercise as a replacement for the daily activity most of us pencil pushers are lacking and HIIT as a means to actually train your heart.

In the end, it doesn't really depend on your current fitness level. The "no pain, no gain" principle is true for everyone. And with "light" always being defined against your current VO2max (the standard measure of cardio-respiratory fitness) - "light" exercise such as the Continuous Endurance Training (CONT) program, 13 out of the 38 subjects in a recent study by Shelley E. Keating and her colleagues from the University of Sydney and the University of Sydney is always defined relative to the your personal fitness level.

Table 1: Frequency, intensity, work : recovery ratio, no. of intervals (INT), duration of continuous work (DUR) and total session time per week (in min; incl. warm-up, cool-down, etc.; Keating. 2014)

For the 38 inactive (exercising <3 days/week) and overweight (BMI 25 to 29.9) 18- to 55-year-old year-old slackers (7 men and 31 women) who were randomly assigned to receive three sessions/week for 12 weeks of

• HIIT (HIIT), or
• Continuous Moderate Intensity (CONT)

training or a sedentary control group (PLA). As you can see in the tabular overview below, the researchers made sure to gradually increase both the volume and intensity of the workouts.

When I am talking to people who complain about not seeing the results they want (strength, size,  conditioning and fat loss - it does not matter), not making "progress" an obligatory part of their training regimen is second only to eating processed foods (no fat loss) and eating way to little (no performance and size increases), when it comes to the most "popular" ;-) reasons for failure.

Don't make either of these mistakes!

What kind of mistakes? Well, the first one is not to acknowledge the progressive overload principle and its reign in both endurance and strength training. You will probably remember the bottom line from the "block peridization article" (see "Block Periodization - Impressive Performance Gains in Pro-Athletes: Revolutionary Training Concept, Or Just a Good Way to Eventually Break Out of the Comfort Zone?" | read more): There is no progression without progression! In other words, if you ain't willing to kick your own ass, you better hire a trainer to do that for your or content yourself with mediocrity.

Figure 1: Changes in body composition (left) and conditioning parameters (right) after 12 weeks (Keating. 2014)

As the results from the study at hand show (see Figure 1), progression is fine and dandy, but without specificity and the blind faith that there was one training method that would deliver it all, i.e

• increases in VO2 (=cardiovascular fitness)
• loss of body fat, and
• compensation for the daily activity you don't get,

... you are off the track. Seriously. Doing only HIIT will help you compensate for the daily activity you don't get, it will also help you lose body fat. However...

• HIIT is not a sensible way to compensate for the lack of daily activity in the long term (specifically for people who lift weights and have another highly CNS taxing type of workout in their routine), and
• HIIT is neither the most effective way to shed body fat for those who need it the most

I know that you will read the exact opposite on all kinds of websites, but the study at hand clearly demonstrates that exercise-induced weight loss, which is what most people want to achieve, when they're hitting the gym. Is not going to happen with HIIT, alone. The data in figure 1 does also leave no doubt that the lack of weight loss in the HIIT group of the Keating study is not a consequence of increases in lean mass.

Figure 2: Greater mass and fat gains in the CONT group are not what the slowly abating hype around HIIT would have you expect (from Keating. 2014)

As the b/w figures on the right hand side of this paragraph reveal (Figure 2), it's actually quite the opposite: The lean mass gains in the "average subject" of the continuous exercise group were (albeit non-significantly) more pronounced than than those of the 13 "HIITer" (2 dropouts in both groups).

In the absence of differences in total energy intake (p = 0.44) or the macronutrient ratios (33% | 42 % | 25% from fat, carbs and protein, respectively), identical sedentary times, a similar energy total expenditure per day (~10,000kJ/day), the training modalities, i.e. CONT vs. HIIT are the only parameter to explain why this "first study to examine the efficacy of HIIT versus that of continuous aerobic exercise training on body fat levels in previously inactive, overweight adults" (Keating. 2014 says: If you want to lose body fat without dieting, you better stick to (relative) low intensity steady state exercise.

Don't worry, HIITers! There is more to it...

... if your goal is a different one, though - in other words, if you aspire to achieve maximal fitness in minimal time, you will appreciate that the HIIT group achieved similar improvements in cardio-respiratory fitness (VO2max) with only "50–60% of the time taken for the same gain in fitness via
continuous aerobic exercise (60–72 versus 108–144 minutes per week)." (Keating. 2014).

Fitness, yes - fatness, no! The fitness effects of the HIIT regimen do not negate the fact that the data from the study at hand clearly demonstrates that continuous aerobic exercise, but not HIIT,
reduces total body fat and android fat in previously inactive, overweight adults.

Tabata is about HIGH intensity as it gets and a perfect means to get in shape for people who are already lean  | learn more

In spite of the fact that Keating et al. rightfully state that their results suggest that HIIT is not as "effective for the management of body fat levels", as previously suggested (e.g. Tremblay. 1994; Tjonna. 2009; Heydari. 2012 - all without CONT, control). You just have to make one minor change to the study protocol that could turn the results upside down. You have no idea what this change could possibly be? Well, if you want to shed fat effectively, you better diet (if you are already lean you must diet) and in this scenario, you've read about that in countless previous SuppVersity articles (read more), short and intense exercise regimen are a suitable means to propel (in this case) diet induced fat loss.

References

• Keating, Shelley E., Elizabeth A. Machan, Helen T. O'Connor, et al., "Continuous Exercise but Not High Intensity Interval Training Improves Fat Distribution in Overweight Adults". Journal of Obesity, vol. 2014. 2014. Article ID 834865. 
• Heydari, M., J. Freund, and S. H. Boutcher. "The effect of high-intensity intermittent exercise on body composition of overweight young males." Journal of obesity 2012 (2012).
• Tjonna, A., et al. "Aerobic interval training reduces cardiovascular risk factors more than a multitreatment approach in overweight adolescents." Clinical science 116 (2009): 317-326.
• Tremblay, Angelo, Jean-Aimé Simoneau, and Claude Bouchard. "Impact of exercise intensity on body fatness and skeletal muscle metabolism." Metabolism 43.7 (1994): 814-818.