Well, let's assume you ' pre-fuel ' in both cases. There is enough glycogen / glucose in the muscles, liver and blood of a typical gym rat to supply about 1,800 calories of energy of weight training - in addition to fuel coming from fat. And, let's also assume that in both cases, a gym rat does proper post workout fueling - assume the weight workout is for 1 hour.

Even if you do weights for 1 hour, it seems to me you aren't going at 95% MHR for a solid hour so - there a lots of rest period between exercises & sets where you'd be at 70% - 90% MHR - your fuel consumption isn't coming 100% from glycogen / glucose but rather from both fat and glycogen. So, what i'm getting at is that it would appear it isn't a complete depletion of glycogen that will trigger muscle to be sourced as fuel during weight training or HIIT - as I doubt 1 hour of weights along with 30 minutes of HIIT would burn any more than 700 of calories derived soley from glycogen / glucose.

Rather, it sounds like what you're saying is that after 45 minutes of weight training , an increase in cortisol is triggered by weight training and these higher levels of cortisol are present before you start 30 minutes of HIIT after the weight workout - and these higher levels of cortisol are present even if you did 30 minutes of ss cardio after the weight workout.

You said that " HIIT wont waste muscle if its done on non weight days ", so doing HIIT in and of itself must not raise cortisol levels. If that is the case, assuming a higher amount of cortisol is present before both a 30 minute HIIT or a 30 minute ss cardio session done after weights - why is it that HIIT will burn more muscle afterwards than ss cardio ?

Again, assuming glycogen stores are a non-issue, what is it about weight training that will make a 30 minute HIIT session done afterwards burn any more muscle a 30 minute ss-cardio session done afterwards ?

Yeah, I know the technique, I'll add those in.

Yes. 3x a week will be deads squats, benches, ups, etc...

Nope, if I lower my cals good and run run run, I usually don't have a problem. Last year during summer vacation I lost about 30lbs by running and cutting, so I don't think I have a problem. Not to mention I've been eating like a horse for the last month and haven't noticed much fat increase.

Probably for 10-12 minutes to start out, then gradually start up to 20 minutes. I don't want to overdo it and then get burnt out.

Well, I'm pretty modivated so that shouldn't be a problem for me

No it doesn't: the studies that looked at endocrine response, like most weight training studies, were done in a fasted state to minimize the variables. As long as you have a real breakfast/pre-workout meal, all of that goes out the window. That's why studies that compare just post-workout meals to pre-workout meals in terms of protein synthesis find that pre-workout meals are more effective. The real-world answer is to utilize both, of course.

With a healthy supply of amino acids and carbohydrates from the food eaten before the workout (1-2 hours before is fine), catabolic endocrine response to the muscle is controlled.

HIIT after weights isn't the best thing to do, but not specifically for catabolic reasons if nutrition is appropriate: it's simply overkill, and you won't be producing any useful effects from it. Remember: HIIT isn't some "magic potion" for weight loss: it's simply a tool, like everything else, and there are reasons to use it, as well as not to use it, depending on the scenario.

Bip.. does that throw the whole max an hour of lifting thingy right out the window? Ofcource, im not saying its a free card to lift for 3 hours, but..

Excellent post ......thanks.

More or less...now, practically speaking, unless you're training specifically for a sport or athletic purpose, you really don't need to be in the gym for much more than an hour...anything more, and you're probably not working out efficiently or intelligently. The more recent research indicates, as jmanjman47 had been alluding to, sipping slowly on a whey shake (which will avoid stomach upset) throughout your workout will be your best bet if you are going to have a long workout. For reference, on my high volume weeks I'm probably in and out of the gym in around ~75 minutes (including warm-up/activation & mobility and cool-down/soft-tissue work) and closer to 45 minutes on low volume days.

cool, thats what i figured! Thanks Bip

Muscle Breakdown: Is Cortisol Leading You Down the Catabolic Pathway? by Rehan Jalali

Please send us your feedback on this article.

Walk into any so-called "hardcore" gym these days, and you’ll likely see ‘em by the dozens. They’re easy to spot… they’re the guys who spend hours on end pushing up plates, searching for supreme physical perfection, yet rarely finding it. They are the hopelessly over trained, and they’re afflicted with that old Protestant work ethic: a little training is good, so a whole lot must be better.

The very idea of producing a peak physique leads to a perverse temptation among these fellows to do all but pitch tent in the weight room and camp out there 24/7. "There’s no such thing as over training," they declare. Indeed, they know a lot of clichés and can spout them off with machine-gun repetition—No Pain, No Gain… If the Bar Ain’t a Bendin’, You’re Just Pretendin’… Go Heavy or Go Home. But ask them anything specific about exercise physiology or the dynamics of muscle-fibre hypertrophy and repair, and they’re as quiet as Tori Spelling playing Trivial Pursuit.

The bottom line is, if you’re among the band of hard-and-heavy lifters, cortisol may be literally eating away at your muscle-building potential. Weight training enthusiasts must declare all-out war on this catabolic hormone if they have any aspirations of building muscle. But before we attack all of your cortisol problems, some background on this intriguing subject is in order. After all, understanding leads to solutions (or was it madness?). Anyways, here goes….

Cortisol is the primary glucocorticoid. It is a natural hormone of the adrenal glands. Although cortisol's precise actions are not completely understood, we know that it is essential for life. Cortisol is necessary to maintain important processes in times of prolonged stress. Most of its effects are not directly responsible for the initiation of metabolic or circulatory processes, but it is necessary for their full response.

Cortisol Synthesis: Cholesterol--> Pregnenolone--> Progesterone -->17-Hydroxyprogesterone-->11-Deoxycortisol --> Cortisol.

Cortisol can exert its effects on peripheral tissue. Once in circulation, cortisol is typically bound to a specific glucocorticoid-binding alpha2-globulin called transcortin. About 75% of cortisol is bound to transcortin, 15% to 20% bound less tightly to albumin, and 5% of circulating cortisol is unbound (1). This is an important factor to take into consideration when measuring cortisol levels. The 24-hour urinary excretion of unmetabolised cortisol is one of the best ways to accurately gauge cortisol levels.

This helps take into account bound and free cortisol. Exogenous cortisol has a half-life of about 70 to 90 minutes. Cortisol can be converted to its 11-keto analogue cortisone (you know, the stuff you take when you have some bad swelling or inflammation).

The major catabolic effects of cortisol involve its facilitating the conversion of protein in muscles and connective tissue into glucose and glycogen (cortisol may increase liver glycogen). Gluconeogenesis involves both the increased degradation of protein already formed and the decreased synthesis of new protein. Cortisol can also decrease the utilization of glucose by cells by directly inhibiting glucose transport into the cells (1).

A cortisol excess can also lead to a decrease in insulin sensitivity. Cortisol also reduces the utilization of amino acids for protein formation in muscle cells. A cortisol excess can lead to a progressive loss of protein, muscle weakness and atrophy, and loss of bone mass through increased calcium excretion and less calcium absorption.

That is one of the reasons long-distance runners tend to have skinny physiques. With the amount of stress that runners place on their bodies, they have high levels of free radicals as well as cortisol.

Excess cortisol can also adversely affect tendon health. Cortisol causes a redistribution of body fat to occur through an unknown mechanism. Basically, the extremities lose fat and muscle while the trunk and face become fatter. Some of the signs of over training include higher cortisol levels, which may cause depression-type effects. Cortisol excess can also lead to hypertension because it causes sodium retention (which can make you appear bloated) and potassium excretion.

In other words, excessively high cortisol levels may turn you into a girly man! So the real challenge becomes how can cortisol levels be controlled but not inhibited completely because of cortisol's necessary anti-inflammatory effects?
One way is to take anti-cortisol supplements in the morning upon rising and then before bedtime, as these are two times that cortisol levels seem to be raised. Timed release would not be an option here because this may suppress cortisol levels over too long of an extended period. The key is to suppress elevated levels of cortisol, not decrease normal physiological levels of this hormone because as I mentioned earlier, a small amount is needed for it's anti-inflammatory and other effects.

Another one of cortisol's undesirable effects for athletes is it causes insulin resistance by decreasing the rate at which insulin activates the glucose uptake system, likely because of a post-insulin receptor block (2).

Any type of stress that occurs to the body signals the nervous system to relay this to the hypothalamus. The hypothalamus then responds by initiating the stress-hormone cascade starting with CRF (corticotrophin releasing hormone) followed by ACTH (adrenocorticotropic hormone) release, and finally glucocorticoid production (pretty intense, huh?). Stress to the human body can include trauma, anxiety, infections, surgery, and even resistance training and aerobics. Recent research has shown that increased cortisol levels also increased protein breakdown by 5% to 20%. (3)

Even mild elevations in serum cortisol can increase plasma glucose concentration and protein catabolism within a few hours in healthy individuals. (4) Cortisol increases with increasing time of intense exercise. In over trained individuals, cortisol levels increase while testosterone levels decrease. That is why one measure of over training is the testosterone-cortisol ratio. By the way, over training is defined as an increase in training volume and/or intensity of exercise leading to a decrease in performance. Cortisol can increase body fat levels especially when it’s increased dramatically in the body. Increased cortisol levels have an adverse effect on testosterone levels.

In fact, one of the primary anti-catabolic effects of testosterone and anabolic steroids is its decreasing muscle cortisol metabolism. (5) That is one reason why many athletes can completely over train when taking anabolic steroids and still increase lean body mass and strength. Some research indicates that cortisol response to resistance training normalizes after about five weeks and that the testosterone- cortisol ratio is not adversely affected after long periods of resistance training. (6) This suggests that the body has an adaptive response.

Cortisol can inhibit growth-hormone levels by stimulating the release of somatostatin (a growth-hormone antagonist). It may also reduce IGF-1 expression (IGF-1 is one of the most anabolic agents in the body and is the substance that is responsible for most of growth hormone’s positive effects because GH converts into IGF-1 in the liver).

Cortisol has other hormone-modifying effects. Cortisol can directly inhibit pituitary gonadotropin and TSH (thyroid stimulating hormone). (7) By doing so, it can make the target tissues of sex steroids and growth factors resistant to these substances. It may also suppress an enzyme known as 5' deiodinase, which converts the relatively inactive thyroid hormone T4 to the active one known as T3 or triiodothyronine. This can decrease metabolic rate and make it harder to lose body fat (it's already hard enough for people and anything making it harder definitely needs to be kicked to the curb).

There are different stages in sleep and during one stage, cortisol levels are elevated because protein is being re-cycled. This is one reason that cortisol-suppressing supplements should be taken before bedtime to help minimize excess cortisol production during sleep.

Cortisol also seems to play a role in various disease states. It is found in higher-than-normal levels in diseases ranging from AIDS and multiple sclerosis to Alzheimer's. Prolonged high levels of cortisol can throw the immune system into chaos and ravage the human body. A growing number of researchers believe that many of the worst, and least-understood, diseases will soon be identified as caused by high cortisol, and subsequently treated with cortisol-reducing drugs or supplements.

There was an anti-cortisol conference (the second one ever conducted) held in Las Vegas in 1997 and headed up by Steroidogenesis Inhibitors Inc. and Dr. Alfred T. Sapse. This conference had many researchers involved in anti-cortisol research. Abstracts were presented on various supplemental and drug therapies for decreasing cortisol levels, especially in excessive cortisol-production disorders. In particular, there was an abstract presented by Dr. Sapse that mentioned some nutritional supplements to lower cortisol levels in the body.

These included gingko biloba, Vitamin A, Zinc, and acetyl l-carnitine (8). Other abstracts presented there discussed the role of DHEA and its metabolites in helping to decrease cortisol levels. (9) Some abstracts presented looked at the progression of cortisol-induced diseases. Overall, the conference was very informative and helped researchers answer many questions on cortisol and anti-cortisol therapies as well as opened the door for further anti-cortisol research.

Cortisol suppression may be an essential part in the recovery process for athletes involved in a rigorous training program. In fact, one of the signs of over training syndrome is high cortisol levels. Moderating (not completely diminishing) cortisol levels is an essential factor in allowing weight-training individuals to completely recover from their exercise session and maximize results (something we would all like to do).

It may be a very good idea to get cortisol levels tested by a qualified physician (when I say qualified, I mean one who has done this sort of thing before and has been to medical school) on a regular basis. One of the best times to test cortisol levels is first thing in the morning on an empty stomach. This reference value or proper range for cortisol first thing in the morning should be between 4 mcg/dl and 19 mcg/dl with the sample being taken from blood. The normal range for free cortisol levels measured from urine is between 10 pg/ml and 110 pg/ml. There is also another way to measure cortisol through a salivary cortisol screening. The normal range for cortisol with this test first thing in the morning is between 100nmol/L and 300nmol/L. These tests may not have the final say in determining high cortisol levels but, it will certainly give you an idea about where your cortisol levels stand.

Controlling Cortisol Levels
Here are some solid tips to help control cortisol levels:

1) Diet: Make sure you are supplying your body with all the essential nutrients you need to prevent deficiencies and for optimal function. This includes plenty of high-quality protein, complex carbohydrates, essential fatty acids, and vitamins and minerals. Try not to restrict calories continuously as some research suggests that restricting normal caloric intake by 50% can lead to a subsequent increase in cortisol levels by 38%. (10)

2) Do not over train: Try not to work out three or more days in a row without taking a day off. KEEP WORKOUTS TO UNDER AN HOUR AT MOST and train efficiently and intensely. I know this phrase has been beaten to death but LISTEN TO YOUR BODY!

Take enough rest days between workouts - If you are really sore, wait an extra day to train until your body fully recovers from your previous workout. Remember, less may be more in this case.

4) Relax and try not to get stressed out easily: Take an evening walk with a loved one or take a nap when you get a chance.

5) Try to get at least eight hours of sleep per night: Sleep is crucial to the recovery and recuperation process.

6) Spike Insulin levels after a workout: Insulin actually interferes with cortisol and may enhance cortisol clearance from the body. Spiking insulin levels after a workout (by consuming a high-glycaemic index carbohydrate) may help minimize excessive cortisol levels since cortisol levels are elevated significantly post resistance training.

yeah, it says dont train for over an hour, but it doesnt show any study where they ate a propper pre workout meal that showes a spike in cortisol levels after an hour.

Its pretty much the same thing as the whole "post workout fast carbs and protein" thing, in most studies the subjects trained just after an overnight fast, which does not make sence since most people eat before they go workout. Id like to see a study on both the whole PWO shake thing and cortisol where the subjects trained maybe at 6 PM and had been up all day eating and drinking like regular people.

I don't think anyone is questioning whether or not the adverse consequences of cortisol exist or not - they do. Although ( judging from bipennate's response to your earlier post ) the ' when & how & if ' of when a cortisol response get's triggered may vary quite a bit......i.e with respect to the duration and frequency of weight training and in conjunction with one's nutrition.

That aside, I was more interested on your views of doing HIIT after weight trainig vs doing ss cardio afterwards vs doing HIIT simply on it's own ......as it pertains to any possible enhanced rate of muscle loss.

You seemed to indicate that after 45 minutes of weight training , an increase in cortisol is triggered by weight training. And these higher levels of cortisol are present before you start 30 minutes of HIIT ( after the weight workout ). It also follows that these higher levels of cortisol are present even if you did 30 minutes of lower intensity ss cardio after the weight workout.

You said that " HIIT wont waste muscle if its done on non weight days ", so doing HIIT in and of itself must not raise cortisol levels. And you also said " but if you do an aerobic exercise "low intensity" [ after weights ] you will be using fat and not muscle " If that is the case, assuming a higher amount of cortisol is present before both a 30 minute HIIT or a 30 minute ss cardio session done after weights - why is it that HIIT will burn more muscle afterwards than say ss cardio done after weights ?

What is it about weight training that will make a 30 minute HIIT session done afterwards burn any more muscle than a 30 minute ss-cardio session done after weight training ?

Perhaps you could elaborate.

WRANGELL
ss-cardio below 70% hr will not utilise sugars/carbs HIIT will,so if after a heavy weights session your body releases cortisol doing another anearobic exercise will most likely use up muscle.
also as you have already taken advantage of EPOC due to the weights why take a chance of using up muscle.
as i have said IMO i would do cardio on a sepperate day altogether if possible,and i doubt doing HIIT on non weight days will have any chance of releasing any cortisol,because HIIT is very short "if its not then its not HIIT".

but if you have to do cardio after weights then IMO ss-cardio is a better bet.

as you pointed out bipenate is infact correct that diet can alter when cortisol is released.but it is a difficult thing to judge,i would rather do a shorter workout than take the chance of wasting a lot of time in the gym and ending up with less than optimum results.

also another point, some studies have shown that the more conditioned you are ie the longer you have trained,the longer it may take before you release cortisol.

here is a study showing bipenates point,but as i said even though i take carbs before i dnever do more than an hour weights.

hope that answers your question


Liquid carbohydrate/essential amino acid ingestion during a short-term bout of resistance exercise suppresses myofibrillar protein degradation.Bird SP, Tarpenning KM, Marino FE.
School of Human Movement Studies, Charles Sturt University, Bathurst, NSW 2795, Australia.

A number of physiological events including the level of contractile activity, nutrient status, and hormonal action influence the magnitude of exercise-induced skeletal muscle growth. However, it is not the independent action of a single mechanism, but the complex interaction between events that enhance the long-term adaptations to resistance training. The purpose of the present investigation was to examine the influence of liquid carbohydrate (CHO) and essential amino acid (EAA) ingestion during resistance exercise and modification of the immediate hormonal response on myofibrillar protein degradation as assessed by 3-methylhistidine (3-MH) excretion. After a 4-hour fast, 32 untrained young men (18-29 years) performed a single bout of resistance exercise (complete body; 3 setsx10 repetitions at 75% of 1-repetition maximum; 1-minute rest between sets), during which they consumed a 6% CHO (n=8) solution, a 6-g EAA (n=8) mixture, a combined CHO+EAA (n=8) supplement, or placebo (PLA; n=8) beverage. Resistance exercise performed in conjunction with CHO and CHO+EAA ingestion resulted in significantly elevated (P<.001) glucose and insulin concentrations above baseline, whereas EAA ingestion only increased the postexercise insulin response (P<.05). Time matched at 60 minutes, the PLA group exhibited a peak cortisol increase of 105% (P<.001) with no significant change in glucose or insulin concentrations. Conversely, the CHO and CHO+EAA groups displayed a decrease in cortisol levels of 11% and 7%, respectively. Coinciding with these hormonal response patterns were significant differences in myofibrillar protein degradation. Ingestion of the EAA and CHO treatments attenuated 3-MH excretion 48 hours after the exercise bout. Moreover, this response was synergistically potentiated when the 2 treatments were combined, with CHO+EAA ingestion resulting in a 27% reduction (P<.01) in 3-MH excretion. In contrast, the PLA group displayed a 56% increase (P<.01) in 3-MH excretion. These data demonstrate that not only does CHO and EAA ingestion during the exercise bout suppress exercise-induced cortisol release; the stimulatory effect of resistance exercise on myofibrillar protein degradation can be attenuated, most dramatically when the treatments are combined (CHO+EAA). Through an "anticatabolic effect," this altered balance may better favor the conservation of myofibrillar protein.

PMID: 16631431 [PubMed - indexed for MEDLINE

Why ' not ' ?

My understanding is that about 70% - 75% MHR your body is using about 50% carbs AND 50% fat. You are always using some amount of carbs during aerobic cardio...it simply varies with intensity.

Even in the mid 60%+ MHR, you are still burning 40% or so from carbs...just a bigger amount from fat - i.e 60%. Ditto for 85% MHR - you're using much much less fat, but some is still being burned.

Besides, what does this have to do with cortisol, HIIT and muscle loss ?

But why ? Why does having more cortisol around trigger anearobic exercise to use muscle as fuel ?

Even though HIIT uses a combo of glycogen ( the much higher percentage ) and fat, the depletion of your glycogen and fat energy stores during a weight workout shouldn't be substantial enough ( during most ' normal ' weight workouts ) to trigger your body turn to muscle for fuel due to a lack of energy. So, the issue must be coitisol and muscle loss.

That said, are you saying that HIIT - in and of itself - triggers cortisol ? And, that the cumulative effect of weight training induced cortisol and HIIT cortisol enhances muscle loss ?

[QUOTE=buzz;202179]also as you have already taken advantage of EPOC due to the weights why take a chance of using up muscle./QUOTE]

Not sure I follow - are you saying EPOC burns muscle ?

I always thought cortisol was triggered due to some ' stress ' stimulus.

So a 45 - 1 hour weight session will trigger a significant enough release of cortisol - enough to possibly promote muscle as fuel. The ' stress ' of lifting weights will trigger the cortisol.

But, doing 30 minutes of flat-out hard HIIT is not stressful enough to trigger cortisol ? I've done both - weights and HIIT - and HIIT always is as ( if not a lot more ) stressful than my weight sessions ! Why is it HIIT is not stressful enough to release cortisol in your view ?

Well, if HIIT doesn't trigger any further cortisol ( as you say ), and ss cardio also doesn't trigger any further cortisol and both have adequate fuel stores to use ( i.e carbs and fat ) there shouldn't be any greater risk if your use HIIT or ss cardio after weights- should there ? What's the difference ?

I think his point was, that assuming proper nutrition, cortisol is a non-issue.

the difference is that HIIT is so darn intense, that you will puke.
All exercise has a chanse of causing you to burn protein and muscle if your nutrition is off (or the session is too long). Generally, the body will start using protein/muscle for fuel, usually after pretty long exercise. A good warning sign is that you start to smell ammonia. Something that smells that way is left after some protein or ammino accid (i cant remember this completley) has been broken down, and it has to be taken out of your body through your sweat.

wrangell
Why ' not ' ?

My understanding is that about 70% - 75% MHR your body is using about 50% carbs AND 50% fat. You are always using some amount of carbs during aerobic cardio...it simply varies with intensity.
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60% to 70% zone doesnt use carbs read below recovery zone
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wrangell

But why ? Why does having more cortisol around trigger anearobic exercise to use muscle as fuel ?
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read below anearobic zone.
your body releases cortisol because its run out of glucose/glycogen/sugars/etc the aerobic zone uses all of these so the energy the body needs will come from the protein you need for muscle growth
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wrangell
I always thought cortisol was triggered due to some ' stress ' stimulus.

So a 45 - 1 hour weight session will trigger a significant enough release of cortisol - enough to possibly promote muscle as fuel. The ' stress ' of lifting weights will trigger the cortisol.

But, doing 30 minutes of flat-out hard HIIT is not stressful enough to trigger cortisol ? I've done both - weights and HIIT - and HIIT always is as ( if not a lot more ) stressful than my weight sessions ! Why is it HIIT is not stressful enough to release cortisol in your view ?

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stress,depression.diet,time of day,all effect cortisol.
if your pre fuelled its most likely your body may take longer to release cortisol,but that depends how long and how intense your weights are IMO doing squats with 200k on my back is a lot more intense than HIIT.so doing 30mins HIIT will not be long enough to release cortisol IF PREFUELLED but doing a 45min weight session which is anearobic then 30 mins HIIT which is also anearobic IMO is to much of a risk.

also HIIT should be done at near maximum intensity 100m 200m sprints etc,if your doing 30mins are you really doing HIIT or just interval training
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wrangell
I think his point was, that assuming proper nutrition, cortisol is a non-issue.
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it could be a non issue with a normal workout,but if your going to be doing 2x hrs at a high intensity i wouldnt want to take the chance of wasting hard earned muscle
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wrangell
Not sure I follow - are you saying EPOC burns muscle ?
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weights and HIIT both use EPOC one of the main effects of EPOC is it speeds up your metabolism after training,how does it do that, by repairing muscle tissue that has been torn down by weights and HIIT ,so effectively EPOC is the result of muscle teardown.
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Heart Rate Training Zones
Heart rate training zones are calculated by taking into consideration your Maximum Heart Rate (MHR) and your Resting Heart Rate (RHR). Within each training zone, subtle physiological effects take place to enhance your fitness.

The Energy Efficient or Recovery Zone - 60% to 70%
Training within this zone develops basic endurance and aerobic capacity. All easy recovery running should be completed at a maximum of 70%. Another advantage to running in this zone is that while you are happily fat burning you may lose weight and you will be allowing your muscles to re-energise with glycogen, which has been expended during those faster paced workouts. Check out the Fat burning zone page.


The Aerobic Zone - 70% to 80%
Training in this zone will develop your cardiovascular system. The body's ability to transport oxygen to, and carbon dioxide away from, the working muscles can be developed and improved. As you become fitter and stronger from training in this zone it will be possible to run some of your long weekend runs at up to 75%, so getting the benefits of some fat burning and improved aerobic capacity.

The Anaerobic Zone - 80% to 90%
Training in this zone will develop your lactic acid system. In this zone, your individual anaerobic threshold is found - sometimes referred to the point of deflection (POD). During these heart rates, the amount of fat being utilised as the main source of energy is greatly reduced and glycogen stored in the muscle is predominantly used. One of the by-products of burning this glycogen is lactic acid. There is a point at which the body can no longer remove the lactic acid from the working muscles quickly enough. This is your anaerobic threshold or POD. Through the correct training, it is possible to delay the POD by being able to increase your ability to deal with the lactic acid for a longer period of time or by pushing the POD higher.

The Red Line Zone 90% to 100%
Training in this zone will only be possible for short periods. It effectively trains your fast twitch muscle fibres and helps to develop speed. This zone is reserved for interval running and only the very fit are able to train effectively within this zone.

if you still want to do weights and HIIT its up to you

Glucocorticoids (Cortisol). Glucocorticoids are released from the adrenal cortex in response to exercise stress. Unlike testosterone and hGH, they are catabolic. Cortisol is 95% of the glucocorticoids produced in the body. In peripheral tissues, cortisol stimulates lipolysis in adipose cells, increases protein degradation resulting in greater release of lipids, and decreases protein synthesis in muscle cells also releasing amino acids into the circulation (p. 348-349).

If an athlete used anabolic steroids, those steroids would reduce cortisol secretion during and after intense resistance exercise. Carbohydrate supplementation also reduces its secretion. A reduction in cortisol presence should result in an increase in the growth response from exercise. Once again, only highly demanding resistance training provokes an elevated cortisol response. The higher the demand, the greater is the response.MODERATE TRAINING HAS NO EFFECT.
from here Drugs in Sport 3