Enjoy HIIT Euphoria But Be on the Lookout for Gotcha

Most noteworthy, High Intensity Interval Training (HIIT) is currently, a very popular form of aerobic exercise. First of all, it pushes you to the limit. Also, it helps you to quickly lose weight and fat. Meanwhile, your body gradually adjusts to the HIIT heart rate.

In addition, impatience to follow HIIT guidelines can cause you harm. As a result, you may get delayed gratification from HIIT.

HIIT Heart Rate

First of all, HIIT involves repetitions of short bursts of intense exercises, like sprinting, spinning, rowing, usually anywhere from 20 to 40 seconds. And, the goal, following HIIT guidelines, is to get your HIIT heart rate as high as possible .  As a result of exercising at the HIIT guidelines HIIT heart rate, more fat burns in the shortest amount of time. Furthermore, studies show that your metabolism stays high for at least 24 hours.

HIIT Risks

Most noteworthy,  HIIT does not reduce your stress level. In fact, HIIT actually makes you feel more frantic and stressful.  By the way, HIIT is a very high stress form of exercise.

And, too much HIIT mimics stress. Furthermore, it stops you from sleeping and ruins your appetite.  Therefore, limit HIIT to three times a week because it puts a strain on your nervous system, joints and muscles. In addition, the three times a week restriction applies to the overweight and unfit.

Study Demonstrating Effects of HIIT

Now, a 2015 report in the BMJ demonstrated the negative effects of HIIT on cardiovascular risk factors in a young healthy population.

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    First of all, neither the amount of time spent nor the intensity of resistance training had an effect on blood pressure.
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    Also, those who participated in low-intensity exercises: a) did not show any effect on systolic blood pressure; b) did not show any effect on the total cholesterol; and  c) showed an increase in HDL cholesterol.
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    In addition, those participating in high intensity exercises showed: a) an increase in the systolic blood pressure; b) a small but significant fall in total cholesterol; c) no effect on HDL cholesterol; and d) a significant increase in the amplitude of T wave alternans (an indicator of arrhythmia risk), as well as increased T an R wave amplitudes.  These cardiac electrical changes resulting in structural remodeling and changes in cardiac repolarization stability.

Furthermore, a number of studies point to the dangers of novices jumping right into HIIT workouts. Most of all, bodies of novices gradually adjust to the high HIIT heart rate.


Also, a study of new participants to HIIT, shows significant suppression of their mitochondrial function.  Most of all, mitochondria uses the breakdown of food and oxygen to generate adenosine triphosphate [ATP], the body’s energy resource needed for muscle function.  

In addition, the suppressed mitochondria function results in reducing the cells capacity to consume oxygen. Furthermore, HIIT reduces the cells ability to produce energy needed to fight damage from free radicals released while exercising. Most noteworthy, the free radicals harm healthy cells and cause damage to gene structures.  Consequenntly, the risk of inflammatory issues and degenerative diseases increases.

Yet, the bodies of those who have been doing HIIT for a while have become used to the regimen.  First of all, the exercise helps mitochondrial biogenesis – essentially duplicating the mitochondria in the cells. And, the more mitochondria, the more ATP.   Furthermore, the more ATP, the more energy the body has to pump blood to working organs and muscles.  In addition, the experienced have built up antioxidant enzymes in their bodies to protect against free radicals.



Rhabdomyolysis means dissolution of striated muscle.  Now, this syndrome occurs when muscle injury leads to leakage of muscle cell contents, including electrolytes, myoglobin, and other sarcoplasmic proteins (creatinine phosphokinase [CPK], aldolase, lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase) into blood circulation and extracellular fluid. Furthermore, exertional rhabdomyolysis is characterized by breakdown and necrosis of striated skeletal muscle.


Most noteworthy, this condition occurs frequently in high intensity spinning classes focused on endurance.  First of all, spinning involves repetitive use of the large muscle groups, mainly the gluteus maximus and quadriceps. Also, the risk factors for rhabdomyolysis are related to the intensity (HIIT heart rate using the HIIT guidelines) of the exercise. Furthermore, the risk factors are related to the conditioning of the spinner’s hydration, body temperature, along with other potential contributing factors.  Finally, the risk of rhabdomyolysis has been related to the inadequacy of the spinner’s physical conditioning, as well as the duration of the exercise.

Now, two objective measures used to evaluate the exercise “intensity” experienced by “spinners” include ventilatory threshold and percentage heart rate reserve. Most noteworthy, ventilatory threshold is a measure of cardiovascular fitness, which refers to the point at which lactate begins to accumulate in the blood. And, the percentage heart rate reserve represents the percent difference between the predicted maximal heart rate and exercise heart rate (HIIT heart rate based on HIIT guidlines).  In conclusion, based on these measures spinning can evolve into an intense exercise.

Most of all, exertional rhabdomyolysis causes overproduction of heat, which leads to an increase in intracellular calcium, activation of proteases, and production of reactive oxygen species. In addition, necrosis of skeletal muscle cells releases intracellular contents, causing pain, swelling, and potential end-organ damage in the spinner.

Especially relevant, symptoms of rhabdomyolysis include fatigue, nausea, vomiting, mild muscle soreness and swelling to organ dysfunction.

In conclusion, prevent rhabdomyolysis by proper hydration, rest periods during training, not going too hard and too fast until your body has had time to adjust to the intensity and the exercise.


This vlog or video features Cat Kom (who has only seen one case in 15+ years of Spinning® hard).  Also, the vlog features fellow Studio SWEAT trainer, Elli -  diagnosed with rhabdomyolysis. Furthermore, they discuss the condition to its core. In addition, they provide factual information about the condition. And they debunk false statements along with myths about cycling and rhabdomyolysis. Finally, they discuss what the condition involves, how to avoid it, and how to watch for symptoms.

Leaky Gut Syndrome

First of all, studies released recently show that intense physiological stress (as experienced during HIIT) on the body can trigger Leaky Gut Syndrome.  Most noteworthy, this is a condition in which the gut lining weakens which in turn causes germs and toxins to enter the bloodstream.  In conclusion, this leakage of toxic waste is one cause of Multiple Sclerosis and Chronic Fatigue.  Also, it also has a role in many other diseases.

Atrial Fibrillation

Most noteworthy, engaging in regular endurance physical activities (where the HIIT heart rate is at the top end of HIIT guidlines) puts you at risk of causing permanent structural changes to heart muscles.  Consequently, these changes predisposes participants to arrhythmia (abnormal heart rhythms).

Also, studies released by the European Heart Journal in 2013 suggest you are more likely to get arrhythmia if you have a family history of irregular heartbeats. Furthermore, it’s not just endurance, but regular workouts (with HIIT heart rate near the top end of HIIT guidelines).

Swedish study, from 2014, found that men who exercised intensely for more than 300 minutes a week, at age 30, were 19 percent more likely to have developed atrial fibrillation by age 60 than those exercising less than 60 minutes a week. Furthermore, the risk increased to 49 percent among those: a) who did more than 300 minutes a week at age 30 and; b) who subsequently did less than an hour a week by age 60.  On the other hand, those who cycled or walked briskly for an hour a day or more by age 60 were 13 percent less likely to develop atrial fibrillation than those who did no exercise at all.

Cortisol Downsides

Most of all, levels of cortisol increase dramatically during moments of intense stress.  Yet, these moments are usually very fleeting and your body stops the cortisol.  However, during a HIIT session, your body is under intense stress (HIIT heart rate at or near HIIT guidelines).  As a result, the levels of cortisol increase dramatically.  Furthermore, regular intense workouts means that the body doesn’t have time to recover.  Consequently, the cortisol level remains high in your body.

First of all, cortisol is a hormone emitted (by the adrenal glands) during physical stress.  Also, cortisol stimulates gluconeogenesis (production of glucose) in the liver and increases the breakdown of proteins in the muscles.  Furthermore, the immunosuppressive effects of cortisol puts you at risk of falling ill.  Therefore, the consistent high cortisol levels in your body weakens your immune system.  Consequently it puts you at risk of falling ill.

In conclusion, cortisol in the bloodstream causes more bone tissue to break down than be deposited.  Consequently, this puts you at higher risk of bone fractures and breakages.  Furthermore, the resultant loss in bone density can lead to conditions such as osteoporosis and arthritis.

Cognitive Performance

High intensity physical exercise leads to a decline in cognitive performance in adults.


First of all, a recent study published in Medicine and Science in Sports and Exercise reported that high levels of chronic intense and long duration endurance training on a regular basis leads to decreased libido in men.  Also, too much exercise can lower the number of sex hormones in the body, diminishing sexual desires.  Furthermore, women who over train tend to develop irregular menstrual periods, or stop having them.  The hormonal imbalance is triggered by physical stress, affecting a woman’s interest in sex and her fertility.

Yet, men who trained at the lowest intensities are seven times more likely to report a normal or high libido. While, men who trained the hardest or the longest have decreased libido.

In addition, HIIT suppresses testosterone and the luteinizing hormone. Consequently, HIIT leads to onset of exercise hypogonadal male condition.  Furthermore, this condition occurs in men with years of chronic endurance exercises.  In addition, exercise can cause temporarily lower sperm count in men when the body regularly becomes too overheated.  Most noteworthy, heat damages sperms.

Mental Ill-Health

Most of all, studies show that those who train relentlessly with weights have the same biochemical markers as those with clinical depression - the emission of serotonin and tryptophan are altered by both disorders.  Furthermore, the clinically depressed and the over trained have lowered motivation, insomnia, and irritability.


In conclusion, you get the most health benefits by following HIIT guidelines (with recommended HIIT heart rate).  Furthermore, your body gradually adjust to the HIIT intensity.  In addition, this goes for the beginner, the serious and the not so serious exerciser. Most noteworthy, guard against scaling up intensity beyond your ability.  Finally, HIIT safely provides tremendous benefits to you in term of lowering your weight and losing fat.