05 Oct 2014

High-Intensity Workouts and the 6 Damaging Effects it has on our Metabolic System

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By: Geoff Rubin, Fitness Propelled, CPT/CIFT/TRX II

High intensity training has reached an all-time high in popularity, mostly because it provides people what they want = results! As a trainer, I constantly hear about high intensity training and all the questions that surround it. Is high intensity training right for me?, is it damaging to the body?, will it help me get that chiseled Tony Horton six pack? Personally, I am a non-believer in the “high-intensity” model and feel that it has narrowed the general public’s view on understanding effective training options. Such options include specific cardiovascular programs with regulated HR monitoring, anaerobic conditioning programs built for hypertrophy / muscle development and core conditioning programs to name a few.

While “high intensity” programs often do deliver the results it is important to understand that these programs can also lead to the following six types of metabolic damage which could keep you from reaching your fitness goals:

1) Elevated blood lactate:

When muscles involved in exercise can no longer meet energy demands through aerobic metabolism they will tap into the ATP-PC and Glycolysis energy pathways to produce ATP anaerobically (without oxygen). One by-product of anaerobic metabolism is lactic acid, which can accumulate quickly during high intensity exercise. The Onset of Blood Lactate (OBLA), commonly called the lactate threshold (LT), is a physiological marker that indicates an elevation in blood acidity, which can inhibit energy production and the ability to do physical work, leading to fatigue. When you feel that burning sensation in your muscles, it’s an indication of OBLA and a sign that it is time for a lower-intensity active recovery interval.

2) Acidosis:

Anaerobic exercise also elevates levels of hydrogen ions (H+), both of which increase blood acidity reducing the levels of oxygen and other nutrients available for aerobic energy production. In extreme cases acidosis can cause severe damage to muscle tissue resulting in a breakdown of muscle protein called myoglobin. When myoglobin is broken down and subsequently enters the blood stream this could ultimately lead to rhabdomyolysis. Rhabdomyolysis can inhibit normal function of the kidneys, potentially leading to hospitalization or possibly death, so it is extremely important to listen to your body and not push physical exertion past your normal comfort levels.

3) Gluconeogenesis:

Protein is normally used to repair tissue damaged during exercise and promote the growth of new muscle. Carbohydrates are converted to glycogen and used for ATP production during anaerobic exercise. Fatty acids require oxygen and take longer to convert to ATP, making them an inefficient energy source for high intensity exercise. When high intensity exercise lasts for extended period of time, the body will convert protein to ATP in a process callused gluconeogenesis, reducing the amount of protein available for muscle growth. The process of converting amino acids (the building blocks of protein) to ATP elevates levels of ammonia, further increasing blood acidity and the risk of acidosis.

4) Increased levels of human growth hormone (HGH):

When muscle damage occurs due to exercise,  the body will produce higher levels of HGH to repair this damaged muscle. This is the metabolic response that most body builders hope for because this increase in HGH can lead to an increase in muscle size. So if your goal is to add lean muscle mass, this is a good thing and one of the most important benefits of high intensity training. But if your goal is to simply lose weight, then all of that high intensity exercise could be having an opposite effect, increasing both muscle size and net bodyweight. One thing to keep in mind is that as you add lean muscle mass, you can increase your resting metabolism, elevating the amount of calories you burn at rest.

5) Increased glycogen storage in muscle tissue:

High intensity exercise frequently relies on muscle glycogen to produce ATP. As a result of extended exposure to high intensity training, muscles become more efficient at storing glycogen for future use. But it’s important to note that when stored in muscle tissue, one gram of glycogen holds approximately three to four grams of water. If weight loss is your goal then training your muscles to store glycogen (and water) may have an impact on the scale that you weren’t hoping for. Remember that weight is one number, but body composition may be a more important measure of overall health.

6) Over-training:

Excessive exposure to high intensity exercise without sufficient rest periods can lead to Overtraining Syndrome (OTS). Signs of OTS include reduced immune system function (leading to lingering colds or flu-like symptoms), elevated heart rate, sleeplessness, increased irritability, weight gain (despite exercise) and a significant decrease in physical performance. It can take anywhere from 24 to 96 hours to fully recover from a metabolically demanding high intensity exercise session.

We know that “High – Intensity” training is here to stay, however, it is important to know the impacts that certain styles of training can and does have on our bodies. It’s always best to be informed.

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