Our bodies are complex machines. And how exercise interacts with our various systems is part of an entire field of study in medicine. We don’t know everything about it, but we do know exercise has a lot to do with our metabolism, and cellular metabolism in particular. Cellular metabolism is controlled by various hormones in our bodies. Some of these hormones are produced in even greater quantities during exercise. They become part of a chain reaction of events in our bodies. It’s interesting to know what’s going on beneath the surface.
Creating Energy in our Cells
First, it helps to understand exactly what happens with our muscles during exercise. Muscles require ATP or energy to make them work, or contract. There are two ways we create ATP in our cells. The standard way is by oxidative metabolism, which uses oxygen. The other way is glycolysis, which uses glucose, or sugar, to release energy. When we are going about our daily routines, or even exercising moderately, we use oxygen to create energy. But extreme exercise requires more ATP, so cells switch over to glycolysis. Glycolysis does not produce as much energy as regular oxidative metabolism; it’s less efficient. But it’s like a supercharged turbo boost that draws on reserves of glycogen or stored glucose to create energy. Then, it produces lactic acid as a byproduct, which has to be further metabolized. You know that feeling when you have produced too much lactic acid and it hasn’t been metabolized yet, like when you’re carrying a heavy suitcase and your muscles fatigue or cramp.
Insulin, Glucose and Diabetes
How does the glucose (sugar) get into our cells to be used? Insulin is a key hormone produced by the pancreas that controls the transfer of glucose into cells, which is then used to make energy. It also controls how glucose is stored, including being stored as fat.
In Type 1 Diabetes, the pancreas fails to produce any insulin. In Type 2 Diabetes, you produce insulin, but it’s not as effective in moving the glucose into cells. Insulin resistance is when you produce insulin, but it doesn’t do its job very well, so glucose often gets stored as fat instead of being transferred into cells for energy. Insulin resistance is more commonly associated with Type 2 Diabetes as it’s viewed as a precursor to the condition in many adults. Type 2 Diabetes also involves high blood glucose, obesity, hypertension and a high homocysteine level.
Hormones and Exercise
When we exercise, our muscles demand more energy. Often our cells go into the glycolysis mode to produce that needed energy. So the pancreas is stimulated to produce insulin to deliver the glucose for it. (Type 1 Diabetes patients respond differently to exercise since the insulin is not released from the pancreas.)
All exercise raises blood glucose somewhat, but intense exercise such as heavy resistance training, sprinting or high intensity intervals causes an immediate rise in your blood glucose and leads to an exaggerated release of hormones. These include adrenaline, norepinephrine, glucagon, growth hormone and cortisol. These hormones all help raise glucose so that your cells can create the fast energy needed for the exercise at hand. Intense exercise can potentially cause a large increase in blood glucose because of your body’s exaggerated release of glucose-raising hormones such as adrenaline and glucagon, according to a paper published in Diabetes In Control. This may not be what you were expecting, thinking that intense exercise uses up all the stored glucose, but therein lies the paradox. This is especially important for diabetics to understand.
Insulin Resistance and Exercise
The article goes on to say that you may be more insulin resistant after intense exercise due to the production of these hormones. So if you are diabetic, watch for elevated blood glucose, you may need extra insulin to bring back down your blood glucose. The article cites a study where exercisers with Type 1 Diabetes on insulin pumps had elevated blood glucose for nearly two hours, while those with Type 2 Diabetes had elevated blood glucose for one hour. Elevated blood glucose has been shown to slow down fat utilization.
Exercise Improving Hormones
On a positive note, exercise has so many benefits because of the hormones it helps produce. Testosterone is a male hormone known to be necessary to build and maintain muscle mass. High intensity resistance training has been shown to have a beneficial effect on testosterone in men, and cardio and resistance training at a moderate intensity has shown similar results on the sex hormones in women. The type of strength training also can determine what’s happening with your hormones. Another study found that back-squats can change the hormonal state of the body after an intense resistance training workout, whereas a bench press, because it uses less muscle mass, has almost no influence on testosterone and cortisol. This is a complicated field and everything in the body is dependent on other hormones and signals, which is why our bodies are the most amazing machines ever.
Definitions of Terms:
Insulin – This hormone is produced by the pancreas and helps move the glucose in the blood into muscle cells and fat cells; it also regulates the storage of glucose
Blood glucose – The amount of glucose (sugar molecules) in your blood. Insulin is the only hormone that lowers your blood glucose.
Adrenaline – This hormone is produced by the medulla of the adrenal gland during intense exercise that stimulates muscle breakdown and mobilized fatty acids from fat cells
Cortisol – This hormone is produced by the cortex of the adrenal gland and is released under stress and during exercise
Glucagon – This hormone is produced by the pancreas and is involved in controlling blood sugar (glucose) levels
Glucose – Simple sugar molecules used to create energy
Glycogen – This form of glucose (sugar) is stored in muscles and liver for use in strenuous exercise
Glycolysis – A faster but less efficient way we create energy in our cells than oxidative metabolism, which uses oxygen
Homocysteine – An amino acid naturally present in the body that in high levels is a precursor for arteriosclerosis
Hormone – A molecule produced by glands that signals internal mechanisms in the body
Lactic acid – Glycogen in muscles is broken down into lactic acid during exercise
Oxidative metabolism – The use of oxygen to create energy in cells Testosterone – Hormone produced in the testes and adrenal gland. Men have more of it than women. It produces strength in muscles and its production is stimulated by high intensity resistance training.