PART 4 of the Series (THE MEAT IS IN THE CONCLUSION)
Glucose Utilization during Exercise- A Function of the Insulin
Insulin, though not mentioned in Table 2, is also important in both aerobic and anaerobic exercise. As discussed, during these two types of exercise, glucose is one of the fuels that energize the body. And so glucose production has been shown to be stimulated by the catecholamines (and at rest, the glucagon). But how can the glucose produced and delivered to the blood be consumed by the cells in the body? The answer to this is through insulin coming from the pancreas.
Insulin facilitates entry of glucose into the cells in order for it to be transformed into energy (glucose utilization). Without insulin, glucose would only be left within the plasma and would be useless. This would also lead to complications as seen in Diabetes Mellitus patients.
The effect of insulin to the body processes is naturally delayed, as seen in Figure 4. We can only observe sudden rush in insulin secretion after exercise (Scheen et al., 1998). This is because the catecholamines limit such secretion during exercise, since the body needs to produce glucose into the blood as energy reserves. And presence of insulin would impede such process.
However after exercise when glucose within the muscle fibers and other cells is depleted, the glucose reserves in the blood have to be mobilized towards the cells to replenish such depletion. This is where insulin comes into play.
The above concepts are useful when choosing what type of exercise a Diabetes Mellitus (DM) patient (especially Type I) is to perform. If we are to exercise a DM patient, what type of exercise is applicable? In order to answer this we have to consider which type of exercise stimulates more glucose production. Obviously this would be the anaerobic type. But as stated glucose produced in this occasion stays in the blood. And so the tendency to have hyperglycemia is natural. And among the normal individuals, this would not be a problem since post-exercise hyperinsulinemia occurs immediately. This hyperinsulinemia would then control excessive blood sugar. But among DM patients, hyperinsulinemia does not take place. And so hyperglycemia remains leading to worsening of the patients’ conditions.
On the other hand, what happens during aerobic exercise? Scheen et al. (1998) do not deny that glucose in blood increases during aerobic exercise (but not as much as in anaerobic). And together with this insulin secretory rate decreases. Nevertheless this would not be a problem. Since the glucose level during aerobic exercise does not cause hyperglycemia, unlike in anaerobic exercise. Also, increased peripheral blood flow augments total insulin delivery to muscles and thus compensates at least in part for the decreases plasma insulin concentration.
We can therefore conclude that aerobic exercise is better among DM patients than anaerobic exercise. However if we still opt to continue with anaerobic programs, we have to ensure that patient has administered insulin infusion before activity.
Oxidation in Aerobic Activity- A Role of the Thyrotropin and Thyroid Hormones
Another question that has to be answered is this: how does the body constantly sustain oxygen to produce aerobic energy? This is through the thyrotropin (TSH) and thyroid hormones. According to a certain Dr. Kennedy, TSH and the thyroid hormones control the rate of oxidation or oxygen utilization in energy production. Figure 5 shows the increase in TSH in response to aerobic exercise.
Without TSH and the thyroid hormones, energy from fats cannot be utilized. This is especially manifested in patients with hypothyroidism, as their physique shows increased fat deposition.
On the other hand excess of these hormones further increases metabolism and fat utilization. This condition results in being ectomorph (as in patients with hyperthyroidism).
Growth in Exercise
Lastly, let us talk about growth in exercise. Growth is another important result of exercise. In an individual exposed to long-term exercise, one of the most significant manifestations of growth is hypertrophy of muscles. We can especially observe this muscle building process during resistance training exercise, which might be considered as anaerobic in nature.
In the case of a muscle fiber, it must be broken down systematically through resistance training. The fiber responds with an increase in the synthesis of new contractile proteins that result in the fiber becoming larger and stronger. This growth response is the result of the presence of potent anabolic (muscle-building) hormones whose function is to promote protein synthesis. And so we can infer that protein synthesis does not only occur to produce energy. It also occurs with the aid of such hormones in order to promote growth especially at the muscular level. The anabolic hormones involved are GH, IGF-1, and the testosterone (Taylor et al., 2000). As more fibers are involved, a greater hormonal response is necessary, and thus greater changes in whole muscle are possible (Stout).
Conclusion
Truly the endocrine system presents different facets of response during exercise. A more comprehensive description of these facets would be more complicated. And so this discourse has presented the basic activities our endocrine glands do in order to sustain homeostasis and provide adaptations to the body in order for it to keep up with the demands of activities. Understanding these basic concepts can give us a huge foundation if we are to pursue more advanced endocrinology. These concepts would also come in handy when we are to choose which exercises are we to prescribe for patients with different conditions and different needs.
And so if we opt to improve strength, agility, and speed, and increase energy storage for immediate use, then anaerobic exercise will be the exercise of choice. It should be since it utilizes our catecholamines and the growth hormones to achieve our goals. Variants of aerobic exercise are those that involve high intensity but low duration exercises, like weights training, sprint, tennis, and even soccer.
But if our goal is weight and fat loss, or even increase in general body endurance then aerobic exercise shall be our choice. It does not only maximize the use of oxygen to burn our fats, it also teaches our body to conserve energy in order to prevent immediate, untimely muscular and cardiovascular fatigue. Aerobic exercise does this through its effect on the body’s release of cortisol, thyroxine, and sex hormones. Aerobic activity or exercise includes jogging, brisk walking, marathon run, treadmill exercise for more than 20 minutes, and even cross-country skating.
And lastly take note that the time of the day when we exercise affects the results. And so if we want to maximize the use of our hormones (like growth hormones and thyroid hormones) for improved growth and fat burning, then evening exercise will do the trick.
THE END>>>
Insulin, though not mentioned in Table 2, is also important in both aerobic and anaerobic exercise. As discussed, during these two types of exercise, glucose is one of the fuels that energize the body. And so glucose production has been shown to be stimulated by the catecholamines (and at rest, the glucagon). But how can the glucose produced and delivered to the blood be consumed by the cells in the body? The answer to this is through insulin coming from the pancreas.
Insulin facilitates entry of glucose into the cells in order for it to be transformed into energy (glucose utilization). Without insulin, glucose would only be left within the plasma and would be useless. This would also lead to complications as seen in Diabetes Mellitus patients.
The effect of insulin to the body processes is naturally delayed, as seen in Figure 4. We can only observe sudden rush in insulin secretion after exercise (Scheen et al., 1998). This is because the catecholamines limit such secretion during exercise, since the body needs to produce glucose into the blood as energy reserves. And presence of insulin would impede such process.
However after exercise when glucose within the muscle fibers and other cells is depleted, the glucose reserves in the blood have to be mobilized towards the cells to replenish such depletion. This is where insulin comes into play.
Figure 4. Mean profile of Insulin Secretion Rate (ISR) in the resting condition (unshaded) and in the exercise condition (shaded)
The above concepts are useful when choosing what type of exercise a Diabetes Mellitus (DM) patient (especially Type I) is to perform. If we are to exercise a DM patient, what type of exercise is applicable? In order to answer this we have to consider which type of exercise stimulates more glucose production. Obviously this would be the anaerobic type. But as stated glucose produced in this occasion stays in the blood. And so the tendency to have hyperglycemia is natural. And among the normal individuals, this would not be a problem since post-exercise hyperinsulinemia occurs immediately. This hyperinsulinemia would then control excessive blood sugar. But among DM patients, hyperinsulinemia does not take place. And so hyperglycemia remains leading to worsening of the patients’ conditions.
On the other hand, what happens during aerobic exercise? Scheen et al. (1998) do not deny that glucose in blood increases during aerobic exercise (but not as much as in anaerobic). And together with this insulin secretory rate decreases. Nevertheless this would not be a problem. Since the glucose level during aerobic exercise does not cause hyperglycemia, unlike in anaerobic exercise. Also, increased peripheral blood flow augments total insulin delivery to muscles and thus compensates at least in part for the decreases plasma insulin concentration.
We can therefore conclude that aerobic exercise is better among DM patients than anaerobic exercise. However if we still opt to continue with anaerobic programs, we have to ensure that patient has administered insulin infusion before activity.
Oxidation in Aerobic Activity- A Role of the Thyrotropin and Thyroid Hormones
Another question that has to be answered is this: how does the body constantly sustain oxygen to produce aerobic energy? This is through the thyrotropin (TSH) and thyroid hormones. According to a certain Dr. Kennedy, TSH and the thyroid hormones control the rate of oxidation or oxygen utilization in energy production. Figure 5 shows the increase in TSH in response to aerobic exercise.
Figure 5. Mean plasma TSH during resting condition (unshaded) and exercise condition (shaded).
Without TSH and the thyroid hormones, energy from fats cannot be utilized. This is especially manifested in patients with hypothyroidism, as their physique shows increased fat deposition.
On the other hand excess of these hormones further increases metabolism and fat utilization. This condition results in being ectomorph (as in patients with hyperthyroidism).
Growth in Exercise
Lastly, let us talk about growth in exercise. Growth is another important result of exercise. In an individual exposed to long-term exercise, one of the most significant manifestations of growth is hypertrophy of muscles. We can especially observe this muscle building process during resistance training exercise, which might be considered as anaerobic in nature.
In the case of a muscle fiber, it must be broken down systematically through resistance training. The fiber responds with an increase in the synthesis of new contractile proteins that result in the fiber becoming larger and stronger. This growth response is the result of the presence of potent anabolic (muscle-building) hormones whose function is to promote protein synthesis. And so we can infer that protein synthesis does not only occur to produce energy. It also occurs with the aid of such hormones in order to promote growth especially at the muscular level. The anabolic hormones involved are GH, IGF-1, and the testosterone (Taylor et al., 2000). As more fibers are involved, a greater hormonal response is necessary, and thus greater changes in whole muscle are possible (Stout).
Conclusion
Truly the endocrine system presents different facets of response during exercise. A more comprehensive description of these facets would be more complicated. And so this discourse has presented the basic activities our endocrine glands do in order to sustain homeostasis and provide adaptations to the body in order for it to keep up with the demands of activities. Understanding these basic concepts can give us a huge foundation if we are to pursue more advanced endocrinology. These concepts would also come in handy when we are to choose which exercises are we to prescribe for patients with different conditions and different needs.
And so if we opt to improve strength, agility, and speed, and increase energy storage for immediate use, then anaerobic exercise will be the exercise of choice. It should be since it utilizes our catecholamines and the growth hormones to achieve our goals. Variants of aerobic exercise are those that involve high intensity but low duration exercises, like weights training, sprint, tennis, and even soccer.
But if our goal is weight and fat loss, or even increase in general body endurance then aerobic exercise shall be our choice. It does not only maximize the use of oxygen to burn our fats, it also teaches our body to conserve energy in order to prevent immediate, untimely muscular and cardiovascular fatigue. Aerobic exercise does this through its effect on the body’s release of cortisol, thyroxine, and sex hormones. Aerobic activity or exercise includes jogging, brisk walking, marathon run, treadmill exercise for more than 20 minutes, and even cross-country skating.
And lastly take note that the time of the day when we exercise affects the results. And so if we want to maximize the use of our hormones (like growth hormones and thyroid hormones) for improved growth and fat burning, then evening exercise will do the trick.
THE END>>>
