When your temperature rises above 102°F, your muscles often start to burn, when your temperature is over 104°F you will usually become short of breath and when your temperature rises above 105°F, you will often have signs of brain distress, such as a headache, blurred vision, ringing in your ears, dizziness, nausea and passing out.
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Your muscles are designed to work well only in a narrow range of almost zero acidity. Arterial blood works best with no acid at all. Acidity is measured by the concentration of hydrogen ions (pH). A pH of 7.0 is neutral, midway between very acidic (pH of 1) and very alkaline (pH of 14). At rest, muscle pH is about 6.9, while arterial blood is about 7.4."
As you begin to exercise, the increased use of muscle glycogen for energy produces lactic acid and pyruvic acid, two substances that contain a lot of hydrogen ions (H+), which drive muscle and blood pH down into the acid zone. (Incidentally, pH is derived from the French pouvoir hydrogene, meaning hydrogen power.) The harder you exercise, the quicker your muscles go acidic. When muscle pH drops below 6.5, the acidity disrupts all sorts of links in the energy chain. For example, the enzyme phosphofructokinase is the rate limiting step in muscle use of glycogen. Below pH 6.5, it stops working altogether. And, acidity also reduces muscle power directly by inhibiting the contractile action of muscle fibres, so unless you reduce acidity during exercise, your muscles will tie up."
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Another inhibitor of exercise, happening simultaneously with the accumulation of acid, is the accumulation of ammonia; anaerobic and endurance exercise produces a lot of it. Ammonia is toxic to cells, it reduces the formation of glycogen, and it inhibits the energy cycle. Although we still do not know how much ammonia contributes to fatigue, we do know that the higher your blood ammonia, the poorer your performance.
Blood flow through tissues is matched with the metabolic needs of the tissues. During exercise, blood flow through tissues is changed dramatically. Its rate of flow through exercising skeletal muscles can be 15 to 20 times greater than through resting muscles.
The increased blood flow is the product of local, nervous, and hormonal regulatory mechanisms. When skeletal muscle is resting, only 20% to 25% of the capillaries are open, whereas during exercise 100% of the capillaries are open. Low oxygen tensions resulting from greatly increased muscular activity or the release of vasodilator substances such as lactic acid, carbon dioxide, and potassium ions causes dilation of precapillary sphincters. As a direct result, resistance to blood flow in skeletal muscle decreases. Therefore blood is forced into skeletal muscles.
The movement of skeletal muscles that compresses veins in a cyclic fashion and the constriction of veins greatly increase the venous return to the heart. The resulting increase in the preload and increased sympathetic stimulation of heart result in elevated heart rate and stroke volume, which increases the cardiac output. As a consequence, the blood pressure usually increases by 20 to 60 mm Hg, which helps sustain the increased blood flow through skeletal muscle blood vessels. In response to sympathetic stimulation, some decrease in the blood flow through the skin can occur at the beginning of exercise. However, as the body temperature increases in response to the increased muscular activity, temperature receptors in the hypothalamus are stimulated. As a result, vasodilation of blood vessels in the skin occurs. Resulting in the skin turning a red or pinkish colour, and a great deal of excess heat is lost as blood flows through the dilated blood vessels.
The overall effect of exercise on circulation is to greatly increase the blood flow through exercising muscles and to keep blood flow through other organs at a low value, which is just adequate to supply their metabolic needs.
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As far as individual differences go, they could well account for many of the differences in the results, not to mention the temperature of the environment in which the individual tests took place. There are many factors that need to be considered in the analysis of the subjects’ results.
These include –
- Age
- Gender
- The subjects personal fitness
- Any illnesses/conditions that the subject may be experiencing
- If one or more of the subjects have only just finished some sort of physical exertion prior to taking the test.
Age
Newborn babies and young children have a significantly higher heart rate that that of an older child/young adult.
OAP’s and the aged also have a slightly higher heart rate than that of the norm, as normative data usually collected is concerning and regarding the average adult.
Gender
Throughout childhood, a difference in heart rate between males and females is not that significant, but as adulthood is reached, it is noted that men tend to have a slightly lower resting heart rate than their female counterparts.
The subjects personal fitness
As stated previously, those who partake in physical exertion regarding the aerobic system often, will, as a result of cardiac hypertrophy, have a lower resting and working heart rate.
The enlargement of the heart due to training allows it to pump the same cardiac output, with less beats. This is because the enlargement results in a larger stroke volume.
Also, the subject’s frequent exposure to aerobic workouts would enable the subject to recover quicker, and return to resting rate a lot quicker.
Any illnesses/conditions that the subject may be experiencing
Should a subject be suffering with an illness, as trivial as a minor cold, the body would still be required to work twice or three times as hard to fight off infection.
The subjects resting and working heart rates would be significantly higher, the subjects temperature would be a lot higher. The subject would not recover as quickly following exercise and would not only find it hard to complete the moderate intensity section, but would not be able to competently complete the chest press section of the investigation.
The results would be very misguiding and inaccurate.
If one or more of the subjects have only just finished some sort of physical exertion prior to taking the test.
Had a subject undergone an intense training session immediately prior to the investigation, the results would be very inaccurate.
The training session would have a similar effect on the body as an infection would.
It would require the body to work harder than usually required to perform such a task and it would also raise heart rate, blood pressure, and also lengthen the time taken for a subject to recover.
