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The primary goals for managing diabetes are glucose control through education, glucose monitoring, diet, exercise, oral drug therapy, and/or insulin therapy. With proper management, diabetes can be controlled and the complications associated with it can be minimized. Individuals who properly manage their disease can live long, productive, and active lives.
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Individuals with type 1 and type 2 diabetes are strongly encouraged to monitor their blood glucose levels. Normal fasting plasma glucose (FPG) levels are less than 100 mg/Dl (Table 5–2). To determine if an individual has diabetes, a fasting plasma glucose test is advised. Values above 126 mg/dL may be indicative of diabetes mellitus and values between 100 mg/dL and 126 mg/dL are considered pre-diabetes (Box 5–2).
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Patients with diabetes should monitor their glucose levels daily. Blood glucose levels are measured using self-monitored blood glucose (SMBG) equipment (Fig. 5–2), which can be used any time during the day as needed. Although most diabetes patients use SMBG equipment, clinicians and physicians usually assess glucose concentrations over time using glycosylated hemoglobin levels (HbA1c). HbA1c is an indicator of average glycemic control for a period of 2 to 3 months, and normal values for individuals without diabetes range from 4 to 6 percent. HbA1c is the preferred test because it is least affected by daily fluctuations in blood glucose.10
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Individuals with type 2 diabetes should be encouraged to monitor their diet and exercise (Table 5–3). Regular exercise, along with diet management, can improve blood glucose control and insulin sensitivity, and possibly lower medication requirements.12,14,21,37–38,41–42 Exercise can also promote weight loss and reduce body fat,3 resulting in decreases in cholesterol and blood pressure.5,18,21,23,27 Exercise and diet may reduce the amount of oral antidiabetic medication or insulin needed for glucose control.3 In addition, exercise may prevent or delay the onset of type 2 diabetes.3
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Type 1 diabetes patients should also be encouraged to exercise (Table 5–3) and to monitor their diet to control glucose responses. During rest, approximately 10 percent of muscle metabolic requirements come from glucose. During exercise, almost all metabolic requirements come from glucose, rapidly depleting muscle glycogen stores and increasing peripheral glucose utilization. As the demand for glucose increases, hepatic glycogenolysis and gluconeogenesis increases. If exercise commences when insulin levels are insufficient, hepatic glucose production will increase and peripheral utilization will decrease, causing hyperglycemia. After exercise, muscle cells need relatively little insulin to facilitate glucose uptake. This glucose uptake into the muscle cells can last for up to 10 to 12 hours after exercise. If adjustments are not made in diet and insulin therapy, individuals can become hypoglycemic.32
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People with diabetes who have glucose levels equal to or exceeding 250 to 300 mg/dL should delay exercising because high glucose levels indicate insulin deficiency. In contrast, excess insulin will enhance peripheral glucose utilization by muscles and suppress hepatic glucose output, resulting in hypoglycemia. Individuals who have glucose levels that are close to normal before exercise have a higher chance of developing hypoglycemia and should be instructed to either ingest 10 to 20 g of carbohydrates before exercise or decrease their dose of insulin.
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Managing insulin levels during exercise can be difficult for athletes with both types of diabetes. These athletes have to experiment with their insulin and carbohydrate intake to participate safely in exercise. Type 1 and 2 diabetes patients must know the hormonal and metabolic responses of their body to exercising and need to avoid dangerous conditions such as hypoglycemia. To avoid hypoglycemia, type 1 diabetes patients must alter insulin therapy (time, location, dose). Type 2 diabetes patients must alter oral antidiabetic agents (time and dose) or ensure appropriate nutritional intake before or during exercise. In addition, both types 1 and 2 diabetes patients should monitor blood glucose and adjust for exercise intensity and dietary requirements. In many cases, these processes are managed not only by individuals but also by their health-care professionals, including their athletic trainer. Therefore it is the responsibility of the athletic trainer to become familiar with diet, exercise, insulin, and oral antidiabetic therapies.
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Insulin Administration
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Insulin is required to treat gestational diabetes, as well as type 1 and sometimes type 2 diabetes, when diet, exercise, and oral antidiabetic agents cannot control symptoms. Regardless of the type of diabetes, insulin dosage must be individualized and balanced with diet and exercise. Insulin was originally manufactured from the pancreases of pigs and cows but now is being replaced by human insulin synthesized using recombinant DNA techniques. With this new technology, a more purified insulin can be prepared biosynthetically that is structurally identical to human insulin and causes fewer allergic reactions (Fig. 5–3).
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The absorption rate of insulin (and ultimately the patient's glucose control) can vary with the site of administration.28 Most patients with diabetes use the upper arms, thighs, abdomen, and buttocks for insulin administration. It is now recommended that insulin be injected in the same anatomical region each day to control for insulin reactions4 and to ensure similar and consistent absorption (Fig. 5–4). Individuals who exercise should inject insulin into the abdomen to avoid accentuated absorption into exercising muscles.
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When storing insulin, one should closely follow the manufacturer's guidelines. Insulin should generally be kept at room temperature; however, when not in use, it should be refrigerated (not frozen). If an individual is traveling for a long period of time in warm weather, insulin can be stored in an insulated container with a cooling agent. Extreme temperatures (<36° or >86°F) and agitation can produce clumping or precipitation (the separation of solids from a solution or suspension) of insulin and affect potency.
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Visual inspection of insulin before administration is necessary. Clumping, frosting, precipitation, or color change may signify a loss of potency. If unsure about the potency of a vial, individuals should always substitute a new vial of the same type. Expiration dates stamped on each vial should remind the user to dispose of any expired insulin.
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The type of syringe used to inject insulin is also important. Most manufacturers produce small syringes (27–30 gauge with a length of 5/16 or 1/2 inch) that can hold 1.0, 0.5, 0.25, or 0.3-mL. Syringe capacities of 0.25 mL and 0.3 mL are recommended for pediatric and insulin-sensitive patients who require less than 25 units of insulin before meals or snacks.
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Most athletes with type 1 diabetes self-administer their own insulin as needed. However, there may be circumstances under which the athletic trainer may be required to inject insulin. To begin, first clean the injection site with alcohol, moving in a circular fashion outward. Grasp the skin around the injection site to elevate the subcutaneous tissue (about 1″ fat fold) (Fig. 5–5.) With the other hand, position the needle bevel up. Insert the needle at a 45° or 90° angle and release the skin. (Fig. 5–6) Inject the insulin and remove the needle gently at the same angle used for insertion. Cover the injection site with an alcohol sponge and check the site for any bleeding or bruising.
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Insulin Injection Devices
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Currently, there are several ways to deliver insulin: (1) drawing a dose from a vial with an insulin syringe and needle; (2) an insulin pump; or (3) prefilled insulin pens.
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Insulin pumps are a more precise way to mimic normal insulin secretion. An insulin pump, which is a battery-operated device with an internal computer, delivers a predetermined amount of insulin, stored in a reservoir, to a subcutaneously inserted catheter or needle. Insulin pumps are designed to be portable and to deliver a basal amount of insulin throughout the day to replicate insulin secretion from the pancreas, as well as to deliver meal-related boluses (concentrated quantities administered rapidly). Individuals may regulate the amount of insulin pumped depending on their circumstances (e.g., time of meals and exercise). Intermittently, depending on individual habits and insulin responses, the pump's reservoir must be refilled.
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Insulin pumps can also be implanted, delivering insulin continuously. Insulin is stored in a reservoir surgically located subcutaneously in the abdomen or the chest wall. However, there can be several complications, ranging from infection to catheter blockage. Currently, the widespread use of implantable pumps is limited.
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Prefilled insulin pens are convenient for individuals who want to carry insulin discreetly. An insulin pen actually looks like a writing pen and has a cartridge that contains fixed amounts of insulin. Each end of an insulin pen has a specialized function. Located on one end of the insulin pen is a needle similar to the needle found on a syringe. There is a plunger on the other end. To use, the patient selects the desired amount of insulin (measured by a dial on the pen) and then uses the plunger to administer it through the skin. Insulin pens can be disposable or have replaceable cartridges (Fig. 5–7).
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Implications for Athletic Trainers
Individuals who have an insulin pump may engage in school/university-sponsored sports. It is recommended that participation in contact sports be limited to decrease the chances of damage to the insulin pump. However, specific decisions to engage in contact sports must be made by the athlete and the physician and may require special protective devices for the insulin pumps.