Lec 8 Diabetes and Exercise - Aerobic

DIABETES AND EXERCISE - AEROBIC

INTRODUCTION

This study guide outlines key concepts related to aerobic exercise and its impact on diabetes management, particularly highlighting recommendations, benefits, potential risks, and strategies to mitigate exercise-induced complications such as hypoglycemia.

LEARNING OUTCOMES

  • Outline evidence-based recommendations for aerobic exercise in people with diabetes.

  • Describe the benefits and possible complications of aerobic exercise in people with diabetes.

  • Identify strategies to reduce the risk of exercise-induced hypoglycemia in insulin-treated clients.

  • Describe the effect of exercise intensity on the blood glucose response to aerobic exercise in people with diabetes.

RECOMMENDATIONS - PHYSICAL ACTIVITY (PA)

  • Medical Clearance: Medical clearance is not necessary for individuals with diabetes who are complications-free before beginning low to moderate-intensity exercise.

  • Factors Influencing Requirement for Clearance: Decisions are based on:

    • Current physical activity levels.

    • Presence of signs or symptoms of known cardiovascular (CV), metabolic, or renal diseases.

    • Desired exercise intensity.

  • Exercise Guidelines:

    • Engage in >150 minutes per week of moderate-to-vigorous intensity aerobic exercise, spread over at least three days, with no more than two consecutive days without activity.

    • Include 2-3 sessions per week of resistance exercise on non-consecutive days.

    • Incorporate 2-3 sessions per week of flexibility and balance training, particularly for older adults.

    • Increase daily incidental physical activity for additional health benefits.

    • Supervised training is preferred over non-supervised training (Colberg et al., 2016).

CLINICAL CONSIDERATIONS

The challenges of blood glucose management vary significantly with:

  • Diabetes type: Different types of diabetes (Type 1, Type 2) can result in different responses to exercise.

  • Activity type: Different exercises can affect glucose levels in various ways.

  • Presence of complications or co-morbid conditions: Conditions such as hypertension or neuropathy can impact exercise safety and efficacy.

  • Medications: The types and dosages of diabetes medications can influence blood glucose levels during exercise.

AEROBIC EXERCISE

  • Definition: Aerobic exercise involves repeated and continuous movements of large muscle groups, relying primarily on aerobic energy systems.

RECOMMENDATIONS - AEROBIC EXERCISE

  • Frequency: 3-7 days per week, with no more than two consecutive days without exercise.

  • Intensity: Moderate to vigorous intensity.

  • Duration: A minimum of 150 minutes per week, with each exercise bout lasting at least 10 minutes and aiming for 30 minutes per day on most days.

  • Type: Focus on prolonged, rhythmic activities utilizing large muscle groups; may include continuous or interval training.

  • Progression: Emphasize increasing exercise intensity when fitness improvement is the primary goal and not contraindicated by complications (Colberg et al., 2016).

BENEFITS OF EXERCISE

  • Improved Insulin Sensitivity: Enhancements acutely facilitate glycogen resynthesis and lead to sustained improvements with training.

  • Improved Blood Glucose Control: Regular aerobic exercise leads to better blood glucose and lipid profiles, delaying the onset and progression of diabetes-related complications.

  • Increased Aerobic Fitness: Exercise improves physical fitness measures, such as increases in mitochondrial density, capillary density, and oxidative enzyme levels.

  • Improved Quality of Life: Participants often experience a reduction in central obesity and improved blood pressure control (Colberg et al., 2016).

AEROBIC EXERCISE AND TYPE 1 DIABETES (T1D)

  • Current Recommendations:

    • Physical activity is recommended for all individuals with diabetes, with the understanding that blood glucose responses can vary based on activity type and timing, necessitating different adjustments.

    • Low to moderate-intensity exercise raises the risk of hypoglycemia in insulin-treated clients (Colberg et al., 2016).

EXERCISE + INSULIN AND GLUC TRANSPORTER 4 (GLUT4)

  • Mechanism:

    • Exercise induces an increase in glucose uptake, facilitated by the synergistic effects of exercise and insulin action.

    • However, this increased uptake also heightens the risk of hypoglycemia during and after exercise.

STRATEGIES FOR MANAGING HYPOGLYCEMIA

  • Current Recommendations: Individuals engaging in exercise typically require adjustments in carbohydrate intake and/or reduced insulin administration.

    • Continuous glucose monitoring systems are effective for tracking blood glucose levels during exercise when they complement regular blood testing.

  • Carbohydrate (CHO) Intake Recommendations:

    • 10-15 g of CHO for low to moderate-intensity exercise every 30-60 minutes when insulin levels are low.

    • 30-60 g of CHO for low to moderate-intensity exercise when insulin levels are high.

    • Timing and quantity of CHO depend on blood glucose levels pre-exercise (Colberg et al., 2016).

PRE-EXERCISE BLOOD GLUCOSE LEVELS (BGL) AND CHO INTAKE

Pre-Exercise BGL (mmol/L)

CHO Intake

<5.0

15-30 g (depending on intensity and duration)

5.1 - 8.3

10-60 g at onset of exercise (depending on intensity, duration, and insulin)

8.4 - 13.9

Delay CHO consumption

>14

Check for ketones; if absent, low to moderate exercise is permissible; avoid intense exercise

STRATEGIES FOR INSULIN ADJUSTMENTS


  • Reduction in Insulin Administration: Insulin doses may be adjusted down by 25%-75% during and after aerobic exercise; this is crucial for planned activities only.


  • Exercise Intensity Impact on Insulin Reduction:

    Exercise Intensity

    Reduction (%)


    ~30 min at ~25% VO₂max

    -25%


    ~60 min at ~25% VO₂max

    -50%


    ~30 min at ~50% VO₂max

    -50%


    ~60 min at ~50% VO₂max

    -75%


    ~30 min at ~75% VO₂max

    -75%


    >80% VO₂max

    No reduction

    *Note: Recommendations apply specifically for activities commenced within 90 minutes post-insulin administration (Colberg et al., 2016).

    POST-EXERCISE HYPOGLYCEMIA

    • During Exercise: Increased glucose uptake occurs in skeletal muscle due to:

      • Muscle contraction.

      • Insulin activity.

    • After Exercise: The risk of hypoglycemia can persist for up to 30 hours post-exercise, due to:

      • Enhanced insulin sensitivity.

      • Replenishment of muscle glycogen stores.

      • GLUT4 availability.

      • Diminished hormonal responses to hypoglycemia.

    EXERCISE INTENSITY AND TYPE 1 DIABETES

    • Low to Moderate Intensity: Tends to increase the risk of hypoglycemia.

    • High Intensity: Associated with a potential increase in blood glucose levels, leading to hyperglycemia.

      • Adrenal response (e.g., adrenaline and noradrenaline) can influence these dynamics.

    ATHLETES WITH T1D

    • Performance: T1D should not impede an athlete's ability to achieve optimal performance, illustrated by athletes across sports such as AFL.

    AEROBIC EXERCISE FOR INDIVIDUALS WITH IMPAIRED GLUCOSE TOLERANCE (IGT)/TYPE 2 DIABETES (T2D)

    • Current Recommendations:

      • Daily exercise is advised, ensuring no more than two days elapse between sessions to enhance insulin action.

      • A combination of aerobic and resistance exercise yields optimal glycemic and health benefits.

      • Recommendations include 150 minutes per week of aerobic activity alongside dietary changes aimed at achieving a weight loss of 5%-7% to prevent or delay the onset of T2D, especially for those at high risk, including those with prediabetes (Colberg et al., 2016).

    HYPOGLYCEMIA IN INDIVIDUALS WITH T2D

    • Response to Treatment: Hypoglycemia primarily affects clients treated with insulin or sulfonylureas; acute complications are often linked to hyperglycemia from conditions or medications.

    CLINICAL CONSIDERATIONS - COMORBIDITIES

    • Hypertension: Individuals should avoid high-intensity aerobic exercise unless cleared by a healthcare provider.

    • Peripheral Neuropathy: Best practice includes keeping feet dry, using appropriate shoes, engaging in non-weight bearing activities, and performing daily foot inspections.

    • Autonomic Neuropathy: Risk factors involve postural hypotension; therefore, activities should avoid rapid positional changes. Recommendations include using Rate of Perceived Exhaustion (RPE), avoiding extreme temperatures, and maintaining hydration.

    • Retinopathy: It's recommended to avoid vigorous activities that significantly raise blood pressure and dangerous activities due to visual impairment (e.g., nighttime cycling).

    • Nephropathy: It's suggested that individuals start with low-intensity activities and gradually increase the volume if significantly deconditioned.

    CLINICAL CONSIDERATIONS - MEDICATIONS

    • Insulin/Sulfonylureas: Deficiencies can lead to hyperglycemia and ketoacidosis; excess can lead to hypoglycemia.

    • Diuretics: Affect fluid and electrolyte balance, necessitating careful monitoring during exercise.

    • β Blockers: These blunt adrenergic responses, potentially reducing physiological responses to hypoglycemia and inappropriate heart rate and blood pressure responses during exercise.

    • ACE Inhibitors: Enhancing insulin sensitivity can result in increased hypoglycemia risk.

    • Cholesterol-Lowering Medications: Statins may result in muscle weakness/inflammation and poor blood glucose control, while nicotinic acid may cause hypotension and impaired glucose tolerance.

    SEDENTARY BEHAVIOUR

    • Definition: Sedentary behavior refers to waking activities with low energy expenditures such as TV viewing and desk work.

    • Health Impact: Increased sedentary behaviors correlate with poor glycemic control and heightened mortality/morbidity risks.

    CURRENT RECOMMENDATIONS FOR SEDENTARY BEHAVIOUR

    • Adults, especially those with T2D, should minimize daily sedentary time.

    • Interrupt prolonged sitting every 30 minutes with light activity to promote blood glucose management.

    • These recommendations should supplement, not replace, increased structured and incidental activities (Colberg et al., 2016).

    BEHAVIOUR CHANGE STRATEGIES

    • Interventions focusing on behavior modification have proven to elevate physical activity levels and decrease HbA1c in clients with diabetes. Strategies include:

      • Emphasizing past successes in behavior change.

      • Identifying barriers and engaging in problem-solving.

      • Utilizing follow-up prompts to encourage participation.

      • Providing clear information on when and where to engage in recommended behaviors.

      • Regular reviews of individual behavioral goals (Colberg et al., 2016).

    REVIEW QUESTIONS

    1. Describe the benefits of aerobic exercise in the management of diabetes.

    2. Why is high-intensity exercise associated with a lower risk of hypoglycemia in T1D?