Nutrition and Physical Activity

Energy Needs for Physical Activity

Physical activity increases the body's energy requirements. The amount of energy needed depends on several factors:

• Intensity, Duration, and Frequency of Activity: More intense, longer, and more frequent exercise increases energy needs.

• Characteristics of the Exerciser: Age, sex, body size, and fitness level all influence energy requirements.

• Location: Environmental conditions (e.g., temperature, altitude) can affect energy expenditure.

For athletes, both the source and amount of dietary energy are important for optimal performance and recovery.

Macronutrient Distribution for Athletes

The recommended macronutrient distribution for athletes and healthy individuals is:

• Carbohydrates: 45–65% of total energy intake

• Fat: 20–35% of total energy intake

• Protein: 10–35% of total energy intake (athletes may require amounts at the higher end, which can be met with food)

Carbohydrates are especially important for maintaining glycogen stores, which fuel prolonged and high-intensity exercise.

Micronutrients of Special Concern for Athletes

Certain vitamins and minerals are particularly important for athletes due to their roles in metabolism, oxygen transport, and bone health:

• B Vitamins: Essential for energy metabolism.

• Antioxidant Vitamins (C and E): Help protect cells from oxidative damage caused by increased oxygen use during exercise.

• Iron: Required for hemoglobin synthesis; deficiency can lead to anemia and reduced performance.

• Calcium: Important for bone health and muscle function.

Female Athlete Triad

The Female Athlete Triad is a syndrome observed in physically active females, characterized by:

• Restrictive Eating Patterns: May include disordered eating or eating disorders.

• Amenorrhea: Absence of menstruation due to low energy availability.

• Bone Formation Issues: Reduced bone density, increasing the risk of osteoporosis and fractures.

Sports Anemia

Sports anemia is a temporary condition seen in athletes, especially those engaged in endurance sports. It is characterized by:

• Reduced Hemoglobin Levels: Caused by an increase in plasma volume, which dilutes red blood cells.

• Adaptation: This is generally a beneficial adaptation to aerobic exercise and does not indicate true iron deficiency.

Fluid Needs for Physical Activity

Proper hydration is essential for exercise performance and safety. Water serves several key functions during physical activity:

• Eliminates Heat: Through sweat and evaporation, helping regulate body temperature.

• Transports Oxygen and Nutrients: Delivers essential substances to working muscles.

• Removes Waste Products: Such as lactic acid, from muscles.

At rest in a temperate climate, the body loses about 4.5 cups of water per day through evaporation from the skin and lungs.

Dehydration

• Definition: Occurs when fluid losses are not adequately replaced.

• Consequences: Impaired ability to dissipate heat, increased body temperature, reduced exercise performance, and potential health risks.

Humidex and Heat-Related Illness

• Humidex: An index that combines temperature and humidity to estimate the risk of heat-related illness during physical activity.

• Risk: High humidex values increase the risk of dehydration and heat illness.

Recommended Fluid Intake

Fluid needs vary based on activity, environment, and individual factors. The following table summarizes general recommendations:

Additional info: Table values inferred from standard sports nutrition guidelines.

Hyponatremia

• Definition: A condition caused by low blood sodium levels, often due to excessive water intake without adequate sodium replacement during prolonged exercise.

• Symptoms: Nausea, headache, confusion, seizures, and in severe cases, coma or death.

Nutrition Strategies for Exercise

• Maximize Glycogen Storage: Glycogen is the primary fuel for endurance exercise.

• Carbohydrate Loading: A strategy to increase muscle glycogen stores before endurance events. Only beneficial for activities lasting longer than 90 minutes.

Meal Timing and Composition

• Pre-Exercise: Consume fluids and a meal with 60–70% carbohydrates 2–3 hours before the event.

• During Exercise: Maintain hydration and consume 30–60 g of carbohydrates per hour after the first hour of exercise.

• After Exercise: Replenish fluids, electrolytes, glycogen, and protein to support recovery and muscle repair.

Label Literacy: Sports Bars

Sports bars may contain added vitamins and minerals. It is important to read labels to understand the nutrient content and ensure it meets individual dietary needs.