Which type of nutrient provides a major source of energy for muscle tissue?

The most significant source of energy for muscle tissue primarily comes from carbohydrates. Carbohydrates are readily broken down into glucose, which muscles utilize during physical activity for immediate energy. This glucose is stored in the muscles in the form of glycogen and serves as a quick energy source, particularly for high-intensity exercise.

While lipids (fats) also serve as an energy source and are particularly important during prolonged, lower-intensity exercise, they are not the primary fuel used for muscle tissue under normal conditions. Instead, fats take longer to metabolize and are more commonly utilized during endurance activities or at rest when the demand for rapid energy supply is lower.

Proteins are generally not a primary energy source for muscle tissue unless other reserves are depleted. Their main role lies in building and repairing tissues rather than providing quick energy.

Vitamins play crucial roles in various metabolic processes and bodily functions but do not provide energy themselves. They are essential in facilitating the body's ability to utilize other macronutrients but do not directly contribute as a major energy source.

Thus, carbohydrates should be recognized as the primary nutrients providing a major source of energy for muscle tissue, especially during active engagement.