Building muscle safely for young athletes requires a combination of proper nutrition, effective training, and adequate rest. Here are some tips for healthy weight gain:

1. Focus on Nutrient-Dense Foods: Encourage young athletes to consume a balanced diet that includes lean proteins, complex carbohydrates, healthy fats, and plenty of fruits and vegetables. Examples of nutrient-dense foods include chicken breast, quinoa, avocado, and leafy greens.
2. Stay Hydrated: Proper hydration is essential for muscle growth and overall health. Encourage young athletes to drink an adequate amount of water throughout the day, especially before, during, and after workouts.
3. Progressive Resistance Training: Incorporate a well-designed strength training program that gradually increases the intensity and volume of exercises. This could include bodyweight exercises, free weights, or resistance machines.
4. Rest and Recovery: Emphasize the importance of rest for muscle recovery and growth. Encourage young athletes to get plenty of sleep and allow time for their muscles to recover between intense training sessions.
5. Seek Professional Guidance: It's crucial for young athletes to work with qualified coaches, trainers, and nutritionists who can provide personalized guidance based on their individual needs and goals.

It's important to note that young athletes should avoid extreme or rapid weight gain, as it can lead to health risks and potential long-term negative effects on their bodies.

References:

• "Nutrition for Young Athletes." American Academy of Pediatrics, https://www.healthychildren.org/English/healthy-living/nutrition/Pages/Nutrition-for-Young-Athletes.aspx
• "Strength Training for Young Athletes." National Strength and Conditioning Association, https://www.nsca.com/education/articles/kinetic-select/strength-training-for-young-athletes/