1. Muscle growth: With the increase of exercise intensity and frequency, muscles will gradually become stronger and stronger. This may be manifested as more distinct lines in arms, chest, abdomen, legs and other parts.
2. Decrease of lean body mass: Through aerobic exercise and healthy diet, the body fat rate of boys may decrease, thus reducing lean body mass. This may lead to tighter skin and clearer lines.
3. Improve strength: With the increase of exercise intensity, the strength of boys will gradually improve. This may be manifested in the ability to complete heavier weight or maintain high strength for a longer period of time during exercise.
4. Improve endurance: Aerobic exercise such as long-distance running and swimming may improve the cardiopulmonary function of boys, thus improving endurance. This may be manifested in the ability to maintain high intensity for a longer period of time during exercise.
5. Improve physical coordination: Through exercise, the physical coordination of boys may be improved. This may be manifested in more flexibility and smoother movements.
6. Enhance bone density: For boys who carry out weight-bearing training, the bone density may increase, thus making the bones stronger.
7. Improve mental state: Exercise can help boys reduce stress and improve their mood, thus improving their overall mental state.
In a word, the training traces of boys' fitness may be manifested in muscle growth, lean body weight loss, strength improvement, endurance improvement, physical coordination improvement, bone density enhancement and mental state improvement. The specific training trajectory depends on the individual's exercise plan and goals.