When a impulse goes down a nerve and into a muscle cell two minerals are very important. To cause the muscle cell to open its door to the impulse calcium is needed. To close the door magnesium is needed. Without adequate magnesium the muscle is slow to close the door. This will impact muscle control and can cause cramps spasms. Magnesium is reduced by stress, anxiety, exercise and sugar and carbs. Krebs cycle The muscle cells need malic acid to create energy. A strength issue. Without malic acid the muscle cell is broken down for energy. So you end up with less muscle than if malic acid is present in adequate amounts. Malic acid is in all fruit.
Hope you find this interesting. Obviously it does not just apply to young teen athletes.