Thanks for your query.
is a large group of blood disorders & the severity varies widely. It is difficult to comment on sports performance without knowings details of illness ,but in general lower than normal Hb is likely to affect oxygen
carrying capacity of blood to tissues & therefore likely to affect sports performance. Also important to know that mental toughness & morale also play a significant role in sport performance. How a person is mentally coping with the condition is also important.
For other answers need to know the precise type of thalassemia( alpha or beta; minor,intermedia or major) & the sickle cell disease
(trait vs disease).
Hope you found the information useful.