This study was performed to determine the impact of sex and sport-discipline on physical fitness and bone markers in young sub-elite track and field athletes. One hundred and forty-four track and field sub-elite athletes (78 males aged 17.8 ± 1.6 years; 66 females aged 17.2 ± 1.9 years) volunteered to participate in this study and were categorized according to their disciplines in endurance (EG: n=67) or power athletes (PG: n=77). A significant main effect of sex was observed for C-telopeptide type I collagen (CTx) (F=11.37; p<0.001; 2=0.10, moderate), for osteocalcin (OC) (F=8.58; p<0.004; 2=0.09, moderate) and for N-terminal propeptide of procollagen type I (PINP) (F=7.96; p<0.05; 2=0.07, moderate). The average CTx, OC and P1NP levels were significantly higher in males compared with females (0.05<p<0.001; 2= 0.07 to 0.10, moderate). In addition, a significant main effect of sport-discipline was observed only for P1NP values (F=10.16; p<0.002; 2=0.09, moderate) with EG showing higher levels than PG. For jumping and sprinting tests, the PG performed better than the EG. For the endurance test, EG had better performance than OG. Endurance and power exercise practices can increase bone formation markers (P1NP, OC), but only anaerobic training (PG group) appears to positively impact on male track and field athletes.