Yamakawa , et al. ( 2001 ) studied hospital admissions in Gifu , Japan , from 1988 to 2000 .
Yamakawa , et al. ( 2001 ) found an increase in spinal injuries due to snowboarders jumping , particularly at intermediate and expert level .
Yamakawa , et al. ( 2001 ) studied hospital admissions in Gifu , Japan , from 1988 to 2000 , and found an increase in spinal injuries due to snowboarders jumping , particularly at intermediate and expert level .