Background Lower back pain occurs more frequently among volleyball than other players and one of the main course affecting their performance on the court.

Objective To identify the reason of the lower back pain, a detailed MRI analysis of disk degeneration (DD) and survey were conducted.

Design, setting and participants There were 48 players from the 2009 and 2010 national teams; mean age, 25.1 years; mean height, 188.7 cm, mean weight, 81.9 kg; mean length of career as a volleyball player, 15.1 years. They practiced volleyball on 5.9 days of the week and for 4.1 h a day, on average.

Intervention DD of each case was evaluated retrospectively based on the signal intensity (rated on a 5-grade scale: I through V) of five intervertebral disks (L1/2 to L5/S1) on MRI using Pfirrmann's classification.

Results The DD grade was I-II in five players (10.4%) and III-V in 43 players (89.6%). It was 20.8% at L1/2, 22.9% at L2/3, 16.7% at L3/4, 45.8% at L4/5, and 75.0% at L5/S1. Of all the players, 95.8% had had lower back pain.

Conclusions Hangai et al.1 reported a higher prevalence of DD among baseball players (59.7%) and swimmers (57.5%) than among non-athletes (31.4%). The prevalence of DD among the volleyball players was as high as 89.6% in this study. With an average of 200 jumps a day, a volleyball player will jump about one million times during a 15-year career. Factors possibly responsible for DD and lower back pain are: (1) shocks from jumping and landing associated with attacks, blocks, jump serves, etc., (2) body trunk twisting in the air at the time of attack, (3) flying receiving, etc. In summary, the prevalence of DD among Japanese male national volleyball players was 89.6%. DD was closely associated with volleyball tactics.