Young elite cross-country skiers and low back pain-A 5-year study. 
To evaluate possible changes in spinal curvature over a period of 5 years of an elite cross-country skiing squad, and to study whether there are any differences in this respect between individuals who report low back pain and those how do not.  Fifteen young cross-country skiers (M age=13.6±0.9) participated voluntarily throughout the entire study period.  Debrunner's kyphometer was used for measuring the difference between thoracic kyphosis and lumbar lordosis of the spine.  All subjects also answered a questionnaire including questions about ski-related low back pain, the amount of ski training, and participation in other sports.  The results at the end of the 5-year period comprise data from 15 skiers (M age=18.5±0.9 years).  The relationship between thoracic kyphosis and lumbar lordosis increased from 3.5° to 13.1°, respectively (p=0.0001).  Of the 15 elite cross-country skiers, seven reported low back pain at the 5-year examination.  At the 5-year follow-up, skiers with low back pain showed significantly higher relationship between thoracic kyphosis and lumbar lordosis than did those skiers without low back pain, 18.2° and 10.5°, respectively (p=0.035).  Of the eight elite cross-country skiers without low back pain, seven were also involved in other sports (p=0.005).  Based on these findings, our advice is that adolescent cross-country skiers also should participate in other physical activities besides cross-country skiing.