Mechanism of Tight Hamstrings in young people : a study of group examination and MRI findings

The Condition called ”Tight Hamstrings” is a contracture of hamstring muscles, but its mechanism is not well known. The purpose of this study is to make its mechanism clear by group examination and MRI findings. First, the aithor examined about 3000 healthy, young prople(aged 15-17), and conducted Straight Leg Raising tests(SLR), Finger Fool Distance tests(FFD), Looseness tests. Next, with MR coronal imaginges, the author measured the distance of the proximal Dorsal Root Ganglia(DRG) border to the root axilla, and the position of the DRG. In each age, the lowest peal of the SLR was seen at the same time as the growth spurt in both sexes. Among three groups(pre-growth spurt, growth spurt, post srowth spurt), the average SLR was lower in the growth spurt group than in the pre-growth spurt group(p＜0.001), and the average FFD is lower in the post-growth spurt than in the growth spurt(p＜0.001). The mean length of spinal nerve roots from their thecal sac exit to the DRG is longer in adults than in young prople, and the lower the nerve roots, the greater the length. The proximal placed DRG ratio increases with age, and the higher for progressively lower nerve roots. But in young people, there is no signidicant difference for proximal placed between the 3 groups. These results suggest that the length of spinal nerve roots is longer in plder people, and for lower nerve roots, but hamstrings are the tighest during the growth spurt. So, ”Tight Hamstrings” tends to appear at this time, especially if some factors of lumbosacral lesion are also present.