Spinal shrinkage in fast bowling

The load on the spine during physical activities may be reflected in decreases in stature, referred to as shrinkage. Spinal shrinkage reflects the creep behaviour of the intervertebral discs and vertebral end-plate compression when loaded. This study was concerned with shrinkage induced during practices corresponding to fast bowling in cricket, an activity associated with risk of back injury. Eight cricketers (aged 19-24 years), all free of back pain, acted as subjects. They were first trained for measurement on the stadiometer until 10 consecutive recordings of stature with SD < 0.5 mm could be produced. A 20 min period of standing was used for standardization purposes prior to experimental work which took place indoors between 12:00 and 16:00 hours. The experimental conditions were (i) standing for 30 min; (ii) bowling for 30 min at a rate of once every 30 s from a 14 m run-up; (iii) a run-up (without bowling) of 14 m for 30 min once every 30 s; (iv) inverted at an angle of 50 degrees for 5 min; (v) inverted at an angle of 50 degrees for 5 min prior to bowling once every 30 s for 30 min from a 14 m run-up. These conditions were presented to the subject on five separate days. Stature was not affected by the 30 min standing, used for control purposes (mean shrinkage 0.1 mm). Bowling caused a decrease in stature of 2.30 (+/- 1.58) mm in 30 min (p < 0.05). Stature did not decrease significantly (mean shrinkage 0.29 mm) when only the run-up was performed (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)