Urinary excretion of hydroxyproline in workers occupationally exposed to vibration

Urinary hydroxyproline excretion was measured in 130 chain saw operators aged 28-59 and in 31 normal control subjects aged 26-59 with no occupational exposure to vibration. The results measured were expressed as a ratio of hydroxyproline to creatinine. (1) No significant correlation between hydroxyproline/creatinine ratio and age was observed among normal subjects. (2) In chain saw operators grip and pinch strength decreased gradually with an increase of the total chain saw operating time, while the prevalence of pain in the hands or motility disturbance in the elbow joints showed a tendency to become greater as total operating time increased. Hydroxyproline/creatinine ratio in the group with over 9000 hours' experience was significantly higher than that in the group with under 3000 hours (p less than 0.05). By comparison with controls, the ratio in the group with over 3000 hours was significantly higher at the 5% level. (3) Hydroxyproline/creatinine ratio in the group with pain in the hands or with motility disturbance in the elbow joints was significantly higher than that in the group without them (p less than 0.05). (4) Hydroxyproline/creatinine ratio was inversely correlated with grip and pinch strength in operators ranging in age from 40 to 49 (p less than 0.01). (5) All individual ratios for operators with lower grip strength showed a higher increment than the mean values obtained from controls. These results indicate that increased urinary hydroxyproline excretion in chain saw operators may occur in association with damage to the musculoskeletal system caused by the prolonged use of vibrating tools.