Morphological and biochemical effects of strenuous exercise on immature long bones.

To determine the effects of intense exercise on the growth of long bones in immature animals, young male white leghorn chickens were run five days per week starting at four weeks of age on motor-driven treadmills. Work intensity was determined on the basis of maximal oxygen consumption (VO2 max) with the exercise intensity maintained at 70-80 percent VO2 max. Young animals ran continuously for 30 minutes, older animals 45 to 60 minutes each day.

Effects of microgravity on the composition of the intervertebral disk.

The lumbar annuli of rats flown on COSMOS 2044 were compared with those of three control groups and a tail-suspension experimental model. The wet and dry weights of the annuli were significantly smaller (P less than 0.05) in the flight group than in three control groups.

Response of immature chicken meniscus to strenuous exercise: biochemical studies of proteoglycan and collagen.

Male white Leghorn chickens were exercised on a treadmill at 70-80% of their maximal oxygen consumption starting at 4 weeks and continuing up to 20 weeks of age. The effect of the strenuous exercise regime on the extracellular matrix of menisci was followed through studies of proteoglycans and collagen. Avian menisci contain type I collagen, chondroitin sulfate proteoglycans, which increase with age in amount and degree of aggregation, and dermatan sulfate proteoglycans, which decrease with age.

Structural and mechanical adaptation of immature bone to strenuous exercise.

To investigate the adaptive responses of immature bone to increased loads, young (3-wk-old) White Leghorn roosters were subjected to moderately intense treadmill running for 5 or 9 wk. The training program induced significant increases in maximal O2 consumption and muscle fumarase activity in the 12-wk-old birds, demonstrating that growing chickens have the ability to enhance their aerobic capacity. The structural and mechanical properties of the runners' tarsometatarsus bones were compared with sedentary age-matched controls at 8 and 12 wk of age.