The motion load of rabbits was increased by treadmill running during a 5-d period. One group ran on a level surface, while the other ran uphill. After the running, the glycosaminoglycan metabolism and scanning electron microscopic photographs of different tendon, ligament and cartilage samples were analyzed. Uphill running decreased the glycosaminoglycan metabolism of articular and costal cartilage. The clearest irregularities of articular cartilage studied by scanning electron microscopy were also seen in the uphill running group. Increasing the motion load increased the glycosaminoglycan synthesis of stretched tendons. The possible combination of general inhibitory and local stimulating effects is discussed.