Complex sentence: The electronically timed event was limited to 5,000 participants, and runners run through the tunnel twice, from Bowen Hills portal to the Woolloongabba portal, and back to Bowen Hills portal.
Split into simpler sentences: The electronically timed event was limited to 5,000 participants. Runners run through the tunnel twice, from Bowen Hills portal to the Woolloongabba portal, and back to Bowen Hills portal.