Like one of those treadmill bikes?

Let's incorporate some numbers into this scenario for a clearer perspective.

Assume a standard Olympic triathlon, which includes a 1.5-kilometer swim, a 40-kilometer bike ride, and a 10-kilometer run. Hippos can swim at speeds around 5 mph (8 kph) and run at up to 20 mph (32 kph) but these speeds are only in short bursts, not sustained over long distances.

For the 1.5-kilometer swim, at an average speed of 8 kph, a hippo could theoretically complete this segment in roughly 11 minutes. A well-trained human could complete the same distance in around 20 minutes.

However, the biking and running segments are where the hippo would struggle due to its short legs and lack of endurance. Even with a specially designed bike, let's assume a hippo could bike at a generous speed of 5 kph due to their physical limitations. Therefore, it would take them around 8 hours to complete the 40-kilometer bike segment. In contrast, a well-trained human could complete this in around 1 hour.

For the 10-kilometer run, even if the hippo could sustain their top speed of 32 kph (which is unlikely), they could theoretically finish in under 20 minutes. However, due to their poor endurance, a more realistic time might be around 1-2 hours. A well-trained human could complete this segment in under 40 minutes.

In summary, even if a hippo performed at its absolute best and a human performed at average speeds, the human would finish the triathlon in roughly 2 hours, while the hippo would take around 9-10 hours. The limitations of the hippo in biking and sustained running, even with hypothetical specialized equipment, make it highly unlikely they could compete effectively in a triathlon.