We hiked a trail in the Haleakala Mountains. The hike was marked "moderate" and it was pretty moderate, but this is coming from a lean female in her early 20s - it may be marked under "strenuous" for some people. It was even a little tough for me at times. The hike was so much fun - it took about 3 hours, and we drove to the spot where tourists can go to gingerly walk around, but we hopped a fence to start our hike and dive right into the "rainforest." We started walking and we were provided with a pack and water for everyone (there were only three in our group and I don't think they'd take more than five or six at a time).
As we went, our tour guide was very knowledgeable and gave us background and stories on Maui itself; he also pointed out things growing such as fruits and roots that we never would've known were there. We walked for a long while and some parts were easy, aside from the large roots to step over here and there, but as the hike got along, we started to sweat and there were inclines to climb. This hike takes you all the way up the mountain so you can stand at the top and see everything. It was a lot easier getting down from the mountain than going up, but we took a nice water break up top and the guides had snacks for us like chips and dried fruit.
We had a lot of fun and laughed a lot, but it is VERY "in the jungle" and outdoorsy, so if you're thinking you're just going to be walking through a park, you're mistaken - it's hiking, and at times the wildlife comes in on you close. There were times we had to hold onto ferns and trees around us to keep our footing, and the ferns did leave small cuts on our legs, but overall, it was so much fun, and definitely worth it. We were back for a relaxing day on the beach by noon after our 8am hike!