The hike was - without a doubt - the single most strenuous physical activity I have ever forced myself through. The first day of the hike we walked from about 9 in the morning until maybe 3 in the afternoon, with a few stops on the way. And was all uphill, going from ca 1800 meters to 3200 meters above sea-level. It was like walking up stairs for hours and hours. The camp we stayed at had proper beds and food so we had a good and well deserved rest.
The second, the Saturday, day we woke up at 1:30 in the morning to start walking so we could catch the sunrise from the summit. After about 3-4 hours we were at the top, at 4095 m. By then it was pretty cold and we didn't stay very long. We walked down again and had lunch (or actually breakfast, because by then it was about 9 in the morning) and continued walking all the way down. That day I think we walked for maybe 12 hours. And the downhill part was maybe not as bad in the way the uphill was - with being constantly panting - but it was quite the challenge for thighs, knees and ankles.
On Sunday and Monday I could hardly walk. Everything hurt.