No - for a large man it is perfectly reasonable and might even be used for someone smaller - a study some years ago in Italy found that 75% of patients achieved an acceptable result in a month with as little as 12,5mg. Small women did better on that dose than large men - go figure! And most people want a result quicker than a few weeks. The 50mg was too high though. The usual “is this PMR?” dose should be 15-20mg as PMR responds to that sort of dose where other options wouldn’t. Then you find the lowest dose that is effective in the range 12,- to 25mg/day - because everyone absorbs different amounts of the oral dose and responds differently.
However - at a guess he thinks he can go back to normal activity now he’s on pred? I’m afraid not - the pred only manages the inflammation that causes the symptoms, the actual underlying disorder continues in the background, making your muscles intolerant of acute exercise and causing fatigue, a bit like flu. That must be managed by pacing, resting appropriately and lifestyle changes.
This is our resources post with a load of useful and reliable links:
and if you ask particular questions someone will help out - someone will have been there!