Even more strength needed on high positions! More bow pressure and speed... which would tire me sooner. This is very interesting. I'm very happy that for me there are no positions above the first position. It would be too much.

Before I started on violin my idea was: For playing the trombone you need to be tough and a little feeling, for playing the violin you need lots of feeling and a good ear. No, you need to be awfully tough to play the violin, because it is physically very demanding!!

I'm already telling people who think about starting on violin: Yes, you also need ear and feeling, but also awfully strong hands. There are definitely people who hardly have enough physical energy to make it through the day. Whenever they start on they violin, they often suffer. All over the internet you hear people crying because they struggle and suffer with  their choice to play the violin. I think there are psychological reasons in many cases, since emotional distress also weakens the body.

These people should be warned in time. They dream to play like those popular violinists, but this involves also vibrato on higher positions. Who out there has an idea how much strength you need for that?

AndrewH said
The reason the violin is physically demanding is not really the amount of strength it requires, it's that it requires strength in muscles that don't normally get a lot of use. Some of the muscles that are heavily involved in playing violin are barely used for anything else humans do, except playing viola. It takes time to build strength in those muscles. I'm badly out of shape these days, but I find playing viola less physically demanding now (while playing much more difficult material) than when I was a college athlete.

Use bow speed more than pressure in high positions. In high positions, heavy bow pressure tends to produce a "choked" sound. Also, when you press the string to the fingerboard, you're lowering it in relation to the other strings, and that effect is more pronounced when you're fingering farther up the fingerboard. As a result, bowing too heavily when playing in high positions risks hitting other strings.

And yes, the contact point needs to be a bit closer to the bridge as you go up beyond 5th position, because you're playing on a much shorter string. In 5th position, your third finger cuts the vibrating length of the string in half.  

That was great. It should be printed and handed to every violin student. Those who need more time to learn it understand it better than. I'm afraid many violin teachers make students change position too early. I told my ex-teacher, "I'm not gonna go there as long as I struggle on the first position."

Very demanding seems to be synchronization between bow and fingerboard hand. If it works it's easy, but whenever you try hard because it's not there, it takes more energy. It is great if you can change to legatissimo for a while and later try synchronization of non-legato again. The longer you play an instrument, the more technical options you can involve. But on high positions those options seem to narrow and that's probably the difficulty. Less choices in things bow speed (you cannot slow down, which is outspokenly baroque!) is definitely an issue. At some point I should do that, whether I will ever use it or not..... Biber was an exceptional violinist and indeed involved high positions already in the 1600s.