Start Break

It's important to stop after the first 5 minutes of practicing and let the musclesgo back to being disengaged.

Also. It's important to not just randomly plow through scales and appegios. Stop, get the metronome set, play the exercise and then stop and take the violin away from the should (for at least 15 seconds) and relax.

Ongoing practice causes hidden muscles tension. All practice should not go for more than a few minutes within a brief break.

... yep. the metronome definately keeps the body moving and the brain accustomed to the challenge.

It's more important to take quick breaks at the start of a practice session. There's nothing wrong with stopping at any point to take a 1 minute break. The end of life is not imminent.

Also. it might be important to warm up without a metronome.

Warmup - physical exercise.
Practice - with metronome.
Perform - any playing without a metronome.