The phrase "arm relaxed" is correct and usable in written English.
It can be used to describe a state of the arm being in a relaxed position, often in contexts related to posture or physical relaxation.
Example: "After a long day at work, I finally sat down with my arm relaxed on the armrest."
Alternatives: "arm at ease" or "arm loose".
At the right time, I'd see him go back there, his arm relaxed at his side, his hand around the wooden stock of an ax.
They were to try to keep their arm relaxed and be open to any of the following possibilities: the illusion of movement may not occur; if it occurs, it may, over time, change direction or speed, and finally the illusion may cease altogether and reappear.
During the monitoring, patients were asked to avoid vigorous physical exercise and to keep their arm relaxed during measurements.
ABPM was performed during a normal day with typical activities, but subjects were asked to avoid vigorous exercises and to keep their arm relaxed during each daytime inflation.
The subjects were instructed to sit with arm relaxed, and the investigator palpated over the biceps brachii, and extended the elbow joint maximally.
And let his arm relax across me.
Leslie Wong caught and pulled into the wave of the day, his back slightly arched, his arms relaxed, making the extremely difficult — no, come on, the ecstatic — look easy.
By the end of the second season, he rousts two would-be meth cooks from his territory with pure assurance: a wide stance, arms relaxed yet poised to strike.
Nine new ways, in fact, to which the company has given names like the Cocoon (reclining, feet on the seat, legs drawn in), the Take It In (slumped way back, arms relaxed while you watch a video) and the Strunch (a stretched hunch from chair edge to table, laptop pushed far away from you, chin propped up with nondominant hand).
Participants were asked to stand on a footstool (34 cm length, 19 cm weight, 23 cm height), grab a wooden stick with both hands while keeping both thumbs closed and both knees completely extended, and, from there on, flex the trunk towards the floor, with head and arms relaxed (see Fig. 1a).
