If I let my left arm naturally hang and just reach for the fretboard by bending at the elbow, I find I can access up to the fifth fret. However for access to say the first fret, I need to lift my arm and basically use some shoulder muscle to keep it in the air. If I'm doing practice exclusively in frets 1-4 I find that my arm fatigues quite quickly from holding up with my muscles. What technique adjustments can I do to fix this? I hold my guitar so that the headstock is roughly in line with my eyes.
Here's a picture of me in the 'relaxed' position:
Here is me 'tensed' because I have to lift my arm to reach the first fret: