Pranayama; Nerve injury?

Hi,

i have an asana and i use breath control. Exhale from one nostril for 20 seconds, inhale same nostril for 10 seconds then alternate with other nostril and so on. I did about an hour, body heated up a bit and started trembling and i appear to have done something to my thigh muscle. It began to 'give way' day after and from then on, although not as bad seeing as i have laid off the Pranayama for such long periods. I think it has something to do with the diaphragm muscles being connected to , well., the thigh muscles..perhaps via a nerve?

What happened? Breath strain perhaps?