What Causes Muscle Tremors?

Hi, I am a 33year old female. I am exercising as I usually do; there are no changes in my programme. Recently I am experiencing leg tremors during exercise. I am maintaining my fluid levels; drinking 2 litres per day plus 500ml per 1hr exercise. My bloods are normal. Over the last 6 months my blood pressure has increased and, despite intervention in both lifestyle and medicines, the level of osteopenia in my body has increased. I do have IBS and this has also recently changed to intermittent periods of diarrhoea. The muscle tremors are new and I wondered if this could be related?