I have been practicing intensive shamatha meditation for many months now. On workdays I manage ~4 hrs of meditation, two very early in the morning and two at night. At weekends I do meditation for 6-8 hrs in intervals. I do have certain basic experiences like intermittent appearances of what I believe to be uggaha nimitta and very rarely what seems to be some early Piti which stays for some time and then vanishes. What I am troubled by, however, are the intense flu-like symptoms that I have been having for the last few weeks or so. There are severe aches and pains all over the body with profound malaise and a severe chill that has crippled me. There is no actual physical disease as such- I know that because I am a doctor by the way- but the distress it has caused me is immense. I have continued with my intensive practice and have not given up on it.I am hopeful that in near future, my meditations will help me to conquer this disability, yet I am worried at the moment. I seek the opinion and help of my senior brethren on the path to deal with this problem. Thanks.
While aches and pains sound very general and while severe chill symptoms are not familiar to me, often various 'excess wind' (prana) & physical/nervous tension (nervous system) symptoms can occur when too much mental energy or 'suppression' is applied to meditation. Therefore, it is likely 'suppression' meditation could result in aches, pains, immature nimittas and other symptoms.
The renowned 'Buddhist' commentary called the 'Visuddhimagga' refers to the 'uggaha-nimitta' and describes the attainment of jhana (absorption) via "suppression" and mental application ("vitakka"). Many Buddhists follow the Visuddhimagga.
However, the techniques & definitions found in the 'Visuddhimagga' in relation to meditation & jhana often have little support in the documented teachings of the Buddha.
To the contrary, the Buddha taught jhana (absorption) is developed by making "letting go" / "surrender" / "relaxation" ("vossagga") the meditation object, as follows:
And what is the faculty of concentration? There is the case where a monk, a disciple of the noble ones, making it his object to let go, attains concentration, attains singleness of mind. Quite withdrawn from sensuality, withdrawn from unskillful mental qualities, he enters & remains in the first jhana
There is no actual physical disease as such- I know that because I am a doctor by the way- but the distress it has caused me is immense.
Since you're a doctor, you'd already knew the importance of physical exercises. Meditation is always good, but don't forget your daily dose of outdoor cardios. Remember that the Buddha and His noble disciples didn't just sit on their behinds all day long back in the good old days. They got great outdoor cardios by walking long distance on bare feet into towns and villages for alms-round! Now even if after doing cardios and you still experience those weird discomforts, then you might want to re-examine those meditation techniques you've been using for it'd sound there's something not quite right. For if one does it right, the benefits are not only in the well being of a much more subtle and refined mind state, but also a much more relaxed, light, and comfy physical body.