### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
I m 40, male, sit at a desk all day. I usually exercise 3 times a wk. 45 minuts cardio with my heart at around 145-160 bpm. Then sit ups, 250 pounds crunch, 50 reps. I then move to the lower back extensions 250 pounds 30-50 reps. I have lower back pain in what feels like my tail bone , shaking legs, arms etc. This is after 3 to 4 days off from exercise (just testing things out to fingure out what is going on). I actually feel my best after the exercise and for a day or two after. Wake up in the morning regardless of any exercise and my lower back hurts like no tomorrw. ANy thought on this? Head aches come and go with sharp pains in my head and then they stop, at time I can get a little dizzy. Around 3:30 in the afternoon I am whipped and very tired.

### output:

Hi. From the details given by you, it appears that you have a good exercise habit. These are the points I can make out from the history given by you:Your back pain is most likely related to your sitting for long hours or some probable injury during exercise. It would be helpful to know if you have morning stiffness in the back lasting for an hour or longer, which gets better after exercise or walking around; or if the back pain runs down the back of thigh or leg on either side. If the back pain is severe and recent onset, you need to stop the back extension exercises for a while and see the response. Maintain good posture while sitting at work, avoid bending forwards and lifting heavy weights till back pain settles down. If it persists, you need a formal clinical evaluation. Shaking legs and arms - need more details to decipher the significance Head ache and dizziness if persistent need attention by formal clinical evaluation. But less likely to be related to the back pain.