Elevating Heart Rate
One of the problems with most home made versions of treadmill desks is that they are not "ergonomically correct" which can cause problems.
The purpose of a treadmill desk is not to elevate you heart rate as in typical exercise but to keep you upright and moving slowly through the day. This is an important distinction.
If you are overweight or out of shape you must only walk the amount of time you are normally accustomed the first week and only add 15 minute increments until your body adjusts. Remember, if you have been sedentary most of your life walking on a treadmill for 8 hours the first day is going to reap sore muscles.
The bike is better than merely sitting but remember that you are still sitting. This places your spine in a C curve position rather than an S curve position. That causes spinal compression and eventual back problems.
There is also a litany of issues that medical science now calls "sitting disease". You can google that term or read more about it at the TrekDesk website.
Try walking slower and building up to more time on your treadmill desk. Just make sure your arms are at a 90 degree angle (forearm to bicep) when you type so you are sure to have the proper ergonomic height setting.
