Most bicycle shops are now selling motor-driven bicycles, which can be an ideal solution for a person who is out of shape or just not strong enough to ride a regular bike.  Motor-driven stationary bicycles make it possible for just about anyone to gain the benefits of an exercise program, even those with severe disabilities.   The more you are able to push the pedals with your muscles, the more fit you will become, but recent studies show that even having your legs moved entirely by a motor (passive exercise) has benefits. 
Passive Exercise Can Help to Prevent or Treat Diabetes and Heart Attacks
The exciting new concept is that passive exercise — sitting on a motor-driven stationary bicycle and letting the pedals move the person's legs for 30 minutes — burns extra calories and lowers blood sugar and insulin levels in inactive people (Med Sci Sprts Ex, Sept, 2016;48(9):1821-1828).  Having their legs moved by motor-driven pedals increases insulin sensitivity by lowering blood sugar rises after eating.  It is well established that exercise markedly improves glucose tolerance by making your body more sensitive to insulin (Appl Physiol Nutr Metab, Feb, 2009;34(1):25-32).  Doctors can predict your chances of becoming diabetic by giving you a glucose tolerance test in which you are given a sugar-meal and then they measure how high your blood sugar level rises and how long it takes for your blood sugar level to return to normal.  Passive movement of your legs by motor-driven pedals would improve glucose tolerance test results.  
In another study, twenty non-exercising people were given electric motor-driven road bicycles that required them to pedal in order for the motor to turn on, and they were told to ride to class each day  (European Journal of Applied Physiology, June 2016).  They all rode at least 40 minutes three times a week. One month later, they were more fit, had better blood sugar control (insulin sensitive) and less body fat. They were able to average 12 miles per hour and none of them crashed.  Several enjoyed the exercise so much that they bought their own electric-assist bicycles after the study ended. 
In non-exercisers, passive exercise can help to prevent and treat diabetes.  Forty percent of North Americans have high rises in blood sugar after meals, and high rises in blood sugar can damage cells throughout the body.  When blood sugar rises too high, sugar can stick on the outer membranes of cells, and once there, it can never get off. The sugar is converted by a series of reactions to sorbitol which destroys the cell.  This cell destruction explains why diabetics and pre-diabetics can suffer blindness, deafness, heart attacks, strokes, certain cancers, impotence, dementia, loss of feeling in the feet, osteoporosis and so forth.  Any type of exercise, including passive movement of muscles by a machine, can help to prevent diabetes or treat existing diabetes.  Resting muscles draw almost no sugar from the bloodstream and the little that they do draw requires insulin to do so.  On the other hand, contracting muscles draw huge amounts of sugar from the bloodstream and don't even need insulin  (Am J Clin Nutr. July, 2008;88(1):51-57).  
Passive Exercise Burns Extra Calories
Scientists have known for more than a hundred years that passive exercise burns extra calories (Benedict, F. G. & Cathcart, E. P. (1913), Publ. Carneg. Instn, no. 187).  More than 60 years ago, researchers measured the amount of energy a person expends being passively moved on a stationary bicycle at different cadences (J. Physiol, I949);8:353-358). They found that a person being passively moved by motor-driven pedals burned at least 7 to 15 at 56 revolutions per minute (RPM) and 19 to 26 at 74 RPM.   Having a motor drive two legs passively rather than just one leg more than doubled the amount of energy expended (Eur J Appl Physiol.,Sept, 2012;112(9):3341-8).  Two-leg passive cycling at 90 RPM resulted in energy expenditures similar to walking. This means that a leg-paralyzed person on a motor-driven stationary bike can get the same amount of exercise as a non-disabled person gets from walking.   
Who Should Use a Motor-Assist Bicycle?
• If you are healthy but out-of-shape or are not sure you are strong enough to ride a bike, get a motor-driven road bicycle.  Try to ride the bike every day, and use the motor whenever you need help getting up a hill, starting up after a stop, or if you just get too tired to make it back home. Always wear a helmet.   Take the day off if your legs feel heavy or sore.   If your legs start to hurt while you are riding, stop for the day. Always stop your workout when you feel localized pain that worsens as you continue to ride.   See How to Start an Exercise Program.  The key to avoiding injuries is to obey all traffic rules, be in control of your bike, never take unnecessary chances and have extra respect for automobiles.  Always listen to your body.  The more you ride and the stronger you get, the less you will depend on your motor.  
• If you have balance problems, do not know how to ride a two-wheel bike or are not comfortable riding one for any reason, consider a motor-assist trike.  Having three wheels instead of two usually corrects balance and stability problems.  If you have a disability and have a non-disabled partner, you might consider a motor-assisted tandem trike.  This is what we use since Diana can no longer ride on a regular upright tandem because of her osteoporosis.  The article on Our Electric-Assist Trike has pictures and a full explanation.
• If you have a major disability, you are likely to need a motor-driven stationary bicycle rather than a road bicycle.  People who have paralysis of their legs are at increased risk for kidney infections, kidney failure, strokes, heart attacks and diabetes, so passive exercise is particularly beneficial because having their legs moved by a motor can help to prevent these serious complications.  You may need to tie your feet to the pedals or use bike shoes with cleats that attach to the pedals, which are readily available at every bike store.  You will have a throttle that you twist to start the motor and you can stop the motor immediately by releasing the throttle.  See How to Start An Exercise Program; the rules for taking days off and stopping exercise apply for every type of disability.  
My Recommendations
Everyone should exercise. Not exercising regularly increases your risk for obesity, diabetes, heart attacks, cancers and premature death.  The new motor-assist bicycles, trikes and stationary bikes make it possible for just about everyone to gain the benefits of exercise, even if they have moderate to severe disabilities.  If you have total paralysis, let the motor drive your legs for you.  If you have partial movement or are working to build up your strength, use your own muscles as much as you can and then let the motor help you when you need it.  Caution: Check with your doctor before starting a new exercise program.
Checked 10/11/17