Peripheral Neuropathy and Lower Limb Ulcers
Loss of sensation in your feet or hands is called peripheral neuropathy, and if you have it, your risk of damaging your feet in particular during exercise increases greatly. Peripheral nerve damage can blunt the usual symptoms of pain or discomfort resulting from impact on your feet or friction and pressure from footwear, making it easy to develop a blister or sore on your foot without being aware of it. In some cases, a simple blister can progress to a full-blown infected abscess or ulcer and ultimately result in a lower-limb amputation if not properly cared for in time.
If you have lost feeling in your feet, the American Diabetes Association recommends that you use shoes with silica gel or air mid-soles (the middle section of the shoe that provides the most stability and shock absorption), as well as polyester or cotton-polyester socks to prevent the formation of blisters and to keep your feet dry during physical activities. (Pure cotton socks tend to get wet and stay wet, which may promote damage to your feet.) It is also imperative that you (or someone else, if you are not able to) check your feet daily for signs of trauma and treat them aggressively to prevent any worsening of the problem.
If you have lost feeling in your feet or already have an ulcer that has not yet healed, it may also be a good idea to switch to activities such as swimming or stationary cycling that minimize the trauma to your lower extremities. Walking, jogging, and other such activities require you to place your full body weight on your feet. Good non-weight-bearing exercises include anything aquatic (swimming, pool walking, water aerobics, and the like), upper-body exercises (rowing, arm crank ergometers, and other upper-body work), chair exercises, stationary cycling, yoga, and abdominal work, among others. These activities, in addition to minimizing potential foot problems while allowing you to remain active, also improve your body tone, balance, and awareness of your lower extremities.
Exercise doesn’t appear to have the capacity to reverse peripheral neuropathy, but it can slow its progression and prevent further loss of fitness from occurring due to inactivity, and it may also improve circulation in your lower legs and feet enough to help prevent ulcers from forming. However, your neuropathy may have progressed to the point that you have some physical difficulties and limitations in exercising; for example, your peripheral nerve damage may cause dull, shooting, or throbbing pain in your extremities after you go for a walk or engage in other weight-bearing activities. If you ever experience this type of painful neuropathy due to a certain activity, then it’s best to limit that activity in the future and switch to others that don’t cause you lasting pain or discomfort.
Other diabetes-related complications may also require some modifications in your exercise program. For example, if you have damage to your central nervous system (autonomic neuropathy), you’re more likely to experience silent ischemia. This could result in a “silent” or undetected heart attack. Your chances of dying suddenly during exercise from such an event are high once your heart has become unresponsive to nerve impulses due to autonomic neuropathy–especially if you have underlying heart disease.
If severe, this complication may also make it harder for you to change your body position (e.g., going from sitting to standing or from lying to sitting) without experiencing orthostatic hypotension, which can result in lightheadedness or fainting. You’re also more likely to overheat and get dehydrated. If this type of nerve damage affects your ability to digest and absorb foods (known as gastroparesis), any carbohydrate you eat to treat a low blood glucose reaction during exercise might be more slowly absorbed, and your hypoglycemia might become more severe as a result. Finally, this complication may cause you to have an elevated heart rate at rest (for example, 100 beats per minutes instead of the normal 72 beats), and it can keep your heart from beating as fast as it should once you start to exercise.
If you have been diagnosed with autonomic nerve damage, take a conservative approach to exercise. Try to avoid rapid changes in movement that may result in fainting and take a longer time (10 minutes or more) to warm up and cool down, particularly when you’re doing strenuous activities. Drink extra fluids during exercise, and avoid being continuously active for long periods during hotter weather conditions. Also, avoid eating a large meal before exercise as it could result in delayed emptying of food from your stomach. Eat only small portions beforehand, and treat hypoglycemia with easily absorbed glucose tablets before blood glucose levels become too low (when they reach 100 mg/dl) to prevent severe hyperglycemia. Finally, monitor your exercise by some means other than your heart rate alone, since it may no longer rise as much as expected or be the best way to monitor your exercise intensity.