Walking is not always the best exercise.
If you can't do any other exercise you can always walk, right? It's symmetrical, it's low impact, it can increase your aerobic capacity and burn calories, plus you get to enjoy being outside in the air and sunshine.
But there are people for whom walking might not be the best. It might actually do more harm than good, especially if you have a herniated disc in your back.
That is when the legs are of different lengths.
Our bodies work best when they are close to being symmetrical, both sides the same. The same length, same muscle tightness, same strengths... and so on. But about five percent of people have significant differences in the lengths of their legs. Generally a difference of less than about 5 millimeters is compensated for by the body, but greater than that and the body above the legs is thrown out of whack, all the way from the lower back up to the neck.
When one leg is shorter than the other, you will be taking different stride lengths and you will be shifting your weight more onto one side than the other. More weight on one side can lead to knee strain, to pelvic unlevelling and to sideways shifts in your spine, putting more stress on the lumbar spine discs.
It's like pounding in a bent nail. a straight nail is going to go straight into the wood, a crooked nail is just going to bend. Then when your spine gets twisted you can end up with abnormal stress on the joints and ligaments and eventually back problems. You may even tend to walk in circles if you close your eyes and try to walk a straight line.
A new study even suggests that knee pain and earlier onset osteoarthritis are often the result of leg length imbalances. The short leg often being the one with the earliest problem.
How do you tell if you have a short leg? One of the outward signs is pelvic unlevelling, you may be able to notice that when looking in the mirror and seeing that your beltline is higher on one side than the other. Sometimes the shoulders will also be unlevel. And there may be abnormal shoe wear with one show wearing out faster than the other. The best clinical measurement is done by xray with special views that allow an accurate measurement of the difference.
But just because there is a difference in the length, you don't always fix it. There are some times when it is best to not do anything about it. The difference must be evaluated based on how much the body has compensated for the differrence. Sometimes a difference that occurs early in life will result in a pelvis that has adapted to the short leg. You must determine the cause of the difference to know what to do about it.
There are two types of leg length differences, anatomical and functional. Your body can develop from birth with bones of different lengths. This is the anatomical type. There is nothing you can do about this short of a major surgery when you are young. The fix for this type is to accommodate for it with either a lift inside the shoe or by adding a lift onto the sole of your shoe. Leg length differences of up to a half inch usually are helped with a lift inside the shoe, while larger differences usually require a lift on the sole of the shoe.
Functional leg length differences occur as a result of imbalances in the nerve control of the muscles of the pelvis and in the flexibility of the ligaments and tendons of the hip, leg and foot. The pelvis may become twisted, or the knees bowed, or the arches may drop. Flat arches, especially if there is a difference between the two feet, will often lead to a leg length difference. Correction of this is by a custom molded orthotic, just using a lift inside the shoe would be the wrong thing for this. These functional changes are not permanent and may be addressed with proper rehab procedures.