High impact is not necessarily bad. Lots of everyday activities are high impact. Running is a high-impact activity because both feet are off the ground with every stride. Walking is a low-impact activity because one foot is always on the ground. Any type of jumping is high impact, involving a high amount of stress on the connective tissues and joints of your legs and lower back.
The problem is that as you age, you become less able to absorb these high-impact forces. Remember when you were a kid, and you could run and fall, and think nothing of it. There are different types of high-impact injuries. Sudden impact with the ground can cause an injury that happens all at once (an acute injury), like if you land poorly and sprain an ankle.
Any time you get pain, treat it as a warning, and stop your activity and treat the injury. However, not all injuries are as easy to spot as acute injuries. Another type of injury, called a “chronic” injury, can sneak up on you over several months. These injuries start as a little twinge, then slowly get worse, until you are living in constant pain. The cause of these chronic injuries is often traced back to participation in high-impact exercise.
Some examples of high-impact chronic injuries are:
- Heel spurs: the bone starts growing out of the end of your heel.
- Neuromas: the nerves in the ball of your feet get inflamed.
- Achilles tendonitis: the Achilles tendon gets rubbed raw, and may even start to harden with calcium.
- Plantar fascia: the ligament supporting the arch of your foot gets sprained or torn.
- Shinsplints: the tissue connecting the muscles to the bones of your lower leg get torn.
- Stress fractures: the bones of your lower legs start to crumble and crack up from the constant impacts.
- Pain in your lower back or hips.
Physiotherapists have a poor opinion of aerobics as an exercise mode because they see all these injuries that result from participation in high-impact classes, or poor exercise class design, poor exercise selection, or just bad instruction from untrained, unqualified, or inexperienced instructors.
The general guideline for a low-impact activity is that the body is never totally airborne — at least one of your feet must stay in contact with the floor at all times. As well, for an exercise class to qualify as a low-impact class, there should never be more than eight repetitions in a row of a particular foot-strike pattern (the angle that the foot comes into contact with the floor).
This means that the old-style class where you kept jogging on the spot for minutes at a time while you endlessly kept your arms up in the air was a sure-fire recipe for chronic injuries. Especially as it was followed by exercises like star jumps, jumping jacks, ski jumps, high kicks, and then a run around the room.
These days, the motto is “gain, not pain”. You should never get any pain or discomfort from a correctly planned and taught low-impact exercise class. That means no fatigue or muscle burn during the class, and no soreness or stiffness in the days following the class.
The instructor should be certified by the ACT Fitness Advisory Council, or accredited by the Fitness Accreditation Council. This means that they have attended courses on fitness leadership, and have passes theory and practical exams. Look for copies of their certificates, and check the expiry date. Fitness Leaders must resit exams every two years to show that they have stayed up to date with the latest information on safe and effective exercise.
Safe and effective exercise classes will always be carefully planned, with proper preparation before exercise, and a good recovery after the exercises. Every exercise is selected because it fits into the exercise goals for that particular class.
During the class, the fitness leader will give you proper instruction on exercise execution, and your body’s form and posture. For example, you will be told the importance of a good heelstrike (landing on the heel of the foot, not the ball of the foot), and the importance of control.
Low impact does not have to mean low, intensity. If you want a hard workout, it can still be done in a low-impact format. A good example of this is the new Reebok STEP classes, run by an instructor who has been to a STEP instructor-training course.
However, keep in mind that there is still a potential for injury in low-impact classes if the instructor puts in sudden changes of direction (bad for the knees), or has the music up too loud (so you can’t hear their instructions), or if the music is too fast (which may cause injuries from too much extension at your joints or too limited a range of motion).
If you want to choose a good low-impact class, take a look at the participants. They will be the fit, uninjured, happy, and healthy ones.