I had come to a stop in traffic. I turned my head to the left and there, in a street front shop with large glass windows, was a fitness center.
What I saw through the window was a man, maybe 60ish in years, on his back on the floor with a medicine ball in his hands. At his feet was either a trainer or a buddy – dressed in black gym shorts and a black exercise shirt – appearing much younger than him.
The man did a partial sit up and threw the ball to the younger man. He held the sit up position as the younger man caught the ball and threw the ball back to the older man who caught it, and then lowered himself to the floor. And they repeated this at least 10 times while I was sitting in traffic.
What’s happening here is this:
sit up motion load + load of ball + load of throwing ball + load of holding situp position + load of catching the ball + load of lowering to the floor = a huge load on your spine.
This drill will exhaust your abdominal muscles, which is why it’s often used, but the price for that success is the fatigue it creates in the supporting tissues of the spine.
The fatigue comes from tapping something referred to as your “biologic reserve” – the amount of energy and capacity your body has to do things and still have something left over.
The greater the demand of the exercise, the greater the demand for energy and that means dipping into your biologic reserve to meet the demand.
Injuries can happen when the demand exceeds the reserve by too much.
Some exercises tap more of your biologic reserve than others and there are a number of factors that influence the demand. Here are a few to consider:
Not all exercise is created equal. Some exercises carry more risk than others and the main reason is the demand on your biologic reserve.
Choosing exercises that will challenge you but not bankrupt your biologic reserve is key to staying healthy and fit as you age.