How do you determine what the best resistance is or intensity to work at when exercising? Physical therapists ascertain the appropriate intensity by using evidence based strength and functional measures. These tests look at the ability for a movement to be executed against a specific amount of force. When these tests are performed the therapists look at whether the participant can first resist the movement (that the force does not break the resistance), usually at mid range of motion, and whether one can maintain good alignment and efficient body mechanics during the test. These tests are reliable predictors of outcome.
But when you are at the gym, the box, the studio, the park, the road what can you do? What you can do is work in proper alignment with good body mechanics (to determine proper alignment and body mechanics check out my blog from October, 2014) and slowly increase the challenge to tolerance. If you are unable to maintain good alignment and body mechanics you may torque your body and use inappropriate muscles to complete the task. For some lucky individuals the first time this occurs will be fine. For others just one wrong move can upset an entire workout, or worse prevent you from working out for quite a while. For the lucky ones continuing to force your body beyond its ability can lead to a repetitive strain or traumatic injury.
Another way to determine whether you are working at the appropriate intensity is by looking at your breathing. If you need to force or hold your breath to complete a task then it is too difficult for you. In addition, this practice is stressful to your body and can be deleterious to your cardiovascular system. It is probably best to avoid exercising with this habit especially if you have an undetected underlying cardiovascular issue. In addition, you should be able to carry on a conversation when exercising. If you are too out of breath to speak you are doing too much.
On the other end of the spectrum is exercising at too low an intensity for your ability. While it is good to simply get up and move, without challenging yourself gains will be small.
So what is the take home message? The take home message is that you should work in proper alignment using efficient body mechanics, be able to carry on a conversation, and increase the challenge to tolerance.