High Intensity Training - The Safety Factor

High intensity training is not dangerous training. It is, in fact, the safest way to train, the safety factor built in - but only under the following conditions: good form; slow, controlled movement. As long as form is good, you can take a muscle to failure, where it can no longer move with a 100% effort, and NOT produce injury. A bold statement? Just the facts, ma'am.

Force produces injury. The higher the force to which a muscle is exposed, the greater the chance of injury. Therefore, the maintenance of low levels of force during exercise assures minimal injury risk. And high levels of intensity with good form assures low force levels.

The force to which a muscle is exposed during the first repetition of an exercise is potentially high because the muscle is fresh and capable of producing its highest level of exertion and greatest speed at that moment. If you initiate the first repetition with a jerk or excess speed, you invite injury. To avoid potential problems, slowly press into the resistance (bar, pad or other) with enough effort to barely allow it to move, then continue (throughout the range of motion) producing a force slightly greater than the weight itself. The effort should produce a slow, controlled movement.

The muscle fatigues as it continues through the second, third and subsequent repetitions at a rate determined by genetics. The average muscle (an average mix of fast- and slow-twitch fibers) fatigues at a rate of approximately 2% (strength loss) per repetition. Therefore after 10 repetitions, the exercising muscle will be down in strength by about 20%.

What does that mean? During the final repetition, when it feels like your limb will disconnect, the muscle cannot produce the potential force it could during the first repetition. It's tired. Even if you tried to jerk the weight through the final repetition (which you should not), you cannot produce enough force to create injury.

Therefore, despite the way it feels, the last repetition of a set is always safer than the first. Unfortunately, many trainees train by feel, quit before they should - somewhere short of muscle failure - and ruin the potential to stimulate tissue change. All because of fear of injury - a fear not supported by fact.

Work as hard as you can - the harder, the safer.