Cheat Reps

A common phenomenon observable in most gyms is the performance of "cheat reps". A cheat repetition is defined by these three points:

1. Using momentum to move the weight (swinging).
2. Changing the range of motion without a plan to do so (stopping short of the bottom position).
3. A breakdown of technique.

There are a few perceived benefits to using cheat repetitions. Generally more weight can be lifted and more repetitions can be completed with the same weight. Both of these would normally improve the results of a resistance training program, but there are a few problems.

Using more weight, but using cheat reps, does not increase the forces experienced by the muscles. Instead, different muscles are used to generate the required force. This does not cause increased growth in the target muscles.

Limiting the range of motion in an exercise limits the number of motor units that become activated during the movement. A motor unit is a group of muscle cells inside of a single muscle that always contract together. For the best muscle growth and strength gains the use of all motor units is important. Additionally a deep stretch at the bottom of a movement helps to cause muscle growth, and limiting the range of motion eliminates this benefit.

Lastly cheat reps "cost" more than regular repetitions and can increase the risk of injury. Using heavier weights puts more strain on connective tissues and the nervous system. Over time this additional strain can cause joint problems, and cheat reps can put your body in precarious positions. For example, when squatting people often "cheat" by letting their knees come towards each other, placing immense stress on the MCL, one of the ligaments responsible for holding the knee together.

Using lighter weights with good form is the best option, it is both safer and more beneficial. If you find yourself "cheating" on exercises there are two options: use a lighter weight with correct form or add an extra set, reducing the number of repetitions in each set.

Fitness expert Dom Mazzetti demonstrates how cheat reps may go wrong.