This exercise is great for increasing the resistance and the benefit of the standard crunch by focusing on the negative aspect of the crunch with great resistance. The only downside is that it does require a partner to execute.
This exercise is very simple to execute but extremely effective for working the negative portion of the crunch.
How to incorporate this exercise into your workouts:
This exercise requires fresh abdominals due to the large eccentric stresses placed on your abs.
1. Pulling too hard or not hard enough
If your partner pulls down too hard you will lose all tension in your abs because your head will get driven into the floor (do this exercise on a mat). Not pulling hard enough will result in ineffective tension on the abs.
2. Not breathing
You should let your breath out through pursed lips as you are fighting the negative. Holding your breath will dramatically increase your blood pressure and is not recommended.
1. Assistance
Along with pulling you down your partner can also assist on the way up to get you to a higher crunched position by pushing you up. This will give you a greater range of motion to fight the negative. This is also useful towards the end of the set when you can barely lift yourself up into the top of the regular crunch!