"When you're prepared, you're more confident. When you have a strategy, you're more comfortable."
- Fred Couples

Here is some interesting discussion on ab training and the lower back. http://www.exrx.net/Adaptation/DangerousExercises.html
Within the scientific community we can find support for the inclusion or exclusion of any exercise.

Row 5 minutes, record meters
Row 5 intervals of 1 minute on/1 minute off, record total meters
Row 10 intervals of 30 seconds on/30 seconds off, record total meters
Row 20 intervals 15 seconds on/15 seconds off, record total meters

Notes:

1. Rest 5 minutes between intervals
2. Use the "m" button to recall meters for each interval
3. Go all out.
4. Compare results of each effort.